Article

Recovery of Endemic Dragonflies after Removal of Invasive Alien Trees

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Because dragonflies are very sensitive to alien trees, we assessed their response to large-scale restoration of riparian corridors. We compared three types of disturbance regime--alien invaded, cleared of alien vegetation, and natural vegetation (control)--and recorded data on 22 environmental variables. The most significant variables in determining dragonfly assemblages were percentage of bank cover and tree canopy cover, which indicates the importance of vegetation architecture for these dragonflies. This finding suggests that it is important to restore appropriate marginal vegetation and sunlight conditions. Recovery of dragonfly assemblages after the clearing of alien trees was substantial. Species richness and abundance at restored sites matched those at control sites. Dragonfly assemblage patterns reflected vegetation succession. Thus, initially eurytopic, widespread species were the main beneficiaries of the removal of alien trees, and stenotopic, endemic species appeared after indigenous vegetation recovered over time. Important indicator species were the two national endemics (Allocnemis leucosticta and Pseudagrion furcigerum), which, along with vegetation type, can be used to monitor return of overall integrity of riparian ecology and to make management decisions. Endemic species as a whole responded positively to restoration, which suggests that indigenous vegetation recovery has major benefits for irreplaceable and widespread generalist species.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Indeed, the modification of vegetation composition to restore "initial" or "natural" vegetation had no effect on the abundance of aquatic insects [72], on the composition of ant communities [73], and on the abundance of Apis mellifera [74]. Similarly, the modification of vegetation did not affect the abundance of 9 Odonata species [75], and the ground beetle biodiversity indices [76]. ...
... Nevertheless, modifications of vegetation composition aiming at getting rid of non-native species promoted bee species richness and abundance [74], the species richness, abundance, taxonomic distinctiveness of Odonata and the abundance of 13 Odonata species [75], as well as the abundance of aquatic insects [77]. The only contrasting result referred to the abundance of Chlorolestes umbratus, a rare Odonata species, which was lower along restored riparian corridors when compared to sites invaded by alien trees [75]. ...
... Nevertheless, modifications of vegetation composition aiming at getting rid of non-native species promoted bee species richness and abundance [74], the species richness, abundance, taxonomic distinctiveness of Odonata and the abundance of 13 Odonata species [75], as well as the abundance of aquatic insects [77]. The only contrasting result referred to the abundance of Chlorolestes umbratus, a rare Odonata species, which was lower along restored riparian corridors when compared to sites invaded by alien trees [75]. ...
Article
Full-text available
Background The role of linear transportation infrastructures (roads, railways, oil and gas pipelines, power lines, rivers and canals) in fragmenting natural habitats is fully acknowledged. Up to now, the potential of linear transportation infrastructures verges (road and railway embankments, strips of grass under power lines or above buried pipelines, or waterway banks) as habitat or corridor for biodiversity, remains controversial. In a context of decreasing natural habitats, the opportunities of anthropogenic areas for contributing to wildlife conservation have to be considered. The present paper is the first synthesis of evidence about the potential of linear transportation infrastructure verges as corridor and/or habitat for insects in temperate landscapes. Methods A systematic literature survey was made using two online publication databases, a search engine and by sending a call for literature to subject experts. Identified articles were successively screened for relevance on titles, abstracts and full texts using criteria detailed in an a priori protocol. We then used six specific questions to categorize and to critically appraise the retained studies. These questions encompassed the potential of verges as habitats and corridors for insects, and the effects of management and landscape context on these potentialities. A user-friendly database was created to sort the studies with low and medium susceptibility to bias. We used these studies to synthesize results of each specific question in a narrative synthesis. Finally, studies that met the meta-analysis requirements were used for a quantitative synthesis. Results Our searches identified 64,206 articles. After critical appraisal, 91 articles that reported 104 studies were included in our review. Almost all of them had “control-impact” design, only two studies used “before-after-control-impact” design, and one study used “before-after” design. In some cases, artificialization of transportation infrastructures lowered insect biodiversity while vegetation restoration had a moderate positive effect; the trend remained unclear for mowing/grazing practices. Urbanization and agriculture in the surroundings tended to lower the biodiversity hosted by verges, while natural and forested areas tended to promote it. No study dealt with the influence of management or surrounding landscape on insect dispersal along the verge. The small number of studies that compared the dispersal along verges and in habitats away from transportation infrastructures, together with the inconsistencies of their results, prevented us from drawing conclusions. Meta-analyses were performed on 709 cases from 34 primary studies that compared biodiversity in verges vs. other habitats. Overall insect species richness did not differ between LTI verges and compared habitats. Globally, insect abundance seemed higher on LTI verges than in compared habitats, a result driven by the higher abundance of pollinators and primary consumers on non-highway road verges than in habitats away from roads. Conclusions A major knowledge gap regarding the potential of linear transportation infrastructure verges as corridors for insects has been identified. Thus, we encourage more research on this topic. Infrastructure practitioners could benefit from our results about linear transportation infrastructure verges as habitat for certain taxa and about the impact of their management practices on insect abundance and species richness.
... Dragonfly assemblages are widely recognized as effective indicators of environmental health in freshwater ecosystems (Clark and Samways, 1996;Chovanec, 2000;Smith et al., 2007;Dutra and De Marco, 2015;de Oliveira-Junior et al., 2015;Golfieri et al., 2016;Valente-Neto, et al. 2016) as they are bright, colorful, conspicuous and well-known insects (Kalkman et al., 2008), making them effective for assessing freshwater bodies and their surrounding water margins according to the health and ecological integrity of these water bodies (Samways, 2005;Smith et al., 2007;Oertli, 2008;de Silva et al., 2010;Simaika and Samways, 2011;Kutcher and Bried, 2014;Golfieri et al., 2016;Martín and Maynou, 2016;Valente-Neto et al., 2016). Their effectiveness comes about from their assemblages being sensitive to both changing landscape and biotope structure and condition (Samways and Sharratt, 2010;Goertzen and Suhling, 2019), as well as in-water conditions (Kietzka et al., 2017). ...
... In turn, the overall assemblage composition is indicative of the extent to which a freshwater ecosystem and its surrounds has moved away from the historic reference condition, either negatively, or positively in the case of restoration (e.g. Samways and Taylor, 2004;Samways and Sharratt, 2010). The effectiveness of the DBI lies in magnifying the difference between, on one hand, species that are geographically widespread, not threatened, and tolerant of human disturbed ecosystems, and on the other hand, those that are geographically restricted, threatened with extinction, and highly intolerant of human disturbances to their habitats. ...
... Dalzochio et al., 2018), while the growth of alien riparian trees is a critical threat to open, sclerophyllous landscapes (e.g. Samways, 2006;Samways and Sharratt, 2010;French and McCauley, 2018). Likewise, the scale of the weights also differed for the three main habitat types. ...
... The order Odonata (dragonflies and damselflies) is considered to be a model group in this sense, due primarily to the amphibious life cycle of these insects, which have aquatic larvae and terrestrial/flying adults, and the rapid response of this group to environmental changes in both aquatic (García-García et al., 2017;Mendes et al., 2019) and terrestrial systems (Dolný et al., 2012;Calvão et al., 2018). Odonates are used frequently as bioindicators of the "health" and conditions of the environments they inhabit (Oertli, 2008;Samways & Sharratt., 2010;Oliveira-Junior et al., 2015;Miguel et al., 2017b). Changes in the canopy cover (Remsburg et al. 2008), riparian vegetation , water quality (Van Praet et al., 2012), and land use (Seidu et al., 2017;Calvão et al., 2018) may all lead to a reduction in environmental integrity, which will modify the structure of the local odonate community (Samways & Sharratt, 2010;Dolný et al., 2012;Oliveira-Junior et al., 2017;Bastos et al., 2021). ...
... Odonates are used frequently as bioindicators of the "health" and conditions of the environments they inhabit (Oertli, 2008;Samways & Sharratt., 2010;Oliveira-Junior et al., 2015;Miguel et al., 2017b). Changes in the canopy cover (Remsburg et al. 2008), riparian vegetation , water quality (Van Praet et al., 2012), and land use (Seidu et al., 2017;Calvão et al., 2018) may all lead to a reduction in environmental integrity, which will modify the structure of the local odonate community (Samways & Sharratt, 2010;Dolný et al., 2012;Oliveira-Junior et al., 2017;Bastos et al., 2021). The sensitivity of the odonates to impacts provides valuable ecological thresholds for the detection of the effects of changes in the environment on these assemblages, which tend to become dominated progressively by generalist and more tolerant species, while the number of specialists tends to decline Miguel et al., 2017b;Oliveira-Junior and Juen, 2019a). ...
... Identifying specimens to the species level provides baseline information on the natural configuration of a community, and detailed insights into its responses to habitat (Godoy et al., 2019). However, while the taxonomy of the odonates is well resolved for the adult phase (Garrison et al., 2010;Samways & Sharratt, 2010), identification to the species level requires considerable time and experience, and is demanding of financial and human resources (Vianna & De Marco, 2012). There are also major knowledge gaps in the natural history and distribution of most odonate species in the Amazon (Kalkman et al., 2008;Miguel et al., 2017a). ...
Article
Full-text available
The insects of the order Odonata have been widely used as bioindicators of environmental quality in different types of ecological research. In general, the taxonomic level used is the species, but higher taxa, such as the family, have received less attention. Assuming that higher taxa can reproduce the impacts that occur at the species level, we use facets of diversity at the community to assess if Odonata families could be an efficient tool for the assessment of environmental impact in Amazon streams. We first assessed to what extent each family retains ecological information from the ecological diversity of the species of the suborder (Anisoptera or Zygoptera). We then quantified the degree of congruence between different taxonomic levels in the Odonata. Next, we evaluated the effects of environmental integrity on the facets of diversity of the families. Finally, we evaluated whether ecological thresholds can be detected using a family-level approach. We sampled adult odonates in 98 streams in the eastern Amazon, in the municipalities of Paragominas, Santarém, and Belterra, in the Brazilian state of Pará. The habitat integrity index (HII) was used to assess the environmental integrity of each stream. The congruence between the different taxonomic levels was evaluated using a Procrustes analysis. The degree of correlation of diversity facets was evaluated between families and each suborder. Linear mixed models and matrix regressions were used to measure the influence of environmental integrity on the diversity facets of the families. Higher-level ecological thresholds were detected using the TITAN analysis. The results of the analyses indicated a high degree of congruence between species-level and higher levels (family and suborder). The ability of the families to represent the diversity facets of the suborder is influenced by the abundance of individuals and the number of species in the family. The environmental integrity of the streams affects the facets of diversity of the families systematically, although cumulative measurements, such as abundance, appeared to be more advantageous as biomonitoring tools. The similarity of the responses observed at species and family levels supports the use of odonate families for the detection of ecological thresholds in stream environments. The sum of the evidence indicates that a family-level approach is effective for the identification of alterations in the environmental integrity of streams, providing valuable insights into the facets of diversity of the odonate community. The adoption of a family-level approach in environmental monitoring programs could optimize the investment of resources, in particular through the identification of specimens by non-specialists, permitting a significant increase in sampling effort and replication.
... Larvae would ideally be sampled for questions related to in-water characteristics, such as nutrient concentrations, because they are more sensitive to conditions in their surrounding habitat than the aerial adults (Raebel et al., 2012). Adult dragonflies would be the obvious life stage choice for research on riparian vegetation for example (Samways and Sharratt, 2010). However, this is not to say that the life stages are not interchangeable for these different scenarios. ...
... For river edges and beds combined, two observers visually estimated percentages of rocks and sand. For vegetation data, average vegetation height, percentage cover of alien vegetation and of indigenous vegetation, as well as the percentage cover of Prionium serratum (palmiet reed) and aquatic macrophytes were recorded as separate variables, as they have a strong influence on dragonflies in the area (Samways and Sharratt, 2010). We assigned values to the categories of land use into binary classifications. ...
... Lower reaches characteristically have warmer water temperatures from lower elevations, wider, and less turbulent sections (Dallas and Day, 2007). These sections are often largely transformed, and agricultural development is likely to increase water temperature, due to reduced riparian shade and lower elevation, important drivers of dragonfly assemblages (Samways and Sharratt, 2010;Piggott et al., 2012), and here at all three spatial scales. ...
Article
Full-text available
Dragonflies are globally renowned bioindicators, with larvae, exuviae and/or adult life stages used in freshwater quality assessments. However, little is known about the extent to which conspecific adults and larvae occur within close proximity of each other, or how they comparably respond to biotic and abiotic factors. Firstly, we test the extent to which adult male dragonflies are congruent with their larvae at three independent sample unit scales (small 10 m × 3 m, medium 90 m × 3 m, and large 450 m × 3 m) along four rivers, along with a subset of 40 randomly selected small scale sites (small 40) to test for a possible effect of sampling design on the outcomes of the spatial scale analyses. Secondly, we test the extent to which adult males and larvae share similar responses to environmental variables. At medium and large spatial scales, larvae and adults were strongly congruent for abundance, species richness, and Dragonfly Biotic Index (DBI) scores. Despite this, at the small spatial scale, only 15% of observations matched (contained adults and conspecific larvae). This increased to 46% at the medium scale, and 60% at the large scale, neither of which were significantly different from the number of mismatches. Dragonfly species composition differed between larval and adult assemblages at the small, small 40, and medium scales but did not differ at the large scale. Water temperature was the only variable that generally elicited similar responses in both life stages, at all spatial scales. Exuviae here were so under-represented that they provided no extra information. Assessments, where medium or large spatial scales are suitable for sampling, such as measuring the state of a river, can utilize either life stage. However, for comprehensive biodiversity surveys, both larvae and adults should be sampled.
... We compare species richness and functional diversity at non-invaded ("natural"), cleared and invaded sites. Given that natural areas can harbour different assemblages with greater species richness relative to invaded areas (Samways and Sharratt, 2010), we hypothesised that cleared and natural areas would harbour greater FD than invaded sites. We asked: ...
