Standardized genetic diversity‐life history correlates for improved genetic resource management of Neotropical trees

Aim

Life history traits and range size are key correlates of genetic diversity in trees. We used a standardized sampling protocol to explore how life history traits and range size relate to the magnitude, variance and structuring (both between‐ and within‐population) of genetic diversity in Neotropical tree species.

Location

The Neotropics

Methods

We present a meta‐analysis of new population genetic data generated for 23 Neotropical tree species (=2,966 trees, 86 populations) across a shared and broad geographic area. We compared established population genetic metrics across these species (e.g., genetic diversity, population structure, fine‐scale genetic structure), plus we estimated the rarely used variance in genetic diversity among populations. We used a multivariate, maximum likelihood, multimodel inference approach to explore the relative influence of life history traits and range size on patterns of neutral genetic diversity.

Results

We found that pioneer and narrow range species had lower levels but greater variance in genetic diversity—signs of founder effects and stronger genetic drift. Animal‐dispersed species had lower population differentiation, indicating extensive gene flow. Abiotically dispersed and pioneer species had stronger fine‐scale genetic structure, suggesting restricted seed dispersal and family cohort establishment.

Main conclusions

Our multivariable and multispecies approach allows ecologically relevant conclusions, since knowing whether one parameter has an effect, or one species shows a response in isolation, is dependent on the combination of traits expressed by a species. Our study demonstrates the influence of ecological processes on the distribution of genetic variation in tropical trees, and will help guide genetic resource management, and contribute to predicting the impacts of land use change.

     

Independent introductions and sequential founder events shape genetic differentiation and diversity of the invasive green anole (Anolis carolinensis) on Pacific Islands

Aim

Natural range expansions and human‐mediated colonizations usually involve a small number of individuals that establish new populations in novel habitats. In both cases, founders carry only a fraction of the total genetic variation of the source populations. Here, we used native and non‐native populations of the green anole, Anolis carolinensis, to compare the current distribution of genetic variation in populations shaped by natural range expansion and human‐mediated colonization.

Location

North America, Hawaiian Islands, Western Pacific Islands.

Methods

We analysed 401 mtDNA haplotypes to infer the colonization history of A. carolinensis on nine islands in the Pacific Ocean. We then genotyped 576 individuals at seven microsatellite loci to assess the levels of genetic diversity and population genetic differentiation for both the native and non‐native ranges.

Results

Our findings support two separate introductions to the Hawaiian Islands and several western Pacific islands, with subsequent colonizations within each region following a stepping‐stone model. Genetic diversity at neutral markers was significantly lower in the non‐native range because of founder effects, which also contributed to the increased population genetic differentiation among the non‐native regions. In contrast, a steady reduction in genetic diversity with increasing distance from the ancestral population was observed in the native range following range expansion.

Main conclusions

Range expansions cause serial founder events that are the spatial analogue of genetic drift, producing a pattern of isolation‐by‐distance in the native range of the species. In human‐mediated colonizations, after an initial loss of genetic diversity, founder effects appear to persist, resulting in overall high genetic differentiation among non‐native regions but an absence of isolation‐by‐distance. Contrasting the processes influencing the amount and structuring of genetic variability during natural range expansion and human‐mediated biological invasions can shed new light on the fate of natural populations exposed to novel and changing environments.

     

Natural rewilding of the Great Basin: Genetic consequences of recolonization by black bears (Ursus americanus)

Aim

In the mid‐20th century, many populations of large‐bodied mammals experienced declines throughout North America. Fortunately, within the last several decades, some have begun to rebound and even recolonize extirpated portions of their native range, including black bears (Ursus americanus) in the montane areas of the western Great Basin. In this study, we examine genetic variation in source and recolonized areas to better understand the genetic consequences of recolonization.

Location

Western Great Basin, USA.

Methods

Using multiple loci, we characterized genetic variation among source and recently recolonized areas occupied by black bears, tested for population structure and applied approximate Bayesian computation to test competing hypotheses of demographic history. We assessed signals of gene flow using expectations of genetic consequences derived from alternative modes of recolonization (bottleneck, metapopulation, island model) and tested for significant signals of genetic bottlenecks in areas recently recolonized by black bears.

Results

As anticipated from field survey data and hypothesized expectations, genetic variation of western Great Basin black bears retain an overall signature of demographic decline followed by recent rebound. Furthermore, results reveal that bears in the recolonized range are minimally differentiated from the source area, but newly established subpopulations have lower effective population sizes and reduced allelic diversity. Nevertheless, recolonized areas fail to show a significant signal of a genetic bottleneck. Moreover, bears occupying recolonized areas experience asymmetric gene flow, yielding strong support for a model of genetic connectivity that is best described as a metapopulation.

