Article

Response of bat activity to land cover and land use in savannas is scale-, season-, and guild-specific

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Abstract

Tropical savannas are biomes of global importance under severe pressure from anthropogenic change, including land-cover and land-use change. Bats, the second-most diverse group of mammals, are critical to ecosystem functioning, but vulnerable to such anthropogenic stresses. There is little information on how savanna bats respond to land cover and land use, especially in Africa, limiting our ability to develop conservation strategies for bats and maintain the ecosystem functions and services they provide in this biome. Using acoustic monitoring , we measured guild-specific (aerial, edge, and clutter forager) responses of bat activity to both fine-scale vegetation structure and landscape-scale land-cover composition and configuration across the wet and dry seasons in a southern African savanna undergoing rapid land-cover and land-use change. Responses were guild-and season-specific but generally stronger in the dry season. Aerial and clutter bats responded most strongly to landscape metrics in the dry season (positive responses to savanna fragmentation and water cover, respectively) but fine-scale metrics in the wet season (positive responses to water cover and grass cover, respectively). Edge bats responded most strongly (negatively) to the distance to water in the dry season and fine-scale shrub cover in the wet season. Our results show it is possible to maintain high levels of bat activity in savanna mosaics comprised of different land covers and land uses. Bats, and the ecosystem services they provide, can be conserved in these changing landscapes, but strategies to do so must consider foraging guild, spatial scale, and seasonal variation in bat activity.

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... Bat species respond differently to the same landscape matrix and show varying levels of sensitivity to habitat destruction, light pollution and other human-induced stressors (Frey-Ehrenbold et al., 2013;Mtsetfwa et al., 2018;Rowse et al., 2016;Russo and Ancillotto, 2015;Shapiro et al., 2019). This varying response is related to their foraging ecology, where three general foraging guilds can be recognised. ...
... Pinaud et al., 2018). However, even open-air feeders, which can be found to exploit monocultures such as southern African sugarcane plantations as foraging grounds, can be affected by the loss of roost sites or alternative prey species abundances (Shapiro et al., 2019). Agricultural monocultures can also cause loss of functional diversity, for example, specialised insectivores are absent from bird communities in cocoa plantations in Cameroon (Jarrett et al., in press). ...
... Lower levels of activity for both edge space and open space aerial foraging guilds in the dry season can be explained by lower prey availability and pest insect abundances (Taylor et al., 2013a;Weier et al., 2018), but may also be due to colder temperatures in winter (Monadjem et al., 2020;Parker and Bernard, 2018). We cannot confirm observations of Shapiro et al. (2019), who found a seasonal dependence of narrow space foraging bats on sugarcane, which could possibly be explained by water availability. Since our study area is within a particularly high rainfall area with the mountain range providing many perennial streams, the artificial water bodies on farmland might be less of an attraction to local bats. ...
Article
Bats have been shown to provide successful pest suppression in different land-use systems globally. Recent research demonstrates high economic values of pest suppression by bats also in macadamia orchards, which is enhanced by natural habitat patches at orchard edges. We investigated the impact of the conversion of natural to agricultural (macadamia-dominated) habitats. Using ~65,000 recorded bat call sequences; we studied bat communities in three land use types: a nature reserve, macadamia orchards with and without adjacent natural habitat patches. All study sites are situated on the southern slopes of the Soutpansberg, northern South Africa. Species richness varied significantly between the nature reserve and the macadamia orchards, but did not between orchards with and without neighbouring natural habitat. Within the orchards, activity of edge space foraging (dependent on e.g. forest edges) bats was greater at natural edges, whereas open space aerial foraging species (hunting above canopy) were more active at human-modified edges. Although seven narrow space foraging (i.e. dense vegetation dependent) bat species were identified at both orchard and reserve, this foraging guild occurred more frequently in the nature reserve (2.9-4.1% of all call sequences) than in the orchards (0.5-2.9% of all call sequences). Narrow space foraging bats were thus largely excluded from simplified agricultural landscapes, in particular where natural edge habitats are missing, compared to our natural control. The current trend in conversion of natural habitat in favour of macadamia monocultures, especially if remnant natural patches at orchard boundaries are removed, will have widespread detrimental effects on bat diversity. The resulting reduced biological pest suppression by bats and increased reliance on chemical control may further exacerbate biodiversity declines.
... Southern African savannas support a rich diversity of bats (Gelderblom et al., 1995;Monadjem et al., 2010aMonadjem et al., , 2010b. Bat community structure in savannas has been shown to be shaped by both abiotic and biotic factors acting at local and regional scales (Weier et al., 2016;Schoeman and Monadjem, 2018), as well as by land use and climate change (Taylor et al, 2013b;Smith et al., 2016;Foord et al., 2018;Mtset fwa et al., 2018;Weier et al., 2018;Shapiro et al., 2019). ...
... The attraction of water bodies to bats in southern African agricultural-savanna mosaic landscapes is guild-, season-and scale-specific (Weier et al., 2018;Shapiro et al., 2019). For example, in the lowlying savanna region of Eswatini, in the dry season (but not the wet season), activity of clutter-feeding and clutter-edge bats (but not open-air feeders) responded positively to water (Shapiro et al., 2019). ...
... The attraction of water bodies to bats in southern African agricultural-savanna mosaic landscapes is guild-, season-and scale-specific (Weier et al., 2018;Shapiro et al., 2019). For example, in the lowlying savanna region of Eswatini, in the dry season (but not the wet season), activity of clutter-feeding and clutter-edge bats (but not open-air feeders) responded positively to water (Shapiro et al., 2019). In a dry deciduous forest in central western Madagascar, bat activity at pools within a riverbed were significantly higher than forest and dry riparian habitats, but only for Vespertilionidae (clutter-edge) and Hipposideridae (clutter-feeding) bats, not for openair-feeding Molossidae (Bader et al., 2015). ...
Article
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... However, studies on biodiversity in sub-Saharan Africa have traditionally focused on natural ecosystems (protected areas), giving only limited attention to modified landscapes, such as agroecosystems (Nkrumah et al. 2017). Moreover, some agroecosystems have been found to serve as a refugium of tropical biodiversity (Perfecto et al. 1996;Somarriba et al. 2004;Sirami et al. 2013;Weier et al. 2018;Shapiro et al. 2020). ...