... Canopy shading has been shown to impact Odonate distribution and richness (Samways and Sharratt, 2010). Riparian canopy closure, which is the proportion of the sky obscured by vegetation when viewed from a single point (Jennings et al., 1999), was recorded along each 50 m transect at 10 m intervals, and averaged to determine canopy cover for each site. ...
... This may explain their absence from invaded sites, as the invasive vegetation may influence temperature regimes, keeping sites cooler than they would ordinarily be, by shading sites in the winter months. Samways and Sharratt (2010) showed that alien woody species negatively impacted terrestrial Odonate diversity. Many southern African Odonates flourish in heterogeneous habitats (Stewart and Samways, 1998;Steytler and Samways, 1995) that provide good sunlight, and a combination of understory and taller structure, as opposed to dense, overshaded alien stands (Ormerod et al., 1990;Samways and Sharratt, 2010). ...
... Of the taxa used, the Odonata (dragonflies and damselflies) comprise some of the most common and sensitive species associated with rivers (Catling, 2005). The group also contains numerous regional endemics, with the GCFR considered a centre of endemism for South African Odonata (Samways and Sharratt, 2010;Samways et al., 2011). This ancient order of wellstudied insects can be strongly affected by water quality (Clausnitzer, 2003;Catling, 2005;Stewart and Samways, 2008;Kietzka et al., 2017). ...
... For vegetation data, the percentage cover and average height of both alien and indigenous vegetation were estimated (trees, shrubs, grass, and aquatic macrophytes), and used to determine average indigenous and exotic cover per entire site (10 × 3 m). The percentage of Prionium serratum (Palmiet Reed) was recorded as a separate variable, as it often dominates natural areas and positively influences Odonata diversity (Samways and Sharratt, 2010). ...
Article
Biological surrogates in conservation biology are valuable for rapid biodiversity and environmental surveys, and as an early warning of potential threats. However, these surrogates need to be simple and inexpensive to apply. The umbrella index was applied here to quantify the selection of surrogate species for biodiversity assessments, but requires interrogation for application in areas rich in threatened endemic species. Aquatic larvae of Ephemeroptera, Plecoptera and Trichoptera (EPT), as well as the adult Odonata, are all highly responsive to changes in freshwater condition. Using the umbrella index, we evaluated the performance of the surrogate species approach for aquatic insect conservation in a region (Greater Cape Floristic Region) with an exceptional level of rare and endemic species, across multiple rivers with different disturbance levels. Due to a lack of species level information, EPT taxa were calculated using morphospecies within families, and Odonata were identified to species level. The umbrella index identified eight EPT species and seven Odonata species as potential sur-rogates. Both these groups co-occurred with high percentages of their own overall groups (EPT surrogates for overall EPT, and Odonata surrogates for overall Odonata), as well as for the other group (EPT surrogates for overall Odonata, and Odonata surrogates for overall EPT). The index was surprisingly flexible, and performed well in an area with so many species of conservation concern, as well as across spatial scales greater than a single river, with varying degrees of disturbance. Both EPT and Odonata showed promise as potential biodiversity surrogates, and for future conservation planning. Ideally, conservationists should aim to use taxa that are easy to identify to species level, with known sensitivities to human disturbance. However, when this is not a possibility, the umbrella index is still applicable and accurate for morphospecies (family level sensitivities).
... findings are in accordance with the results of other restoration studies (e.g.,D'Amico et al., 2004;Samways and Sharratt, 2010;Modiba et al., 2017). Restored habitats are usually occupied within a short time period by several species across different taxonomic groups(Mazerolle et al., 2006;Elo et al., 2015;Noreika et al., 2015). ...
... However, the species A.Krieger, et al. Biological Conservation 237 (2019) 291-298 composition of the restored habitats often differs from that of the control(van Duinen et al., 2003;Mazerolle et al., 2006;Samways and Sharratt, 2010;Taillefer and Wheeler, 2012;Remm and Sushko, 2018). ...
Article
Even though bogs function as the most important terrestrial carbon store on Earth and play a crucial role in the conservation of highly endangered species, the area covered by peatlands is declining globally. Consequently, numerous restoration efforts within degraded bogs have been realized. In many cases, however, it is unknown whether the conservation measures have been successful. We used Odonata (hereafter referred to as dragonflies) as ecological indicators to evaluate the restoration success of rewetting measures in central European degraded raised bogs. Depending on their land-use history (rewetted industrial peat cuts with and without former agricultural use), two types of bog restoration were compared with rural peat cuts (control). Our study demonstrated that restored bogs are important habitats for dragonfly conservation. Both types of restored bogs were as diverse in overall species richness as the control plots. However, land-use history had a strong effect on restoration success. All raised-bog species of the study area were able to recolonize at least some of the nutrient-poor restored bogs. The situation was different for the nutrient-rich restored bogs. Due to the high nutrient content-caused by the former agricultural use-the characteristic dragonfly fauna of raised bogs will be unlikely to be able to recolonize in these locations in the long term. Nevertheless, the nutrient-rich restored bogs represent an important secondary habitat, especially for transition-bog species. In conclusion, the conducted restoration measures created a network of small oligo-to mesotrophic water bodies, which fosters aquatic macroinvertebrate diversity in bogs.
... Headwater streams in Afromontane regions are renowned for harbouring unique forms of aquatic fauna, particularly macroinvertebrates and fishes (Chakona et al., 2018;de Moor and Day, 2013;Samways and Sharratt, 2010). There is increased interest in providing ecological information on aquatic communities in these ecoregions to inform conservation planning (Chakona et al., 2020;Simaika and Samways, 2009;Stewart and Samways, 1998). ...
... Overall, however, our results appeared to be inconsistent with findings on the impacts of non-native riparian vegetation on instream aquatic macroinvertebrates. For example, although loss of sensitive macroinvertebrates in invaded riparian zones have been reported (Samways and Sharratt, 2010), other studies have shown that some macroinvertebrates are either unaffected or may be favoured by the presence of non-native vegetation (Samways et al., 2011). Similarly, Chakona and Marshall (2008) reported functional similarities between macroinvertebrate communities occurring in headwater streams with natural deciduous forests and those with non-native pine plantations. ...
Article
Headwater streams in Afromontane ecoregions harbour locally adapted aquatic communities. However, across many regions in Africa, these ecosystems and their unique aquatic biodiversity have been severely impacted by unsustainable land use practices. We tested the hypothesis that land use disturbances were the primary drivers of community dynamics by comparing spatial and temporal dynamics together with trait-environment relationships of macroinvertebrate communities in three headwater streams influenced by different land use practices. The three headwater streams were distinguished based on high conductivity, total dissolved solids and alkaline pH in the agriculture-disturbed stream, and low temperature in a stream whose riparian zone was invaded by non-native vegetation compared to a near-natural stream. Macroinvertebrate taxonomic diversity was, nevertheless, comparable among these three streams. Constrained canonical ordination revealed that seasonality was a major driver of macroinvertebrate dynamics that was reflected mostly by the abundances of six macroinvertebrate taxa (Baetis, Dicentroptelum, Afronurus, Tricorythus, Simulium and Cheumatopsyche), whereas land use contributed a small but significant difference. Trait-environment relationships reflected seasonal changes that included the importance of benthic substratum in winter, the occurrence of collector-gatherer invertebrates in spring and aerial breathing traits in summer. Land use-related traits were, nevertheless, reflected by gill respiration and grazer feeding traits represented by Afronurus in the near-natural stream, predator traits represented by Aeshna and Lestes in the invaded stream, and aerial respiration represented by Enithares, Orectogyrus and Rhagovelia in the agriculture-disturbed stream. Our results suggest that environmental variability associated with seasonality probably played a deterministic role within which land use disturbances operated. Overall, our study suggest that importance of using multiple metrics to unpack the patterns associated with land use disturbances in headwater streams.
... Although herbicides are widely used, chemical control is considered ineffective in the case of IAAP species. Herbicide application also has additional, indirect effects associated with the destruction of non-target organisms, changes in aquatic invertebrate and fish composition, changes to aquatic microalgae (phytoplankton and periphyton) behaviour, and alterations in the chemical and biochemical processes taking place in the water column and sediments (Ashton et al., 1981;Murphy and Barrett 1990 to the system (Samways and Sharratt, 2010;Bellingan et al., 2019). ...
... The dual approach to restoration has allowed the return of and reestablishment of native vegetation communities, followed by associated invertebrates and vertebrates recruitment, leading to the return of ecosystem structure and function. South Africa employs mainly passive restoration strategies for invasive alien riparian and aquatic weeds management and it has been successful in doubling aquatic macroinvertebrate taxa and functional biodiversity returns in natural environments (Pryke and Samways, 2009;Magoba and Samways, 2010;Samways and Sharratt, 2010). However, recent field observations and mesocosm experiments show evidence of regime-shift (free-floating IAAP species replaced by submerged IAAP species), following successful biological control of the primary invader (Strange et al., 2018). ...
Thesis
Full-text available
Invasive alien aquatic plants (IAAP) species are known to have deleterious effects on the freshwater ecosystems they invade. This includes both socio-economic and ecologically important ecosystem goods and services. Thus, IAAP species can be declared a serious threat, second only to habitat modification for causing a loss of aquatic biodiversity. Three control methods have been widely applied to control IAAP species invasion globally; mechanical, chemical and biological control. Both mechanical and chemical control methods are considered short-term and expensive, whereas biological control methods are regarded an effective and long-term solution for the control of IAAP species, mostly at the landscape level. But, little is known of the ecological recovery following the biological control of IAAP species, with mechanical control known to have had mixed success and chemical control to have nontargeted effects on aquatic ecosystems, causing harm to wildlife and human well-being. Biological control practitioners measure the success of biological control based on: (1) the biological control agents establishment and the negative impacts they impose on the targeted weed; and (2) non-native macrophyte species biomass reduction and an increase in native macrophytes species. Arguably, measure of biological control success has been subjective and variable across the globe. Although some field studies have demonstrate biological control success to have positive socio-economic returns, there is little literature on ecological benefits. Furthermore, there is limited understanding on ecosystem recovery and restoration efforts following the biological control IAAP species, as compared to alien weeds in terrestrial and riparian ecosystems. Thus, this thesis aimed to quantify the ecological recovery e.g. aquatic biodiversity, ecosystem processes and trophic interactions following the management of Salvinia molesta in freshwater ecosystems. The research employed a suite of Before-After Control-Impact mesocosm experiments and field studies to investigate the response of aquatic microalgae, macroinvertebrates and their interactions (food web structure and function) during S. molesta infestation and after mechanical and biological control. The mesocosm experiment (Before invasion, During invasion & After successful biological control) showed that both aquatic microalgae and macroinvertebrate diversity indices were reliable biological indicators to detect S. molesta ecological impacts and recovery following control. The restored treatment (100% S. molesta + biological control agents), demonstrated complete aquatic microalgae and macroinvertebrates recovery following biological control, similar to the reference treatment (open water), where the degraded/impacted treatment (100% S. molesta with no biological control agents) showed a drastic decline in aquatic biodiversity and a complete shift in aquatic biota assemblage structure. Thus, the biological control effort by Cyrtobagous salviniae, the biological control agent for S. molesta assisted in the recovery of aquatic biota following successful biological control. The field study (four field sites, two sites controlled mechanically and two biologically) investigated water quality, aquatic biodiversity and community trophic interactions (aquatic food web) ‘Before and After’ S. molesta control. The study showed a drastic decline in aquatic biodiversity (with three sites showing no record of aquatic macroinvertebrates, thus no biotic interactions during infestation) and poor water quality due to the shade-effect (abiotic filter) by free-floating S. molesta during the Before S. molesta control phase. However following both mechanical and biological control (After S. molesta control phase), there was a significant shift in abiotic and biotic ecosystem characteristics as compared to the Before S. molesta control phase. Thus, rapid ecosystem recovery was apparent as a result of aquatic microalgae and macroinvertebrates recolonisation. Sites showing a normal functioning ecosystem had improved water quality, increased biodiversity, productivity and trophic interactions, indicative of the return of biologically and functionally important species which were lost during the Before S. molesta phase. However, the Westlake River following the mechanical control of S. molesta demonstrated a series of multiple macrophyte dominated states, moving from a S. molesta infestation to a clear-water state (After S. molesta control), then to a cosmopolitan submerged Ceratophyllum demersum-dominated state, which was later replaced by a floating leaved emergent IAAP Nymphaea mexicana-dominated state. Each state was responsible for a significant shift in both biotic and abiotic characteristics, affirming macrophyte abilities to influence aquatic environments structure and functions. Furthermore, this event showed a clear example of a secondary invasion. Thus, a holistic IAAP species management strategy is warranted to restore previously invaded ecosystems and prevent secondary invasion and ecosystem degradation In conclusion, the S. molesta shade-effect (abiotic barrier) like any other free-floating IAAP species, was identified as the main degrading factor and responsible for water quality reduction, loss of aquatic diversity and shift in aquatic biota assemblage structure. Following S. molesta removal (or shade-effect elimination), there was a positive response to aquatic ecosystem species abundance, richness, diversity and community structure. Therefore, in combination, aquatic biota recolonisation rate and increases in biological and functional diversity were instrumental in the recovery of ecosystem structure and functions, following the control of S. molesta. Echoing existing literature, this thesis recommends: (1) IAAP species management to be integrated on broader freshwater conservation and environmental management strategies to aid in ecological restoration, instead of stopping after control; (2) biological control should be used where appropriate to combat free-floating IAAP species in freshwater ecosystems, followed by active introduction of native macrophyte propagules since they are limited by anthropogenic activities; and (3) more freshwater case studies are needed to add to our understanding of IAAP species management and restoration effort incorporating long-term monitoring.