Main Conclusion

This study presents one of the few empirical examples of genetic consequences of natural recolonization in large‐bodied mammals. Furthermore, these results have implications for understanding the complexities associated with the genetic consequences of recent and ongoing recolonization and highlight the need to develop management strategies uniquely tailored to support connectivity between source and recolonized areas.

     

Ecological correlates of mammal β‐diversity in Amazonian land‐bridge islands: from small‐ to large‐bodied species

Aim

Mega hydroelectric dams have become one of the main drivers of biodiversity loss in the lowland tropics. In these reservoirs, vertebrate studies have focused on local (α) diversity measures, whereas between‐site (β) diversity remains poorly assessed despite its pivotal importance in understanding how species diversity is structured and maintained. Here, we unravel the patterns and ecological correlates of mammal β‐diversity, including both small (SM) and midsized to large mammal species (LM) across 23 islands and two continuous forest sites within a mega hydroelectric reservoir.

Location

Balbina Hydroelectric Dam, Central Brazilian Amazonia.

Methods

Small mammals were sampled using live and pitfall traps (48,350 trap‐nights), and larger mammals using camera traps (8,160 trap‐nights). β‐diversity was examined for each group using multiplicative diversity decomposition of Hill numbers, which considers the importance of rare, common and dominant species, and tested to what extent those were related to a set of environmental characteristics measured at different spatial scales.

Results

β‐diversity for both mammal groups was higher when considering species presence–absence. When considering species abundance, β‐diversity was significantly higher for SM than for LM assemblages. Habitat variables, such as differences in tree species richness and percentage of old‐growth trees, were strong correlates of β‐diversity for both SMs and LMs. Conversely, β‐diversity was weakly related to patch and landscape characteristics, except for LMs, for which β‐diversity was correlated with differences in island sizes.

Main conclusions

The lower β‐diversity of LMs between smaller islands suggests subtractive homogenization of this group. Although island size plays a major role in structuring mammal α‐diversity in several land‐bridge islands, local vegetation characteristics were additional key factors determining β‐diversity for both mammal groups. Maintaining the integrity of vegetation characteristics and preventing the formation of a large set of small islands within reservoirs should be considered in long‐term management plans in both existing and planned hydropower development in lowland tropical forests.

     

Are all data types and connectivity models created equal? Validating common connectivity approaches with dispersal data

Aim

There is enormous interest in applying connectivity modelling to resistance surfaces for identifying corridors for conservation action. However, the multiple analytical approaches used to estimate resistance surfaces and predict connectivity across resistance surfaces have not been rigorously compared, and it is unclear what methods provide the best inferences about population connectivity. Using a large empirical data set on puma (Puma concolor), we are the first to compare several of the most common approaches for estimating resistance and modelling connectivity and validate them with dispersal data.

Location

Southern California, USA.

Methods

We estimate resistance using presence‐only data, GPS telemetry data from puma home ranges and genetic data using a variety of analytical methods. We model connectivity with cost distance and circuit theory algorithms. We then measure the ability of each data type and connectivity algorithm to capture GPS telemetry points of dispersing pumas.

Results

We found that resource selection functions based on GPS telemetry points and paths outperformed species distribution models when applied using cost distance connectivity algorithms. Point and path selection functions were not statistically different in their performance, but point selection functions were more sensitive to the transformation used to convert relative probability of use to resistance. Point and path selection functions and landscape genetics outperformed other methods when applied with cost distance; no methods outperformed one another with circuit theory.

Main conclusions

We conclude that path or point selection functions, or landscape genetic models, should be used to estimate landscape resistance for wildlife. In cases where resource limitations prohibit the collection of GPS collar or genetic data, our results suggest that species distribution models, while weaker, may still be sufficient for resistance estimation. We recommend the use of cost distance‐based approaches, such as least‐cost corridors and resistant kernels, for estimating connectivity and identifying functional corridors for terrestrial wildlife.

     

Conservation implications of divergent global patterns of ant and vertebrate diversity

Aim

Global conservation planning is often oriented around vertebrates and plants, yet most organisms are invertebrates. To explore the potential conservation implications of this bias, we assessed how well patterns of diversity for an influential group of invertebrates, the ants, correspond with those of three vertebrate groups (birds, mammals and amphibians).

Location

Global.

Methods

We compiled data on the number of genera of ants and the three vertebrate groups for 370 political regions across the world. We then compared their correlations both for overall diversity and between subsets of genera likely to be of conservation concern. We also developed generalized additive models (GAM) to identify regions where vertebrates and ants diverged in their diversity patterns.

