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Identifying high-quality pond habitats for Odonata in lowland England: Implications for agri-environment schemes
Abstract
1. Agricultural intensification has contributed to severe declines in odo-nate (dragonfly and damselfly) populations. The objective of our study is to benefit current measures for the conservation of odonates by establishing the conditions favourable to Odonata and focusing on ponds within agricultural land. 2. Our landscape-scale study used exuvial counts and habitat measurements from 29 ponds across a catchment in England, over 3 years, to determine key factors affecting odonate abundance and species richness. 3. Ponds dominated by floating and submerged vegetation were the most transpar-ent, supported the highest abundance and species richness of exuviae, and were always fully or partially surrounded by buffer strips. Ponds lacking vegetation were turbid, yielding no exuviae even if they were buffered. English agri-environment schemes (AES) currently support pond and buffer strip creation and management. 4. Abundance of exuviae was higher in recently created ponds compared to older ponds, whereas ponds that had dried out the previous summer had fewer exuviae. 5. Species richness of exuviae decreased with increasing distance to the nearest via-ble pond, falling by more than 40% for distances over 100 m. 6. We conclude that odonate conservation would be more effective if AES would consider the spatial scale at which ponds are created and the location, type, and quality of ponds targeted for buffer strips.
... In general, species richness of ponds is affected by land-use at different spatial scales (Raebel et al. 2011(Raebel et al. , 2012, ponds represent heterogeneous habitats that can host large numbers of species (Williams 2004;Davies et al. 2007). ...
... In addition, many groups of aquatic organisms are using vegetation structure as indicators of habitat quality (Resetarits 2001;Šigutová et al. 2015). Fish farming management also has an indirect influence on the hydro-physicalproperties such as concentration of dissolved oxygen, and additively enriches the already relatively high water trophy (Raebel et al. 2011;Oertli and Parris 2019). ...
... It is probably related to the fact that farm ponds are artificial habitats that were created to fulfill certain functions, and the protection of biodiversity is usually not the primary goal. A reduction in fish stocking density and a significant change in management on the scale of the entire networks of ponds (pondscapes) are essential to achieve the highest possible biodiversity of freshwater organisms at the local level (Raebel et al. 2011;Lemmens et al. 2013;Briggs et al. 2019). ...
In some European regions, ponds are the dominant freshwater habitat type. The ecological value of ponds is decreasing owing to human activities, including intensive fish farming involving predation pressure from fish, reduction of macrophytic vegetation, high nutrient loads, and turbidity. Studies have shown the negative effects of high fish stocks on the diversity of macroinvertebrates. Nevertheless, the effect of fish predation on invertebrate communities could be strongly influenced by other factors, such as the structural complexity of aquatic vegetation. Consequently, we aimed to analyze the effects of environmental-trait interactions on the responses of amphibians, odonates, aquatic true bugs, and diving beetles that are directly or indirectly related to pond management. Each monitored group reflected very different variables. Odonates were sensitive to variables reflecting the quality of the aquatic environment and the overall landscape structure, and accurately reflected differences in the management intensity of ponds. Amphibians reflected only the landscape structure, while diving beetles reflected the quality of the aquatic environment. The aquatic Heteroptera community structure was very indifferent to the management and habitat quality. With the exception of oviposition strategies, we were unable to identify functional traits that could present adaptive advantages or disadvantages in relation to management intensity. We deduced that fish farming management is a selective mechanism that operates with an enormously high intensity which fundamentally homogenizes the structure of assemblages and therefore there is no morphological or phenological variability among species. It is therefore difficult to implement appropriate management measures that would benefit species across taxonomic groups. The key is to maintain the variability of the ponds and surrounding landscape mosaic. Moreover, farm ponds are secondary habitats whose role in supporting biodiversity may be important but cannot be seen as an equal alternative to natural wetlands.
... The short term stability of the aquatic ecosystems is of crucial importance for the breeding success and generational continuity of populations in most of species 27 . Furthermore, the quality of the terrestrial environment is also important for the populations because it provides habitats for mating, egg laying, feeding, resting and facilitates dispersal 28 . The results show that both local and landscape variables were important for the occurrence and abundance of Odonata. ...
... A longer watercourse network provides an extended habitat which provides more food, more oviposition site and more conspecific females, and higher survival chance. It was reported that in England the number of ponds in the surrounding area had no effect on species richness of dragonflies 28 . However, their largest spatial scale was of a 1600-meter-long radius, contrary to the 5 km long radius scale used in this study. ...
... Species diversity of Zygoptera showed a marginally significant decreasing trend with the increasing forest patch proportion in the surrounding habitat at the small scale (1.25 km). This relationship was underlined in a study where Odonata species richness decreased with increasing amounts of forest, especially on a 200 m scale 28 . Although the role of forests for Odonata has a voluminous literature 5,14,39 the results showed that for the lowland Zygoptera species the increased amount of woodland could be an obstructive factor. ...
Habitat loss and fragmentation causes a decline in insect populations. Odonata (both dragonflies and damselflies) are especially threatened by the destruction of both aquatic and terrestrial environment. Moreover, effects of large-scale habitat heterogeneity on Odonata assemblages are poorly studied. In a two years study along East-European lowland watercourses both aquatic and terrestrial environment were studied to reveal the importance of local (e.g. water depth, macrovegetation cover, etc.) and landscape-scale (e.g. farmland patch size, forest patch proportion, etc.) variables to Odonata (as well as to dragonflies and damselflies separately) through increasing spatial sampling scales. The specimens were sampled using 500 m long transects from May to September. Results, both on local and landscape scales emphasized the importance of terrestrial environment on Odonata. Local variables influence damselflies, while dragonflies are more sensitive to landscape variables. Damselfly’s diversity decreased with increasing macrovegetation cover, while dragonfly’s diversity decreased with the increasing degree of land use intensification, but increased with the length of watercourses. It is thus vital to stress the importance of partial watercourse clearing, and moderate maintenance of traditional farm management based on small parcel farming near watercourses to maintain diverse and healthy Odonata assemblages.
... The most important drivers of dragonfly diversity are vegetation structures (e.g. aquatic and semi-aquatic plants), insolation and water chemistry (Sahlén and Ekestubbe 2001;Mabry and Dettmann 2010;Raebel et al. 2010Raebel et al. , 2012. While a number of studies address the effect of various environmental factors on dragonfly communities and diversity (e.g. ...
... While a number of studies address the effect of various environmental factors on dragonfly communities and diversity (e.g. Schindler et al. 2003;Carchini et al. 2007;Raebel et al. 2012;Goertzen and Suhling 2013;Harabiš and Dolný 2015), the quantitative evaluation of restoration schemes is rare (see also Bried and Samways 2015). However, for conservation practitioners and volunteers, these are the commonly accepted instruments for enhancing dragonfly diversity. ...
... McCauley (2006) and Raebel et al. (2012) showed that isolation, in contrast to connectivity, had a negative influence on dragonfly diversity. To assess connectivity of every pond, we measured the distance to the nearest three water bodies (also including all perennial ponds not assessed by us) in ArcGIS 10.2 and calculated mean distance as a proxy for connectivity. ...
Ponds are home to a diverse community of specialized plants and animals and are hence of great conservation concern. Through land-use changes, ponds have been disappearing rapidly and remaining ponds are often threatened by contamination and eutrophication, with negative consequences for pond-dependent taxa like amphibians or dragonflies (Odonata: Anisoptera and Zygoptera). Increasingly, restoration measures such as removal of shading terrestrial vegetation or submerged organic matter are implemented to counteract current threats, but how these measures affect the target taxa is rarely assessed. We tested if and how simple pond restoration measures affectionate diversity. We propose that pond restoration influences the light regime, which promotes aquatic and riparian vegetation important for different dragonfly life stages, thus increasing their diversity. Additionally, we assume that this changes dragonfly species composition between restored and unrestored ponds. We surveyed exuviae in the riparian and aquatic vegetation along the shore of 29 (12 restored, 17 unrestored) man-made ponds in southwest Germany and assessed environmental variables known to affect dragonfly diversity. We identified the cover of tall sedges and submerged macrophytes as the driving biotic variables for dragonfly diversity and species composition, with restoration measures affecting submerged macrophyte cover directly but tall sedges indirectly via available sunlight. This study demonstrates that simple restoration measures not only have a positive effect on overall dragonfly diversity, but also increase habitat suitability for several species that would otherwise be absent. We therefore propose dragonflies as a suitable flagship group for pond conservation. © 2018 Springer Science+Business Media B.V., part of Springer Nature
... While agricultural intensification has undoubtedly had highly detrimental impacts on biodiversity, our findings offer a glimmer of hope for the restoration of aquatic habitats and macrophyte communities ostensibly lost to agriculture. We demonstrate that buried ghost pond propagule banks can act as a key source of aquatic macrophytes to ponds and other wetlands in modern agricultural landscapes, where dispersal barriers often limit the effectiveness of conventional habitat creation methods (Raebel et al., 2012;Williams et al., 2008). While temporal dispersal is a known mechanism for the persistence of aquatic organisms in extant habitats (Beltman and Allegrini, 1997;Weyembergh et al., 2004), our study is the first to demonstrate at least centennial-scale survival of aquatic plants in 'extinct' aquatic habitats beneath intensively cultivated agricultural fields. ...
... In contrast to the generally observed loss of viable propagules from wetlands due to drainage and lowered water levels (Brown et al., 1997;Stroh et al., 2012), the rapid burial of pond sediments during in-filling appears to effectively conserve long-term propagule viability. Several of the taxa surviving prolonged burial are keystone species; charophytes provide complex habitat structure and promote water clarity (Schneider et al., 2015), and they have become increasingly scarce in lowland agricultural landscapes (Lambert and Davy, 2011), while floatingleaved species like P. natans (Fig. 2d) strongly enhance the diversity of Odonata (Raebel et al., 2012). With UK farmland ponds typically supporting between 6 and 14 aquatic macrophyte species (Davies et al., 2008;Sayer et al., 2012), the 8 species shown here to survive prolonged burial represent a significant proportion of the expected species diversity in these farmland ponds. ...
... Further, in regions where pond conservation strategies exist, including the US (Dahl, 2014), and parts of Europe (Céréghino et al., 2008), prevailing approaches focus on the creation of new ponds (Dahl, 2014;Forestry Commission et al., 2016;Freshwater Habitats Trust, 2015). The success of pond creation relies heavily upon plant dispersal from existing habitats (Raebel et al., 2012;Williams et al., 2008), which may be severely hampered in modern-day, highly fragmented agricultural settings. Ghost pond restoration may therefore provide an effective method of returning lost aquatic habitats and their associated macrophyte communities to agricultural landscapes. ...
The widespread loss of wetlands due to agricultural intensification has been highlighted as a major threat to aquatic biodiversity. However, all is not lost as we reveal that the propagules of some aquatic species could survive burial under agricultural fields in the sediments of ‘ghost ponds’ - ponds in-filled during agricultural land consolidation. Our experiments showed at least eight aquatic macrophyte species to germinate from seeds and oospores, following 50–150 years of dormancy in the sediments of ghost ponds. This represents a significant proportion of the expected macrophyte diversity for local farmland ponds, which typically support between 6 and 14 macrophyte species. The rapid (< 6 months) re-colonisation of resurrected ghost ponds by a diverse aquatic vegetation similarly suggests a strong seed-bank influence. Ghost ponds represent abundant, dormant time capsules for aquatic species in agricultural landscapes around the globe, affording opportunities for enhancing landscape-scale aquatic biodiversity and connectivity. While reports of biodiversity loss through agricultural intensification dominate conservation narratives, our study offers a rare positive message, demonstrating that aquatic organisms survive prolonged burial under intensively managed agricultural fields. We urge conservationists and policy makers to consider utilizing and restoring these valuable resources in biodiversity conservation schemes and in agri-environmental approaches and policies.
... When multiple surveys are carried out, these are normally spread during the season (e.g. Raebel et al. 2012;Golfieri et al. 2016). The rationale behind spreading surveys during the year is to maximize the number of species detected. ...
... Similarly, Hardersen and Corezzola (2014) found that surveying butterflies during a single visit for 75 min resulted in the observation of an average of 76% of estimated total richness. However, normally, sampling regimes for exuviae involve repeated visits to the same site (D'Amico et al. 2004;Giugliano et al. 2012;Raebel et al. 2012;Golfieri Fig Our results showed that for any given total amount of time, a higher number of species was detected when more short surveys were carried out, rather than fewer surveys lasting longer. The difference was most pronounced for the resulting species richness from ten short surveys when compared to the richness estimates achieved by one long sampling event. ...
... Five sampling occasions during the year is also an effort which has commonly been applied. When analysing studies which studied Odonata assemblages by means of exuviae, it was found that five surveys during the year is an average value as most studies repeated searches 2-8 times (Honkanen et al. 2011;Raebel et al. 2012;Giugliano et al. 2012;Subrero et al. 2013;Bried et al. 2015;Golfieri et al. 2016). ...