... A loss of vegetation cover also brings about a number of consequences for a variety of organisms, given that temperature is one of the most crucial environmental conditions shaping organismal fitness (Angilletta, 2009). Insects are often affected (May, 1976;Remsburg et al., 2008;Samways and Sharratt, 2010) due to their limited ability to shift their body temperature above or below the ambient temperature (Alemu et al., 2017;González-Tokman et al., 2020;Schowalter, 2012). For example, differences in dung beetle diversity among patches differing in canopy cover have been associated mainly with an increment in ground level temperature (Giménez Gómez et al., 2018;Halffter and Arellano, 2002;Nichols et al., 2013) and with low tolerance of forest dung beetles to high temperatures in open habitats (Davis et al., 2002;Giménez Gómez et al., 2020;Nichols et al., 2007;Sowig, 1995). ...
... This could indicate that odonates have a reduced ability to maintain their temperature below ambient temperature. Thus, higher temperatures in sites with loss of vegetation cover could have negative consequences for odonates, especially those that have been described to have lower tolerance, like the zygopterans (da Silva Monteiro Remsburg et al., 2008;Samways and Sharratt, 2010). Moreover, it has been demonstrated that ectothermic insects can also acclimatize to temperature, such that previous exposure to high temperature can increase their CT max (Coutts et al., 2016;Diamond et al., 2017;Hoffmann et al., 2013;Rohr et al., 2018). ...
Article
Disturbance (e.g. loss of plant cover) increases ambient temperature which can be lethal for ectotherm insects especially in hot places. We compared the thorax temperatures of 26 odonate species as a function of body size, habitat quality (“conserved” and cooler vs “perturbed” and warmer) and suborder (Anisoptera vs Zygoptera), as well as critical thermal maximum (CTmax) and as a function of habitat quality in Argia pulla (Zygoptera) and Orthemis ferruginea (Anisoptera). We expected thorax temperatures to differ between suborders based on their differences in body size and habitat quality status, and that populations in perturbed sites would have higher critical thermal maxima compared to those in conserved sites. This study was done in a tropical region with high ambient temperatures. Anisopterans had a higher body temperature than zygopterans, with no difference between habitats. Thoracic and air temperature were positively related, yet body temperatures were higher than the ambient temperature. A. pulla had higher CTmax in the perturbed sites, while O. ferruginea showed the opposite trend. Microenvironmental changes increase the ambient temperature, perhaps filtering insect species. The apparent resilience of odonates to disturbance should be examined more closely (using more species), especially in small species like the zygopterans which appear to be more strongly affected by ambient temperature.
... On a global scale, dragonflies have demonstrated species-specific responses to the presence of canopy cover over aquatic habitats. In tropical regions, the adults of some dragonfly species are very shadetolerant (e.g. in Mayotte; Samways, 2003), whereas others thrive when [invasive] tree species are removed (e.g. in South Africa; Smith et al., 2007;Samways & Sharratt, 2010) or in urbanized habitats with little canopy cover (e.g. in Brazil; Monteiro-Júnior et al., 2014). Similarly, larval and adult dragonflies in Borneo have demonstrated species-specific distributions in response to gradients of forest, oil palm, and riparian cover (Dolný et al., 2012;Luke et al., 2017). ...
Article
Full-text available
The mechanisms structuring aquatic communities across environmental gradients are often difficult to distinguish from one another and can produce similar patterns of species distributions. In freshwater systems, the amount of canopy cover from surrounding trees is often associated with transitions in local community structure. These community changes could be driven by habitat selection prior to colonization of the aquatic habitat and/or species-sorting post-colonization. To assess the contributions of pre- versus post-colonization processes in structuring larval dragonfly assemblages, we tested the impact of artificial and natural canopy cover on the selection of experimental aquatic mesocosms by adult dragonflies, and monitored the performance (i.e. growth and survival) of larval dragonflies that were placed in mesocosms under a gradient of natural canopy cover. We found that greater levels of canopy cover resulted in fewer adult visits to mesocosms, and more natural canopy cover decreased the species richness of visitors. There were no effects of canopy cover on the growth and survival of larvae added to the mesocosms. Our results suggest that adult habitat selection plays a dominant role in structuring larval dragonfly assemblages across a canopy cover gradient, and that canopy cover can be an important environmental filter on species distributions.
... In contrast, adult odonates are conspicuous animals which are easily found (Kalkman, 2008). In addition, their identification is much less complicated, and the specimens may be identified visually in the field, often using close-focus binoculars (e.g., Kietzka et al., 2015;Samways and Sharratt, 2010), thus avoiding community disturbance and killing of specimens. Problematic specimens may be captured for closer examination and released in the field immediately after their identification, or, alternatively, may be photographed for later identification (e.g., Clausnitzer, 2003;Dolný et al., 2011;Kalkman et al., 2008). ...
Article
Odonata have proven to be good indicators of freshwater as well as terrestrial habitat conditions. Several studies have shown changes in odonate species richness and/or community composition in response to deforestation, suggesting their potential as bioassessment tools in the tropics. However, former approaches using Odonata as an indicator group required comparative samples from differently disturbed sites and/or knowledge of the focal species environmental specificity. Here, we tested a robust, adult-based bioassessment method assuming that the level of tropical forest degradation reflects the proportional representation of the taxa above species. Based on Web of Science, ScienceDirect, and Scopus databases, we used data from previously published studies linking odonate assemblages to human-mediated disturbances in tropical forests. We hypothesized that along a disturbance gradient (from primary forest to non-forest), (i)the proportion of the suborder Zygoptera (mostly habitat specialists sensitive to deforestation)will decrease in favor of the suborder Anisoptera (high proportion of generalists); and (ii)the proportions of largely generalist families Coenagrionidae and Libellulidae will increase at the expense of other Zygoptera and Anisoptera, respectively. Our results revealed that a ratio of Zygoptera/Anisoptera is a poor indicator of tropical forest conditions, probably because of ecological diversity within these groups. However, the proportions of Coenagrionidae/other Zygoptera and Libellulidae/other Anisoptera significantly increased along a disturbance gradient, suggesting their potential to be a good indicator of well-preserved, altered, and heavily degraded forest habitats. Therefore, our results are in line with studies presenting the usefulness of adult Odonata as versatile indicators for assessing human-mediated changes in tropical forest environments, supporting the practical use of this group in biological monitoring.
... Although the expectation is that vegetation would contribute towards aquatic biodiversity, there must not be too much cover, which otherwise results in shading of the water and causes dragonfly (Samways & Sharratt, 2010) and macroinvertebrate impoverishment (Samways, Sharratt, & Simaika, 2011), especially of rare and endemic species. Differences are also expected between the two insect taxa in response to environmental conditions which may change with catchment, land use and season (Tscharntke, Klein, Kruess, Steffan-Dewenter, & Thies, 2005). ...
Article
1. Farmland ponds promote regional aquatic biodiversity; however, optimally managing these ponds requires knowledge on how the biodiversity differs between ponds across catchments with different land uses. 2. This study investigated the response of macrophytes, both those in the pond and on the bank, as well as dragonfly and water beetle species richness, diversity and composition in artificial ponds, to numerous environmental variables in catchments dominated by three land uses: protected areas (as reference sites), sugarcane-dominated and forestry-dominated landscapes, across two seasons. 3. There was a strong association between insect species richness and vegetation cover, particularly sedges (Cyperus spp.) in spring and bulrushes (Typha capensis) in summer. There was also a positive response between insect species richness and sedges up to 70% cover, and bulrushes up to 40% cover, after which there was a decrease. Furthermore, the protected area ponds contained more rare and specialist insect species. Pond size was not a major variable for biodiversity overall. 4. Although there was generally little congruence in composition among the three taxa, dragonflies were a good surrogate for water beetles and floating macrophytes. 5. Well-vegetated ponds, both in the water and along the margin, are the most suited to promoting biodiversity, as long as the vegetation is not too dense, and not dominated by one plant species. 6. Artificial ponds in production landscapes have great potential for conserving aquatic species, irrespective of land use, as long as there is management for macrophyte density and heterogeneity.
... Dragonflies are excellent indicators of habitat quality as they are highly sensitive to local environmental changes, are well known taxonomically, are highly visible and widely distributed, and have life cycles with aquatic larval and terrestrial adult stages. Adults are highly mobile and respond strongly to vegetation composition (Kietzka, Pryke, & Samways, 2016;Samways & Niba, 2010), allowing them to select suitable habitats (Samways & Sharratt, 2010). As a result, diminishing or improving habitat conditions can be ascertained from the complement of dragonfly assemblages occupying various freshwater habitats. ...
Article
Hydrological extremes have negative impacts on natural, agricultural, and urban landscapes and place substantial ecological pressure on freshwater habitats. However, the role of artificial freshwater habitats during hydrological drought is poorly understood. Insects make up much of total aquatic fauna and lend themselves to understanding how drought impacts freshwater ecosystems. Using the Greater Cape Floristic Region as an example of a drought‐prone area, we determined the effects of a severe drought on a subset of insects occupying lentic habitats in terms of their species richness, diversity, and assemblage composition. Here, we: (1) calculated the percentage change in average precipitation between a record dry season and the last consistently wet decade; (2) identified the environmental variables driving aquatic insect species richness, diversity and composition; (3) identified the environmental differences between natural ponds and artificial reservoirs; (4) determined whether artificial reservoirs act as suitable habitats for focal taxa during drought; and (5) compared these results to other, pre‐drought studies. Environmental variables related to water chemistry and physical characteristics were drivers of species richness, diversity, and composition, yet vegetation cover remained a major driver. In terms of marginal vegetation cover, most artificial reservoirs did not resemble natural ponds, yet overall 38.4% of sampled aquatic insect species were shared between natural ponds and artificial reservoirs. We found some rare endemic species in artificial reservoirs that had never before been recorded in this habitat during wet years. When our drought findings were compared to earlier, wet years, species richness did not change significantly, although abundance was much lower during the drought year. We postulate that historically, these aquatic insects, which have been through many ecological filters such as drought, must have sought low‐quality habitats to survive water stress periods. Artificial reservoirs, being novel landscape features, cannot fully replace natural ponds, but enable some aquatic insects to survive drought. Artificial reservoirs can be attractive habitats to aquatic insects when they resemble natural ponds, with specific reference to their marginal vegetation characteristics.
... The results of the present study reinforce this role, indicating a strong link between odonates and environmental integrity, and their capacity to indicate changes in this integrity over time (Butler & de Maynadier, 2007;Carle, 1979;Carvalho et al., 2013;Castella, 1987;Monteiro Junior et al., 2013;Samways & Sharratt, 2010;Samways & Steytler, 1996), as well as the existence of indicator species of preserved and impacted environments (Chovanec, 2000;Chovanec & Waringer, 2001;Clark & Samways, 1996;D'Amico, Darblade, Avignon, Blanc-Manel, & Ormerod, 2004;Samways & Steytler, 1996), fluctuating asymmetry under different levels of environmental pollution (Hardersen, 2000;Hardersen & Frampton, 1999;Palmer & Strobeck, 1986;Pinto et al., 2012), and bio-accumulation in polluted environments (Corbi, Trivinho-Strixino, & Santos, 2008). ...
Article
The insects of the order Odonata have an aquatic larval stage and land-dwelling adults. These insects play an important role in aquatic ecosystems and are excellent bioindicators. The present study was based on a scientometric analysis of the research available on the Odonata, which aimed to identify the principal trends and gaps in the database on these organisms, compiled online from databases of the Institute for Scientific Information – ISI, Scielo and journals Odonatologica and International Journal of Odonatology. A total of 2317 papers were analyzed, permitting the detection of the following tendencies: a gradual increase in the number of papers occurred over time, most of the papers had an ecological perspective, most focused primarily on the adult stage and species level, and 49 studies focused on bio-indication by examining variation in the composition of the community, fluctuating asymmetry, bioaccumulation, species richness and abundance, and odonate habitat index (OHI). The increase in the ecological studies of odonates may reflect the dynamic characteristics of this order, and its relatively well-defined systematics, principally in the case of the adults. Despite the increase in the number of publications, there are still many gaps, such as biogeography, parasitism, competition within and among species, evolutionary and phylogenetic relationships, as well as studies of the larval stages of these organisms. Given the sensitivity of the members of this order to environmental variables, they may be used for the evaluation of aquatic systems, given their roles as detectors, exploiters or accumulators, depending on the type of response to environmental modifications.
... Goertzen and Suhling (2013) suggest that conservation urban planning in urban centers must focus on a general improvement of habitat structure; for example, they proposed that moderate anthropogenic disturbance can increase habitat diversity and promote species of temporary and pioneer ponds especially at ruderal sites. Increasing biological value of urban wetlands through reduction of impact level, for example restoration of degraded shorelines and banks, removal of invasive alien trees, and recovering of riparian natural vegetation, can significatively increase specific richness, specially insects (Samways and Taylor 2004;Suren and McMurtrie 2005;Samways and Sharratt 2010;Goertzen and Suhling 2013). Also, Goertzen and Suhling (2013) have suggested at the city scale that different pond types regarding water level and succession stage would be beneficial for increasing biodiversity levels. ...
Chapter
The increasing growth of urban areas on natural ecosystems has seriously affected wetlands. Aquatic insects, as key components of urban wetlands, are critically impacted by human environmental changes and practices. The main threats are those derived from the lost, replacement, or fragmentation of natural habitats, ecosystem homogenization, and modification of hydrological, sedimentological, and thermal wetland characteristics due to the surrounding urban matrix. Therefore, understanding the mechanisms by which urbanization processes affect biodiversity, and in particular how the biota responds to alteration of their habitats, is crucial for integrating the environment in proper urban planning. In this chapter we analyze the relationships between aquatic insects and environmental factors, including human influences and threats in urban wetlands. For this purpose, we compiled studies from around the world, especially from the neotropical region, addressing biological patterns and associated environmental processes in urban areas and endeavors. We discerned the main environmental threats and clues for the maintenance of the increase of the insect biodiversity, including the creation of new, man-made, wetlands. In addition, we focus on the importance of insect knowledge as indicators of environmental health in urban wetlands and the promotion of the citizen science to improve their conservation.