... Moreover, the presence of species that mainly exploit densely cluttered habitats, such as Hipposideros fuliginosus and H. ruber in these agricultural areas can be attributed to the fact that the vegetation structure of some agricultural areas is similar to natural cluttered habitats. A study by Shapiro et al. (2020) in savanna fragments showed the importance of sugarcane farms in providing complementary resources lacking in the monocultures, such as particular prey items or roosting sites. Indeed, we also recorded Chaerephon pumilus in cultivated farms (12 individuals). ...
Article
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The western region of Cameroon is one of the leading agricultural production areas in sub-Saharan Africa, and this ongoing anthropogenic perturbation has led to the replacement of natural forests with agroecosystems. Such anthropogenic landscape transformations may have affected bat species composition and abundance in the area. Our study assessed the response of bat assemblages to these changes, by comparing species diversity and abundance across four distinct habitat types within the region: cultivated farms (transformed landscape), savannah and gallery forest (both representing degraded areas), and secondary forest. A total of 442 individuals assigned to 25 species were captured using ground-level mist nets. The cultivated farms recorded the highest bat species richness (13 species) and abundance (145 individuals), whereas the gallery forest had the lowest species richness (six species) and abundance (62 individuals). Myonycteris angolensis had the highest relative abundance in the region, with large numbers captured in cultivated farms. According to the rank-frequency diagram, bat assemblages in cultivated farms (Akaike’s Information Criterion (AIC) = 53.7), gallery forest (AIC = 27.7), and secondary forest (AIC = 48.5) are distributed according to the pre-emption model, whereas the distribution in the savannah (AIC = 40.0) follow the null model. Generalised linear models revealed significant differences in species and relative abundance across the four habitat types.
... Water sources are well known as hotspots for bats in South Africa, supporting high species richness and high activity levels (Monadjem and Reside, 2008;Sirami, Jacobs and Cumming, 2013;Shapiro et al., 2020;Taylor et al., 2020). However, most work has been conducted in savanna habitats and agricultural landscapes, with few studies investigating the association of bats with rivers and waterbodies in forested habitats (Rautenbach, Whiting and Fenton, 1996). ...
... The association of functional diversity with river length was particularly driven by miniopterid and vespertilionid bats of the clutter-edge foraging guild that hunt for prey along riparian vegetation of watercourses (Monadjem, Taylor, et al., 2010). Similar use of rivers by the clutter-edge guild has been found for savanna habitats (Shapiro et al., 2020;Taylor et al., 2020). However, this study shows how rivers allow for the penetration of clutter-edge species into forest interiors. ...
Thesis
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Bats are a highly diverse mammalian order and are some of the most economically important non-domesticated vertebrates, providing many ecosystem services that contribute to the global economy. Yet, they remain a largely understudied taxon, particularly in the Eastern Cape province of South Africa, in which basic surveys of bat assemblages utilising indigenous forests are lacking. Indigenous forests constitute South Africa’s smallest and most fragmented biome yet support disproportionally high biodiversity. They have been fragmented throughout most of their evolutionary history due to global palaeoclimatic shifts; the responses of bats to forest fragmentation and historical climatic shifts in this habitat have been poorly studied. This study addresses these gaps with the broad aims of compiling a species inventory from 17 forests across the Eastern Cape and KwaZulu-Natal provinces; assessing the effects of fragmentation and biogeography on taxonomic and functional diversity of bat assemblages; and determining how genetic diversity and population genetic structure are informed by forest habitat associations and fragmentation. A multi-faceted approach of sampling methods, including capture and acoustic recording, and species identification techniques (morphology, acoustics, and DNA barcoding) were used to assemble an inventory of 25 species, with range extensions noted for six species. The first reference call library of hand released bats for forests in this region is presented, which may be used for species identification in further acoustic surveys. A minimum acoustic monitoring period of 6 to 7 nights per forest is recommended for future surveys. Forest biogeography was an important determinant of the functional diversity of insectivorous bat assemblages. Forest edge effects were found to demonstrate a positive relationship with functional evenness, thus motivating for maintenance and conservation of forest edges, particularly in temperate regions. Larger forearm length and low wing loading were identified as morphological traits exhibiting greater sensitivity to fragmentation, flagging species exhibiting these traits as potentially vulnerable to habitat fragmentation. The effect of historical climate-induced fluctuations of forest extent on population genetic structuring and demographic histories for six species was investigated using two mitochondrial markers, cytochrome b and D-loop. Population genetic trends were not informed by forest habitat associations, but rather by species-specific traits of dispersal ability, philopatry, and roost utilisation. Low genetic diversity and high population structure identify two species, Rhinolophus swinnyi and Laephotis botswanae, for conservation priority. Demographic responses to the Last Glacial Maximum (LGM) were not detected, with all six species displaying population expansions over this time. It appears that volant insectivores in eastern South Africa were less affected by the harsh conditions of the LGM than elsewhere. The dusky pipistrelle (Pipistrellus hesperidus) was used as a model organism to investigate the gene flow, genetic diversity, and migration of a forest-utilising species across the region with the use of eight microsatellite markers. The effects of urbanisation and agricultural development on gene flow were also examined. Findings of low population structure, low migration rates, and two genetic discontinuities were presented. This species does not depict dependence on forested habitats to maintain genetic connectivity on the landscape. The data also suggest that agricultural development and urbanisation have not yet had an impact on gene flow, thus providing a baseline with which to monitor the effects of future anthropic development on this species. Overall, this study has provided novel insights into the taxonomic, functional, and genetic diversity of forest-utilising bats in relation to biogeographical history and fragmentation within eastern South Africa.
... Therefore, we investigated the prevalence of coronaviruses in bats belonging to eight species from four families (Pteropodidae: Epomophorus wahlbergi; Emballonuridae: Taphozous mauritianus; Molossidae: Chaerephon pumilus, Mops condylurus, and Mops midas; and Vespertilionidae: Afronycteris nana, Scotophilus dinganii, and Scotophilus viridis). These species are all widely distributed and abundant across southeastern Africa and are commonly found in or near human settlements in northeast Eswatini (Monadjem et al. 2020b(Monadjem et al. , 2021Shapiro et al. 2020). We subjected fecal samples to virion enrichment followed by RNA sequencing to noninvasively investigate the prevalence and types of coronavirus in the bats of this region. ...