Freshwater species are in serious decline all over the world. Thus, monitoring of freshwater ecosystems and species is crucial to guide policy actions and dragonflies are generally considered to be good indicators for these systems. The aquatic life stage of the Odonata is inherently more susceptible to changes in water quality than the imago and therefore exuviae give better insights into site-specific effects. However, utilizing exuviae for monitoring purposes introduces a number of problems. For example, they often do not persist long in the environment. Some of these problems have been addressed. However, there are no published data that distinguish the influence of sampling frequency and total sampling effort on the faunal completeness. Also the number of exuviae necessary to define local assemblages has not been investigated. These questions were addressed by analyzing the data on exuviae collected in seven sites and we found that for any given total amount of time invested, it was always preferable to conduct more short surveys, rather than fewer surveys lasting longer. The study also showed that a sample size of 300 exuviae allowed us to reliably estimate the similarity of two assemblages from different sites. However, when collecting 40 exuviae or less, the reliability was low. Based on our findings we recommend sampling exuviae for a minimum of five days, evenly spread out over the entire season during which Odonata emerge, to sample each time for approximately 60 minutes and aim to collect not less than 300 exuviae in total.
... All species recorded here are known to be resident in the area (Samways, 2008). As in other studies, our results emphasize the high value of ponds as contributors to regional biodiversity (Briers and Biggs, 2005;Davies et al., 2008a;Kietzka et al., 2015;Indermuehle et al., 2004;Raebel et al., 2012b;Williams et al., 2003). Furthermore, and importantly, our results showed the equivalence of the protected area (PA) and the agroforestry mosaic, with its ecological network (EN), in terms of species richness (with ¾ of all species shared between them). ...
... Furthermore, large mammals (particularly hippos and elephants) are engineering these water bodies, creating channels and removing vegetation from the edge, provided their populations do not get too high, will they will continue to positively influence the dragonfly diversity (Samways and Grant, 2008). Finally, there is the option to create artificial ponds (Declerck et al., 2006;Raebel et al., 2012a) to reduce distance to water bodies, which has an influence on dragonfly communities (Raebel et al., 2012b). This will allow less mobile species to disperse more easily across a greater spatial scale. ...
... Furthermore, these wallows were small in size and had almost no vegetation. This is consistent with the results of Kadoya et al. (2004), Smith et al. (2007 and Raebel et al. (2012b), who showed that freshwater quality and thus dragonfly species diversity, results, among other variables, from the richness and structural complexity of the vegetation which increases the microhabitat diversity. In addition, the oftentimes temporal character of wallows only permits rapidly growing (as larvae) and readily dispersing species to complete a full life cycle e.g. ...
Freshwaters are highly threatened ecosystems, with agro-forestry being a major threat to subtropical wetlands. In the Maputaland–Pondoland–Albany global biodiversity hotspot of South Africa, large-scale ecological networks (ENs) of remnant vegetation have been set aside with the aim of mitigating the adverse effects of plantation forestry. However, the effectiveness of these ENs for maintaining freshwater biodiversity, especially that of still waters, is poorly known. In response, we compare mud wallows of large mammals, ponds and small marshes in an EN with those in an adjacent World Heritage Site protected area (PA) as reference. For this comparison we used dragonfly adults in view of their effectiveness as bioindicators. A total of 47 species was recorded at 105 sites. The EN shared 74% of its species with the PA. However, equal numbers of range restricted species were recorded from the EN and the PA. Five species were recorded as particular to the EN and seven to the PA, probably due to habitat heterogeneity across this type of landscape. Pond size, habitat heterogeneity, elevation and dissolved oxygen were important determinants for species richness and diversity. Proximity of plantation trees had only a minor effect, and then only on species composition. Mud wallows were the poorest habitat in terms of dragonfly diversity, owing to the intense disturbance. Wallows, ponds and marshes were largely complementary in their species composition. Overall, the freshwater system in the EN was a good surrogate for that in the PA, indicating the effectiveness of these ENs for maintaining the dragonfly assemblage.
... Fishponds can support highly diverse local odonate communities and both fishponds and sandpit ponds can harbour rare species (Buczyński, 1999;Hassall et al., 2012). However, most odonate species prefer vegetated, fishless waters and avoid habitats in which fish occur at high densities (Wellborn et al., 1996;Raebel et al., 2012). We thus expected that (i) all else being equal, the highest species richness will be found in sandpit ponds in an ongoing successional stage with well-developed aquatic vegetation and without fish, (ii) sandpit ponds in an early successional stage will support specialist species preferring habitats without aquatic vegetation, and (iii) community composition will be strongly associated with the extent and type of littoral vegetation. ...
... Fishponds are an integral part of the pondscape in many parts of the world. They can support high species richness (Hassall et al., 2012;Le Gall et al., 2018;Raebel et al., 2012). However, most fishponds in Central Europe are intensively managed, and many of them are used for the production of marketable fish in two-year cycles (Francová et al., 2019;IUCN, 1997). ...
Man-made freshwater habitats are an important part of the European landscape, especially in areas with mostly absent or degraded natural habitats. To assess the role of different man-made standing waters in anthropogenic landscapes, we surveyed adult odonate communities in a cluster of 20 water bodies including fishponds and sandpit ponds in early and ongoing successional stages. We found 35 odonate species (i.e., 47% of the fauna of the Czech Republic), but their presence differed significantly among the three habitat types. The highest species diversity, driven mainly by the presence of generalists, was found in fishponds. Sandpit ponds in an early suc-cessional stage hosted the least diverse communities dominated by pioneer and vagrant species. Specialist species occurred in both types of sandpit ponds, especially those in an ongoing successional stage, more than in fish-ponds. Although the dragonfly biotic index did not differ among the three types of localities, all four species from the national Red list recorded during the study occurred only in sandpit ponds. The main environmental drivers of local odonate communities included the coverage of shoreline by emergent vegetation, water depth and bottom substrate; the latter two characteristics largely corresponded to the distinction between sandpit ponds and fishponds. We conclude that both sandpit ponds and fishponds play an important role in maintaining freshwater biodiversity that requires a mosaic of habitats in different successional stages.
... Since algal mats and other aquatic vegetation shared relative importance within models and had similar coefficients (data not shown), our findings suggest that aquatic vegetation structure was important in predicting dragonfly abundance, but not species richness. In other studies, however, increased macrophytes are associated with increases in dragonfly species richness (Clark & Samways, 1996;Clausnitzer, 2003;Raebel et al., 2012;Sahlén & Ekestubbe, 2001). In our study, aquatic vegetation effects on species richness may have been masked by the relationship between canopy cover and aquatic vegetation. ...
... In our study, aquatic vegetation effects on species richness may have been masked by the relationship between canopy cover and aquatic vegetation. Other studies show that the increased availability of oviposition substrates, prey breeding grounds, and hiding locations associated with increased macrophyte density in ecotones better predicts dragonfly abundance (Clark & Samways, 1996;Clausnitzer, 2003;Foote & Hornung, 2005;Raebel et al., 2012). ...
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.
... During their complex life history, odonate species need both aquatic and terrestrial habitats for their larval and adult life stages. The use of adult odonates as indicator species can reflect not only the condition of ponds (Angélibert et al. 2010;Dolný et al. 2014) but also the condition of the surrounding terrestrial habitats interrupted by human activities (Simaika and Samways 2011;Raebel et al. 2012). In the present study, adult odonate biodiversity was investigated to understand their relationship with pond management practices and environmental conditions in a rapidly urbanized landscape. ...
... The floating and emergent macrophytes can provide a suitable habitat for various aquatic macroinvertebrate activities, such as foraging, breeding, and predator avoidance (Thomaz and Cunha 2010). Ponds with macrophytes were positively associated with odonate diversity and abundance (Carchini et al. 2007;Honkanen et al. 2011;Raebel et al. 2012;Le Gall et al. 2018). In this study, aquatic macrophytes were found to be major factors contributing to the Odonata composition of the 24 ponds studied. ...
Adult odonate biodiversity was investigated to understand their relationship with pond management practices and environmental conditions in a rapidly urbanized landscape. Twenty-four farm ponds in Taoyuan City were selected and classified into five pond groups based on pond management practices. In total, 21 species, 17 genera, and 6 families of odonates were recorded for a total of 5701 individuals between June 2014 and July 2015. The abundance of Odonata was unrelated to pond size or distance to the nearest pond; however, odonate species richness was negatively and significantly correlated with pond size. Pond management practices considerably affected pond aquatic macrophytes and dike construction materials. Ecology park ponds under intense human management and undisturbed ponds without any human management had higher species richness than did the ponds in the other three fish farming groups. Species richness was highest in small and human-modified ponds. By contrast, species richness was lowest in two fish farming pond groups. These results suggest that pond management practices can increase or reduce odonate species richness depending on the alteration of pond microhabitat features. Our observations suggest that the enhanced habitat quality of small ponds provides an opportunity to protect freshwater biodiversity for local governmental civil servants in urbanized landscapes.
... This suggests that other variables not considered in our study are involved in predicting odonate richness. The effects of human activity on odonate populations have been documented in lentic (standing) waters in temperate zones (Findlay & Houlahan, 1997;Hamasaki et al., 2009;Hall, McCauley, & Fortin, 2015;Raebel et al., 2012), but rarely in tropical zones and lotic systems (Monteiro- Junior, Juen, & Hamada, 2015). Anthropogenic disturbance in the form of, for example, road construction, may have significant effects on wetlands biodiversity (Findlay & Houlahan, 1997). ...
... On one hand, stressors in the aquatic environment are usually agrochemicals which in many cases increase eutrophication or decrease macrophyte presence (e.g. Kadoya et al., 2011;Raebel et al., 2012;Weisner et al., 2007). On the other hand, stressors such as the reduction of tree cover imply a number of negative actions for odonates such as: fewer perching refuges for resting and predation protection, less available food, increased sun exposure and less humidity. ...
It is unclear how land use change, reduction in tree cover and human footprint impact species occurrence and co-occurrence especially at a large regional scale. This is particularly prevalent for species with complex life cycles, for example odonates (dragonflies and damselflies). We evaluated richness of odonates in Mexico in terms of land use, tree cover and human footprint. We also analyzed how odonate species co-occur to interpret our richness analysis using a community perspective. We used odonate collecting records from year 2000 to 2014. Odonate geographical records were more abundant in forest and agricultural areas, and decreased in areas without vegetation. Although our results may suffer of incomplete samplings, there was a positive relationship between species richness and tree cover, and a quadratic relationship with human footprint was observed. These results indicate that some degree of forest disturbance may still sustain relatively high odonate richness levels. Finally, species tend to co-occur in particular ensembles with some species being key in their ecological communities. Further studies should detail the role these key species play in their environments to provide community stability.
... Freshwater research has, to a large extent, focused on rivers and lakes while smaller water bodies, such as ponds, despite often being present at high densities in the landscape, have generally been undervalued by scientists and conservationists alike (Collinson et al. 1995;Angelibert et al. 2004;Biggs et al. 2005;Oertli et al. 2009). This trend is starting to change, however, with recent conservation biology and landscape and dispersal ecology studies focusing on ponds (De Meester et al. 2005;Raebel et al. 2011;Sayer et al. 2012;Hassall & Anderson 2015;Hill et al. 2016;Heino et al. 2017;Vad et al. 2017). In particular, a number of studies have highlighted the value of ponds for supporting species of conservation concern in Europe such as great crested newt Triturus cristatus (Griffiths & Williams 2000;Edgar & Bird 2006;Gustafson et al. 2009), common spadefoot toad Pelobates fuscus (Nystrom et al. 2002;Rannap et al. 2009), crucian carp Carassius carassius (Copp et al. 2008;Sayer et al. 2011) and European otter Lutra lutra (Ruiz-Olmo et al. 2007;Almeida et al. 2012). ...
... While fish occurrence in shallow lake studies has almost always been determined via active sampling, for ponds fishes have generally been recorded by casual field observations, landowner interview and inadvertently via invertebrate surveys (e.g. Ruggiero et al. 2008;Le Viol et al. 2009;Raebel et al. 2011;Jeliazkov et al. 2014). Such an approach is likely prone to underestimating the occurrence of pond fish, especially less visually evident benthic species such as crucian carp and tench. ...
Traditionally, fish have been neglected in pond ecology and conservation studies and it has frequently been assumed that they have a detrimental impact on pond biodiversity and ecosystem function. In order to assess the consequences of fish for pond biodiversity and ecosystem structure we sampled a set of 40 small farmland ponds (20 with and 20 without fish) in eastern England and compared their water chemistry as well as assemblage characteristics (abundance, diversity, species composition) for three biological groups: cladocerans (zooplankton), water beetles and macrophytes. Water depth was significantly greater in fish ponds, while pond bottom oxygen levels and pH were significantly higher in the ponds without fish. The presence of fish significantly reduced the abundance of macrophytes and altered the community composition of cladocerans and macrophytes, but had no detectable influence on water beetles. Variation partitioning using environmental and spatial variables, indicated that all three biological groups were spatially structured. The inclusion of fish, however, reduced the importance attributed to space in the case of both cladocerans and macrophytes, suggesting that space effects for these two groups were at least partly the result of a spatially structured predator (i.e. fish). In most cases fish did not have an effect on cladoceran and water beetle alpha diversity (number of species, Shannon’s and Simpson’s index), although the opposite was true for macrophytes. Nevertheless, at the landscape level, gamma diversity (i.e. total number of species) was enhanced for all three biological groups. Our results suggest that fish, at least small, typical, pond-associated species, are an important component of heterogeneity in farmland pond networks, thereby increasing landscapescale diversity across several faunal and floral elements. Consequently, we propose that fish should be more fully included in future pond biodiversity surveys and conservation strategies.