... Goertzen and Suhling (2013) suggest that conservation urban planning in urban centers must focus on a general improvement of habitat structure; for example, they proposed that moderate anthropogenic disturbance can increase habitat diversity and promote species of temporary and pioneer ponds especially at ruderal sites. Increasing biological value of urban wetlands through reduction of impact level, for example restoration of degraded shorelines and banks, removal of invasive alien trees, and recovering of riparian natural vegetation, can significatively increase specific richness, specially insects (Samways and Taylor 2004;Suren and McMurtrie 2005;Samways and Sharratt 2010;Goertzen and Suhling 2013). Also, Goertzen and Suhling (2013) have suggested at the city scale that different pond types regarding water level and succession stage would be beneficial for increasing biodiversity levels. ...
Chapter
The increasing growth of urban areas on natural ecosystems has seriously affected wetlands. Aquatic insects, as key components of urban wetlands, are critically impacted by human environmental changes and practices. The main threats are those derived from the lost, replacement, or fragmentation of natural habitats, ecosystem homogenization, and modification of hydrological, sedimentological, and thermal wetland characteristics due to the surrounding urban matrix. Therefore, understanding the mechanisms by which urbanization processes affect biodiversity, and in particular how the biota responds to alteration of their habitats, is crucial for integrating the environment in proper urban planning. In this chapter we analyze the relationships between aquatic insects and environmental factors, including human influences and threats in urban wetlands. For this purpose, we compiled studies from around the world, especially from the neotropical region, addressing biological patterns and associated environmental processes in urban areas and endeavors. We discerned the main environmental threats and clues for the maintenance of the increase of the insect biodiversity, including the creation of new, man-made, wetlands. In addition, we focus on the importance of insect knowledge as indicators of environmental health in urban wetlands and the promotion of the citizen science to improve their conservation.
... The results of this study support previous findings that canopy cover, or shade, is the primary driver of dragonfly assemblages (Clark & Samways, 1996;Clausnitzer, 2003;Samways & Sharratt, 2010;Smith et al., 2007;Thornhill et al., 2017). Canopy cover was present in all competing models and was associated with decreased dragonfly species richness and abundance for stream and ecotone habitats. ...
Article
Dragonflies (Odonata: Anisoptera) are often used as indicators of habitat type and quality due to their varied use of aquatic and terrestrial habitats. Species differ in their preferences for lotic and lentic waters, but community changes across ecotones, or transitional zones between distinct habitats (e.g. lotic and lentic), are not well understood. We quantified dragonfly species richness, abundance, and composition along a gradient of habitat types, including streams, stream mouths (ecotones), and open waters (lakes and ponds). We tested if dragonfly assemblages in aquatic ecotones differ from adjacent stream and open water habitats, and how species respond to riparian forest cover across these habitat types. Adult dragonflies were sampled in all habitat types at four sites in southwest Ohio during the summer of 2016. Riparian canopy cover and relative densities of algal mats and emergent vegetation were recorded. We sampled 157 individuals of 12 dragonfly species and found significant differences in community composition between stream and ecotone habitats, both forming subsets of the open water community. Canopy cover explained 55% and 75% of abundance and species richness variance across habitat types, respectively, but these relationships were strongest at ecotones. Finally, the Odonata Index of Wetland Integrity (OIWI), which uses sensitivities of adult odonates to habitat disturbances to evaluate wetland conditions, showed that species composition at ecotones uniquely represents the ecological integrity of the entire wetland system. Thus, transition zones may provide an effective and more efficient alternative to rapidly assess wetland quality for conservation monitoring than sampling the entire wetland.
... Invasive alien trees are a major but reversible threat to odonate species in this area (Samways and Sharratt 2010), with these trees shading out the naturally open and sunny habitats. Significantly, S. angusta was only rediscovered where invasive alien trees had been removed (Samways et al. 2005). ...
Article
Full-text available
The damselfly Spesbona angusta is one of the world’s rarest insects, is Red Listed as Endangered, and occurs today at only one known locality in the Cape Floristic Region (CFR), South Africa. It has some unusual characteristics, including rapid and reversible colour change in both sexes, and a larva with frilled lamellae that lives in a micro-habitat free of competitors and large anisopteran enemies. We define here the characteristics of its habitat and record some other unusual behavioural traits, including the adult male’s ability to sail on the water surface, very strong site selection for oviposition, and female approach to males, all in the context of its conservation. We used satellite imagery to determine the location of habitats within its locality. We further used infrared imagery to identify warmer and cooler habitats within the area. Details of its occurence were mapped, based on observational data acquired throughout the flight season. From this, we were able to establish that its population moves around its locality, and we also establish its environmental requirements for conservation. We also indicate its umbrella value for representing two other threatened odonate species, Endangered Proischnura polychromatica and Vulnerable Syncordulia legator, as well as some other CFR endemic odonates. Conservation of this species requires continual monitoring and removal of invasive alien trees as a priority. Translocation should also be considered as various risks to this one locality are high. A potential site is identified.
... In line with this reasoning, several studies considered Odonata as indicators of success of different kind of restoration interventions (e.g. removal of invasive vegetation, reconstruction of shallow water areas and reconnection of side channels) both in lentic and lotic habitats (D'Amico et al., 2004;Samways and Sharratt, 2010;Chovanec et al., 2015;Termaat et al., 2015). We therefore suggest to also test the ORI in different geographical contexts and to use this index to monitor the success of restoration interventions. ...
Article
River management and planning of restoration actions require a detailed analysis of stream conditions. However, most biotic and hydromorphological indices that have been developed for implementing the European Water Framework Directive (WFD) are characterized by limited spatial and temporal scales of application. In addition, the indices based on the biological quality elements defined by the WFD are sensitive to water quality but not to hydromorphological alterations. To overcome these limitations, alternative hydromorphological and biotic indices have recently been developed. In this study we compared the results obtained with the Morphological Quality Index (MQI) to those of three biotic indices, the Odonate River Index (ORI) and two BQE-based indices, in seven rivers of northern Italy. MQI and ORI resulted highly and significantly correlated, and alterations of river functionality and continuity were the most relevant impacts affecting dragonfly assemblages. Conversely, no significant relationships were found between the MQI and both BQE-based indices and assemblages. The significant correlation between MQI and ORI can be explained by the correspondence of the spatial scale of application (i.e. the whole river corridor). In contrast, the lack of correlation between the BQE-based indices and MQI can probably be attributed to the different spatial scales at which the indices work. The results of this study underline the importance of evaluating the lateral dimension of the river corridor and the need to apply reach-scale indices to achieve a comprehensive evaluation of river corridor conditions and to define appropriate management actions.
... Among other applications, the DBI has proved also to be an excellent indicator of stream habitat recovery, especially of narrow-range endemic dragon y species, when the adverse impact of alien trees has been lifted (Samways & Sharratt, 2010, Samways, Sharratt, & Simaika, 2011Simaika & Samways, 2009a). Indeed, in areas of high endemism, such as Table Mountain in the Cape Floristic Region, the high recovery of 600%, as measured by the Dragon y Recovery Score (simply calculated as the percent ratio of the total DBI after restoration to that before restoration), was demonstrated after the removal of invasive alien vegetation from riparian areas (Simaika & Samways, 2009b). ...
Article
Sustainable use of freshwater is globally important. Yet implementation of changes in water management is poor, especially in developing countries. This is an indication that, despite our dependence on freshwater, we lack awareness of the need to protect these systems. Here we promote dragonflies as an easy-to-learn tool in environmental education programs. Dragonflies have been employed successfully as indicators of ecosystem health in environmental impact assessments and monitoring programs globally. They can be used as environmental sentinels and as whistleblowers for freshwater health, providing an effective tool for environmental impact assessments and freshwater monitoring. We give detailed examples here of some successful projects from South Africa, Tanzania, and Japan. The approaches developed are models that pave the way for more water awareness projects elsewhere, especially in developing countries, where biodiversity and pressures on freshwater systems are high.
... In the case of insects, only dragonfly assemblages have been assessed across the KBR zones, and were found to be complementary, owing to the great variety of aquatic habitats among the zones. There is no indication that human activities are impacting these assemblages Samways 2007, 2011), aside from invasive, alien trees, which when removed, lead to natural dragonfly assemblage recovery (Samways and Sharratt 2010). ...
Article
Globally, biosphere reserves (BRs) conserve biodiversity across a gradient of human disturbance, yet there is very little empirical research investigating the effectiveness of BRs. The aim here is to compare katydid song diversity and abundance across the three zones of the Kogelberg BR using acoustic monitoring techniques. An index of Acoustic Activity was used to determine katydid abundances from recordings. Only eight katydid species were recorded over the entire summer season, with the species accumulation curve reaching an asymptote. Katydid diversity and abundances were very similar across the three zones. Habitat quality had a greater effect on abundance than on species richness. No single katydid species was identified as a bioindicator, rather the entire assemblages are responsive to habitat quality. The low diversity of katydids relative to other biomes and to other insects within the KBR appears to come from a long history of fire and extreme weather events, as is the case for other vegetation dependent insect taxa in the region. While we expect lower biodiversity away from the BR core zone, some groups, like these katydids, are maintained equally well in the three zones, and have not to date been adversely affected by human activity.
... Furthermore, twice as many Zygoptera species were at sugarcane ponds compared to forestry ponds. This highlights the general preference for sunny ponds by damselfly species, as reflected by their recovery when alien invasive trees with dense canopies are removed (Samways & Sharratt, 2010) compared to naturally shady areas of the world like Brazil (De Marco J unior et al., 2015). Here, the abundance of Anisoptera and Zygoptera both increased significantly with an increase in grass/reed cover, especially in the sugarcane ponds, irrespective of size. ...
Article
• Networks of ponds (pondscapes) are becoming increasingly significant for resilient landscape planning in rural areas. Farmland and forestry ponds are habitat islands that support heterogeneous communities of aquatic organisms. • Species richness, Dragonfly Biotic Index (DBI), Shannon's index, and species composition are used here to assess the complementary conservation value of adult dragonfly assemblages associated with forty ponds across a protected area‐sugarcane‐forestry mosaic. • Despite differences in environmental variables among the various ponds, dragonfly species richness, DBI, Shannon index scores, as well as responses to particular environmental variables, did not differ between ponds in sugarcane, plantation forestry, and protected areas. Dragonfly composition differed in response to vegetation cover. • Our results highlight the importance of catchment and regional management for all ponds within the pondscape, and show that ponds in the transformed areas (i.e. sugarcane and forestry areas) are important contributors to regional conservation. As the various ponds were complementary in their dragonfly assemblages, we recommend conservation focus at the level of the pondscape rather than on individual ponds.
... Indeed, many studies have highlighted the importance of forest riparian conditions in structuring odonate assemblages (e.g. Dolný, Harabis, Bárta, Lhota, & Drozd, 2012;Modiba, Joseph, Seymour, Fouché, & Foord, 2017;Samways & Sharratt, 2010;Seidu, Danquah, Nsor, Kwarteng, & Lancaster, 2017) and controlling the emergence rates of aquatic insects (e.g. Banks, Li, & Herlihy, 2007;Progar & Moldenke, 2009). ...
Article
Full-text available
Emergence substrate and sunlight penetration inherently trade off in patchy vegetation. Given the importance of solar radiation at emergence, we expected greater sunlight availability in sparse vegetation to advance emergence timing and reduce the average height of emergence fixation. We used outdoor mesocosms stocked with varying cattail (Typha) densities and late-stage Pachydiplax longipennis (Odonata: Libellulidae) larvae. As predicted, emergence based on exuviae observations began significantly earlier (5 d) at lower cattail density and greater sunlight exposure, with over 60% of the emergence completed midway into the experiment period, compared to about 50% in the medium and higher density cattail. This finding suggests lag effects under relatively limited light availability in a temperate-centered lentic-breeding heliotherm. Contrary to our prediction, we found significantly greater emergence heights at lower cattail density ( 18.0 cm) than at medium ( 13.0 cm) and higher ( 10.0 cm) densities. We recommend further study of emergence heights using larval choice experiments in natural settings. Variation in emergence timing and fixation height under the substrate–sunlight tradeoff may be driven proximally by larval choices/development and ultimately by adult activity.
... Furthermore, vegetation provides habitat for food items for both adult and larval dragonflies. Here, margins of natural ponds were predominantly covered by a mixture of grasses and forbs, with little variation between ponds, and were neither extensive, nor casting much shade which otherwise diminishes local dragonfly assemblages [30]. ...
Article
Full-text available
Natural ponds are rich in biodiversity, contributing greatly to regional aquatic biodiversity. Artificial reservoirs used for irrigation can be significant additional features of the landscape. They infill the local natural pondscape, and are attractors for aquatic insects. Here, we determine the extent to which artificial reservoirs represent the local natural pond biota, and how they contribute to the pondscape in conservation corridors used to mitigate the impact of plantation forestry in a global biodiversity hotspot. We did this by: 1) identifying the environmental factors, including plants, that drive dragonfly, water beetle, and water bug species richness, diversity and composition, and 2) determining the value of natural ponds vs. artificial reservoirs for maintaining the population size and expanding the area of occupancy for dragonflies, beetles and bugs in conservation corridors. While vegetation cover was central for maintaining species richness and composition of the assemblages in general, many other environmental variables are necessary to encourage the full suite of local diversity. Artificial reservoirs are attractive habitats to many species, overall increasing area of occupancy for 75% of them (ranging from 62–84% for different taxa). These reservoirs provide complementary alternative habitats to natural ponds, leading to improved ecological resilience across the pondscape. We conclude that maintaining a diverse and heterogeneous pondscape is important for conserving local aquatic insect diversity, and that artificial reservoirs increase the local area of occupancy for a range of pond insects in conservation corridors, and improve the biodiversity value of these pondscapes.