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We investigated the prevalence of coronaviruses in 44 bats from four families in northeastern Eswatini using high-throughput sequencing of fecal samples. We found evidence of coronaviruses in 18% of the bats. We recovered full or near-full-length genomes from two bat species: Chaerephon pumilus and Afronycteris nana , as well as additional coronavirus genome fragments from C. pumilus , Epomophorus wahlbergi , Mops condylurus , and Scotophilus dinganii . All bats from which we detected coronaviruses were captured leaving buildings or near human settlements, demonstrating the importance of continued surveillance of coronaviruses in bats to better understand the prevalence, diversity, and potential risks for spillover.
... Landscape heterogeneity has been shown to have a strong influence on the distribution of mammals in agricultural mosaics Shapiro et al. 2020 ), but the response of scavengers to fragmentation and patch size is not uniform. In a cornfield-woodlot agroecosystem of the central United States, patch connectivity did not influence carcass detection ( Olson et al. 2016 ). ...
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... We captured bats using 12 m x 3 m mist nets (EcoTone, Poland) placed around suspected roosts and areas of likely bat activity, such as water bodies or pathways (Shapiro et al. 2020). We set mist nets before sunset (before bat emergence) and kept them open for four hours, during which time we checked nets at least every 10 minutes. ...
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... A small increase in bird abundance was noticed when the use of herbicide was simulated to be restricted to the vine rows (in the equilibrium scenario). Schaub et al. (2010), Arlettaz et al. (2012) and Paiola et al. (2020) provided evidence that patches of grassy habitats are important for the birds that feed on seeds and soil invertebrates and even for some bat species (Wickramasinghe et al., 2003;Shapiro et al., 2020). The simulation of "sustainable management" (eco-friendly scenario) substantially increased bird abundance, possibly mimicking the associated resources to more diverse and complex LULC Kirk and Lindsay, 2017;Steel et al., 2017). ...
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The Brazilian Cerrado is a Neotropical savanna extremely threatened by human-driven habitat changes while simultaneously one of the formations with the highest degree of floristic endemism in the world. In the last decades, more than half of the Cerrado area has been converted by agriculture and livestock production, leading to a significant loss of its natural vegetation. Here we evaluated changes in bat diversity between varying agricultural land use intensity levels and phytophysiognomies of the Cerrado. Because processes behind the patterns of community assembly act on ecological redundancies and complementarities of organisms and not only, or necessarily, on the number of species present in a certain region, we focused on taxonomic, functional and phylogenetic diversity of bats. We predicted that all three dimensions of bat diversity were negatively correlated with increasing levels of land-use intensity in the Cerrado, and that this pattern was mirrored in distinct phytophysiognomies of the domain. We sampled bats in the central Brazilian Cerrado using a comprehensive sampling scheme of mist-nets and automated real-time ultrasound-recording units in 27 sampling points covering different physiognomies and levels of land-use modification for two consecutive years. To our knowledge our sampling was unique in combining these two techniques, returning information on close-, edge- and open-space foraging guilds, rarely all sampled in Neotropical bat studies. A remarkable total of 64 species of six families were registered in the study area. In general no statistical differences were found in any of the diversity metrics between the sampled physiognomies, but a decrease in taxonomic, functional and phylogenetic diversity was observed in all physiognomies associated with land use intensification and this was consistent across guilds. This demonstrates the potential negative impact of land use intensification in ecosystem services provided by bats, including pollination, seed dispersal and insect control.
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Accurate taxonomy is central to the study of biological diversity, as it provides the needed evolutionary framework for taxon sampling and interpreting results. While the number of recognized species in the class Mammalia has increased through time, tabulation of those increases has relied on the sporadic release of revisionary compendia like the Mammal Species of the World (MSW) series. Here, we present the Mammal Diversity Database (MDD), a digital, publically accessible, and updateable list of all mammalian species, now available online: https://mammaldiversity.org. The MDD will continue to be updated as manuscripts describing new species and higher taxonomic changes are released. Starting from the baseline of the 3rd edition of MSW (MSW3), we performed a review of taxonomic changes published since 2004 and digitally linked species names to their original descriptions and subsequent revisionary articles in an interactive, hierarchical database. We found 6,495 species of currently recognized mammals (96 recently extinct, 6,399 extant), compared to 5,416 in MSW3 (75 extinct, 5,341 extant)—an increase of 1,079 species in about 13 years, including 11 species newly described as having gone extinct in the last 500 years. We tabulate 1,251 new species recognitions, at least 172 unions, and multiple major, higher-level changes, including an additional 88 genera (1,314 now, compared to 1,226 in MSW3) and 14 newly recognized families (167 compared to 153). Analyses of the description of new species through time and across biogeographic regions show a long-term global rate of ~25 species recognized per year, with the Neotropics as the overall most species-dense biogeographic region for mammals, followed closely by the Afrotropics. The MDD provides the mammalogical community with an updateable online database of taxonomic changes, joining digital efforts already established for amphibians (AmphibiaWeb, AMNH’s Amphibian Species of the World), birds (e.g., Avibase, IOC World Bird List, HBW Alive), non-avian reptiles (The Reptile Database), and sh (e.g., FishBase, Catalog of Fishes).
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Context The landscape heterogeneity hypothesis states that increased heterogeneity in agricultural landscapes will promote biodiversity. However, this hypothesis does not detail which components of landscape heterogeneity (compositional or configurational) most affect biodiversity and how these compare to the effects of surrounding agricultural land-use. Objectives Our objectives were to: (1) assess the influence of the components of structural landscape heterogeneity on taxonomic diversity; and (2) compare the effects of landscape heterogeneity to those of different types of agricultural land-use in the same landscape across different taxonomic groups. Methods We identified a priori independent gradients of compositional and configurational landscape heterogeneity within an agricultural mosaic of north-eastern Swaziland. We tested how bird, dung beetle, ant and meso-carnivore richness and diversity responded to compositional and configurational heterogeneity and agricultural land-use across five different spatial scales. Results Compositional heterogeneity best explained species richness in each taxonomic group. Bird and ant richness were both positively correlated with compositional heterogeneity, whilst dung beetle richness was negatively correlated. Commercial agriculture positively influenced bird species richness and ant diversity, but had a negative influence on dung beetle richness. There was no effect of either component of heterogeneity on the combined taxonomic diversity or richness at any spatial scale. Conclusions Our results suggest that increasing landscape compositional heterogeneity and limiting the negative effects of intensive commercial agriculture will foster diversity across a greater number of taxonomic groups in agricultural mosaics. This will require the implementation of different strategies across landscapes to balance the contrasting influences of compositional heterogeneity and land-use. Strategies that couple large patches of core habitat across broader scales with landscape structural heterogeneity at finer scales could best benefit biodiversity.