... At 4 km resolution, many New York sites within the same preserve had the same precipitation and temperature data, but these data could still be useful in explaining community differences among the preserves. Nearest distance to water and total area of waterbodies in the surrounding landscape may influence adult odonate occurrence and diversity patterns (Raebel et al., 2012;Harms, Kinkead & Dinsmore, 2014). Nearest distance to a wetland and the total area of wetlands at nested buffer scales (0.1, 0.5, 1.0, 2.0 km) from the study site perimeter were extracted from National Wetlands Inventory data. ...
... For example, one might ignore all covariates except WetArea500 for New York total damselflies because D i > 2.0 for all other covariates. Area of water in the surrounding landscape may indeed influence adult odonate species occurrence and local diversity (Raebel et al., 2012;Harms et al., 2014). This model, however, did not have a large normalised weight (38%), the null model ranked second, and most remaining models landed in the grey zone. ...
Species occurrences have multiple ecological states that may strongly influence community analysis and inference. This may be especially true in freshwater systems where many animals have complex life cycles with adult dispersal and juvenile resident stages. The effects of ecological state variation on standard empirical approaches are largely unknown. Here, we analysed the effects of natal resident versus non-natal immigrant species occurrence on community-level environmental gradient modelling and spatial–environmental hypothesis testing using adult dragonflies and damselflies as model taxa. Resident and total (resident + immigrant) occurrences of these taxa responded to different sets of environmental variables and resident occurrences reduced model selection uncertainty in 75% of test cases. Effects of environmental gradients, spatial gradients or both were observed in residents but not immigrants, and supported predictions of dispersal limitation and niche-based species sorting often implicated for structuring freshwater communities. These results indicate that resident-only analysis of the dispersal stage should improve multi-model inference and detection of spatial–environmental effects in freshwater community ecology. The species resident–immigrant dichotomy neglects population dynamics and individual variation yet apparently marks an ecologically significant boundary that scales up to influence community-level occurrence patterns.
... The relationship between the abundance of M. marcella and transparency was present in most of the wetlands. Raebel et al. (2012) found that greater transparency increases the abundance of odonates. This may be due to better water quality , the relationships may be due to the presence of aquatic macrophytes, which provide resources for odonates and their prey (Brito et al. 2021). ...
This study aims to assess the physicochemical characteristics regulating the distribution and abundance of M. marcella larvae in six wetlands in the northern Colombia. Standardized techniques for collecting invertebrate and physicochemical data were used in 29 sampling points in an intraannual period. Mean pH and temperature oscillated in narrow ranges within wetlands (7.7 ± 0.09–8.6 ± 0.07; 28.1 ± 0.29–32.8 ± 0.17 °C, respectively), whereas ammonium concentrations and conductivity exhibited a wide variation (0.2 ± 0.03–2.8 ± 0.54 mg NH4 L⁻¹; 861 ± 30.7–19254 ± 1706 µS cm⁻¹, respectively). A total of 2586 individual M. marcella larvae were collected. Abundance was greater in wetlands influenced by the Magdalena River, with 19.4 ± 1.7 and 9.3 ± 1.4 individuals; followed by wetlands hydrologically influenced by seasonal runoff, with 8.1 ± 0.4 and 6.4 ± 0.4 individuals; and lowest in wetlands with influence of the Caribbean Sea, with 3.9 ± 0.3 and 0.3 ± 0.1 individuals. Abundances of M. marcella larvae exhibited similar variations at different months during the sampling period. Abundance and distribution of M. marcella larvae in wetlands of northern Colombia is strongly dependent on water conductivity, transparency and alkalinity. This study evidence that Odonata larvae are a valuable tool as bioindicators for wetland assessment and monitoring.
... Odonates are useful habitat quality indicators in a variety of ecosystems (Butler & deMaynadier, 2008;Chovanec et al., 2002;Flenner & Sahlén, 2008;Raebel et al., 2012;Remsburg & Turner, 2009) and have been used to study urbanization effects on freshwater faunae (Villalobos-Jiménez et al., 2016). The effects of urbanization on odonate assemblages have been studied in the Tropics (Abdul et al., 2017;Monteiro-Júnior et al., 2014), but most of our understanding comes from temperate regions, such as the United States, Germany, Japan, and South Africa (Villalobos-Jiménez et al., 2016). ...
Urbanization has considerable impacts on stream ecosystems. Streams in urban settings are affected by multiple stressors such as flow modifications and loss of riparian vegetation. The richness and abundance of aquatic insects, such as odonates, directly reflect these alterations and can be used to assess urban impacts on streams. The effects of urbanization on odonate richness and abundance on tropical islands is as yet poorly understood. The objective of this study is to identify the effects of urbanization on stream habitat quality and associated odonate assemblages in Puerto Rico. We sampled 16 streams along a rural to urban gradient in the San Juan Metropolitan Area, where each stream was characterized using the Stream Visual Assessment Protocol (SVAP) for Puerto Rico and by analyzing their surrounding land cover. A 100-m segment of each stream was surveyed to assess adult odonate richness and abundance during the rainy and dry seasons. Adults were identified visually, and their abundance was recorded. Favorable local scale factors, like improved habitat quality, as measured with the SVAP, resulted in higher abundances of odonates. However, regional factors such as percent urban cover did not appear to significantly affect richness and abundances of odonates. Overall, our study indicates that odo-nate assemblages are affected by the loss of habitat integrity, and conservation of tropical odonates may benefit from focusing on local scale factors.
... In principle, there is a spatial component for explaining the structure of bird or Odonate communities throughout a pond complex, with fewer species in water bodies situated too far from other source habitats (Mc Cauley, 2006). For Odonates, Raebel et al. (2011) found that the presence of another wetland in the surroundings of a pond (within 1600 m for Anisoptera, within 100 to 400 m for Zygoptera) could be a necessary condition for reaching high species richness. For each studied pond, we therefore measured the distance to the closest neighbouring water body. ...
Conséquences de la déprise piscicole sur la richesse spécifique des oiseaux et des Odonates dans des étangs de pisciculture français.
Les étangs piscicoles sont des écosystèmes artificiels au sein desquels la biodiversité a été modelée par la pisciculture traditionnelle. Les conséquences d’une déprise piscicole y ont été peu étudiées. Ce travail décrit la variabilité de la richesse spécifique des oiseaux nicheurs et des Odonates, sur des étangs 1) encore gérés par des pisciculteurs, 2) abandonnés depuis 4-10 ans, ou 3) abandonnés depuis plus de 10 ans, en Sologne (région Centre Val-de-Loire ; départements : Cher, Loir-et-Cher, Loiret). La richesse de l’avifaune s’avère être principalement favorisée par le développement des ceintures de végétation aquatique, mais cet effet positif n’a pas été constaté sur les étangs abandonnés depuis plus de dix ans. Quatre espèces, le Fuligule milouin Aythya ferina, le Fuligule morillon Aythya fuligula, le Grèbe à cou noir Podiceps nigricollis et le Phragmite des joncs Acrocephalus schoenobaenus ont été plus fréquemment trouvées sur les étangs encore gérés pour la pisciculture. Trois d’entre elles sont des benthivores, ce constat pouvant refléter un effet de la présence des Cyprinidés sur la productivité primaire de l’écosystème aquatique. Nos résultats suggèrent donc que la déprise piscicole peut être défavorable à l’avifaune, même si des sites de nidification a priori accueillants sont disponibles. Mais l’on doit souligner que les étangs solognots sont de faible productivité piscicole (≤ 150 kg/ ha). Nos observations ne sauraient donc être extrapolées à des étangs de pisciculture intensive. La richesse en Odonates semble dépendre de l’étendue des formations végétales riveraines peu élevées. Aucune des espèces observées ne semble être favorisée par l’absence de Cyprinidés. La préservation des ceintures d’hélophytes bas suffit à maintenir la richesse des étangs, indépendamment de la présence/absence de la pisciculture.
... On the contrary, specialist species have restricted environmental tolerances, which often limit them to particular habitats (Büchi and Vuilleumier 2014;Mykrä and Heino 2017). The landscape context is determinant for odonate assemblages, since some species can respond strongly to habitat and land use changes (Oertli et al. 2008;Raebel et al. 2012b). A general gradient in community composition can be observed, from species inhabiting field ponds to those inhabiting forests ponds, with urban ponds often hosting a mix of both (Le Gall et al. 2018). ...
Ponds are lentic waterbodies with a high conservation value for biodiversity that have long been overlooked by management policies. Recent initiatives aimed to promote the conservation of these ecosystems by restoring or creating new ponds throughout Europe. Therefore, studying responses of aquatic invertebrates to local pond characteristics and connectivity between them is determinant to understand community dynamics and colonization processes of these scattered ecosystems. We studied larval communities of odonates in 20 created or restored ponds to assess their colonization during the first 2 or 3 years. Community dynamics in relation to pond vegetation, landscape context and connectivity with other ponds were also investigated. No difference in species richness was found between restored and created ponds. Most species colonized the ponds during the first year, but a different pattern in colonization was observed between Anisoptera and Zygoptera. Community composition was related to the landscape context of ponds and the time since pond creation or restoration. Abundances were positively related to pond connectivity, especially in the suborder Zygoptera. No relationship was found between vegetation and Anisopteran larvae, while Zygoptera seem more sensible to the vegetation structure due to their endophytic oviposition. This work confirms the high colonization capacity of odonates and shows that creation of new ponds could be as efficient as pond restoration to enhance the conservation of freshwater species. It also highlights that landscape characteristics and connectivity between ponds are determinant to support higher abundances and a posteriori increase population viability at the landscape scale.
... OERTLI et al. 2002, JOHANSSON et al. 2019) and the differentiation of the structure of the accompanying water and marsh vegetation (e.g. SAHLÉN & EKESTUBBE 2001, RAEBEL et al. 2011, GOERTZEN & SUHLING 2013BUCZYÑSKI 2015;HARABIŠ 2016), which can potentially be used by adult odonates e.g. for oviposition and resting, or as a place where larvae can hide (CORBET 1999). The results of the redundancy analysis conducted on the data from the studied mine confirmed that these two factors also affect the diversity of odonate on a local scale (individual ponds located within one complex of post-excavation reservoirs), explaining about half of the variance in the structure of their assemblages. ...
In this study, the species composition and diversity of dragonfly and damselfly assemblages of six post-mining ponds differing in habitat conditions, located within a single sand pit in the central part of the Sandomierz Forest (SE Poland) were assessed. In total, 42 species were recorded in 2019, including 35 species considered resident to the site. In the six studied ponds, a range of 8 to 30 species were recorded, including 5 to 26 resident species. In each pond, at least one unique species was found, and one-third of all species were confined to single ponds only. As a result, the qualitative (Jaccard) and quantitative (Bray-Curtis) similarity indices between the pairs of ponds were low, reaching 12-61% and 19-53%, respectively. Thus, despite a lack of distinct barriers and negligible distances between the ponds (max. 350 m), the structure of assemblages in adjacent water bodies differed considerably. This is probably largely due to the habitat selectivity of species. A redundancy analysis (RDA) showed, that factors such as area and plant diversity of the pond were shaping odonate assemblages, explaining 49.1% of the total variance in the dataset. Due to the high species richness and the identification of several species of special concern, the studied sand pit should be considered a valuable secondary habitat for odonates, which – after termination of exploitation – should be regarded as a good candidate for a site designated for the conservation of biodiversity.
... As depressional wetlands, playas are highly influenced by land use/land cover in their surrounding watersheds and precipitation availability, which jointly affect the amount of runoff reaching a playa [18][19][20]. Playas in agricultural settings experience inputs of agrochemicals and erosional sediments in runoff [12,14,21,22], and urbanization likewise affects water quality via pollutants [9,23]. However, just as in other parts of the world, some anthropogenic activities can increase the hydroperiod in the wetlands of this region by deepening basins or providing supplemental water, such as from irrigation runoff. ...
In western Texas, most wetlands are fed from precipitation runoff, making them sensitive to drought regimes, anthropogenic land-use activities in their surrounding watersheds, and the interactive effect between these two factors. We surveyed adult odonates in 133 wetlands (49 in grassland settings, 56 in cropland, and 28 in urban areas) in western Texas from 2003–2020; 33 species were recorded. Most species were widespread generalists, but urban wetlands had the highest species richness, as well as the most unique species of any of the three wetland types. Non-metric, multidimensional scaling ordination revealed that the odonate community in urban wetlands was distinctly different in composition than the odonates in non-urban wetlands. Urban wetlands were smaller in surface area than the other wetland types, but because they were fed from more consistently available urban runoff rather than seasonal precipitation, they had longer hydroperiods, particularly during a multi-year drought when wetlands in other land-cover contexts were dry. This anthropogenically enhanced water supply was associated with higher odonate richness despite presumably impaired water quality, indicating that consistent and prolonged presence of water in this semi-arid region was more important than the presence of native land cover within which the wetland existed. Compared to wetlands in the regional grassland landscape matrix, wetlands in agricultural and urban areas differed in hydroperiod, and presumably also in water quality; these effects translated to differences in the regional odonate assemblage by surrounding land-use type, with the highest richness at urban playas. Odonates in human environments may thus benefit through the creation of a more reliably available wetland habitat in an otherwise dry region.
... 280 Anisoptera while 2,739 species in 19 families are under suborder Zygoptera (Silsby, 2001;Kalkman et al., 2008). However, many Odonata species are threatened (Clausnitzer et al., 2009) due to habitat loss and fragmentation (Raebel et al., 2011), increased human pressure (Clausnitzer et al., 2009), and climate change (Hassall and Thompson, 2008). For instance, the population of Orthetrum coerulescens declined between 2004 and 2007 due to severe drought during such periods (Herzog and Hadrys, 2017). ...