... Land transformation especially affected national endemic species, which require particular riparian habitats and aquatic conditions ( Kietzka et al. 2017). This leads us to conclude that a first goal for conservation of these assemblages could be to restore the riparian zones by removing alien trees and estab- lishing indigenous vegetation (Samways & Sharratt 2010). Besides, restoring the habitat, structurally and functionally, would also buffer any toxic or harmful run-off from both agricultural and urban activity, and so improve aquatic con- ditions ( Heino et al. 2015). ...
Article
Rivers of the Cape Floristic Region (CFR) biodiversity hotspot are threatened by land transformation. This region is a centre of endemism for many taxa, including Odonata. These insects are highly sensitive to changes in physical habitat structure, which makes them good bioindicators, and this led to the development of the Dragonfly Biotic Index (DBI). We investigated the effects of local agricultural and urban land transformations on Odonata species richness, assemblage composition and DBI scores in three CFR rivers. A total of 48 sites were selected and categorized as natural, agricultural or urban land use. Adult male Odonata and four environmental variables were recorded over two seasons. Land transformation significantly influenced Odonata assemblage composition but did not always significantly reduce species richness. Average vegetation height also affected Odonata assemblage composition and decreased species richness. Agricultural and urban sites had Odonata assemblages differing from those in the natural areas. Agricultural and urban local land use types reduced opportunities for some endemic species but provided for the persistence and establishment of widespread, generalist species, as indicated by great changes in DBI scores. Mitigating the adverse influences of land transformation through establishment of protected areas is essential for the conservation of rare taxa, particularly in an area with a high number of endemic species.
... L'enrichissement des milieux en nutriments conduit également à des changements dans la structure et la compsition des communautés floristiques susceptibles d'affecter les papillons qui en dépendent (Marini et al., 2009 ;Feest et al., 2014). L'introduction et l'expansion d'espèces envahissantes a également un effet négatif sur de nombreuses espèces, par une action directe sur les individus (Fincke et al., 2009) ou indirecte via une modification de leurs habitats (Samways & Sharratt, 2010 ;Gallien et al., 2017). Ces différentes pressions sont sous-tendues à l'échelle globale par deux phénomènes principaux auxquels les papillons de jours et les libellules sont particulièrement sensibles : la modification de l'occupation des sols et le changement climatique (Travis, 2003 ;Stefanecu et al., 2011 ;. ...
Thesis
Full-text available
Insects are still poorly considered in biodiversity conservation programs, despite their major role in the functioning of terrestrial ecosystems. Because of their great diversity, and a great lack of knowledge of community structuring patterns, the conservation of these organisms faces major challenges related to the evaluation and prioritization of issues as well as the estimation of the species richness of communities. Because they constitute two groups of insects particularly impacted by environmental changes, butterflies and dragonflies are an important part of protected insects in Europe. In this context of low consideration of entomological diversity in conservation biology, this thesis aims to (1) measure the recent dynamics (decline, stability or expansion) of these two taxa in France, and to identify the climatic and ecological factors likely to condition them, (2) for butterflies, to use a fine description of the interactions network between the larvae and their hostplants to question the conservation status according to a systemic approach (3) and finally, with a clearly operational objective, to evaluate the links between the information gains and the efforts / sampling costs mobilized during environmental impact assessments. The comparative study of the temporal dynamics of the populations of these two taxa was carried out at the scale of three countries of Western Europe through a diachronic analysis of the species distribution patterns on a time step of 35 years. This work has highlighted a strong correlation between the artificialisation of landscapes (urbanization, agricultural intensification, regression of wetlands) and the decline of many species, mainly characterized by strict ecological requirements and currently unprotected. On this same scale, the analysis of the architecture of the interactions network between butterfly larvae and their food plants revealed a modular structure in relation to the taxonomy of the partners, as well as a link between the degree specialization and species vulnerability (although the similarity of the species' diet did not seem to condition their conservation status). A final part was focused on the evaluation of the completeness of entomological surveys carried out during environmental impact assessments. A systematic and calibrated return procedure, on sites sampled in Mediterranean scrublands, allowed highlighting the limits of the current protocols in the estimation of species richness and the detection of protected or vulnerable species. This thesis contributes to the articulation between fundamental issues and operational needs, by allowing both a better understanding of the structuring mechanisms of insect communities and the formulation of recommendations for a better local application of conservation policies
... Alien plants not only extract water from estuarine systems, they also restrict water flow and colonize large areas, suppressing the growth of the natural vegetation. The removal of alien plant species is not only of benefit to aquatic organisms, but may also benefit less-obvious indigenous species such as dragonflies (Samways & Sharratt 2009). Alien plant removal in the catchment areas of Overstrand's estuaries is of prime importance for ensuring ecological functionality and productivity. ...
... They spend most of their time in a local area but are mobile as adults and may search for new habitats when local environmental conditions degrade. Adult odonates are highly visible and countable and may signal environmental changes (negative or positive) through shifts in species abundance and composition (Miguel et al., 2017;Samways and Sharratt 2010) or offer a degree of surrogacy for less conspicuous aquatic taxa such as mayflies, stoneflies, and caddisflies (Chapter 25; Kietzka et al., 2019). Perhaps most importantly, odonate species vary widely in their responses and sensitivities to local and surrounding (e.g. ...
Chapter
The Odonata have well resolved taxonomy, conspicuous diurnal adults, contact with aquatic and terrestrial environments, and a broad range of environmental sensitivity across species, making them a valuable group for environmental appraisals. Odonate nymphs are commonly tested in aquatic ecotoxicological and bioaccumulation studies and often applied with other aquatic macroinvertebrate taxa in pollution-based biotic indices. Some of the more recent work aims to explain the evolutionary context of contamination risk and to increase mechanistic understanding of contaminant effects. Adults or exuviae are typically featured in habitat quality assessments with tools such as the Dragonfly Biotic Index, regional lotic quality indices, and coarse taxonomic metrics that will be especially useful in regions lacking descriptions and keys. Adults are further being used in landscape distur- bance assessments where removal of non-breeding occurrences can reduce noise and strengthen signal. The future may move toward macro-ecological health assessments enabled by extensive citizen science and vulnerability trait data.
... These characteristics can be important, because a study of Casas et al. (2011) demonstrated that the diversity and structural complexity of pond marginal vegetation was higher in those ponds which conserved their natural substrate when compared with the ones made of cement or polyethylene-lined. Indeed, riparian vegetation has been identified in several studies as one of the ecological variables which most affect dragonflies (Steytler and Samways 1995;Samways and Sharratt 2010;Monteiro-Júnior et al. 2014). ...
Article
Freshwater ecosystems are exceptionally threatened habitats and suffer biodiversity losses that exceed those in any other ecosystem. Small waterbodies have been typically neglected and excluded from conservation strategies, even though they are essential for maintaining freshwater biodiversity. Dragonflies are considered effective surrogates of the diversity of other taxa and bioindicators of the state of aquatic environments. This study compares, in an intensified farmland landscape of western Spain, the capacity of farm ponds to maintain dragonfly diversity by comparing the Odonata communities of the four type of aquatic systems (river, stream, reservoir and farm pond) present in this region, in which the extant of permanent water bodies is scarce. The results showed higher diversity and abundance values in farm ponds than in any other aquatic system, agreeing with previous studies. Also, farm ponds harbour species from every other aquatic system, thereby occupying an intermediate position in the MDS, which demonstrated their potential value to act as stepping stones. Nevertheless, investigation of the dragonfly community composition revealed a generally low degree of ecological integrity of the studied systems, which are negatively impacted by agricultural and livestock farming intensification. These findings support the role of farm ponds in the maintenance of dragonfly diversity in the study area and emphasise the need of a specific legislation to regulate and protect them.
... Adult Odonata have been neglected, although these amphibiotic insects are versatile and widely used indicators of freshwater and the terrestrial health (e.g., Foote and Hornung, 2005;Oertli, 2008). They highlight environmental changes, with different species responding differently to particular changes (Samways and Sharratt, 2010); this feature is exploited in commonly used indices such as the dragonfly biotic index (DBI; Samways and Simaika, 2016;Simaika and Samways, 2011). Odonates are often abundant; adults are relatively long-lived, highly visible, and easy to sample, providing information on other taxa which are more difficult to sample such as the Ephemeroptera, Plecoptera, and Trichoptera (EPT) group (Bried et al., 2020;Kietzka et al., 2019;Oertli, 2008;Simaika and Samways, 2009). ...
Article
Stormwater management ponds, which are constructed to retain excess runoff and pollutants from traffic, play an important role in the freshwater biodiversity in highly modified areas. However, their roles in agricultural and semi-natural landscapes remain largely unexplored. In this study, we used Odonata as a bioindicator to compare a set of highway stormwater ponds and surrounding ponds within an agricultural and semi-natural landscape to examine the extent to which stormwater ponds act as biodiversity refuges. We analyzed the differences in environmental parameters and the richness, compositions, and conservation values of the odonate communities of stormwater and surrounding ponds. We also examined the factors controlling the differences in the communities of both pond types. The stormwater ponds were smaller, less eutrophicated, less shaded by trees, less stocked with fish, and less connected with other waterbodies than the surrounding ponds. However, they had a higher plant diversity and pH values and were more densely overgrown with vegetation. Compared with surrounding ponds, stormwater ponds had a higher Odonata richness and β-diversity, but their taxonomic distinctness was significantly lower. Therefore, stormwater ponds hosted more variable communities but their assemblages were taxonomically similar. Indicator species were only identified in stormwater ponds. Furthermore, stormwater ponds harbored more species with higher conservation values. The most important factors affecting the differences between stormwater and surrounding ponds were the trophic state, relative tree shading, and fish stocking intensity. With their increase, the richness and rarity decreased. Our results highlight the potential of stormwater ponds to enhance the biodiversity outside urban areas by providing specific habitat conditions that are unique to the surrounding agricultural landscape. In addition, we suggest management practices that can be used to enhance their biodiversity conservation function.
... D. spatulifera was found in the dense riparian vegetation dominated by the herbaceous canopy (Table 1). The high density of riparian canopy reflects a good and stable habitat (Samways & Sharratt 2010). The stable habitat territory of male damselflies is followed by short dispersal behavior (Dolný et al. 2014). ...
Article
Full-text available
Drepanosticta spatulifera is a Javan endemic damselfly. The population is spread unevenly in the Petungkriyono Forest and is threatened due to environmental pressure. The aims of this research are to know the variation of the movement, dispersal, and morphometric among subpopulations of D. spatulifera. Movement and dispersal variation data collection was done using Mark Release Recapture (MRR) for six weeks from early August until mid-September 2020. The collection of morphometric samples was done during the last week of the MRR survey and 46 individuals were measured with 12 continuous characters. During the MRR survey, 596 males of D. spatulifera were marked and 302 were recaptured. D. spatulifera had short movement and dispersal thus no individuals were found across the subpopulations. The distance moved of successive capture and net lifetime movement were dominantly less or equal to five meters. The duration of the MRR survey had a low correlation with the dispersal distance of D. spatulifera. In the morphometric variations, closer subpopulations tended to have a similar cluster of morphometric characters. Variation of distance moved between successive capture and wing size from Mangli Stream was significantly different from other sites. The subpopulation of Mangli, the farthest and higher altitude of the sites, had the highest distance move, more disperse, and the largest wing size. Our study showed that D. spatulifera was extremely sedentary damselfly. It will enhance inbreeding and vulnerability to extinction. Therefore, the interaction between the subpopulations of D. spatulifera in the Petungkriyono Forest needs to be done more.
... In SAR, rare and endemic odonates are threatened overwhelmingly by invasive alien trees (mostly Acacia spp.) along running water courses in particular. However, the large-scale national Working for Water Program (Van Wilgen et al., 1998) has removed alien trees from along many of these water courses, resulting in many species, including several endemics and threatened species, recovering remarkably well (Samways et al., 2005;Samways and Sharratt, 2010). This highly active and positive conservation activity has even resulted in downlisting of some species on the Red List (e.g. ...
Article
Full-text available
Freshwater habitats worldwide are experiencing many threats from environmental and anthropogenic sources, affecting biodiversity and ecosystem functioning. In Africa, particularly in Mediterranean climate zones, rapid human population growth is predicted to have great impact on natural habitats besides naturally occurring events such as unpredictable drought frequency and severity. Here, we analyze the potential correlation between odonate assemblage conservation priority (measured with the Dragonfly Biotic Index: DBI) and the magnitude of climate change and human perturbation in African regions with a dominant Mediterranean climate, namely Northern (NAR: Morocco, Algeria and Tunisia) and Southern African region (SAR: South Africa). Using a compilation of studies assessing odonate assemblages in lotic and lentic habitats of both regions (295 sites in NAR and 151 sites in SAR), we estimated DBI, temporal change in average annual temperature (T), annual precipitation (P), and human footprint index (HFI) in each site, then we tested whether sites with different levels of DBI were associated with different magnitudes of climatic and anthropogenic change. We estimated past (between 1980–1999 and 2000–2018) and future changes (between 1980–1999 and 2081–2100) in T and P based on three CMIP6 scenarios representing low (SSP126), moderate (SSP245), and high emission (SSP585), as well as the change in HFI from 1993 to 2009. We found that assemblages with higher DBI (i.e. higher conservation priority) encountered lower increase in T and slightly greater decrease in P than assemblages with lower DBI (i.e. lower conservation priority) in NAR during 1980–2018, but are projected to experience higher increase in T and lower decrease in P in future projections for 2081–2100. In SAR, the increase in T was mostly similar across assemblages but the decline in P was higher for assemblages with higher DBI during 1980–2018 and 2081–2100, suggesting that assemblages of higher conservation priority in SAR are threatened by drought. While HFI showed an overall increase in NAR but not in SAR, its temporal change showed only minor differences across assemblages with different DBI levels. We discuss the importance of management plans to mitigate the effects of climatic and anthropogenic threats, so improving conservation of odonate assemblages in these regions.
... Invasive stands of river red gum in South Africa decrease the richness and abundance of certain bird feeding guilds (Mangachena and Geerts, 2017) and arthropod communities (Samways and Sharratt, 2010;Samways et al., 2011;Roets and Pryke, 2013). For example, a study by Mangachena and Geerts (2017) showed that bird assemblages at sites invaded by E. camaldulensis are almost a complete subset (24 species) of those in nearby areas without river red gums (42 species); only two species are unique to invaded sites. ...