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Understanding the distributions and environmental associations of rare species is a critical 1st step in their conservation and management. Federally endangered Florida bonneted bats (Eumops floridanus) are endemic to southern Florida and are believed to have one of the most limited geographic distributions of any bat in the United States. We conducted a large-scale acoustic survey of 330 points spread across approximately 38,000 km 2 over a 2-year period and used a hierarchical Bayesian approach accounting for imperfect detection to model the distribution and environmental associations of the Florida bonneted bat. Bat occupancy was negatively correlated with the amount of developed land within 5 km of the sampling point and positively correlated with the amount of crop-based agriculture within 5 km of the sampling point. Bat occupancy probabilities increased with the 30-year mean for minimum spring temperature and levels of annual precipitation, and decreased with the 30-year mean for levels of spring precipitation. Bat detection was positively influenced by Julian date and minimum temperature of the survey night. This study offers new insight into the habitat use of this endangered species. Results confirm that predicted changes in land cover and climate will be threats to the Florida bonneted bat.
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Bats are a critical component of most terrestrial systems, yet accurately assessing species richness and abundances remains a challenge. The use of acoustic monitoring has increasingly been used to assess bat communities. Compared with more traditional trapping surveys, acoustic monitoring is relatively easy to use and vastly increases the amount of data collected. However, the ability to accurately identify bat calls from acoustic detectors is limited by the availability of regional call libraries describing the calls of local species. Further, the lack of knowledge of detection distances for different species limits the ability to compare activity levels or abundances between species. We developed an echolocation call library based on zero-crossing recordings with Anabat Express detectors that can be applied broadly to bat acoustic detector surveys across the savanna systems of Swaziland and South Africa, and potentially the broader region of Southern Africa. We also compared detection distances for different species and provide a correction factor that will increase our ability to accurately compare activity between different species.
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Seasonality causes fluctuations in resource availability, affecting the presence and abundance of animal species. The impacts of these oscillations on wildlife populations can be exacerbated by habitat fragmentation. We assessed differences in bat species abundance between the wet and dry season in a fragmented landscape in the Central Amazon characterized by primary forest fragments embedded in a secondary forest matrix. We also evaluated whether the relative importance of local vegetation structure versus landscape characteristics (composition and configuration) in shaping bat abundance patterns varied between seasons. Our working hypotheses were that abundance responses are species as well as season specific, and that in the wet season , local vegetation structure is a stronger determinant of bat abundance than landscape-scale attributes. Generalized linear mixed-effects models in combination with hierarchical partitioning revealed that relationships between species abundances and local vegetation structure and landscape characteristics were both season specific and scale dependent. Overall, landscape characteristics were more important than local vegetation characteristics, suggesting that landscape structure is likely to play an even more important role in landscapes with higher fragment-matrix contrast. Responses varied between frugivores and animalivores. In the dry season, frugivores responded more to compositional metrics, whereas during the wet season, local and configurational metrics were more important. Animalivores showed similar patterns in both seasons, responding to the same group of metrics in both seasons. Differences in responses likely reflect seasonal differences in the phenology of flowering and fruiting between primary and secondary forests, which affected the foraging behavior and habitat use of bats. Management actions should encompass multiscale approaches to account for the idiosyncratic responses of species to seasonal variation in resource abundance and consequently to local and landscape scale attributes. K E Y W O R D S Chiroptera, fragmentation, landscape structure, local vegetation structure, seasonality
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The coefficient of determination, a.k.a. R², is well-defined in linear regression models, and measures the proportion of variation in the dependent variable explained by the predictors included in the model. To extend it for generalized linear models, we use the variance function to define the total variation of the dependent variable, as well as the remaining variation of the dependent variable after modeling the predictive effects of the independent variables. Unlike other definitions which demand complete specification of the likelihood function, our definition of R² only needs to know the mean and variance functions, so applicable to more general quasi-models. It is consistent with the classical measure of uncertainty using variance, and reduces to the classical definition of the coefficient of determination when linear regression models are considered.
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ContextSpecies site-occupancy patterns may be influenced by habitat variables at both local and landscape scales. Although local habitat variables influence whether the site is suitable for a given species, the broader landscape context can also influence site occupancy, particularly for species that are sensitive to land-use change. Objectives To examine the relative importance of local versus landscape variables in explaining site occupancy of eight bat species within the Brazilian Cerrado, a Neotropical savanna that is experiencing widespread habitat loss and fragmentation. Methods Bats were surveyed within 16 forest patches over two years. We used a multi-model information-theoretic approach, adjusted for species detection bias, to assess whether landscape variables (percent cover and number of patches of natural vegetation within a 2- and 8-km radius of each forest site) or local site variables (canopy cover, understory height, number of trees, and number of lianas) best explained site occupancy in each species. ResultsLandscape variables were among the best models (ΔAICc or ΔQAICc < 2) for four species (top-ranked model for black myotis), whereas local variables were among the best for five species (top-ranked model for vampire bats). Neither local nor landscape variables explained site occupancy in two frugivorous species. Conclusion Species associated with a particular habitat type will not respond similarly to the amount, distribution or relative suitability of that habitat, or even at the same scale. This reinforces the challenge of species distribution modelling, especially in the context of forecasting species’ responses to future land-use or climate-change scenarios.
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ContextThe conversion of natural environments into agricultural land has profound effects on the composition of the landscape, often resulting in a mosaic of human-altered and natural habitats. The response to these changes may however vary among organisms. Bats are highly vagile, and their requirements often imply the use of distinct habitats, which they select responding to both landscape and local features. Objectives We aimed to identify which features influence bat richness and activity within Baixo Vouga Lagunar, a heterogeneous landscape located on the Central-North Portuguese coast, and to investigate if that influence varies across a gradient of focal scales. Methods We sampled bats acoustically, while simultaneously sampling insects with light traps. We assessed the relationships between species richness, bat activity, and activity of eco-morphological guilds with landscape and local features, across four scales. ResultsOur results revealed both scale- and guild-dependent responses of bats to landscape and local features. At broader scales we found positive associations between open-space foraging bats and habitat heterogeneity and between edge-space foraging bats and greater edge lengths. Woodland cover and water availability at an intermediate scale and weather conditions and insect abundance at a local scale were the factors that mostly influenced the response variables. Conclusions Globally, our results suggest that bats are sensitive to local resource availability and distribution, while simultaneously reacting to landscape features acting at coarser scales. Finally, our results suggest that the responses given by bats are guild-dependent, and some habitats act as keystone structures for bats within this mosaic.