... developmental rate, seasonal regulation) (Corbet, 1999), while factors such as rainfall play a major role in determining the availability of suitable habitats (Hering et al., 2010). Landscape factors mostly define the quality of terrestrial habitats, which is important for mating, egg-laying, foraging, shelter, and dispersal activities of Odonata (Bried & Ervin, 2006;Raebel et al., 2012a). Landscape structure can also influence the quality and stability of water resources that are of crucial importance for breeding success and generational continuity of Odonata populations (Tang et al., 2005). ...
1. Freshwater habitats are among the most threatened and least studied habitats in arid regions of Iran. Discovering factors responsible for the spatial variation of biodiversity are one of the main considerations in conservation biology. As a first step towards developing conservation strategies, we aimed to investigate the beta diversity and response of Odonata assemblages to climate and landscape variables in arid and semi‐arid regions of Iran.
2. A total of 120 water bodies were surveyed. The beta diversity distance matrices were calculated for Odonata, Anisoptera, and Zygoptera, using the Jaccard dissimilarity coefficient. Also, the replacement and richness difference components of Odonata beta diversity were computed. Each of the five dissimilarity matrices was modelled by generalised dissimilarity modelling (GDM).
3. We recorded 58 species of Odonata that represent 58% of the Odonata species in Iran. The average total beta diversity was high (0.873). GDMs results showed that the most influential variables varied between the replacement and richness difference components of Odonata beta diversity as well as between the two Odonata suborders. Anisoptera were most strongly affected by the temperature annual range, while the most important variable for Zygoptera was the average wind speed in April.
4. Our results suggest that the studies of the drivers of biodiversity patterns benefit from beta diversity partitioning also from comparing species groups with different ecological preferences. The high biodiversity of the studied water bodies as well as the anthropogenic and climate threats that they are faced with, make these ecosystems a conservation priority.
... Knowledge of odonate habitat preferences and movement patterns is needed to support management schemes for ponds and improve connectivity between them (Khelifa, 2019;Maynou et al., 2017;Raebel et al., 2012). Females were already known to travel further from their natal sites than males (Dolnỳ et al., 2014). ...
1. Local movements of aquatic insects within the surroundings of waterbodies aim essentially to find food, mates, resting sites, or avoid predation. Distances moved are very variable among species and may also differ depending on sex or age at the intraspecific scale. Despite a large panel of studies on odonate activities near wa-terbodies, little is known about their movements and behaviour in the surrounding landscape matrix. This knowledge is, however, crucial to support management schemes of pond networks and allow improvement of connectivity between them.
2. In this study, 87 individuals of the large dragonfly Anax imperator were identified with a unique code on the wings and monitored visually on five ponds during summers 2017 and 2018. Simultaneously, 54 individuals were equipped with radio transmitters and tracked for up to 15 days.
3. We built Cormack Jolly Seber models to test which factors are important for movement and survival of individuals, and calculated home ranges. Additionally, we performed a step selection analysis on the telemetry data to identify the terrestrial habitats selected by A. imperator at the interface between a rural area and a suburban area in northwestern France.
4. A reduction of the survival rate was observed on the day immediately following capture regardless of the marking method. Individuals equipped with radio transmitters had a lower estimated daily survival (0.78; 95% confidence interval = 0.70-0.85) compared to wing-marked individuals (0.89; 95% confidence interval = 0.85-0.92). Wing loading and age were the main variables influencing dragonfly survival for both methods.
5. The probability of movement between ponds was similar for both sexes, but radio-tracking data showed that females moved significantly further away in the landscape matrix than males, with one female detected up to 1,902 m away from the release pond. Females also had a larger home range (mean 95% kernel: 50 ha) than males (mean 95% kernel: 5 ha). Reproductive behaviour of males and flying behaviour of females were positively related to air temperature. Individuals of both sexes were present on ponds more often than in all other habitats whatever their activity. High trees were the preferred place to rest when air temperatures were low, especially for females.
6. Overall, this study highlights the importance of integrating neighbouring trees in management schemes of ponds. It also confirms that preservation of pond.
... known that adults follow visual cues to detect breeding habitats, and that shorter and scarcer littoral vegetation can be perceived as lower habitat quality, affecting Odonata oviposition and reproduction (Lee Foote and Hornung 2005;Raebel et al. 2012). Furthermore, because dragonflies and particularly damselflies rely on aquatic vegetation for oviposition (Corbet 1980), declines observed in larval odonate richness have been linked to trampling and removal of vegetation from the littoral zone that can interrupt odonate emergence (Lee Foote and Hornung 2005). ...
Herbivory by non-native species can create strong direct and indirect effects on plant and arthropods communities that can potentially cross ecosystem boundaries. Yet, the cross-ecosystems impacts of non-native species are poorly understood. We took advantage of ongoing invasions by non-native ungulates in Patagonia, Argentina, to examine their cross-ecosystem impacts on water parameters, littoral vegetation and aquatic macroinvertebrate assemblages in wetlands. We found a gradient of invasion by non-native ungulates from intact (non-invaded) to highly invaded wetlands. These highly invaded wetlands had ~ 24% less vegetation cover, which was 72% shorter in height than vegetation in intact wetlands. As a result, the abundance of predatory macroinvertebrates such as Odonata (dragonflies) was reduced by ~ 90%; while Diptera were ~ 170% more abundant, and Oligochaeta were recorded mostly at invaded sites. In contrast, we did not find evidence that non-native ungulates altered water parameters. Understanding the indirect consequences of invasive non-native species is crucial for quantifying the real impacts of global change. Our results show strong cross-ecosystem impacts of non-native ungulates on macroinvertebrate wetland communities, highlighting the importance of indirect interactions beyond ecosystem boundaries.
... The habitat heterogeneity hypothesis proposes that more heterogeneous habitat provides greater multidimensional niche space that can hold a higher diversity and abundance of organisms (MacArthur and MacArthur 1961). This scenario was found in the Forested Habitat, with its greater structural diversity in riparian vegetation that helps maintain high Odonata population sizes, because it affords greater protection against predators (Braccia et al. 2007;Luke et al. 2017;Raebel et al. 2012), a greater variety of prey and hunting habitats (perches) (Foote and Hornung 2005), and mating and oviposition sites (Corbet 1999). The more favorable conditions offered by the Forested Habitat are linked to a greater survival rates, life expectancy and odds of recapture in this Odonata population (Tables 1, 2). ...
Land use change, notably the conversion of natural habitats into agriculture, has strong negative effects on wild animal populations. Effects of disturbance and seasonality on demographic parameters of the damselfly Mesamphiagrion laterale Selys, 1876 were assessed to investigate how individual survival probability and over population size changed according to season and anthropogenic disturbance (agricultural habitat vs. forested habitat). For each habitat type, forest cover, area covered by vegetation, percentage of macrophytes and water physicochemical attributes were measured. Likewise, population parameters such as sex ratio, population size, life expectancy, survival and recapture rates were estimated using Cormark-Jolly-Seber (CJ-S) models. Life expectancy of the total population was lower during the rainy season, while population size and survival in males were lower in agricultural habitats during this same season. Human activities related to agriculture and livestock production in the Colombian Andes threaten the long-term viability of odonate populations through degradation of aquatic habitats. Contrary to our initially proposed hypotheses, these effects were more intense for males due to their closer association with riparian vegetation and thus greater exposure to aquatic pollutants.
... Coenagrion puella 169 ± 22 m (Conrad et al. 2002) High quality ponds and connecting habitat (Raebel et al. 2012) 1 year (Lowe et al. 2009) 3.85 (SD 2.89) clutches of 250 (± 150) eggs (Banks and Thompson 1985) with high spatial bias. As no duplicate records were found in these different databases, they were considered to be independent. ...
Connectivity is vital for the maintenance of spatially structured ecosystems, but is threatened by anthropogenic processes that degrade habitat networks. Thus, connectivity enhancement has become a conservation priority, with resources dedicated to enhancing habitat networks. However, much effort may be wasted on ineffective management, as conservation theory and practice can be poorly linked. Here we evaluate the success of landscape management designed to restore connectivity in the Humberhead wetlands (UK). Hybrid pattern-process models were created for six species, representing key taxa in the wetland ecosystem. Habitat suitability models were used to provide the spatial context for individual-based models that predicted metapopulation dynamics, including functional connectivity. To create models representing post-management conditions, landscape structure was modified to represent local improvements in habitat quality achieved through management. Models indicate that management had limited success in enhancing connectivity. Interventions have buffered existing connectivity in several species’ habitat networks, with inter-patch movement increasing for modelled species by up to 22% (for water vole, Arvicola amphibius), but have not reconnected isolated habitat fragments. Field surveys provided provisional support for the accuracy of baseline models, but could not identify predicted benefits from management interventions, likely due to time-lags following these interventions. Despite lacking clear empirical support as yet, models suggest the management of the Humberhead wetlands has successfully enhanced the landscape-scale ecological network, achieving management targets. However we identify key limitations to this success and provide specific recommendations for improvement of future landscape-scale management. Our developments in model application and integration can be developed further and be usefully applied to studies of species and/or community dynamics in a range of contexts.
... Coenagrion puella 169 ± 22 m (Conrad et al. 2002) High quality ponds and connecting habitat (Raebel et al. 2012) 1 year (Lowe et al. 2009) 3.85 (SD 2.89) clutches of 250 (± 150) eggs (Banks and Thompson 1985) 1 3 with high spatial bias. As no duplicate records were found in these different databases, they were considered to be independent. ...
Connectivity is vital for the maintenance of spatially structured ecosystems, but is threatened by anthropogenic processes that degrade habitat networks. Thus, connectivity enhancement has become a conservation priority, with resources dedicated to enhancing habitat networks. However, much effort may be wasted on ineffective management, as conservation theory and practice can be poorly linked. Here we evaluate the success of landscape management designed to restore connectivity in the Humberhead wetlands (UK). Hybrid pattern-process models were created for six species, representing key taxa in the wetland ecosystem. Habitat suitability models were used to provide the spatial context for individual-based models that predicted metapopulation dynamics, including functional connectivity. To create models representing post-management conditions, landscape structure was modified to represent local improvements in habitat quality achieved through management. Models indicate that management had limited success in enhancing connectivity. Interventions have buffered existing connectivity in several species’ habitat networks, with inter-patch movement increasing for modelled species by up to 22% (for water vole, Arvicola amphibius), but have not reconnected isolated habitat fragments. Field surveys provided provisional support for the accuracy of baseline models, but could not identify predicted benefits from management interventions, likely due to time-lags following these interventions. Despite lacking clear empirical support as yet, models suggest the management of the Humberhead wetlands has successfully enhanced the landscape-scale ecological network, achieving management targets. However we identify key limitations to this success and provide specific recommendations for improvement of future landscape-scale management. Our developments in model application and integration can be developed further and be usefully applied to studies of species and/or community dynamics in a range of contexts.
... Estas variables se encuentran relacionadas, dado que la menor pendiente favorece el asentamiento de plantas acuáticas a través de la reducción de la velocidad de la corriente y el consiguiente aumento en el depósito de sedimentos de grano fino (Nilsson, 1987;Chambers et al., 1991). El efecto positivo de la presencia de plantas acuáticas sobre el número de especies de odonatos se ha señalado en repetidas ocasiones, tanto en medios lénticos (Carchini et al., 2007;Remsburg & Turner, 2009;Raebel et al., 2012) como en ríos (Fulan et al., 2008;Golfieri et al., 2016). Además de su uso como sustrato de puesta para las especies de puesta endofítica (Askew, 2004), la importancia de este tipo de vegetación para los odonatos se relaciona con su papel como refugio para las larvas (Johansson, 2000), especialmente relevante dado que la predación sobre estas puede ser el principal factor que regula la abundancia local de numerosas especies (McPeek, 2008). ...
Los ríos del norte de la provincia de Burgos fueron muestreados en 2019 mediante 52 estaciones prospectadas dos veces (junio-julio y agosto-septiembre) en busca de imagos de odonatos. En ellas se registraron 31 especies, 15 de zigópteros y 16 de anisópteros. Se observó una correlación negativa del número de especies de odonatos con la pendiente del río, y positiva con la presencia de helófitos y de vegetación sumergida/flotante. Estas relaciones se debieron básicamente a la variación en la riqueza de especies generalistas, ya que la riqueza de especialistas fluviales únicamente se relacionó con la presencia de vegetación sumergida/flotante. Se añaden Ischnura pumilio y Gomphus vulgatissimus como nuevas especies para Burgos, y se aportan las primeras citas provinciales para Coenagrion caerulescens en el presente siglo.
... Hofhansl and Schneeweihs (2008) showed that ponds in agricultural areas in Costa Rica had a higher Odonata species richness and supported more individuals than ponds in forest sites. Similar results have been found by Raebel et al. (2011) and Pires et al. (2013) in England and Brazil, respectively. ...
... It might be due to similar vegetation structure of these two study sites. Study of odonate exuviae is essential to avoid biased surveys in odonates studies because sometimes larvae might be found at water bodies, but no emerging of individuals cannot be identified due to changes of habitat quality (Raebel et al., 2012). Odonates larvae strongly depend on the substratum type such as aquatic vegetation present of the water body (Clausnitzer et al., 2009). ...