Results

While ant and vertebrate diversity do positively correlate, the correlations are substantially weaker for the ant lineages of the greatest conservation concern. Vertebrates also notably fail to predict ant diversity in specific geographic areas, including Australia and Southeast Asia, parts of Africa and Madagascar, and south‐western China. These failures may be genuine differences in diversity patterns, or they may indicate important gaps in our knowledge of ant and vertebrate diversity.

Main conclusions

We conclude that it is currently unwise to assume that global conservation priorities based on vertebrates will conserve ants as well. We suspect that this also applies to other invertebrates.

     

Ecological traits modulate bird species responses to forest fragmentation in an Amazonian anthropogenic archipelago

Aim

We assessed patterns of avian species loss and the role of morpho‐ecological traits in explaining species vulnerability to forest fragmentation in an anthropogenic island system. We also contrasted observed and detectability‐corrected estimates of island occupancy, which are often used to infer species vulnerability.

Location

Tucuruí Hydroelectric Reservoir, eastern Brazilian Amazonia.

Methods

We surveyed forest birds within 36 islands (3.4–2,551.5 ha) after 22 years of post‐isolation history. We applied species–area relationships to assess differential patterns of species loss among three data sets: all species, forest specialists and habitat generalists. After controlling for phylogenetic non‐independence, we used observed and detectability‐corrected estimates of island occupancy separately to build competing models as a function of species traits. The magnitude of the difference between these estimates of island occupancy was contrasted against species detectability.

Results

The rate of species loss as a function of island area reduction was higher for forest specialists than for habitat generalists. Accounting for the area effect, forest fragmentation did not affect the overall number of species regardless of the data set. Only the interactive model including natural abundance, habitat breadth and geographic range size was strongly supported for both estimates of island occupancy. For 30 species with detection probabilities below 30%, detectability‐corrected estimates were at least tenfold higher than those observed. Conversely, differences between estimates were negligible or non‐existent for all 31 species with detection probabilities exceeding 45.5%.

Main conclusions

Predicted decay of avian species richness induced by forest loss is affected by the degree of habitat specialisation of the species under consideration, and may be unrelated to forest fragmentation per se. Natural abundance was the main predictor of species island occupancy, although habitat breadth and geographic range size also played a role. We caution against using occupancy models for low‐detectability species, because overestimates of island occupancy reduce the power of species‐level predictions of vulnerability.

     

Ancient DNA identifies post‐glacial recolonisation,not recent bottlenecks,as the primary driver of contemporary mtDNA phylogeography and diversity in Scandinavian brown bears

Aim

Brown bear populations in Scandinavia show a strong mitochondrial DNA (mtDNA) phylogeographic structure and low diversity relative to other parts of Europe. Identifying the timing and origins of this mtDNA structure is important for conservation programs aimed at restoring populations to a natural state. Therefore, it is essential to identify whether contemporary genetic structure is linked to post‐glacial recolonisation from divergent source populations or an artefact of demographic impacts during recent population bottlenecks. We employed ancient DNA techniques to investigate the timing and potential causes of these patterns.

Location

Scandinavia and Europe.

Methods

Ancient mtDNA sequences from 20 post‐glacial Scandinavian bears were used to investigate phylogeographic structure and genetic diversity over the last 6000 years. MtDNA from 19 Holocene Norwegian bears was compared with 499 sequences from proximate extant populations in Sweden, Finland, Estonia and western Russia. A single mtDNA sequence from a Holocene Denmark sample was compared with 149 ancient and modern bears from Western Europe.

Results

All nineteen Holocene Norwegian samples are identical to or closely related to the most common mtDNA haplotype found in northern Europe today. MtDNA diversity was low and not significantly different from extant populations in northern Europe. In Denmark, we identified a single mtDNA haplotype that is previously unrecorded from Scandinavia.

Main conclusions

The current discrete phylogeographic structure and lack of mtDNA diversity in Scandinavia is attributed to serial founder effects during post‐glacial recolonisation from divergent source populations rather than an artefact of recent anthropogenic impacts. In contrast to previous interpretations, the recolonisation of southern Scandinavia may not have been limited to bears from a single glacial refugium. Results highlight the importance of conserving the long‐term evolutionary separation between northern and southern populations and identify southern Scandinavia as an important reservoir of mtDNA diversity that is under threat in other parts of Europe.

     

Divergent introduction histories among invasive populations of the delicate skink ( Lampropholis delicata): has the importance of genetic admixture in the success of biological invasions been overemphasized?