Article
Eucalyptus camaldulensis can be seen as an iconic tree of superlatives. It is the eucalypt with the widest native range, and one of the most widely planted eucalypts around the globe. In South Africa, it is the most widespread and the most aggressively invasive eucalypt. It has many uses, but also causes major impacts. However, little is known about key aspects of its ecology in South Africa, including its invasion history, invasion processes and dynamics, and people’s perceptions of its positive and negative effects on ecosystems. Such knowledge is crucial for developing robust and defendable guidelines for sustainable management of the species. This paper provides a comprehensive dossier of the species in South Africa. It reviews what is known of its introduction and planting history, its current distribution, its value for commercial forestry and other uses, its impacts as an invasive species, pests and pathogens associated with the species, people’s perceptions of the species and conflicts of interest, and the options for management and restoration. The review reveals that E. camaldulensis is a tree of many contradictions in South Africa, making it a poster-child example of a conflict-generating non-native species. Based on available knowledge, we assess options for improved management. We highlight several knowledge gaps which need to be addressed in more detail through future research. It is hoped that this species profile will serve as a model for the types of information that are needed for developing objective management strategies for non-native tree species in different parts of the world.
... Dragonflies and damselflies are a flagship group of insects that form an important component of aquatic ecosystems. Their sensitivity to environmental conditions makes odonates excellent biological indicators of environmental conditions (Samways and Sharratt, 2010) Hence, they are very useful for monitoring the ecological integrity or degradation of aquatic ecosystems (Chovanec and Waringer, 2001;Ferreras-Romero et al., 2009) and assessing habitat restoration measures (Samways and Taylor, 2004). Numidia (north-eastern Algeria) is known to be an odonate biodiversity hotspot, with a high rate of endemism at least six endemic species is recorded, according to (Riservato, 2009;Benchalel and Samraoui, 2012). ...
Article
Aspects of the phenology, reproductive biology and larval cycle of natural populations of the Calopteryx haemorrhoidalis (Vander Linden, 1825) are described. Populations of this species in Brabtia sector (eastern Numidia, NorthEast Algeria) were studied between March 2017 and April 2018. An overview of the current state of the population is provided. The streams of Eastern Numidia have suffered over recent years from major disturbances including the effects of 20 rapid climate changes. Although the status of autochthony is preserved in the site, the populations are currently diminished compared to that recorded two decades ago. Aspects of the species reproductive behavior, biology, and ecology are reported. The species is univoltine with a direct development in 12 larval stages. The effects of some climatic conditions, particularly air temperature, included an extension of the adult phenology period. The species is unable to tolerate a certain amount of stress similar to stagnant water species. The correlation established between the abundance of C. haemorrhoidalis and the physico-chemical parameters from the principal correspondence analysis (PCA) shows an ecological gradient, in the distribution of the species, significantly (P<0.001) explained by a requirement for dissolved oxygen, both temperatures and pH.
... This difference between the RZ and TZ does not hold the same importance for grasshoppers. So while invasion of the RZ by alien trees can lead to local extinction of the endemic dragonflies and other stream insects (with recovery on removal of alien trees) (Samways and Sharratt 2010;Samways et al. 2011) there is no special significance attached to the RZ endemic grasshopper fauna which is better represented in the TZ. ...
Article
Full-text available
Riparian zones (RZs) functionally connect aquatic and terrestrial ecosystems, and have azonal and geographically widespread plant communities that differ from those of the neighboring terrestrial zone (TZ). Although well studied botanically, RZs are not well understood in terms of their terrestrial insect diversity, including grasshoppers. The Cape Floristic Region (CFR) is a global biodiversity hotspot with small rocky rivers running through highly diverse sclerophyllous vegetation. It has high levels of endemism among many taxa, including grasshoppers, making it ideal for testing the effect of azonal vegetation on grasshopper assemblages of the RZ, and determining whether conservation efforts should be focused on the RZ as well as the TZ. We determine grasshopper dispersion patterns along the RZ of an important CFR river, and compare these patterns with those of the TZ to understand the habitat occupancy relative to 27 environmental variables of the zones and geographical distribution of the grasshoppers. Forty percent of individuals we collected were CFR endemics. We found only weak differences in the grasshopper assemblages between the RZ and TZ, apparently driven by deep history, complex geomorphology, stressful environmental conditions, a diverse vegetation and land mosaic, and probable high predator pressure. There were two groups: large-sized, well-flighted, geographically widespread generalists that were overall more abundant in the RZ than TZ, and small, flightless or poorly-flighted, vegetation-specialists which are narrow-range endemics adapted to both RZ and TZ, but still more abundant in the TZ. We conclude that although the vegetation of this riparian zone may require some special conservation attention, this is not so for the grasshoppers which overall are best conserved in the TZ.
... Alien plant species, especially trees, are detrimental to local dragonfly diversity, mostly due to habitat shading (Samways and Sharratt 2010;Kietzka et al. 2015). Shade reduces species richness, and was greatest in years when the system had reverted back to a stream. ...
Article
Full-text available
Pond construction in urban areas can mitigate loss of aquatic insects by providing refuges. Urban ponds are also an interface between civil society and aquatic insects, especially via charismatic dragonflies. Ponds have therefore been constructed specifically for dragonfly conservation awareness in many countries. Yet they require regular management, especially when an inflow to a shallow pond supplies inorganic and organic material, leading to vegetation overgrowth and natural infilling, rendering a pond back into a stream, unsuitable for many lentic species. Here, we assess changes in dragonfly diversity over a 32-year period at a pond constructed for dragonfly conservation awareness, and which underwent system changes: stream→pond→vegetation overgrowth and infilling and then following restoration from stream→pond. Adult male dragonflies and 13 environmental variables were recorded along 31 transects, and compared with previous data collected at the same sites before pond construction and then in the short- and medium-term after. Years when the system comprised a pond had higher dragonfly abundance and species richness than when a stream, and both increased after the pond was restored. Shortly after restoration, the dragonfly assemblage closely resembled that of the earlier pond. Vegetation cover and alien vegetation presence were significant drivers of dragonfly assemblage change and decreased dragonfly abundance and species richness. Lessons learned here for maintaining a dragonfly awareness pond include periodical dredging to remove excessive vegetation overgrowth and infilling from organic and inorganic matter, and aim for high microhabitat heterogeneity using selective management of marginal vegetation, alongside a range of flow regimes.
... These green corridors buffer urban impacts and are attractive breeding sites for some dragonflies. Dragonfly assemblages recover remarkably well when alien vegetation is cleared, and some endemic species recover their area of occupancy and part of their former distribution ranges [70]. Artificial wetlands in urban areas initially attract only common and widespread dragonfly species, but they may also attract rare and localized species once native vegetation has had enough time to establish [71]. ...
Article
Full-text available
Urban settlements range from small villages in rural areas to large metropoles with densely packed infrastructures. Urbanization presents many challenges to the maintenance of freshwater quality and conservation of freshwater biota, especially in Africa. There are many opportunities as well, particularly by fostering contributions from citizen scientists. We review the relationships between dragonflies and urbanization in southern Africa. Shifts in dragonfly assemblages indicate environmental change, as different species are variously sensitive to abiotic and biotic water and bank conditions. They are also conservation umbrellas for many other co-occurring species. Major threats to southern African dragonflies include increasing infrastructure densification, frequent droughts, habitat loss, pollution, and invasive alien vegetation. Mitigation measures include implementation of conservation corridors, maintenance of healthy permanent ponds, pollution reduction, and removal of invasive alien trees. Citizen science is now an important approach for supplementing and supporting professional scientific research.
... A quarter of the South African dragonfly species are endemic, and 7% are red-listed as threatened, almost entirely through shading effects from invasive alien tree canopies . However, when these alien trees are removed, dragonflies, even narrow-range endemics, show rapid recovery (Samways and Sharratt 2010). ...
... A quarter of the South African dragonfly species are endemic, and 7% are red-listed as threatened, almost entirely through shading effects from invasive alien tree canopies . However, when these alien trees are removed, dragonflies, even narrow-range endemics, show rapid recovery (Samways and Sharratt 2010). ...
Article
Full-text available
Artificial ponds assure continuous societal water supply, especially during droughts. Obligate aquatic and amphibiotic insects readily inhabit novel water bodies, as many possess mobility traits for opportunistic colonization. We review here the value of artificial ponds (< 2 ha) (and reservoirs; > 2 ha) for local aquatic insect diversity in mostly dry and drought-prone southern Africa. We compare these ponds to natural pools, wetlands, and stream deposition pools. The region has a highly varied topography and physiographical zones. Flat, arid areas largely support widespread insect generalists, while the mountainous orographic zones support an additional rich fauna of localized endemics. However, the many ponds (> 0.5 million) have greatly changed the local distribution patterns of surface freshwater across the region, increasing the area of occupancy for many aquatic insect species, especially dragonflies. We focus on the extent to which aquatic insect assemblages have benefitted from new ponds and reservoirs. We conclude that these novel ecosystems benefit almost all lentic aquatic insect species, while also enabling population resilience during droughts. However, while these benefits are substantial, these ponds are not a substitute for natural still waters, which are still required to maintain all indigenous lentic aquatic insect diversity.
... Similarly, it is possible that the threshold level for complete restoration of the aquatic ecosystem, postcontrol of P. stratiotes, is higher than 50%. Samways & Sharratt (2010) showed that dragonfly assemblages that had been impacted by alien invasive riparian vegetation in rivers in the Western Cape of South Africa recovered quickly once the vegetation had been removed. Similarly, here we have shown that aquatic ecosystems can recover after effective biological control of floating alien macrophytes. ...
Article
Full-text available
Floating aquatic weed infestations have negative socio-economic and environmental consequences to the ecosystems they invade. Despite the long history of invasion by macrophytes, only a few studies focus on their impacts on biodiversity, while the ecological benefits of biological control programmes against these species have been poorly quantified. We investigated the process of biotic homogenization following invasion by Pistia stratiotes on aquatic biodiversity, and recovery provided by biological control of this weed. Biotic homogenization is the increased similarity of biota as a result of introductions of non-native species. The study quantified the effect of P. stratiotes, and its biological control through the introduction of the weevil, Neohydronomus affinis on recruitment of benthic macroinvertebrates to artificial substrates. Mats of P. stratiotes altered the community composition and reduced diversity of benthic macroinvertebrates in comparison to an uninvaded control. However, reduction in percentage cover of the weed through biological control resulted in a significant increase in dissolved oxygen, and recovery of the benthic macroinvertebrate community that was comparable to the uninvaded state. This highlights the process of homogenization by an invasive macrophyte, providing a justification for sustained ecological and restoration efforts in the biological control of P. stratiotes where this plant is problematic.
Chapter
Anthropogenic changes to inland waters have significantly affected an estimated >83% of land surface surrounding aquatic systems.
Article
Many wetland systems are being lost or degraded by human activities such as plantation forestry. Therefore, efforts to restore these wetland systems are important for biodiversity recovery. We assess the recovery of arthropod assemblages that occupy hydromorphic grassland topsoil and leaf litter after the removal of exotic pine trees. We sampled arthropods in three biotopes (natural untransformed hydromorphic grasslands, restored hydromorphic grasslands and commercial pine plantations) replicated across a large‐scale timber‐grassland mosaic in the KwaZulu‐Natal Midlands, South Africa. In the restored sites, overall species richness, as well as species richness of spiders, ants and orthopterans was significantly higher than in plantations, and was as high as in natural, untransformed sites. Additionally, overall assemblage structure along with spider, beetle, ant, and orthopteran assemblages showed no significant differences between restored and natural grasslands. Therefore, pine tree removal enables recovery of these arthropod taxa to levels similar to those in natural hydromorphic grassland. Recovery was rapid, with the assemblages in some restored sites resembling those in untransformed sites after only six years, indicating a high level of resilience and recovery in these systems. Contrary to expectations, time since pine removal had a negative effect on arthropod recovery. This was due to the strongly negative effect of alien invasive American bramble (Rubus cuneifolius), which was most common in older restored sites, causing deviation from their restoration trajectory. The potential for arthropod recovery in these hydromorphic grasslands is high, but successful restoration is dependent on ongoing appropriate grassland management, especially removal of bramble. This article is protected by copyright. All rights reserved.
Article
Mountains supply essential resources, making them attractive areas for human settlement. Variation in elevation in mountainous areas determines local and regional climates, leading to complex biodiversity patterns. Mountains in the Cape Floristic Region have high species richness and beta diversity, and very high levels of local endemism. Table Mountain is an iconic mountain in the region, and unusual, as it is in the centre of the city of Cape Town. It is exceedingly rich in biodiversity, including many localized endemic species. However, increasing urbanization in the area is adversely affecting the local biodiversity, especially in the lowlands. Climate change effects to date are minimal, but projected to interact with the impacts of urbanization. Here we review the biodiversity patterns of green and blue spaces in and around Cape Town, including Table Mountain, focusing on aquatic arthropods. We also review the major threats that lead to biotic impoverishment, and provide information on current conservation efforts aimed at protecting the rich biodiversity of Table Mountain and its surrounds. Finally, we focus on the shortcomings of existing conservation actions, and then provide conservation strategies to limit aquatic arthropod biodiversity losses, based on actions that have already worked well. To ensure protection of all arthropods, freshwater habitats across all elevations require further conservation action. Education and creating awareness must continue to close the gaps between scientists, conservation practitioners and civil society as a crucial part of the conservation plan.