The present study was conducted to reveal the odonate diversity and distribution patterns in selected habitats with reference to habitat quality and climate variability in order to determine the conservation status of odonate species and to predict any future threats to odonate assemblages in selected habitats. Odonate assemblages were investigated for six month period at seven different sites in Matara and Hambantota district, Sri Lanka. Their exuviae, key vegetation types, water quality parameters and habitat disturbances were also studied. Climate data from 1998 to 2018 for studied habitats were analyzed. A total 40 odonate species were identified including 11 endemic species. Heat tolerant species and species which can scarcely be seen in dry zone were abundantly recorded at dry zone habitats in the present study. The present study reveals that there might be a significant direct effect of habitat quality on odonate species assemblages and distribution patterns in studied habitats and there might be an indirect effect of climate variability on odonate species assemblages and distribution patterns in studied habitats. Therefore, these data of relationship among odonate species diversity, habitat quality and climate variability in different ecological habitats will useful for conservation of odonates in particular habitats.
... Because these numbers each reflected the abundance of two or more species, any effect of the area of forest may have been offset by differences in ecological properties among the species. Additionally, landscape elements other than forest may be more important for damselflies than for Sympetrum dragonflies, because the former prefer stable water bodies such as high-quality and nearby ponds as alternative habitat (Sugimura et al. 1999;Ozono et al. 2012;Raebel et al. 2012b); coenagrionids, in particular, require these water bodies for overwintering. We could not evaluate the effect of surrounding water habitat because there were few water bodies (other than a river) in the study area. ...
Odonata species can be used to indicate the effects of anthropogenic disturbance on agrobiodiversity. In Japan, populations of some odonate species inhabiting rice paddy fields have decreased strongly owing to their high susceptibility to insecticides, and they therefore need to be conserved. To identify effective conservation strategies, we investigated how agricultural practices (conventional vs. environmentally friendly: EF) and surrounding landscape (area of forest at three spatial scales, namely 50, 100 and 200 m from the edge of the paddy field) influenced the abundance of odonates in rice paddies in Tochigi Prefecture, Japan. Generalized linear mixed-effect models revealed that EF farming increased the abundance of odonate adults and the number of nymphal exuviae, suggesting a strong negative effect of insecticides. The influence of forest area at the local scale on the numbers of odonate adults and nymphal exuviae was small, with the exception of a strong negative influence on adult Sympetrum infuscatum: the presence of a large area of forest within 200 m of the edge of the paddy field reduced their abundance, probably reflecting this dragonfly’s oviposition site preference. Our results suggest that EF farming could generally support the conservation and recovery of local populations of odonates, but its effectiveness potentially varies depending on the ecological aspects of each species.
... Several studies have shown that landscape structure or landscape connectivity may be important factors shaping dragonfl y distribution (e.g. Raebel et al., 2012;Baguette & Van Dyck, 2007). However, such infl uences may be species-and landscape-specifi c, and range from high to negligible ( Baguette & Van Dyck, 2007;Bolliger et al., 2011). ...
Infrastructure is one of the main causes of landscape fragmentation, which results in isolation and loss of populations. Although the negative effect of roads on insects is well documented, only a minority of studies has focused on roads in the contextof barriers to dispersal. Flying species in particular have been neglected. We investigated the effect of a four-lane motorway as a barrier to the movement of an isolated population of the threatened dragonfly Sympetrum depressiusculum in an agricultural landscape in Central Europe. Generalized additive models were used to assess the motorway’s effect on (i) the distribution ofadult dragonflies in patches of terrestrial habitat surrounding their natal site, and (ii) individual flight behaviour (i.e. willingness or unwillingness to cross the motorway). Movement patterns of marked adults throughout the landscape were also investigated. During one season, significantly fewer adults were found at patches located on the far side of the motorway, indicating it has a barrier effect. Observations on flight behaviour revealed no apparent effect of the motorway. The possible barrier effect for the species studied was therefore presumed to be a consequence of road mortality. Our results indicate that the motorway may influence the dispersal of this threatened species of dragonfly, which is a habitat specialist with particular requirements for its terrestrial environment. Negative effects on other species with similar behaviour and strategy can be presumed. When establishing new habitats, carrying out reintroductions or translocations, it is necessary to consider that roadways may reduce population size and affect population dynamics by limiting dispersal.
... In conclusion, we suggest that environmental complexity may be an underlying factor in the population dynamics of tropical damselflies by influencing time of emergence and mortality rates. Our study highlights the importance of habitat complexity and macrophyte populations for the integrity and maintenance of aquatic insect communities, as well as the distribution and occurrence of odonates in relation to aquatic vegetation conservation status and structure (Guillermo-Ferreira and Del-Claro, 2011;Raebel et al., 2012;Oliveira-Júnior et al., 2015). Future studies on habitat complexity are fundamental for better understanding the ecological processes that mediate recruitment and emergence syndromes in Odonata, providing useful information for species conservation and population studies. ...
Environments with higher complexity harbor a greater biodiversity and can directly influence on certain behaviors of aquatic animals. Here, we tested whether habitat complexity predicts odonate larvae emergence and mortality rates by rearing larvae in aquaria with or without artificial complexity. The results show a shorter emergence time in more complex environments, and a higher mortality rate on less complex habitats.
... For macroinvertebrates, these almost exclusively involve the use of a 'pond net' and the application of a sweep sampling technique for a fixed/standardised time period (Oertli et al. 2005;Hassall and Anderson 2015) with sampling effort divided between different habitat units (Gioria et al. 2010;Becerra-Jurado et al. 2012). However, there are a number of specific variations and modifications to the protocol that can be used when sampling particular macroinvertebrate groups, such as Odonata (Oertli et al. 2005;Ruggiero et al. 2008;Raebel et al. 2011) and Chironomidae (Rufer and Ferrington 2008;Michelutti et al. 2011;Ruse 2013). Other protocols have been designed to cover multiple groups, for example, the European Plans d'eau Suisses (PLOCH) sampling methodology focusses on five target groups: aquatic macrophytes, Coleoptera, Odonata, Gastropoda and Amphibia. ...
Ponds are sites of high biodiversity and conservation value, yet there is little or no statutory monitoring of them across most of Europe. There are clear and standardised protocols for sampling aquatic macroinvertebrate communities in ponds, but the most suitable time(s) to undertake the survey(s) remains poorly specified. This paper examined the aquatic macroinvertebrate communities from 95 ponds within different land use types over three seasons (spring, summer and autumn) to determine the most appropriate time to undertake sampling to characterise biodiversity. The combined samples from all three seasons provided the most comprehensive record of the aquatic macroinvertebrate taxa recorded within ponds (alpha and gamma diversity). Samples collected during the autumn survey yielded significantly greater macroinvertebrate richness (76 % of the total diversity) than either spring or summer surveys. Macroinvertebrate diversity was greatest during autumn in meadow and agricultural ponds, but taxon richness among forest and urban ponds did not differ significantly temporally. The autumn survey provided the highest measures of richness for Coleoptera, Hemiptera and Odonata. However, richness of the aquatic insect order Trichoptera was highest in spring and lowest in autumn. The results illustrate that multiple surveys, covering more than one season, provide the most comprehensive representation of macroinvertebrate biodiversity. When sampling can only be undertaken on one occasion, the most appropriate time to undertake surveys to characterise the macroinvertebrate community biodiversity is during autumn, although this may need to be modified if other floral and faunal groups need to be incorporated into the sampling programme.
... Moreover, habitat requirements of odonates often reflect the quality of surrounding environments (Sahlén and Ekestubbe, 2001). Precisely these qualities make dragonflies very good indicators of ecosystem health and its change (Oertli, 2008;Raebel et al., 2011;Remsburg and Turner, 2009). A bit surprisingly, perhaps, recent studies have shown that diversity of odonates may be high in post-mining habitats even relative to that in some very valuable natural habitats such as fens or wetlands Harabiš et al., 2013). ...
A growing number of studies indicate high conservation potential of freshwater habitats occurring in post-mining areas. The overall diversity of these habitats depends on many factors, however, even a high diversity may diminish significantly over time. Therefore, it is difficult to identify and understand the importance of key habitat properties for diversity. Here I present analysis of three studies comparing the diversity of dragonflies and damselflies (Odonata). Each study was performed in different coal mining basins within the Czech Republic (a total of 94 sites). In this analysis, I used generalized linear mixed models and several multivariate methods to analyze the effects of a number of environmental characteristics such as depth, bottom substrate or bank slope, reflecting not only the current quality but also the succession and formation of individual pools. The occurrence of overall 14 nationally red listed species indicates the high conservation value of these habitats, while the 40 species found indicate that these areas contribute significantly to regional diversity. Species richness of individual pools was associated with habitat type (spoil heap vs. mine subsidence) and with several habitat variables, in particular the character of vegetation around aquatic habitats. In conclusion, the results indicate that diversity and species composition are significantly influenced by factors reflecting the formation and subsequent succession of pools. Effective conservation management should concentrate primarily on modifying pools’ initial properties such as bottom substrate. Subsequent management should then sustain landscape dynamics, which means in particular to sustain minor disturbances that subsequently affect vegetation succession and prevent excessive overgrowing of expansive vegetation, as doing so is promoting the habitat heterogeneity which is essential to high biodiversity in these areas.
... Odonata is an insect group of high interest for biodiversity conservation (Clausnitzer et al., 2009), as ecosystem indicators (Sahl en & Ekestubbe, 2001;Acquah-Lamptey et al., 2013), and for environmental education (Niba & Samways, 2006). Odonata declines in Western Europe are mainly attributed to habitat loss and fragmentation, changes in farm management practices, and water pollution/eutrophication caused by use of agrochemical pesticides/fertilisers (Raebel et al., 2012). Mosquito control using Bti should be acknowledged as a non-negligible potential threat to these insects in relatively pristine wetland ecosystems. ...
Bacillus thuringiensis var. israelensis (Bti) has become the most commonly used larvicide to control mosquitoes worldwide. Bti is considered non-toxic to most organisms, except some Diptera such as chironomids, which are a major prey in wetland food webs. Although Odonata are important predators of mosquitoes and chironomids at the larval and adult stages, no study has ever considered the potential indirect effects of Bti on Odonata abundance through trophic interactions. We addressed this topic in the Camargue where 2500 of the 25 000 ha of mosquito larval biotopes are Bti-sprayed (aqueous solution of VectoBac 12AS at 2.5 L ha−1) whenever mosquito larvae appear in water bodies (i.e. 30–50 aerial treatments overall annually). Adult Odonata were surveyed along a 100-m line transect in spring, summer and autumn at three control and three treated sites over a 5-year period. Mean number of species (9.9 vs. 5.2) and of individuals (100 vs. 50) detected per year were significantly higher in control areas compared to Bti-sprayed areas. Bti treatment contributed to 87.3% of the explained variance in Odonata richness, compared to 2.9% for site, 6.8% for year and 3.0% for salinity effects. These results are coherent with other studies carried out in the same area and time period highlighting a lower abundance of chironomids, and a lower intake of odonates by breeding birds in treated areas. We conclude that mosquito control using Bti should be acknowledged as a potential threat to Odonata.
... Agri-environment schemes cost-efficiency can be improved by developing effective support payments for targeted low-intensity farming systems (Warren & Bourn 2011), and by identifying farmland features and management options that are both straightforward to integrate within high-intensity farming systems and beneficial to the overall biodiversity levels (Merckx et al. 2009a;Raebel et al. 2012). The extent to which any overall biodiversity benefit of these farmland features is dependent on the intensification degree of the surrounding landscape (Gabriel et al. 2010) is also important. ...
... It is thus apparent that creation of lower and gentle banks will effectively support stream biodiversity. The character of emergent vegetation has also been recognised as a key factor structuring dragonfly communities in various freshwater habitats (Schouten et al. 2008;Allen et al. 2010;Raebel et al. 2012;Harabiš et al. 2013). Channels overgrowing by common reed substantially decreased both the biodiversity indicators of the local dragonfly communities. ...
Headwaters and small streams are crucial components of riverine systems, harbouring many highly specialized and unique invertebrate species. Unfortunately, the overwhelming majority of the Central European lowland headwaters are channelized, eutrophicated and/or polluted, and many related species have become critically endangered. Artificial streams established to drain some post-mining sites supplement a network of headwaters and generally do not suffer from agricultural pollution. Nevertheless, the biodiversity and conservation potential of the streams at post-mining sites has never been evaluated. We studied the biodiversity of dragonflies and damselflies (Odonata) at 53 sections (30 m) of an extraordinarily dense system of drainage ditches at a large lignite spoil heap in the Czech Republic. We recorded 22 dragonfly species, of which eight are threatened according to the national Red List. Moreover, four of them are closely associated with the endangered environment of small streams. Overall diversity was generally low at very tiny and/or narrowed streams and was also strongly reduced by high water velocity, high bankside inclination and dominance of expansive common reeds. Sufficient cover of rather shallow sediment layers strongly supports the studied diversity indicators. We thus conclude that post-mining streams in drainage ditches could have a strong potential to offer secondary habitats for threatened headwater biodiversity. However, intermittent reed suppression and the establishment of gently sloping banks and a structured stream bottom are necessary measures for maximizing post-mining stream conservation.
... However, large-scale geographical studies of odonate body size suggest that an interaction between temperature and photoperiod-mediated time stress operates in the field to create U-shaped latitudesize relationships (Johansson 2003, Hassall 2013. Odonata also are a model system for a variety of questions in ecology and evolution (Córdoba-Aguilar 2008), including effects of other anthropogenic stressors, such as habitat fragmentation (Watts et al. 2004), environmental pollution (Van Praet et al. 2012), and landuse change (both agricultural: Raebel et al. 2012, andurban: Goertzen andSuhling 2013). ...