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Human pressures on the environment are changing spatially and temporally, with profound implications for the planet's biodiversity and human economies. Here we use recently available data on infrastructure, land cover and human access into natural areas to construct a globally standardized measure of the cumulative human footprint on the terrestrial environment at 1 km(2) resolution from 1993 to 2009. We note that while the human population has increased by 23% and the world economy has grown 153%, the human footprint has increased by just 9%. Still, 75% the planet's land surface is experiencing measurable human pressures. Moreover, pressures are perversely intense, widespread and rapidly intensifying in places with high biodiversity. Encouragingly, we discover decreases in environmental pressures in the wealthiest countries and those with strong control of corruption. Clearly the human footprint on Earth is changing, yet there are still opportunities for conservation gains.
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Species distribution models were used to predict bat species richness across southern Africa and to identify potential drivers of these spatial patterns. We also identified species richness within each biotic zone and the distributions of species considered of high conservation priority. We used this information to highlight conservation priorities for bats in southern Africa (defined here as between the latitudes of 8° S, slightly north of Zambia, to the southern tip of Africa 34° S, an area of approximately 9781840 km 2). We used maximum entropy modelling (Maxent) to model habitat suitability for 58 bat species in order to determine the key eco-geographical variables influencing their distributions. The potential distribution of each bat species was affected by different eco-geographic variables but in general, water availability (both temporary and permanent), seasonal precipitation, vegetation, and karst (caves/limestone) areas were the most important factors. The highest levels of species richness were found mainly in the eastern dry savanna area and some areas of wet savanna. Of the species considered to be of high priority due to a combination of restricted distributions or niches and/or endemism (7 fruit bats, 23 cave-dwellers, 18 endemic and near-endemic, 14 niche-restricted and 15 range-restricted), nine species were considered to be at most risk. We found that range-restricted species were commonly found in areas with low species richness; therefore, conservation decisions need to take into account not only species richness but also species considered to be particularly vulnerable across the biogeographical area of interest.
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Model-based global projections of future land use and land cover (LULC) change are frequently used in environmental assessments to study the impact of LULC change on environmental services and to provide decision support for policy. These projections are characterized by a high uncertainty in terms of quantity and allocation of projected changes, which can severely impact the results of environmental assessments. In this study, we identify hotspots of uncertainty, based on 43 simulations from 11 global-scale LULC change models representing a wide range of assumptions of future biophysical and socio-economic conditions. We attribute components of uncertainty to input data, model structure, scenario storyline and a residual term, based on a regression analysis and analysis of variance. From this diverse set of models and scenarios we find that the uncertainty varies, depending on the region and the LULC type under consideration. Hotspots of uncertainty appear mainly at the edges of globally important biomes (e.g. boreal and tropical forests). Our results indicate that an important source of uncertainty in forest and pasture areas originates from different input data applied in the models. Cropland, in contrast, is more consistent among the starting conditions, while variation in the projections gradually increases over time due to diverse scenario assumptions and different modeling approaches. Comparisons at the grid cell level indicate that disagreement is mainly related to LULC type definitions and the individual model allocation schemes. We conclude that improving the quality and consistency of observational data utilized in the modeling process as well as improving the allocation mechanisms of LULC change models remain important challenges. Current LULC representation in environmental assessments might miss the uncertainty arising from the diversity of LULC change modeling approaches and many studies ignore the uncertainty in LULC projections in assessments of LULC change impacts on climate, water resources or biodiversity. This article is protected by copyright. All rights reserved.
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Context Scale dependence of bat habitat selection is poorly known with few studies evaluating relationships among landscape metrics such as class versus landscape, or metrics that measure composition or configuration. This knowledge can inform conservation approaches to mitigate habitat loss and fragmentation. Objectives We evaluated scale dependence of habitat associations and scaling patterns of landscape metrics in relation to bat occurrence or capture rate in forests of southwestern Nicaragua. Methods We captured 1537 bats at 35 locations and measured landscape and class metrics across 10 spatial scales (100–1000 m) surrounding capture locations. We conducted univariate scaling across the 10 scales and identified scales and variables most related to bat occurrence or capture rate. Results Edge and patch density, at both landscape and class levels, were the most important variables across species. Feeding guilds varied in their response to metrics. Certain landscape and configuration metrics were most influential at fine (100 m) and/or broad (1000 m) spatial scales while most class and composition metrics were influential at intermediate scales. Conclusions These results provide insight into the scale dependence of habitat associations of bat species and the influence of fine and broad scales on habitat associations. The effects of scale, examined in our study and others from fine (100 m) to broad (5 km) indicate habitat relationships for bats may be more informative at larger scales. Our results suggest there could be general differences in scale relationships for different groups of landscape metrics, which deserves further evaluation in other taxonomic groups.
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Land-use change is a key driver of the global biodiversity crisis and a particularly serious threat to tropical biodiversity. Throughout the tropics, the staggering pace of deforestation, logging, and conversion of forested habitat to other land uses has created highly fragmented landscapes that are increasingly dominated by human-modified habitats and degraded forests. In this chapter, we review the responses of tropical bats to a range of land-use change scenarios, focusing on the effects of habitat fragmentation , logging , and conversion of tropical forest to various forms of agricultural production. Recent landscape-scale studies have considerably advanced our understanding of how tropical bats respond to habitat fragmentation and disturbance at the population, ensemble, and assemblage level. This research emphasizes that responses of bats are often species and ensemble specific, sensitive to spatial scale , and strongly molded by the characteristics of the prevailing landscape matrix . Nonetheless, substantial knowledge gaps exist concerning other types of response by bats. Few studies have assessed responses at the genetic , behavioral , or physiological level, with regard to disease prevalence , or the extent to which human disturbance erodes the capacity of tropical bats to provide key ecosystem services . A strong geographic bias, with Asia and, most notably, Africa, being strongly understudied, precludes a comprehensive understanding of the effects of fragmentation and disturbance on tropical bats. We strongly encourage increased research in the Paleotropics and emphasize the need for long-term studies , approaches designed to integrate multiple scales, and answering questions that are key to conserving tropical bats in an era of environmental change and dominance of modified habitats (i.e., the Anthropocene).