Article
Full-text available
An inventory of Odonata was carried out in the southern half of the state of Rio Grande do Sul, Brazil, in the Pampa biome. Originally, this biogeographical region was covered mostly by open fields and grassland, with sections of higher vegetation surrounding water bodies and rocky hills. Today the landscape is fragmented due to agricultural activities, mainly cattle farming, rice crops and forest plantations. Our survey was conducted in three municipalities from this region, between March 2015 and April 2016. Aiming at a general overview of the species composition, our sampling sites were selected on a wide basis, including lakes, bogs, temporary water bodies, small streams and river sections. Eighty two species of Odonata were collected comprising 40 genera and seven families. The dominant families were Libellulidae (56,1%), Coenagrionidae (24,5%) and Aeshnidae (7,3%). We found a diverse odonate assemblage, adding 19 new species records for the state of Rio Grande do Sul.
Article
Full-text available
The effects of various aquatic habitats on the abundance, species richness, diversity and taxonomic distinctness of Odonata were studied. The impact of environmental factors and living conditions in lentic habitats were expressed by the composition of coenoses, on the evaluation we used the Dragonfly Biotic Index. The positive effects of habitat heterogeneity on biodiversity are well known, but it is not clear how the diversity of studied and ecologically important taxa, such as odonates, may vary in different water reservoirs. We investigated how Odonata community metrics (composition, abundance, diversity and environmental compatibility) differ in lentic water: ponds, fishponds, excavation of mineral material and in marshlands, where biodiversity plays an important role. Using an entomological mesh, we took samples in the south-western part of Slovakia in six geo-morphological units at 54 study sites during four years. This study detected distinct odonates assemblage variations among habitats and heterogeneity among gradients. Wide ranges of microhabitats with different environmental properties create appropriate conditions for living span of them. Surprisingly, the highest species richness was recorded in the excavation of mineral materials habitats. Stagnicolous Odonata species correlated (CCA) with the habitats of excavation of mineral material and marshlands; showed links to the littoral vegetation and dense vegetation cover. While the euryecious species have been linked to the ponds and fishponds; and correlated with the water body size. It seems to be degraded habitats are not so much suitable for rare and endangered species, but to preserve the biological value of the environment and for the existence of the high abundance and species richness of odonates.
Thesis
Full-text available
The pervasiveness of threats posed by biological invasions presents significant challenges to human well-being, biodiversity conservation, and natural resource management, which has contributed to the growth of invasion science as a discipline. However, several studies have shown that the social-ecological complexity of invasions, the compartmentalisation of knowledge into disciplines and the lack of integrative research approaches, current invasion research has not informed management decision making effectively. Thus, to maximise the impact of research investments, there is a need to explore and evaluate how research informs management practices and processes linked to biological invasions. Accordingly, this dissertation outlines the state of invasion management-related research in South Africa, using the internationally recognised Working for Water (WfW) programme as a case study. Drawing on insights from science studies and evaluation research, a mixed-method approach is used to assess the processes, conditions and outputs associated with research produced under the programme’s auspices. The research comprised two areas of inquiry 1) the exploration of textual information (journal articles, grey literature, and their content), and 2) the social dimensions of research and decision making linked to invasion science and management, with a specific focus on collaborative relationships amongst scientists and decision makers. It sought to determine the extent to which published research aligned with the programme’s needs, research and management strategies. The research also aimed to identify effective ways for organising and producing knowledge relevant to decision making; and to provide insights into how the social dimensions, the people and organisations, their interactions and impact, have shaped research and decision-making processes. Findings suggest that there are significant gaps in the knowledge base particularly in relation to the social dimensions of biological invasions, which were poorly represented and aligned with the mandate and priorities set by the programme. This research showed significant deficiencies in knowledge management and the uptake of research funded by the programme, despite its potential relevance to decision making as evidenced by the recommendations presented in the research. Moreover, research produced under WfW’s auspices was authored by a handful of key researchers who fulfil a significant role in shaping research collaborations both across disciplines and institutions. The loss of these key individuals, including those involved in management-related decision making, would be detrimental to the stability of collaboration networks and research productivity. Finally, findings show that research productivity, collaborative relationships between scientists within and across research organisations, and between research and decision-making processes are positively influenced by collegiality and cooperation between actors, while increased competition and bureaucratisation in the workplace negatively influence research productivity. To address the shortcomings concerning the invasion research and management identified in this dissertation, efforts towards improving the relationship between researchers and decision-makers and building more resilient collaboration networks need to be implemented. Firstly, institutions must engage in and fund more targeted, long-term transdisciplinary or integrative research that incorporates appropriate structures that foster collaboration, knowledge coproduction and knowledge sharing. Secondly, systems and strategies for monitoring and evaluating research, including the use of bibliometric indicators, social network analyses and qualitative assessments, should be developed to ensure that research relevant to managing biological invasions is not lost to the decision-making process. Such an undertaking would in turn require the development of an integrated research strategy and action plan that accounts for both the knowledge management and the social processes underpinning research and decision making.
Article
Full-text available
Background: Increasing numbers of invasive alien plant (IAP) species are establishing around the globe and can have negative effects on resident animal species function and diversity. These impacts depend on a variety of factors, including the extent of invasion, the region and the taxonomic group affected. These context dependencies make extrapolations of IAP impacts on resident biota from region to region a substantial challenge. Objectives: Here, we synthesised data from studies that have examined the effects of IAPs on animal diversity in South Africa. Our focus is on ectothermic organisms (reptiles, amphibians and invertebrates). Method: We sourced relevant articles using keywords relating to (1) the effects of IAPs on species diversity (abundance, richness and composition), (2) the IAP and (3) the native ectotherm. We extracted the taxonomic and spatial coverage of IAPs and affected native species and assessed the extent of information given on potential mechanisms driving IAP impacts. Results: Across the 42 studies, IAPs had a decreasing or neutral effect on native animal abundance and richness and significantly changed species composition. This review highlighted the paucity of studies and the research deficits in taxonomic and geographic coverage and in the mechanisms underlying IAP impacts on ectotherms. Conclusion: By assessing the status of knowledge regarding the impacts of IAPs on resident animal species in South Africa, this study identifies information gaps and research priorities at the country level with a view to informing monitoring and conservation efforts, such as alien plant removal and control programmes, and ensuring that endemic terrestrial animal diversity is maintained.
Article
Full-text available
Ecological restoration projects often have variable and unpredictable outcomes, and these can limit the overall impact on biodiversity. Previous syntheses have investigated restoration effectiveness by comparing average restored conditions to average conditions in unrestored or reference systems. Here, we provide the first quantification of the extent to which restoration affects both the mean and variability of biodiversity outcomes, through a global meta‐analysis of 83 terrestrial restoration studies. We found that, relative to unrestored (degraded) sites, restoration actions increased biodiversity by an average of 20%, while decreasing the variability of biodiversity (quantified by the coefficient of variation) by an average of 14%. As restorations aged, mean biodiversity increased and variability decreased relative to unrestored sites. However, restoration sites remained, on average, 13% below the biodiversity of reference (target) ecosystems, and were characterised by higher (20%) variability. The lower mean and higher variability in biodiversity at restored sites relative to reference sites remained consistent over time, suggesting that sources of variation (e.g. prior land use, restoration practices) have an enduring influence on restoration outcomes. Our results point to the need for new research confronting the causes of variability in restoration outcomes, and close variability and biodiversity gaps between restored and reference conditions. For the first time, we assess the response of terrestrial biodiversity to restoration measures considering variability alongside mean response. We find that on average, restoration increases mean biodiversity and decreases variability of biodiversity. However, reference sites consistently display both the highest mean and least variable levels of biodiversity.
Preprint
Full-text available
A total of 419 individuals under 5 families, 8 genera and 10 species of Odonata were recorded in the present study. Among them family Libellulidae had 6 species followed by Chlorocyphidae (2 species), and Coenagrionidae and Euphaeidae had1 species. The dominance order of Odonata was Pantala flavescens (44.40%) > Diplacodes trivialis (22.70%) > Orthetrum chrysis (7.40%) while rest of the fauna ranged from (1.40 to 6.90%). Pantala flavescens was maximum during NEM (50.0%) followed by summer and winter (43.8% each) and minimum during SWM (38.5%). Margalef Index of Species Richness was highest (2.00) during winter. Simpson Index of Diversity was highest (0.75) during SWM while Shannon-Wiener Index of Dominance was highest (1.75) during summer. The species were evenly distributed during summer with Pielou’s Evenness Index value of 0.76. The community change was 80.00 per cent change during January, 2018 and had a steep fall in February and April, 2018 and reached a peak of 66.67 per cent during March and November, 2018.
Article
Full-text available
Commercial afforestation of natural ecosystems is increasing worldwide. There is little information however, on the extent to which biodiversity is being affected by this practice. This especially so for stream fauna, including the conspicuous Odon. Some dragonflies and damselflies may decline when their natural environment is anthropogenically changed and, as a group, they are sensitive to the impact of afforestation. The sites were four pine plantations in KwaZulu-Natal, South Africa.14 environmental factors were recorded along stretches of streams running through each of the four sites. The diversity of Odon. spp. and their abundances along these streams were measured. There was a strong positive correlation between certain abiotic factors, for example, boulder cover and shade, with the local distributions of these insects. Water pH was also a strong correlate. Most spp. required both unpolluted water and a sunlit stream. Particular vegetation type and exact distance of pine trees from the water's edge (so long as they did not shade the stream) were not strong correlates. This meant that species diversity dropped dramatically where the water was completely shaded by a closed canopy, whether it was from natural forest or from exotic trees. It is recommended that no plantation trees should shade a stream edge, and should be planted at least 30m from the water. All highly invasive, dense-canopy weeds, especially Acacia mearnsii, should be removed, and extensive and intensive cattle trampling of the banks avoided.
Article
Full-text available
Adult Odonata species assemblage patterns were studied at 8 ponds near Pietermaritzburg, South Africa. Different ponds had different assemblages. Strong inferential evidence from multivariate analysis and correlation suggested that the main determinants of assemblage patterns were certain biotic and abiotic environmental variables. In other words, assembly 'rules' may be governed more by factors external to the taxon than by interspecific competition. Larger ponds were not necessarily richer in species than smaller ponds because factors such as water quality, vegetation type and microsite diversity overrode biotope size. Species richness was greatest at shallow, well-vegetated ponds with clear, oxygenated water. Such ponds provide suitable conditions for both larvae and adults. Sunlight/shade and marginal/submerged vegetation gradients were the main drivers of assembly patterns at the ponds. Species assemblage patterns were determined by several variables acting together. In turn, the assemblage patterns at each pond were influenced by different variables representing different ecological successional stages.
Chapter
Full-text available
Dragonflies are quintessential forest animals, and forests are essential to them. The majority of odonate species are associated with forests, especially in the neotropical region. Forests are important in furnishing a variety of larval habitats and favorable conditions for adults. Adult odonates can use both sunshine and shade available in forests, but forests also offer constraints to odonate activity. Forest odonates are poorer dispersers than those of open country, this factor contributing to the very high biodiversity of the tropics.
Article
Full-text available
A further biodiversity index is proposed, based on taxonomic (or phylogenetic) relatedness of species, namely the 'variation in taxonomic distinctness' (VarTD, Lambda (+)) between every pair of species recorded in a study. It complements the previously defined 'average taxonomic distinctness' (AvTD, Delta (+)), which is the mean path length through the taxonomic tree connecting every pair of species in the list. VarTD is simply the variance of these pairwise path lengths and reflects the unevenness of the taxonomic tree. For example, a species list in which there are several different orders represented only by a single species, but also some genera which are very species-rich, would give a high Lambda (+) by comparison with a list (of equivalent Delta (+)) in which all species tended to be from different families but the same order. VarTD is shown to have the same desirable sampling properties as AvTD, primarily a lack of dependence of its mean value on the sample size (except for unrealistically small samples). Such unbiasedness is of crucial importance in making valid biodiversity comparisons between studies at different locations or times, with differing or uncontrolled degrees of sampling effort, This feature is emphatically not shared by indices related to species richness and also not by properties of the phylogeny adapted from proposals in other, conservation contexts, such as 'average phylogenetic diversity' (AvPD, Phi (+)). As with AvTD, the VarTD statistic for any local study can be tested for 'departure from expectation', based on a master taxonomy for that region, by constructing a simulation distribution from random subsets of the master list. The idea can be extended to summarising the joint distribution of AvTD and VarTD, so that values from real data sets are compared with a fitted simulation 'envelope' in a 2 d (Delta (+), Lambda (+)) plot. The methodology is applied to 14 species lists of free-living marine nematodes, and related to a master list for UK waters. The combination of AvTD and VarTD picks out, in different ways, some degraded locations (low Delta (+), low to normal Lambda (+)) and the pristine island fauna of the Scillies (normal Delta (+), high Lambda (+)). The 2 indices are also demonstrated to be measuring effectively independent features of the taxonomic tree, at least for this faunal group (although it is shown theoretically that this will not always be the case). The combination of Delta (+) and Lambda (+) is therefore seen to provide a statistically robust summary of taxonomic (or phylogenetic) relatedness patterns within an assemblage, which has the potential to be applied to a wide range of historical data in the form of simple species lists.