Many investigators have described a footprint of global environmental change in macroecological trends across multiple taxa. However, little comparative analysis has been done to evaluate whether some taxa are responding more than others. I tested 2 hypotheses: 1) taxa vary strongly in terms of range shifts and phenological advances in their responses to changing climate, and 2) taxa that shift ranges also advance phenology. I used an initial database of ≥4 million recorded sightings of UK animal species from 24 orders and found descriptions of range shifts for 612 species and phenological trends for 923 species. I compared the 2 responses for 464 species and found wide variation in the extent to which taxa are responding. Vertebrate taxa were the least well recorded and showed weak or nonsignificant responses. Invertebrates were well recorded and responded strongly in range and phenology, but evidence of an association between range shifts and phenological advances was equivocal. My results show that different taxa are exhibiting different responses to the same environmental change, and that mechanistic and traits-based studies may reveal the causes of that variation. Spatial responses may be constrained by mode of dispersal, and insects and arachnids typically respond strongly, whereas terrestrial vertebrates do not. Phenological responses are complex and may involve species-specific physiological relationships between development and seasonal cues. Use of a model taxon could increase efficiency of monitoring regimes by simplifying monitoring targets and techniques. Potential exists for ≥1 taxa to be indicators of climate change, whereby the responses of one or a group of species could be used to infer changes at a broader taxonomic scale. I highlight Odonata as a taxon that responds strongly in multiple modalities, is charismatic enough to appeal to citizen scientists, and is an emerging physiological and genetic model.
There is a consensus that human activities affect biodiversity in pond ecosystems. However, the majority of studies have mainly focused on the direct effect of human activities on a single group, despite the fact that anthropogenically induced biodiversity loss in ecosystems occurs across multiple trophic levels and may depend on both altered habitat (e.g., water chemistry) and on trophic interactions cascading up the trophic network. In this study, we analyzed the simultaneous direct, water-chemistry mediated and trophic network cascading effects of the overall human-impact intensification on density (biomass/abundance) and richness (number of taxa) across all trophic levels in pond ecosystems. For this, we collected and combined multi-taxon data (341 taxa) for macrophytes, phytoplankton, zooplankton, benthic and epiphytic macroinvertebrates, and fishes. We showed that human-impact intensification affected the densities and richness of almost all trophic levels across the study ecosystems, and resulted in an overall negative effect on the multitrophic diversity of the entire community. We detected direct effect of human-impact intensification, but no indirect effects, on the richness of primary producers. In contrast, the indirect effects mediated through the nutrient content in the water were the most influential drivers of multitrophic diversity in the invertebrate communities. At the same time, the indirect effects through the trophic network cascades were detected mainly within the fish community. Our findings improve the mechanistic understanding of multitrophic diversity responses in ponds under the ongoing intensification of anthropogenic pressure.
The enormous ecological and taxonomic variety of aquatic insects, many of them endemic and localised in occurrence in Australia, is still to be appreciated fully. Many of the ‘rarer’ freshwater insects in Australia occupy equally restricted habitats, whose loss and degradation pose the most severe threats to those insects, with many of those threats continuing to increase insect vulnerability.
The vital importance of conserving freshwater ecosystems is acknowledged globally, with the central relevance of environmental flow regimes in running waters emphasised as a core driver of much of their functioning and sustainability of their biota.
In dry areas, natural and artificial ponds experience frequent water level fluctuation, affecting conditions for some aquatic and amphibiotic taxa. Water beetles, bugs, and dragonflies make up much of pond diversity, and are responsive to changes in environmental conditions. Using a drought-prone pondscape within the Greater Cape Floristic Region biodiversity hotspot, we determine (1) the relative extent to which species richness, abundance, and composition are affected by pond water level fluctuation, (2) the effects of environmental variables and vegetation characteristics relative to fluctuating water levels, and (3) make recommendations to improve pondscape conservation. We found that the degree of fluctuation had a significant effect on beetle species richness, but had no significant effect on the other focal taxa. Water temperature, pH, and conductivity, and vegetation cover and composition were drivers of aquatic insect species richness, abundances, and assemblage structures. Habitat heterogeneity supported rich aquatic insect assemblages. We recommend that a range of ponds with various degrees of water level fluctuation should be maintained, along with naturally diverse marginal vegetation. Such a dynamic pondscape can contribute greatly towards maintenance of local and regional aquatic insect diversity in drought-prone regions and should be considered as a main focus in conservation efforts.
Central Iran has been faced with deterioration of water quality and quantity, but yet the biodiversity of freshwater-associated insects in this area remains uncertain and without this information the development of conservation strategies is not possible. Here we explore Odonata diversity patterns and species assemblages in three terrestrial ecoregions of Central Iran. We used the first three Hill numbers and phylogenetic generalizations of these indices to compare the species diversity between the ecoregions. To compare Odonata species composition a PERMANOVA analysis was performed. Alpha-diversity of each water body was estimated by Hill numbers, taxonomic diversity, taxonomic distinctness and average taxonomic distinctness. The effects of habitat and environmental factors on Odonata diversity indices were modelled using a linear mixed model. About 42% of all Odonata that have been reported in Iran were found during this study. Species richness in the Desert and Steppe ecoregions were almost equal, the same pattern was observed for phylogenetic diversity indices. The Steppe ecoregion also had significantly different Odonata assemblage. Results of the linear mixed model showed that environmental factors have different effects on different diversity indices. Additionally different diversity indices resulted in different outcomes when comparing ecoregions, demonstrating that single measure cannot precisely assess the properties of an assemblage’s diversity. The high diversity of Odonata observed in such an arid environment shows the importance of man-made water bodies, as well as the necessity of preparing a conservation plan for these ecosystems.
Species assemblages are related to environmental factors acting at different landscape scales. Local habitat heterogeneity also contributes to maintain the regional species pool. Understanding factors determining species presence is therefore crucial for formulation of successful conservation and management strategies.
Odonates can reveal much about patterns of species assemblages since their presence at a site reflects both their dispersal ability and life cycle constraints. Odonate assemblages were studied at 31 ponds located in three different landscapes: forest, urban and field. The impact of pond geographical distribution and their local characteristics (i.e., vegetation, suspended matter, freshwater macroinvertebrates, pond area and temporariness) on odonate composition, species richness and larval presence were studied.
According to their intrinsic requirements, damselfly and dragonfly presence on ponds depended on local characteristics. Some species of the two orders were only detected in field or forest ponds. Moreover, some species were never detected in urban ponds. Differences in odonate assemblages were mainly related to vegetation, freshwater macroinvertebrates and pond area. Species richness was related to predator abundance and pond area, especially for dragonflies. The presence and abundance of odonate larvae were both related to aquatic vegetation, and to contrasted aquatic variables of ponds. Therefore, this study confirms that vegetation within and around ponds determines odonate presence. Interestingly, in a pond, species detected at the adult stage were not always detected at the larval stage, highlighting the need to really consider both parts of the lifecycle when studying odonate assemblages.
Diversity of local habitats within and around ponds depends strongly on the surrounding landscape and influences the assembly of odonates. Forest and field ponds presented particularly dissimilar species assemblages. Urban ponds had no specific environmental habitats compared to the other contexts. Species present on these ponds are rather generalist and able to support human disturbances. Overall, this study confirms that pond heterogeneity may be a key factor in maintaining the regional pool of odonate species.
Although a full life cycle approach is optimally needed to make conservation decisions, the egg stage is often neglected for insect species of special conservation interest. Water management and related abiotic factors are relevant factors to consider in aquatic species. Lestes macrostigma is a threatened damselfly restricted to temporary brackish waters. Here we provide detailed information on its hatching success and phenology in two natural field populations. Shoots containing fresh egg clutches of L. macrostigma were sampled in late June, just after the oviposition period. In the fall, shoots were separately placed in plastic boxes in two ponds in southern France. Examination of eggs indicated L. macrostigma overwinters at an early embryonic stage. The following spring we monitored hatching in detail. Hatching began on 15 March in both ponds and ended on 27 April. Hatching was synchronized, with half of the eggs hatching within five days in the first pond and 14 days in the second pond. Lower water temperatures decreased hatching success and likely also delayed hatching. Embedment of shoots in ice increased egg mortality. Based on our data, wildlife managers are encouraged to maintain water levels high during winter to reduce the risk of freezing of L. macrostigma eggs.
Odonata are usually regarded as bioindicators and model organisms in many studies and are subjected to increasing threats worldwide. Such insects populate freshwater ecosystems at both natural and urban landscapes and they are also well-known by common people. This work is aimed at summarizing and updating the current knowledge concerning Odonata species inhabiting two parks located at the northern boundary of the Milan outskirts (Italy, Lombardy). Occupancy status for odonate species were obtained merging the field data of surveys conducted during 2014 and 2015 with spare information from specialistic websites and forums, grey literature, and pictures collected at the same sites by occasional observers. The total number of species found in both parks showed an increase of species richness when compared with two previous studies. Morevoer, Odonata communities of the two parks showed a common chorological composition and similarity in the species assemblages. This work had also a positive impact about the perception of urban biodiversity: some of the untrained observers, who shared their pictures for species identification, rapidly acquired sufficient knowledge to easily recognize the most common species present in both parks.
Human demands have led to an increased number of artificial ponds for irrigation of crops year-round. Certain insect species have established in these ponds, including dragonflies (Insecta: Odonata). There has been discussion around the value of artificial ponds for encouraging dragonfly diversity, with little work in biodiversity hotspots rich in rare and endemic species. We focus here on the Cape Floristic Region (CFR) global biodiversity hotspot, which has many endemic dragonfly species but has few natural ponds. Yet it has many artificial ponds mostly used for irrigation on local farms. This leads to an interesting question: to what extent do these artificial ponds provide habitats for dragonflies in this biologically rich, agriculturally fragmented landscape? To answer this, we recorded dragonfly species richness and abundances from 17 artificial ponds and 13 natural stream deposition pools as reference, in an area of the CFR where there are no local, natural, perennial ponds. Thirteen environmental and physical variables were recorded at the ponds and pools. We found that although ponds attracted no rare or threatened dragonfly species, they increased the area of occupancy and population sizes of many generalist species. These came from nearby natural deposition pools or from unknown sources elsewhere in the region, so providing refuges which otherwise would not be there. Interestingly, some CFR endemic species were also recorded at our artificial ponds. Overall dragonfly assemblages and those of true dragonflies (Anisoptera) and
damselflies (Zygoptera) differed between artificial ponds and deposition pools, suggesting
that artificial ponds are to some extent a novel ecosystem. Habitat type, elevation and
temperature were significant drivers in structuring overall species assemblages. For the Anisoptera, riparian vegetation and level of landscape connectivity was important, while temperature was not. In contrast, Zygoptera species were most affected by river catchment, habitat type and temperature. In sum, these artificial ponds are stepping stone habitats across an increasingly fragmented landscape. Managing these ponds with perennial water, constant water levels, and maximum complexity and heterogeneity of habitats in terms of
vegetation will conserve a wide range of generalists and some specialists.
Brackish water ecosystems in estuaries are highly threatened due to land development, the improvement of embankments, and reclamation. Several threatened species of dragonflies and damselflies inhabit these ecosystems. The brackish water damselfly, Mortonagrion hirosei Asahina, 1972, has been an important focus of conservation studies. Here, we describe a conservation project for M. hirosei begun in 2003, and review the data collected in order to quantify details of the species' life cycle, especially larvae and larval environment. An artificially established reed community was created as a habitat for this damselfly, and water depth, salinity, and water temperature in the reed bed were continuously monitored thereafter. Because this damselfly is univoltine, the number and distribution of the odonate larvae in the experimental habitat in May, or presence of last-instar larvae of M. hirosei, were considered suitable indices of colonisation success. Since many odonate adults, including M. hirosei, visited the habitat in the first year and laid eggs, high larval diversity was found in the second year. Although the salinity of water in the reed bed varied because cyclical tidal fluctuations, the saline water gradually excluded odonate larvae that inhabit freshwater only. However, M. hirosei survived, and the larval population increased year by year. Consequently, the odonate larval diversity in the artificial habitat decreased, while the population of M. hirosei was maintained.
The literature on ecological effects of recent climate change in fresh waters has been reviewed, with particular reference to freshwater conservation in the UK. Least emphasis is given to predictive models of future change, because of considerable uncertainties even in the climate models, let alone their biological implications. Climate change effects on fresh waters have been superimposed on existing large human impacts, which make separation of climatic effects particularly difficult. Research in fresh waters has concentrated on communities and processes and there is less emphasis on individual charismatic species than in terrestrial systems. This approach lends itself to space-for-time studies on climate effects. There has been a modest amount of experimentation, particularly in mesocosms, and analysis of long-term biological data sets, the most extensive from lakes. The most detailed information on ecological effects comes from lake plankton. No species is yet known to have been lost from the UK as a result of climate change but there is extensive evidence of changes in phenology and distribution, and in processes in the plankton. It is likely that temperature effects per se will be less important than effects of changed hydrology and that idiosyncratic behaviour of each species will lead to many indirect effects through biological interactions in communities. Experimental studies suggest major likely changes in plant, fish and invertebrate communities with a several degree increase in temperature and associated hydrological changes expected in the 21st century. Freshwater organisms, however, are well adapted to disturbance and through invasion, redistribution, adaptation and microevolution will re-form functioning communities, though with likely different biodiversity than at present. Some invasive species may come to dominate the new communities. There will be important consequences for the estimation of ecological quality, which will inconvenience statutory obligations under the Water Framework Directive, and symptoms of eutrophication will be exacerbated. Some coastal lakes may revert to estuaries. Much more important, however, may be the consequences of climate change for the important part of the carbon cycle that is focussed on fresh waters, particularly if the ratio of community respiration to gross primary production increases with rising temperature. Several studies suggest large increases in this ratio with temperature rises of up to 4 °C. A much more radical approach to conservation, involving re-establishment of entire, connected catchment systems rather than the present piecemeal attention to biodiversity issues is likely to be needed if a comfortable human future is to be guaranteed.