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Natural bodies of open water in desert landscapes, such as springs and ephemeral pools, and the plant-life they support, are important resources for the survival of animals in hyper arid, arid and semi-arid (dryland) environments. Human-made artificial water sources, i.e. waste-water treatment ponds, catchments and reservoirs, have become equally important for wildlife in those areas. Bodies of open water are used by bats either for drinking and/or as sites over which to forage for aquatic emergent insects. Due to the scarcity of available water for replenishing water losses during roosting and flight, open bodies of water of many shapes and sizes may well be a key resource influencing the survival, activity, resource use and the distribution of insectivorous bats . In this chapter, we review the current knowledge of bats living in semi- and arid regions around the world and discuss the factors that influence their richness , behaviour and activity around bodies of water. We further present how increased anthropogenic changes in hydrology and water availability may influence the distribution of species of bats in desert environments and offer directions for future research on basic and applied aspects on bats and the water they use in these environments.
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The landscape surrounding protected areas influences their ability to maintain ecosystem functions and achieve conservation goals. As anthropogenic intensifica-tion continues, it is important to monitor land-use and land-cover change in and around protected areas. We measure land-cover change surrounding protected areas in the Maputaland-Pondoland-Albany Biodiversity hotspot from the 1980s to present. Using Landsat imagery, we classified land cover within and around each protected area. Agricultural land uses were increasing and often directly border protected area boundaries. Human settlements increased around every protected area, potentially increasing human activity along the edges of protected areas and threatening their ecological integrity. Urban expansion around protected areas varied but increased as much as 10%. Woody vegetation cover varied both within and around protected areas with possible evidence of deforestation and shrub encroachment throughout the hotspot. We recommend monitoring land cover across southeastern Africa to better understand regional trends in land-use impacts to protected areas.
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An analysis of observed trends in African annual-average near-surface temperatures over the last five decades reveals drastic increases, particularly over parts of the subtropics and central tropical Africa. Over these regions, temperatures have been rising at more than twice the global rate of temperature increase. An ensemble of high-resolution downscalings, obtained using a single regional climate model forced with the sea-surface temperatures and sea-ice fields of an ensemble of global circulation model (GCM) simulations, is shown to realistically represent the relatively strong temperature increases observed in subtropical southern and northern Africa. The amplitudes of warming are generally underestimated, however. Further warming is projected to occur during the 21st century, with plausible increases of 4–6 °C over the subtropics and 3–5 °C over the tropics by the end of the century relative to present-day climate under the A2 (a low mitigation) scenario of the Special Report on Emission Scenarios. High impact climate events such as heat-wave days and high fire-danger days are consistently projected to increase drastically in their frequency of occurrence. General decreases in soil-moisture availability are projected, even for regions where increases in rainfall are plausible, due to enhanced levels of evaporation. The regional dowscalings presented here, and recent GCM projections obtained for Africa, indicate that African annual-averaged temperatures may plausibly rise at about 1.5 times the global rate of temperature increase in the subtropics, and at a somewhat lower rate in the tropics. These projected increases although drastic, may be conservative given the model underestimations of observed temperature trends. The relatively strong rate of warming over Africa, in combination with the associated increases in extreme temperature events, may be key factors to consider when interpreting the suitability of global mitigation targets in terms of African climate change and climate change adaptation in Africa.
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A new activity index for acoustical bat data is presented. The AI (acoustic activity index) was highly correlated to bat passes but proved to be a less biased index of activity. The method dispenses with the need to define, identify and account bat passes and provides a simple means to quantify activity. It uses the Anabat system where acoustic surveys are carried out in real time with the data saved directly to a computer hard drive, taking advantage of the date-time information encoded into each file. The method is based upon the presence/absence of a species occurrence during one-minute time intervals and avoids skewing an index of activity that may reflect the behavior of the species sampled. Examples are given showing that the AI is an effective measure of bat activity allowing comparisons between sites, times and species.
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Bat distributions are still comparatively poorly known in Africa and updated national species lists do not exist for many countries. We present a revised checklist of the bats of Swaziland, which includes seven species not previously listed. Of these, two species are recent additions (Mops midas and Myotis bocagii) and these records marginally extend their known distributional range. A total of 26 species of bats are now known from the country , but additional surveys are predicted to add more taxa to the list. These new records predominantly come from human-modified landscapes, underscoring the importance of further surveys in such transformed habitats.
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Nakagawa & Schielzeth extended the widely used goodness-of-fit statistic R2 to apply to generalized linear mixed models (GLMMs). However, their R2GLMM method is restricted to models with the simplest random effects structure, known as random intercepts models. It is not applicable to another common random effects structure, random slopes models. I show that R2GLMM can be extended to random slopes models using a simple formula that is straightforward to implement in statistical software. This extension substantially widens the potential application of R2GLMM.
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Maximum likelihood or restricted maximum likelihood (REML) estimates of the parameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R. As for most model-fitting functions in R, the model is described in an lmer call by a formula, in this case including both fixed- and random-effects terms. The formula and data together determine a numerical representation of the model from which the profiled deviance or the profiled REML criterion can be evaluated as a function of some of the model parameters. The appropriate criterion is optimized, using one of the constrained optimization functions in R, to provide the parameter estimates. We describe the structure of the model, the steps in evaluating the profiled deviance or REML criterion, and the structure of classes or types that represents such a model. Sufficient detail is included to allow specialization of these structures by users who wish to write functions to fit specialized linear mixed models, such as models incorporating pedigrees or smoothing splines, that are not easily expressible in the formula language used by lmer.
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Across the planet, grass-dominated biomes are experiencing shrub encroachment driven by atmospheric CO2 enrichment and land-use change. By altering resource structure and availability, shrub encroachment may have important impacts on vertebrate communities. We sought to determine the magnitude and variability of these effects across climatic gradients, continents, and taxa, and to learn whether shrub thinning restores the structure of vertebrate communities.