Article
Full-text available
Biological indicators are being increasingly used to rapidly monitor changing river quality. Among these bioindicators are macroinvertebrates. A short-coming of macroinvertebrate rapid assessments is that they use higher taxa, and therefore lack taxonomic resolution and species-specific responses. One subset of invertebrate taxa is the Odonata, which as adults, are sensitive indicators of both riparian and river conditions. Yet adult Odonata are not necessarily an umbrella taxon for all other taxa. Therefore, we investigated whether the two metrics of aquatic macroinvertebrate higher taxa and adult odonate species might complement each other, and whether together they provide better clarity on river health and integrity than one subsetalone. Results indicated that both metrics provide a similar portrait of large-scale, overall river conditions. At the smaller spatial scale of parts of rivers, Odonata were highly sensitive to riparian vegetation, and much more so than macroinvertebrate higher taxa. Odonate species were more sensitive to vegetation structure than they were to vegetation composition. Landscape context is also important, with the odonate assemblages at point localities being affected by the neighbouring dominant habitat type. Overall, benthic macroinvertebrates and adult Odonata species provide a highly complementary pair of metrics which together provide large spatial scale (river system) and small spatial scale (point localities) information on the impact of stressors such as riparian invasive alien trees. As adult Odonata are easy to sample and are sensitive to disturbance at both small and large spatial scales, they are valuable indicators for rapid assessment of river condition and riparian quality. KeywordsRiparian ecosystems-Bioindicators-Benthic macroinvertebrates-Adult Odonata-Complementarity
Article
Full-text available
Prioritizing and assessing the condition of sites for conservation action requires robust and ergonomic methodological tools. We focus here on prioritizing freshwater sites using two promising biodiversity indices, the Dragonfly Biotic Index (DBI) and Average Taxonomic Distinctness (AvTD). The AvTD had no significant association with either species richness or endemism. In contrast, the DBI was highly significantly associated with species richness and endemism, although the strengths of the associations were weak. These associations are related to how the sub-indices in the DBI are weighted, and how species are distributed geographically. Additionally, the DBI was found to be very useful for site selection based on its ability to measure ecological integrity, combined with level of threat, at multiple spatial scales. The AvTD was found to be useful principally for regional use. As the DBI is a low-cost, easy-to-use method, it has the additional use as a method for assessing habitat quality and recovery in restoration programs. The DBI operates at the species level, and is therefore highly sensitive to habitat condition and has great potential for environmental assessment and monitoring freshwater biodiversity and quality. Practical, worked examples of river restoration are given here. In view of the ease and versatility by which the DBI can be employed, we recommend its testing and possible integration into freshwater management and conservation schemes elsewhere in the world.
Article
Full-text available
This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the "sampled patch size," i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
Article
Full-text available
Invasive plants and plantations may be detrimental to native, ground-living, invertebrate fauna. Using pitfall traps at 20 sites in Pietermaritzburg, South Africa, an assessment was made of the distribution of epigaeic fauna under stands of the exotic invader plants: Acacia longifolia (long-leaved wattle), Acacia mearnsii (black wattle), Lantana camara (lantana) and Solanum mauritianum (bugweed), and also under a canopy of two major plantation trees: Eucalyptus grandis and Pinus patula. Control plots were minimally disturbed grassland and woodland in the same area. The effects of the invasive and cultured plants suggest that the impact is a complex interaction of factors. In general, there was a lower (but not significantly so) species richness, and also diversity, of invertebrates in exotic compared with indigenous vegetation. Certain individual species rather than whole families were affected most by these types of vegetation. There was a different assemblage of species associated with exotic compared with indigenous vegetation, with some species being good indicators for exotic or for indigenous vegetation. Although the weeds and vegetation caused a few species to increase in abundance, many other species decreased or even disappeared locally. Whereas different species assembled according to whether vegetation was exotic or indigenous, families and orders assembled along a gradient of closed to open canopy vegetation irrespective of origin. Although a few species were restricted to exotic vegetation (presumably having invaded at some time in the past from somewhere apart from the control sites), many others were restricted to indigenous vegetation. Vegetation management should be sensitive to the needs of certain invertebrate species so as to conserve them when native vegetation is replaced by exotics. Some management recommendations for conserving local invertebrate diversity are made.
Article
Full-text available
This paper examines the evidence for the effects of invasive alien plants in natural and semi-natural ecosystems in South Africa. Invasive alien plants are concentrated in the Western Cape, along the eastern seaboard, and into the eastern interior, but there is a shortage of accurate data on abundance within this range. Most information on site-specific impacts comes from the fynbos biome, and is generally poor for other biomes. The consequences of invasions for the delivery of ecosystem goods and services to people are, with the notable exception of their influence on water resources, inadequately studied. The understanding of many of the broader aspects of invasion ecology needs to be enhanced, and identify important challenges for research to address critical gaps in knowledge. Priorities for future research include the development of a predictive understanding of the rates of spread of invasive alien plants, and the development of achievable goals for ecosystem repair after clearing, including measurable criteria for assessing the success of restoration. Climate change could significantly exacerbate problems with invasive species and work is needed to accommodate plausible trajectories in planning and management frameworks. Perhaps the greatest challenge for South African ecologists is to address the twin issues of skills development and social transformation, to ensure that adequate and relevant ecological expertise is maintained to meet future research and management needs. Formal collaboration between organizations to address capacity building and educational transformation in the field of invasion ecology would represent a significant step forward.
Article
For South African butterflies that congregate on hill summits, the vegetation type that clothes hills has a major influence on behaviour and species assemblages. Congregation of individuals occurred on grass-covered hills in a grassland matrix, while little congregation occurred on hills covered with undisturbed natural forest, nor on those with closely packed, mixed, plantation trees. Hill-summit congregation was not prevented by small differences in hilltop grassland vegetation type, nor by low densities of the alien plant Eucalyptus grandis. This study demonstrates the importance of taking into account the interplay of topography, vegetation type and architecture when planning for conservation.
Article
The distribution of larvae of the dragonfly Cordulegaster boltoni was assessed in eighteen streams in contrasting land use in the upper catchment of the River Tywi, mid-Wales, in each year during 1985–1989, inclusive. Larvae occurred abundantly in moorland streams and in a deciduous woodland stream, but were never found in five streams draining plantations of conifer forest. Although the latter were the most acidic, transplant experiments and distributional data showed that larvae were tolerant of the water conditions found there. Conifer forest streams were also generally cooler than moorland streams, but experimental removal of bankside trees to a width of over 10 m did not lead to colonization by Cordulegaster despite increased temperature. Dietary studies also revealed no likely restriction by food availability in conifer forest streams, though we could not exclude the possibility that foraging conditions for adults were impaired in conifers. However, larvae were strongly associated with habitats at the stream margins which were highly eroded and often absent from conifer forest streams. These habitat features probably explained their absence under forest conditions. Further data are required to assess whether other aquatic resources of high conservation value are affected in similar ways by conifer forestry. The effectiveness of aspects of new forest design, such as buffer strips around streams, also requires consideration.
Article
Biologists are nearly unanimous in their belief that humanity is in the process of extirpating a significant portion of the earth's spe­ cies. The ways in which we are doing so reflect the magnitude and scale of human enterprise. Everything from highway construction to cattle ranch­ ing to leaky bait buckets has been implicated in the demise or endan­ germent of particular species. Ac­ cording to Wilson (1992), most of these activities fall into four major categories, which he terms "the mind­ less horsemen of the environmental apocalypse": overexploitation, habi­ tat destruction, the introduction of non-native (alien) species, and the spread of diseases carried by alien species. To these categories may be added a fifth, pollution, although it can also be considered a form of habitat destruction. Surprisingly, there have been reIa­ tively few analyses of the extent to which each of these factors-much less the more specific deeds encomDavid S. Wilcove is a senior ecologist at the Environmental Defense Fund, Wash­ ington, DC 20009. David Rothstein re­ ceived his J.D. in 1997 from Northeastern
Article
Adult male dragonflies were sampled from 42 sites on four variously disturbed rivers and three reservoirs in Kruger National Park, South Africa. Fifty-one species and 2671 individuals were recorded. Large flow fluctuations resulted in a high species turnover during sampling. Dragonfly species richness mostly conformed with the intermediate-disturbance hypothesis, with species richness high on the rivers with moderate disturbance and low on the most disturbed ones. Ordination of dragonfly species data separated rivers into clear groups, indicating that the dragonfly assemblages reflected the distinct plant physiognomic and physical environmental conditions of each river system. Species that were abundant on any particular river had biotope preferences that reflected the overall environmental conditions of that river. Aquatic macrophytes, including two exotic invasive species, promoted dragonfly species richness. These species, however, were not rare or threatened. Highly disturbed rivers were characterized by species that preferred highly exposed situations with broad environmental conditions. In contrast, long grass or shady trees were important for some species because they buffered larger-scale, unpredictable environmental changes. Biotic disturbance was also important because trampling by buffalo reduced local species richness and composition. Dragonfly assemblages were highly visible and sensitive indicators of aspects of long-term environmental conditions of the water body. Management recommendations for dragonflies and other aquatic invertebrates include maintaining water and riparian biotope heterogeneity, maintaining constant flow rates and water levels, and allowing some macrophyte cover. A little natural and anthropogenic disturbance encourages much greater species richness than more extreme disturbance. The Sabie River is a major subject for conservation action in the premier protected area of Kruger National Park.
Article
The dragonfly fauna of the 374 km2 island of Mayotte in the western Indian Ocean comprises some widespread African species and some Comoro endemics, and is a biodiversity hotspot. This dragonfly assemblage is under threat from increasing human impact as it creeps up the water courses from the periphery of the island towards the centre. Among these impacts are indigenous tree removal and replacement growth by alien vegetation. An even greater impact and threat is detergent input into streams. The intensity of this impact is so great that the streams and rocks become white. To date, although often the wings and bodies of odonates become stained white with detergent, the dragonfly assemblage appears remarkably tolerant of this impact. However, there is differential impact, with loss of island endemic species in the most impacted areas. In contrast, the geographically widespread and eurytopic species continue to thrive in these impacted areas, at least in the short term. It is urgent to change people's water-usage behaviour, both for their benefit and for the endemic dragonfly assemblage.
Article
Fragmentation and modification of the landscape with increasing human population pressure influences the movement patterns of animals. Butterfly flight paths are modified by the structure and orientation of the landscape elements arising from these landscape changes. Here, butterfly flight paths relative to landscape elements were mapped in the National Botanic Gardens, Pietermaritzburg, South Africa, as part of an ecological landscaping project aimed at maximizing biodiversity conservation. Ecotones such as the edge of a water stand and of a forest were the most heavily used flight corridors. A disturbed and naturally regenerated mixed vegetation patch was also an important flight pathway. A stand of large exotic plane trees and cut grass had a highly negative influence, causing the butterflies to change direction. There were differences between species, with some finding the water stand a major barrier, and others not able to cross the forest. Knowledge of the interaction between landscape elements and butterflies, as well as many other animals, has important management implications. Biologically, it contributes to deciding where to position nectariferous and food plants, and socially it helps decide where the public may view butterflies.
Article
Odonata species are particularly sensitive to human disturbances. Their diversity relative to four landscape types (plantation forest, parkland, residential area, industrial area) along a small river (the Dorpspruit) that runs through Pietermaritzburg, South Africa, is described. Individual species-environment relations were investigated using the multivariate analysis package CANOCO. Four biotope types were identified and characterised. The analysis also illustrated the extent to which the urban, suburban and forestry environments affected the Odonata species. Multispecies assemblages were good environmental indicators. Individual indicator species included Chlorolestes tessellatus and Crocothemis erythraea. Chlorolestes tessellatus is a good indicator of the minimal width (> 30 m) of the indigenous strip of riparian vegetation between the stream edge and commercial plantations. This study suggests that there should be a riparian strip between the water's edge and plantation trees of at least 20 m (preferably 30 m). This finding is integrated with earlier ones to arrive at a general conservation management recommendation, at least for dragonflies, for rivers in South Africa.
Article
A large pond at the National Botanical Gardens, Pietermaritzburg, South Africa was created as part of an ecological landscaping urban project for plant and insect conservation. Biotope preference by resident adult male dragonflies was used to determine the conservation value of the created conditions. Various biotopes were created to cater for the apparent preferences of adult male dragonflies. Stenotopic species were highly sensitive to a number of factors such as sunlight or shade, to still or flowing water, and to vegetation structure. The provision of a wide range of appropriate biotopes was shown to increase local species richness more than two-fold, but with loss of one riverine species that was formerly present. Most of the colonisers were eurytopic and vagile, but some were more local, stenotopic species.
Article
This paper presents a new and simple method to find indicator species and species assemblages characterising groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomisation procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the clssification method. Because indicator species give ecological meaning to to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level
Article
Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.
Article
The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community. This may not happen if gradual changes in climate favor different species. If equilibrium is reached, a lesser degree of diversity may be sustained by niche diversification or by a compensatory mortality that favors inferior competitors. However, tropical forests and reefs are subject to severe disturbances often enough that equilibrium may never be attained.
Threat levels to odonate assemblages from invasive alien tree canopies. Pages 209-224 in A. Codero Rivera, editor. Forests and dragonflies
  • M J Samways
Samways, M. J. 2007. Threat levels to odonate assemblages from invasive alien tree canopies. Pages 209-224 in A. Codero Rivera, editor. Forests and dragonflies. Pensoft, Sophia, Bulgaria.
Forests and dragonflies Vanishing waters
  • Cordero Rivera
  • A Pensoft
  • Sophia
  • Bulgaria
  • D Davies
  • J Day
Cordero Rivera, A., editor. 2006. Forests and dragonflies. Pensoft, Sophia, Bulgaria. Davies, D., and J. Day. 1998. Vanishing waters. University of Cape Town Press, Cape Town, South Africa.
Allochthonous organic matter as a food resource for aquatic invertebrates in forested streams
  • M A S Graça
Graça, M. A. S. 2006. Allochthonous organic matter as a food resource for aquatic invertebrates in forested streams. Pages 37-47 in A. Codero Rivera, editor. Forests and dragonflies. Pensoft, Sophia, Bulgaria.
Forests and dragonflies. Pensoft
  • A Cordero Rivera
Cordero Rivera, A., editor. 2006. Forests and dragonflies. Pensoft, Sophia, Bulgaria.
Niche specialisation in dragonflies
  • Sternberg
Sternberg, K. 1994. Niche specialisation in dragonflies. Advances in Odonatology 6:177-198.
University of Cape Town Press
  • D Davies
  • J Day
Davies, D., and J. Day. 1998. Vanishing waters. University of Cape Town Press, Cape Town, South Africa.
The importance of forests to neotropical dragonflies. Pages 79-101 in A. Codero Rivera, editor. Forests and dragonflies
  • D Paulson
Paulson, D. 2006. The importance of forests to neotropical dragonflies. Pages 79-101 in A. Codero Rivera, editor. Forests and dragonflies. Pensoft, Sophia, Bulgaria.