The still-growing effect of human activities on aquatic habitats has led to proportionately increasing need for restoration activities. Paradoxically, restoration actions can constitute a major threat to freshwater assemblages if they do not respect the specific nature of the target biotopes. We investigated the dynamics of dragonfly assemblages in 20 mine-subsidence pools (habitats with very high and very unpredictable dynamics). We
used multivariate methods and diversity indices to compare species richness and species composition of assemblages before and after reclamation actions. During the 10 y of the study, we recorded 10 cases in which aquatic habitats disappeared completely and 6 cases of recovery and successful recolonization of aquatic pools. Disturbances
caused by reclamation actions led to significant reduction of diversity and to extirpation of sensitive dragonfly species. Moreover, unlike natural disturbances, disturbances caused by reclamation activity do not support the occurrence of species associated with early successional stages. Major interventions in freshwater habitats can cause alterations that often paradoxically may result in local extinction of sensitive species rather than strengthening of existing populations.
The paper discusses the role of dragonflies as bioindicators in wetland creation programmes. Two projects are presented: The Tritonwasser Project as an example for a study at a man-made pond which is situated in an urban recreational area; the Marchfeld Canal Project as an example for investigations at an artificial running water with stagnant water sections situated in a region intensively used by agriculture. In both projects counts of dragonflies (as well as of amphibians and birds) are used for long-term monitoring purposes: efficiency control of planning and constructing the waters, description of successional processes, assessment of the ecological capability of the wetlands and deduction of management measures. Results of the first six years (Tritonwasser Project) and five years (Marchfeld Canal Project) of investigations reveal a conclusive relationship between the development of the dragonfly fauna and structural components of the waters (especially vegetation structures) as well as hydrologic conditions. The results obtained so far show that ecologically valuable wetlands can be created even in intensively used areas. Although the preservation of pristine biotopes has to be the first goal in nature conservation, artificial wetlands created along ecological principles may serve as refugia for endangered species.
Fewer than half of the anisopteran odonate species that oviposited in a North Carolina farm pond successfully metamorphosed from that pond. Odonates metamorphosed during two periods: early April though early June, and late May through early September. I used an experiment designed for variance analysis to measure the impact of fish and early-breeding odonates on the abundance and species composition of late-breeding odonates. Odonates recruited naturally in open-topped screened pens that either excluded or contained fish. I placed pens in the pond either during or after the early species breeding season to alter the abundance of larval early breeders. Fish exclusion increased the combined abundances of all anisopteran species 5-10 times above abundances in pens containing fish. However, fish also facilitated the recruitment of one species, Perithemis tenera. Placement of fish exclusion pens in late June instead of early May reduced abundance of early breeders and increased abundances of two late breeders, Perithemis tenera and Pachydiplax longipennis. Early-breeders did not reduce late-breeder recruitment in pens with fish. Abundances of early and late breeders were significantly negatively correlated in pens without fish, but abundances of the same species were not significantly correlated in pens with fish. Different histories of colonization by early breeders influenced interspecific interactions among odonates only if fish were absent. Most variation in the composition of experimental communities was explained by a hierarchy of negative effects of fish on odonate abundance, and negative effects of early-breeders on late-breeders in the absence of fish.
Abstract Odonate,assemblages,were,compared,between,replicate sets of shallow,lakes that had,been,created,and acidified by open-cast mining across a large area (2,451ha) of south- west France (Arjuzanx, Landes); one set of lakes (n 55) was,experimentally,restored,by,liming,with,calcium carbonate, whereas another group (n 55) was left as untreated,reference,lakes. Both,odonate,adults,and exuviae,were,sampled,bimonthly,during,MayAugust 1998. Elevated,turbidity,and,conductivity,in limed,lakes were,the only physicochemical,measures,differing between restored and reference lakes, because deacidification occurred naturally, even in reference lakes during the 17 years after the onset of restoration. Restoration,by liming can apparently,lead to effects on lake turbidity that might be,considered,adverse.,Twenty-four,and,19 odonate species occurred among adults and exuviae, respectively, but,there,were,no,significant,differences,in,richness between restored and reference sites. However, signifi- cantly, more exuviae were collected from the reference sites (588 vs. 180), where exuvial diversity and rank abundance,indicated,more,evenly,structured,assemblages than those in restored,lakes. Ordination,showed,that adult assemblages,differed,significantly,between,restored,and reference lakes, and varied highly significantly with lake turbidity. This effect occurred,because,a small,group,of generally,scarce,adults,were,characteristic,of reference sites (Chalcolestes viridis, Lestes virens, Cordulia aenae, Leucorrhinia albifrons ,a ndSympetrum sanguineum).
1. Freshwater communities are often structured by predation. In permanent lentic freshwater habitats dragonfly larvae are major predators which, in return, suffer predation by fish. Antipredator traits vary between the dragonfly species, and the dragonfly communities are therefore shaped by the presence of fish. But fish communities vary, and as different fish species affect dragonflies in different ways, the species composition of the fish community may affect the composition of the dragonfly community.
2. We sampled dragonfly larvae in 24 lakes with a known fish stock in south-western Sweden, and explored the impact of fish as well as vegetation structure on dragonfly communities by means of multivariate analyses.
3. We found that the presence of four fish species affected the community structure of dragonflies. The impact strength depended mainly on the abundance of Perca fluviatilis, with which most dragonfly species were negatively correlated. Many dragonfly species were also positively correlated with the occurrence of at least one fish species, which may reflect similar habitat requirements or imply indirect positive effects of these fish species.
4. Of the 24 recorded dragonfly species, four did not occur in lakes dominated by P. fluviatilis, whereas only one species was lacking in lakes dominated by Rutilus rutilus. The dragonfly species diversity was higher in R. rutilus lakes than in P. fluviatilis lakes.
5. Our results suggest that the fish species composition is a major determinant of the dragonfly community, which in turn will influence the lower trophic levels.
1.Agriculture is known to have a range of deleterious impacts on freshwater habitats and biota and many countries have introduced measures to attempt to mitigate these impacts through agri-environment initiatives. Despite the protection they provide, water bodies (any discrete body of surface fresh water) in farmland landscapes commonly remain impaired by agriculture. In some areas of the UK there have been calls to halt farming completely, indicating that the measures offered for the widespread protection of aquatic systems, particularly the use of buffer strips, may not be extensive enough to provide sufficient protection for freshwater biota.2.This study investigated whether existing agri-environment measures for the widespread protection of aquatic habitats could be better deployed to provide a higher level of protection for the aquatic macrophytes and macroinvertebrates of a study area in southern England.3.Reserve selection procedures were used to reallocate the area of land that could be remunerated under the Environmental Stewardship scheme as buffer strips bordering water bodies, so that a higher level of protection was provided for both the richness and rarity of aquatic species in the study area.4.Almost 395 ha were available for reallocation in the reserve selection process, which was found to provide a satisfactory level of protection for up to 90% of the surveyed species.5.The results showed that the agri-environment scheme in England has a great deal of potential to provide more effective protection for the aquatic biodiversity of agricultural landscapes if measures are targeted. Copyright © 2008 John Wiley & Sons, Ltd.
A set of 21 ponds was sampled three times for odonate larvae during spring 2002. At the same time 17 environmental variables were recorded including area, wet phase duration, total nitrogen, total phosphorus, aquatic macrophytes and land use. A total of 16 odonate species belonging to Lestidae, Coenagrionidae, Aeshnidae and Libellulidae were recorded, and the total number of species per pond varied from zero to six. The relationships between species richness, assemblages and environmental variables were studied by simple and multiple correlation and by Canonical Correspondence Analysis (CCA). The results showed that permanent ponds were larger, deeper, had more macrophyte species, had more extensive macrophytes cover and lower concentrations of nitrogen and phosphorus than temporary ponds. Multiple regression analysis showed that the number of odonate species was positively affected firstly by the number of macrophyte species, and then by pond depth. However, pond depth appeared to be interchangeable with several others variables, such as pond area and water duration and negatively correlated with nitrogen concentration, variables which are all linked with the permanent or temporary status of the ponds. CCA analysis indicated that odonate species presence was linked with a few environmental variables, showing a tendency of Odonata to avoid ponds with higher nitrogen concentrations, with the exception of Lestes barbarus, a species typical of temporary water in central Italy. At the same time, the majority of species were linked with longer water phase duration and with greater macrophyte species richness. A comparison with previous studies, and in particular with those carried out in central Italy, confirmed the positive influence of macrophytes, water duration, and also the negative effect of nutrient load. However, several other variables, in particular land use, shade, presence of fish, which were influential in other studies, were not significant in this study.
We assessed the importance for biodiversity of man-made farm ponds in an agricultural landscape in SW France lacking natural
wetlands. The ponds were originally created to provide a variety of societal services (irrigation, visual amenity, water for
cattle, etc.). We also assessed the environmental factors influencing invertebrate assemblages in these ponds. Only 18 invertebrate
taxa out of 114 taxa occurring in the study area were common to ponds and rivers indicating that the contribution of farm
ponds to freshwater biodiversity was potentially high. A Self-Organizing Map (SOM, neural network) was used to classify 36
farm ponds in terms of the 52 invertebrate families and genera they supported, and to specify the influence of environmental
variables related to land-use and to pond characteristics on the assemblage patterns. The SOM trained with taxa occurrences
showed five clusters of ponds, most taxa occurring only in 1–2 clusters of ponds. Abandoned ponds tended to support higher
numbers of taxa, probably because they were allowed to undergo a natural succession. Nevertheless, abandoned ponds were also
amongst the largest, so that it remained difficult to separate the effects of pond size and abandonment, although both factors
were likely to interact to favour higher taxon richness. The invertebrate communities in the ponds appeared to be influenced
mainly by widely acting environmental factors (e.g. area, regionalization of assemblages) with little evidence that pond use
(e.g. cattle watering, amenity) generally influenced assemblage composition. Our results support the idea that agricultural
landscapes containing man-made ponds make a significant contribution to freshwater biodiversity indicating that protection
of farm ponds from threats such as in-filling and pollution can make a positive contribution to the maintenance of aquatic
biodiversity. This added value for biodiversity should be considered when calculating the economic costs and benefits of constructing
water bodies for human activities.
KeywordsAgriculture-Artificial ponds-Wetlands-Macroinvertebrates-Land-use-Self-organizing maps
Odonate populations and species numbers are declining globally. Successful conservation requires sound assessments of both
odonate distributions and habitat requirements. Odonates have aquatic (larval) and terrestrial (adult) stages, but most surveys
that are used to inform conservation managers are undertaken of the adult stage. This study investigates whether this bias
towards adult records in odonate recording is misinterpreting the environmental quality of sites. The habitat focus is farmland
ponds, a key feature of agricultural landscapes. We tested whether or not, adult, larval and exuvial surveys lead to similar
conclusions on species richness and hence on pond quality. Results showed that pond surveys based upon larvae and exuviae
are equally suitable for the reliable assessment of presence/absence of odonates, but that adult surveys are not interchangeable
with surveys of larvae/exuviae. Larvae were also found at ponds with no emerging individuals due to changes in habitat quality,
therefore presence of exuviae remains the only proof of life-cycle completion at a site. Ovipositing females were recorded
at all ponds where exuviae were totally absent hence adult surveys over-estimate pond quality and low-quality ponds are functioning
as ecological traps. Highly mobile and generalist species were recorded at more locations than other species. Adult surveys
also bias recording towards genera, species and populations with non-territorial mate-location strategies. Odonate biodiversity
monitoring would benefit from applying the best survey method (exuviae) to avoid wasting valuable financial resources while
providing unbiased data, necessary to achieve conservation objectives.
KeywordsOdonata-Survey methods-Exuviae-Ecological traps-Conservation
A successful conservation strategy for an insect species should address the habitat requirements of all life stages and all
activities performed by those life stages. In this paper the night-time roosting habitat and behaviour of the endangered damselfly
Coenagrion mercuriale (Odonata: Coenagrionidae) was investigated by marking damselflies with UV fluorescent paint. Night-time observations revealed
that individuals did not roost together and those that were recorded on more than one occasion did not return to the same
spot each night. There was no apparent preference for roosting close to the watercourses. C. mercuriale roosted towards the top of the vegetation and this vegetation was considerably taller than the mean height of the vegetation
in the study area. Adults were strongly associated with two tussock-forming monocots, Juncus inflexus and Deschampsia cespitosa. Differences in the abundance of these plants were shown to result in large differences in the numbers of C. mercuriale roosting in different parts of the site. The importance of providing these structural elements of habitat as part of a wider
conservation strategy for this species is discussed.