Article
Many bat species in Europe have suffered severe population declines during the 20th century, and the main drivers of this decline is likely the loss of foraging habitats at local and landscape levels due to farmland in-tensification, which also poses a serious threat to biodiversity and affects species interactions and ecosystem functions. Several studies reported positive effects of organic compared to conventional farming on bat populations and on nocturnal insect prey abundance. We registered the flight and feeding activity of 12 bat species in rice paddies in Northwestern Italy to test the effect of wetland farm management and agricultural intensification on bats habitat use. Our study evaluated the different ecological roles of organic vs conventional rice farms and natural wetlands in conservation of bat species. For the 12 species under study, flying activity was recorded in all three land management types. Only the genus Pipistrellus hunted in conventional and organic farms. Myotis sp, Eptesicus serotinus and Hypsugo savii were recorded hunting only in natural wetlands. Rinolophus ferrumequinum was detected only in natural wetlands. Bats fed in organic farms as well as in natural wetlands, whereas they were unlikely to forage in conventional farms. Conventional rice paddies do not provide ideal foraging sites for bats, likely due to the widespread use of pesticides, water management, and intensive weed control on embankments. Organic rice paddies, due to the less aggressive management, appear to have a higher habitat quality compared to conventional ones, and are therefore more suitable for feeding activities, possibly due to the greater availability of prey. Furthermore, while the limited ecological value of conventional farms for bat conservation is confirmed in this research for rice paddies, further effort should be made to preserve natural wetlands. We argued that farmland practices that maximise organic farming and ensure the conservation of natural wetlands, in accordance with the recent reform of the Common Agricultural Policy, are essential for bat conservation in agricultural environments and, more generally, to preserve biodiversity.
Article
For decades, there has been enormous scientific interest in tropical savannahs and grasslands, fuelled by the recognition that they are a dynamic and potentially unstable biome, requiring periodic disturbance for their maintenance. However, that scientific interest has not translated into widespread appreciation of, and concern about threats to, their biodiversity. In terms of biodiversity, grassy biomes are considered poor cousins of the other dominant biome of the tropics—forests. Simple notions of grassy biomes being species-poor cannot be supported; for some key taxa, such as vascular plants, this may be valid, but for others it is not. Here, we use an analysis of existing data to demonstrate that high-rainfall tropical grassy biomes (TGBs) have vertebrate species richness comparable with that of forests, despite having lower plant diversity. The Neotropics stand out in terms of both overall vertebrate species richness and number of range-restricted vertebrate species in TGBs. Given high rates of land-cover conversion in Neotropical grassy biomes, they should be a high priority for conservation and greater inclusion in protected areas. Fire needs to be actively maintained in these systems, and in many cases re-introduced after decades of inappropriate fire exclusion. The relative intactness of TGBs in Africa and Australia make them the least vulnerable to biodiversity loss in the immediate future. We argue that, like forests, TGBs should be recognized as a critical—but increasingly threatened—store of global biodiversity. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’.
Code
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes. [Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
Article
Understanding how animal groups respond to contemporary habitat loss and fragmentation is essential for development of strategies for species conservation. Until now, there has been no consensus about how landscape degradation affects the diversity and distribution of Neotropical bats. Some studies demonstrate population declines and species loss in impacted areas, although the magnitude and generality of these effects on bat community structure are unclear. Empirical fragmentation thresholds predict an accentuated drop in biodiversity, and species richness in particular, when less than 30% of the original amount of habitat in the landscape remains. In this study, we tested whether bat species richness demonstrates this threshold response, based on 48 sites distributed across 12 landscapes with 9-88% remaining forest in Brazilian cerrado-forest formations. We also examined the degree to which abundance was similarly affected within four different feeding guilds. The threshold value for richness, below which bat diversity declines precipitously, was estimated at 47% of remaining forest. To verify if the response of bat abundance to habitat loss differed among feeding guilds, we used a model selection approach based on Akaike's information criterion. Models accounted for the amount of riparian forest, semideciduous forest, cerrado, tree plantations, secondary forest, and the total amount of forest in the landscape. We demonstrate a nonlinear effect of the contribution of tree plantations to frugivores, and a positive effect of the amount of cerrado to nectarivores and animalivores, the groups that responded most to decreases in amount of forest. We suggest that bat assemblages in interior Atlantic Forest and cerrado regions of southeastern Brazil are impoverished, since we found lower richness and abundance of different groups in landscapes with lower amounts of forest. The relatively higher threshold value of 47% suggests that bat communities have a relatively lower resistance to habitat degradation than other animal groups. Accordingly, conservation and restoration strategies should focus on increasing the amount of native vegetation of landscapes so as to enhance species richness of bats.
Article
The recent trend of agricultural intensification in tropical landscapes poses a new threat to biodiversity conservation. Conversion of previously heterogeneous agricultural landscapes to intensive plantation agriculture simplifies and homogenizes the landscape, reducing availability, and connectivity of natural habitat for native species. To assess the impact of agricultural intensification on bats, we charac- terized the bat assemblage in the Sarapiqui region of Costa Rica, where heterogeneous land uses are being converted to intensive, large- scale pineapple plantations. In 2012 and 2013, we sampled bats in 20 remnant forest patches surrounded by varying proportions of pasture, mature forest, and pineapple and captured 1821 individual bats representing 39 species. We used ordination analyses to evaluate changes in species composition, where pineapple is the main component of the agricultural matrix. We identified landscape metrics specifically correlated with pineapple and used multiple linear regression to test their effects on bat species richness, diversity, and guild- specific relative abundance. Results suggest pineapple expansion is driving changes in assemblage composition in remnant forest patches, resulting in new assemblages with higher proportions of frugivorous bats and lower proportions of insectivorous bats than in continuous mature forests. In addition, while pineapple does not diminish total bat species richness and diversity, the reduced forest cover and increased distance between forest patches in pineapple plantations has a significant negative impact on the relative abundance of insectivores. We also identify a potential threshold effect whereby patches surrounded by more than 50 percent forest can retain assemblage composition similar to that found in continuous mature forest.