Aim

Invasive species are predicted to experience a reduction in genetic diversity during the introduction process because of founder effects, yet they are able to successfully establish in new regions and outcompete the native biota. Admixture has been proposed as a potential solution to this genetic paradox. We adopted a phylogeographic approach to investigate the invasion history of the delicate skink ( Lampropholis delicata) in the Pacific region and test the hypothesis that admixture is important for the success of biological invasions.

Location

Eastern Australia and the Pacific region (Lord Howe Island, New Zealand, Hawaii).

Methods

We obtained mitochondrial DNA sequence data ( ND2, ND4) from across the native Australian range (238 samples, 120 populations) and 371 samples from the introduced range of L. delicata. Genetic distances and Analysis of molecular variance (AMOVA) were used to examine the level of genetic variation across the native and introduced ranges.

Results

Fourteen haplotypes were evident in the introduced range (1 in Hawaii, 7 in New Zealand, 7 in Lord Howe Island), with a shared haplotype present in both New Zealand and Lord Howe Island. Five source regions were identified (Brisbane, Tenterfield, Border Ranges, Yamba‐Coffs Harbour, Sydney) from across four distinct native‐range genetic lineages. The Hawaiian population stems from a single introduction from Brisbane, whereas one or more introductions from the Tenterfield region led to the New Zealand populations. Multiple introductions from across all five source regions have resulted in extreme admixture (up to 8.3% sequence divergence) within Lord Howe Island.

Main Conclusions

L. delicata introductions are capable of being successful both in the presence and absence of admixture. Contrary to the predictions of the sequential two‐step model, the presence of admixture was not related to the time since initial introduction. We suggest that the importance of admixture in determining the success of biological invasions has been overemphasized.

     

Species‐poor and low‐lying sites are more ecologically unique in a hyperdiverse Amazon region: Evidence from multiple taxonomic groups

Aim

We analysed beta‐diversity patterns of various biological groups simultaneously, from the perspective of site ecological uniqueness. We also investigated whether ecological uniqueness variation could be explained by variations in environmental conditions and spatial variables.

Data

Central Amazonia.

Methods

We estimated the total beta diversity and ecological uniqueness for 14 biological groups, including plants and animals, sampled at the same sites on a mesoscale in central Amazonia, Brazil. The uniqueness values for all biological groups were combined in a single matrix (multi‐taxa matrix of site uniqueness), which was then used as a response variable matrix in a partial redundancy analysis. We also investigated differences in the uniqueness patterns between plant and animal groups.

Results

In general, plants showed higher total beta diversity than animals. For plants, uniqueness was explained mainly by environmental conditions, while for animals, uniqueness was also related to spatial variables. Although variation in uniqueness was mainly related to soil clay content, it is difficult to determine a single major environmental variable underlying the variation in uniqueness because the topographical gradient influences many of them, including soil clay content.

Main Conclusion

The uniqueness values were higher in low‐lying areas, indicating that near‐stream sites were more ecologically unique. Despite the lower number of species in the lowlands, their unique biota contributed strongly to the maintenance of the total beta diversity of the area. This finding should be considered in conservation plans that aim to represent and preserve the regional biota. Our approach proved to be useful to analyse and compare the ecological uniqueness of multiple taxa.

     

Congruent phylogeographic patterns in a young radiation of live‐bearing marine snakes: Pleistocene vicariance and the conservation implications of cryptic genetic diversity

Aim

To investigate phylogeographic patterns among and within co‐occurring sea snake species from Australia's endemic viviparous Aipysurus lineage, which includes critically endangered species, and evaluate the conservation implications of geographically structured patterns of genetic divergence and diversity.

Location

Australia's tropical shallow water marine environments spanning four regions: Great Barrier Reef (GBR), Gulf of Carpentaria (GoC), Timor Sea (TS) and coastal WA (WAC).

Methods

Samples from >550 snakes representing all nine nominal Aipysurus group species were obtained from throughout their known Australian ranges. Coalescent phylogenetic analyses and Bayesian molecular dating of mitochondrial DNA, combined with Bayesian and traditional population genetic analyses of 11 microsatellite loci, were used to evaluate genetic divergence and diversity.

Results

Mitochondrial DNA revealed highly congruent phylogeographic breaks among co‐occurring species, largely supported by nuclear microsatellites. For each species, each region was characterized by a unique suite of haplotypes (phylogroups). Divergences between the TS, GoC and/or GBR were invariably shallow and dated as occurring 50,000–130,000 years ago, coinciding with the cyclic Pleistocene emergence of the Torres Strait land bridge. By contrast, sea snakes from coastal WA were consistently highly divergent from other regions and dated as diverging 178,000–526,000 years ago, which was not associated with any known vicariant events.