Conservation buffers can have a tremendously positive impact on the ecological health of rural landscapes by reducing erosion, improving water quality, increasing biodiversity, and expanding wildlife habitats. Yet, in spite of our knowledge of their value, conservation buffers have not been fully embraced by landowners, or even by policy makers in the United States (US). In this critical review, we examine why conservation buffers remain underutilized in US agroecosystems. We examine the literature on the environmental benefits of buffers, the economic issues related to buffer adoption, and the importance of the aesthetic quality and design of buffers. We propose that many questions related to buffer design and management remain unanswered, and suggest a variety of areas in which future research is necessary to improve buffer functionality and adoption. The implications of this synthesis for designers, planners, scientists, policy makers, and citizens are discussed. Recommendations include: modifying policies to better reflect the preferences of landowners and society, studying buffer systems at the watershed scale using multidisciplinary approaches, and designing buffers that consider aesthetic preferences and regional variation.
Information about the relative biodiversity value of different waterbody types is a vital pre-requisite for many strategic conservation goals. In practice, however, exceptionally few inter-waterbody comparisons have been made. The current study compared river, stream, ditch and pond biodiversity within an 80 km2 area of lowland British countryside. The results showed that although all waterbody types contributed to the diversity of macrophytes and macroinvertebrates in the region, they differed in relative value. Individual river sites were rich but relatively uniform in their species composition. Individual ponds varied considerably in species richness, with the richest sites supporting similar numbers of taxa to the best river sections, but the poorest sites amongst the most impoverished for all waterbody types. At a regional level, however, ponds contributed most to biodiversity, supporting considerably more species, more unique species and more scarce species than other waterbody types. Streams typically supported fewer species and fewer unique species at local and regional level than either ponds or rivers. Ditches (most of which were seasonal) were the least species-rich habitat, but supported uncommon species, including temporary water invertebrates not recorded in other waterbody types. Multivariate analysis indicated that permanence, depth, flow and altitude were the main environmental variables explaining invertebrate and plant assemblage composition. The findings, as a whole, suggest that ponds and other small waterbodies can contribute significantly to regional biodiversity. This contrasts markedly with their relative status in national monitoring and protection strategies, where small waterbodies are largely ignored.
Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift habitats during their life cycles and provide potent conduits coupling ecosystems. Thus, local interactions that affect predator abundance in one ecosystem (for example a larval habitat) may have reverberating effects in another (for example an adult habitat). Here we show that fish indirectly facilitate terrestrial plant reproduction through cascading trophic interactions across ecosystem boundaries. Fish reduce larval dragonfly abundances in ponds, leading to fewer adult dragonflies nearby. Adult dragonflies consume insect pollinators and alter their foraging behaviour. As a result, plants near ponds with fish receive more pollinator visits and are less pollen limited than plants near fish-free ponds. Our results confirm that strong species interactions can reverberate across ecosystems, and emphasize the importance of landscape-level processes in driving local species interactions.
Studies in lakes show that fish and crayfish predators play an important role in determining the abundance of freshwater snails. In contrast, there are few studies of snails and their predators in shallow ponds and marshes. Ponds often lack fish and crayfish but have abundant insect populations. Here we present the results of field surveys, laboratory foraging trials, and an outdoor mesocosm experiment, testing the hypothesis that insects are important predators of pulmonate snails. In laboratory foraging trials, conducted with ten species of insects, most insect taxa consumed snails, and larval dragonflies were especially effective predators. The field surveys showed that dragonflies constitute the majority of the insect biomass in fishless ponds. More focused foraging trials evaluated the ability of the dragonflies Anax junius and Pantala hymenaea to prey upon different sizes and species of pulmonate snails (Helisoma trivolvis, Physa acuta, and Stagnicola elodes). Anax junius consumed all three species up to the maximum size tested. Pantala hymenaea consumed snails with a shell height of 3 mm and smaller, but did not kill larger snails. P. acuta were more vulnerable to predators than were H. trivolvis or S. elodes. In the mesocosm experiment, conducted with predator treatments of A. junius, P. hymenaea, and the hemipteran Belostoma flumineum, insect predators had a pronounced negative effect on snail biomass and density. A. junius and B. flumineum reduced biomass and density to a similar degree, and both reduced biomass more than did P. hymenaea. Predators did not have a strong effect on species composition. A model suggested that A. junius and P. hymenaea have the largest effects on snail biomass in the field. Given that both pulmonate snails and dragonfly nymphs are widespread and abundant in marshes and ponds, snail assemblages in these water bodies are likely regulated in large part by odonate predation.
The Equilibrium Theory of Island Biogeography (ETIB) attempts to explain how island area and island isolation can affect patterns of species diversity. Studies that evaluate the effect of area on the diversity or one taxonomic group with different environmental requirements and dispersal abilities for each life stage may provide additional insight into the validity of this theory. The effects of various physical and chemical habitat parameters, including area, on adult and larval dragonfly species diversity were investigated in twenty-eight desert sinkholes. As predicted by the ETIB, both adult and larval species diversity increased with increasing sinkhole surface area, but the slopes of the respective species-area curves indicate that the sinkhole complex functions as a mainland landscape for adult dragonflies and as an island system for larval dragonflies. Although water chemistry bad more influence on species diversity than did area in this system, the ETIB still offers insight into the origin and maintenance of this community.
IIntroduction: In the mid 1990s interest in the British dragonflies amongst amateur naturalists had probably never been greater. The British Dragonfly Society had a membership of over 1500 and the Dragonfly Recording Network was receiving thousands of records each year. Several field guides to the British species had been published in the preceding decade but by 1997 most were out of print. The time was right for a new style field guide that, as well as featuring high-quality illustrations and descriptions of the British species, would include for the first time all the age- and sex-related colour forms, as well as detailed autecological information, which was recently becoming available from field observations. This new field guide would encourage dragonfly enthusiasts to take their interests beyond simple identifications and distributional recording and also draw in new recruits, especially from amongst bird-watchers, by presenting the guide in a modern, attractive and informative format. Background Dragonflies (Odonata) are captivating insects and consequently have featured in some of the earliest books describing the natural world (e.g. Mouffet, 1634; Ray, 1710; Harris, 1782; Curtis, 1823–1840). These early books sought to catalogue Nature and also inspire an interest in natural history by providing, in many cases, beautiful and lavish colour paintings of the animals and plants the authors described.
In the absence of weeds, Notonecta exhibited a Type 2 functional response, but this changed to a Type 3 response as weed density increased. -from Author
1. Monitoring programmes that assess ecosystem changes depend on indicator species or assemblages. Indicators should be sensitive and their response easily measured. This study assessed the suitability of adult male Odonata as indicators of biotope quality along the Sabie River in the Kruger National Park (KNP). 2. Odonate diversity was investigated at 25 sites along the Sabie River using univariate statistical procedures. The KNP supports 81 species, 59 recorded during this study (16 for the first time). 3. Sampling sites were classified by Two Way INdicator SPecies Analysis (TWINSPAN) and ordinated by DEtrended CORrespondence ANAlysis (DECORANA), based on the abundance of adult male Odonata. A predictive model relating Odonate species-groups to biotope variables, was formulated. 4. Classification led to the recognition of 10 ecologically meaningful biotope groups, each with an indicator species and a characteristic assemblage of associated species. 5. Multiple Discriminant Analysis (MDA) indicated that shade cover, permanency and flow rate could discriminate between biotope types defined by TWINSPAN. Variation in site membership between MDA and TWINSPAN suggests interaction between variables in determining species membership. 6. Biotope variables were incorporated into a model which predicted the membership of 82% of sites to the TWINSPAN groups; shade cover alone correctly predicted 44% of the sites. 7. The suitability of the Odonata as indicators of biotope quality, and its consequences for management are discussed.
1. Monitoring programmes that assess ecosystem changes depend on indicator species or assemblages. Indicators should be sensitive and their response easily measured. This study assessed the suitability of adult male Odonata as indicators of biotope quality along the Sabie River in the Kruger National Park (KNP). 2. Odonata diversity was investigated at 25 sites along the Sabie River using univariate statistical procedures. The KNP supports 81 species, 59 recorded during this study (16 for the first time). 3. Sampling sites were classified by Two Way INdicator SPecies Analysis (TWINSPAN) and ordinated by DEtrended CORrespondence ANAlysis (DECORANA), bused on the abundance of adult male Odonata. A predictive model relating Odonata species-groups to biotope variables, was formulated. 4. Classification led to the recognition of 10 ecologically meaningful biotope groups, each with an indicator species and a characteristic assemblage of associated species. 5. Multiple Discriminant Analysis (MDA) indicated that shade cover, permanency and flow rate could discriminate between biotope types defined by TWINSPAN. Variation in site membership between MDA and TWINSPAN suggests interaction between variables in determining species membership. 6. Biotope variables were incorporated into a model which predicted the membership of 82% of sites to the TWINSPAN groups; shade cover alone correctly predicted 44% of the sites. 7. The suitability of the Odonata as indicators of biotope quality, and its consequences for management are discussed.
The PASS project has as its goal the implementation of solutions to the foreseen data access problems of the next generation of scientific experiments. It is in the process of transitioning from an exploratory phase, where the focus has been on understanding the requirements and available technologies to an implementation phase, where detailed design work is commencing on a conunon framework for scientific applications.
. 1. Most ecological processes at the population and community level act on multiple spatial scales. We identified the influence of grassland management, vegetation traits and landscape on orthopteran and butterfly diversity in 44 meadows located in a forest-dominated region in the Italian Alps. The meadows were sampled in landscapes characterised by different proportions of woody vegetation and grasslands quantified at 11 spatial scales (95–3000 m).2. We applied a multi-scale approach to investigate the scale-dependent effects of landscape. Then, we built generalised linear models (Poisson and log-link function) to test simultaneously vegetation traits and landscape variables on insect species richness.3. High fertilisation and cutting frequency created tall, species-poor plant communities. This change reduced orthopteran diversity by providing an unsuitable sward structure, and butterfly diversity by creating disturbed plant communities with low species richness and abundance of flowering forbs and host plants.4. The proportion of woody vegetation had a strong positive effect on the richness of both groups at the smallest spatial scale (95 m), indicating the importance of undisturbed vegetation in the surrounding of mown meadows. The effect tended to disappear with increasing spatial extent.5. A multi-scale approach was necessary to identify the effects of landscape factors in this study system. Conservation measures should endorse the maintenance of species-rich, sparse and short plant communities by reducing organic fertilisation and cutting frequency. However, these schemes should also promote the presence of undisturbed woody vegetation in the immediate surrounding landscape or at least should prevent the complete mowing of large areas.
At the nature reserve “Bosco della Fontana” (Lombardy, Italy) the communities of larval and adult dragonflies were studied at three sites in small streams. The larval communities were investigated by collecting exuviae. Site 1, a stream section which falls dry in March–April due to human intervention, had a community of larval dragonflies where species typical of running water were almost absent. Here Ischnura elegans was the dominant species, accounting for more than 64% of the total number of exuviae. Additionally, other species typical for stagnant water were present. However, reproductively active adults of rheophilous species were dominant when flowing water was abundant at this site in summer. In contrast, at the two other sites, where flowing water is present throughout the entire year, rheophilous species were dominant in the larval community and in the adult communities. It is concluded that streams with a highly modified hydrology may represent “ecological traps” for specialized species and that dragonfly surveys solely based on the observation of adults can be misleading.
We studied the abundance and species richness of adult dragonflies in 11 artificial ponds which were recently established (within 2 years). We found that the adult dragonfly assemblage patterns were influenced by pond size as well as pond age. The species richness was positively correlated with the pond size, which was because the distributional patterns of species were significantly nested according to pond area. The species richness was highly correlated with pond age in association with the vegetation cover within ponds. It was suggested that the species richness was enhanced by the increasing immigration rate of species which favor well-vegetated ponds.
1. The effects of weed detisity oti the predalion of damseifly larvae by Notonecta were investigated iti a laboratory experimetit.
2. In the absence of weeds. Notonecta exhibited a Type 2 functional response, but this changed to a Type 3 response as weed density increased. Consideration is given to the possible significance of these results for the regulation of field populations of damseifly larvae.
1. Aquatic macro-invertebrates have frequently been used as biological indicators in lotic environments but much less commonly so in lentic habitats. Dragonflies and damselflies (Order Odonata) satisfy most selection criteria for lentic bioindicators of grazing impacts.2. Intensive cattle grazing affects most of the Canadian prairie pothole region but the effects of grazing on wetlands are poorly understood.3. Here the vegetation structure and invertebrate community composition of 27 prairie potholes in Alberta, Canada were studied and compared. Wetlands were evenly divided into three treatments of different grazing regimes.4. Removal of emergent vegetation by cattle grazing decreased odonate abundance and reproductive effort. Shorter Scirpus acutus stems resulted in significantly fewer damselflies (Suborder Zygoptera) and lower reproductive efforts.5. Overall odonate diversity was affected by the height of key plant species, highlighting the importance of the vegetation structure of both emergent vegetation for breeding and adjacent upland vegetation for nocturnal roosts. Wetland vegetation structure was more important than vegetation composition to the life history of odonates.6. Wetland water quality parameters of nitrogen, phosphorus, total dissolved solids (TDS), and chlorophyll-a concentration did not change due to the presence of grazing cattle at wetlands so water quality influences were rejected as mechanisms of change.7. Larval odonate diversity and abundance was positively correlated with overall aquatic macro-invertebrate diversity and abundance, hence it was concluded that the larval odonate community can be an accurate bioindicator of intactness and diversity of overall aquatic macro-invertebrate communities in Canadian prairie wetlands.