Article
Global change will likely affect savanna and forest structure and distributions, with implications for diversity within both biomes. Few studies have examined the impacts of both expected precipitation and land-use changes on vegetation structure in the future, despite their likely severity. Here we modeled tree cover in Sub-Saharan Africa, as a proxy for vegetation structure and land cover change, using climatic, edaphic and anthropic data (R2 = 0.97). Projected tree cover for the year 2070, simulated using scenarios that include climate and land-use projections, generally decreased, both in forest and savanna, although the directionality of changes varied locally. The main driver of tree cover changes was land-use change; the effects of precipitation change were minor by comparison. Interestingly, carbon emissions mitigation via increasing biofuels production resulted in decreases in tree cover, more severe than scenarios with more intense precipitation change, especially within savannas. Evaluation of tree cover change against protected area extent at the WWF Ecoregion scale suggested areas of high biodiversity and ecosystem services concern. Those forests most vulnerable to large decreases in tree cover were also highly protected, potentially buffering the effects of global change. Meanwhile, savannas, especially where they immediately bordered forests (e.g. West and Central Africa), were characterized by a dearth of protected areas, making them highly vulnerable. Savanna must become an explicit policy priority in the face of climate and land use change if conservation and livelihoods are to remain viable into the next century. This article is protected by copyright. All rights reserved.
Article
The focus of conservation biology has been predominantly the study of single species, and conservation management and legislation has been directed mostly at the species level. Increasingly, however, there has been a recognition that ecosystems and landscapes need to be considered, since they form the physical and biotic context within which species exist. Increased emphasis on the landscape scale suggests that the emerging discipline of landscape ecology might have much to offer conservation biology. Landscape ecology is still a young science with no well-defined theoretical framework and little rigorous quantitative methodology. It aims to study patterns, processes and changes at the scale of hectares to square kilometers. Its focus on the pattern and dynamics of ecosystems or patches within a landscape offers much which is of relevance to conservation biology. Topics such as disturbance, patch dynamics, metapopulation dynamics, landscape flows, connectivity and fragmentation all have relevance to the conservation of biodiversity in natural, altered and rapidly changing systems. The papers in this issue provide a cross section of Australian research into landscape ecology which is of relevance to conservation biology. Methodological, theoretical and practical aspects are covered. I suggest that effective conservation of biodiversity will be achieved only if the landscape context is taken into account.
Article
Regression models allow us to isolate the relationship between the outcome and an explanatory variable while the other variables are held constant. Here, we introduce an R package, visreg, for the convenient visualization of this relationship via short, simple function calls. In addition to estimates of this relationship, the package also provides pointwise confidence bands and partial residuals to allow assessment of variability, outliers, and deviations from modeling assumptions. The package also provides several options for visualizing models with interactions, including lattice plots, contour plots, and both static and interactive perspective plots. The implementation of the package is designed to be as generic as possible, allowing visualization not only of linear models, but of generalized linear models (glm), proportional hazards models (coxph), generalized additive models (gam), robust regression models (rlm), and more.
Article
AimTo identify characteristics of a human-modified landscape that promote taxonomic (TD), functional (FD) and phylogenetic (PD) dimensions of bat biodiversity.LocationCaribbean lowlands of northeastern Costa Rica.Methods During the dry and wet seasons, we quantified TD (Simpson's diversity), as well as FD and PD (Rao's quadratic entropy) of phyllostomid bat assemblages at 15 sites that represented a forest loss and fragmentation gradient. FD was estimated separately for each of seven functional components that reflect particular niche axes (e.g. diet, foraging strategy) and for all functional components combined (FDall). PD was based on relatedness of species derived from a supertree. We identified the best explanatory landscape characteristics of each dimension using hierarchical partitioning.ResultsLandscape effects were dimension and season specific. During the dry season, TD and PD increased with increasing proportions of pasture or size of forest patches, whereas FDall decreased with increasing size of forest patches. During the wet season, TD increased with increasing forest patch size, whereas FDall and PD increased with increasing compactness of forest patches and decreasing proximity. Decomposition of FD into separate functional components revealed different landscape effects on ecological aspects of assemblages.Main conclusionsOne dimension of biodiversity was not a good surrogate for another. Rather, decomposition of biodiversity into different dimensions and functional components facilitated identification of the aspects of assemblages that are most affected by forest conversion and fragmentation. Areas with intermediate amounts of forest and pasture during the dry season harboured highest diversity from taxonomic, functional and phylogenetic perspectives. During the wet season, areas with large, compact forest patches promoted the dimensions of biodiversity. Placement of areas with even amounts of forest and pasture adjacent to large, compact forest patches (e.g. reserves) may maintain high biodiversity of bats and the ecosystem functions that they provide throughout the year.
Article
Agriculture is a dominant land use worldwide with approximately 40% of the land's surface used for farming. In many countries, particularly parts of Europe, this figure is substantially higher and most agricultural land is under intensive practices aimed at maximising the production of food. The intensification and expansion of modern agricultural practices led to the biological simplification of the farmed environment, which has resulted in declines in farmland biodiversity during the last century. As with other taxa, many bat species have suffered severe population declines during the 20th century, with agriculture believed to be one of the main drivers reducing roost availability and foraging habitat. Lower intensity farming methods, and the creation or management of habitat features on farmland could potentially mitigate some of these negative impacts but the effects of this on bats, in comparison to other taxa, have received relatively little attention. Here, I review evidence on the impacts of efforts to increase biodiversity in agricultural landscapes on bat populations, and explore whether responses of bats to agricultural activities are similar to those of other taxa, a necessary requirement if they are to be used as bioindicator species.
Article
1.Shipley et al. (2006) proposed a maximum entropy approach to studying how species relative abundance is mediated by their traits, “community assembly via trait selection” (CATS).2.In this paper we build on recent equivalences between the maximum entropy formalism and Poisson regression to show that CATS is equivalent to a generalised linear model for abundance, with species traits as predictor variables.3.Main advantages gained by access to the machinery of generalised linear models can be summarised as advantages in interpretation, model-checking, extensions and inference.4.A more difficult issue however is the development of valid methods of inference for single-site data, as species correlation in abundance is not accounted for in CATS (whether specified as a regression or via maximum entropy). This issue can be circumvented for multi-site data using design-based inference.5.These points are illustrated by example - our plant abundances were found to violate the implicit Poisson assumption of CATS, but a negative binomial regression had much-improved fit, and our model was extended to multi-site data in order to directly model the environment-trait interaction. Violations of the Poisson assumption were strong and accounting for them qualitatively changed results, presumably because larger counts had undue influence when overdispersion had not been accounted for. We advise that future CATS analysts routinely check for overdispersion, and account for it if present.This article is protected by copyright. All rights reserved.