Main Conclusions

Previously unappreciated highly divergent sea snake lineages in coastal WA potentially represent cryptic species, highlighting this region as a high‐priority area for conservation. The cyclic emergence of the Torres Strait land bridge is consisted with observed divergences between the TS, GoC and/or GBR; however, processes involved in the earlier divergences involving the WAC remain to be determined. The observed strong population genetic structures (as surrogates for dispersal) indicate that sea snakes have limited potential to reverse population declines via replenishment from other sources over time frames relevant to conservation.

     

The phylogenetic and functional diversity of regional breeding bird assemblages is reduced and constricted through urbanization

Aim

Urbanization broadly affects the phylogenetic and functional diversity of natural communities through a variety of processes including habitat loss and the introduction of non‐native species. Due to the challenge of acquiring direct measurements, these effects have been studied primarily using “space‐for‐time” substitution where spatial urbanization gradients are used to infer the consequences of urbanization occurring across time. The ability of alternative sampling designs to replicate the findings derived using space‐for‐time substitution has not been tested.

Location

Global.

Methods

We contrasted the phylogenetic and functional diversity of breeding bird assemblages in 58 cities worldwide with the corresponding regional breeding bird assemblages estimated using geographic range maps.

Results

Compared to regional assemblages, urban assemblages contained lower phylogenetic diversity, lower phylogenetic beta diversity, a reduction in the least evolutionary distinct species and the loss of the most evolutionarily distinct species. We found no evidence that these effects were related to the presence of non‐native species. Urban assemblages contained fewer aquatic species and fewer aquatic foraging species. The distribution of body size and range size narrowed for urban assemblages with the loss of species at both tails of the distribution, especially large bodied and broadly distributed species. Urban assemblages contained a greater proportion of species classified as passerines, doves or pigeons; species identified as granivores; species that forage within vegetation or in the air; and species with more generalized associations with foraging strata.

Main conclusions

Urbanization is associated with the overall reduction and constriction of phylogenetic and functional diversity, results that largely replicate those generated using space‐for‐time substitution, increasing our confidence in the quality of the combined inferences. When direct measurements are unavailable, our findings emphasize the value of developing independent sampling methods that broaden and reinforce our understanding of the ecological implications of urbanization.

     

Phylogenetic dimension of tree communities reveals high conservation value of disturbed tropical rain forests

Aim

The conversion of old‐growth tropical forests into human‐modified landscapes threatens biodiversity worldwide, but its impact on the phylogenetic dimension of remaining communities is still poorly known. Negative and neutral responses of tree phylogenetic diversity to land use change have been reported at local and landscape scales. Here, we hypothesized that such variable responses to disturbance depend on the regional context, being stronger in more degraded rain forest regions with a longer history of land use.

Location

Six regions in Mexico and Brazil.

Methods

We used a large vegetation database (6,923 trees from 686 species) recorded in 98 50‐ha landscapes distributed across two Brazilian and four Mexican regions, which exhibit different degrees of disturbance. In each region, we assessed whether phylogenetic alpha and beta diversities were related to landscape‐scale forest loss, the percentage of shade‐intolerant species (a proxy of local disturbance) and/or the relatedness of decreasing (losers) and increasing (winners) taxa.

Results

Contrary to our expectations, the percentage of forest cover and shade‐intolerant species were weakly related to phylogenetic alpha and beta diversities in all but one region. Loser species were generally as dispersed across the phylogeny as winner species, allowing more degraded, deforested and species‐poorer forests to sustain relatively high levels of evolutionary (phylogenetic) diversity.

Main conclusion

Our findings support previous evidence indicating that traits related to high susceptibility to forest disturbances are convergent or have low phylogenetic signal. More importantly, they reveal that the evolutionary value of disturbed forests is (at least in a phylogenetic sense) much greater than previously thought.

     

Multispecies assessment of core areas and connectivity of desert carnivores in central Iran

Aim

Central Iran is a priority area for biodiversity conservation, which is threatened by encroachment on core habitats and fragmentation by roads. The goal of this study was to identify core areas and connectivity corridors for a set of desert carnivores by predicting habitat suitability and calculating resistant kernel, factorial least‐cost path modelling and graph network indices.

Location

Iran.

Methods

We used an ensemble model (EM) of habitat suitability methods to predict the potential habitats of leopard, cheetah, caracal, wild cat, sand cat and grey wolf and used resistant kernel and factorial least‐cost path modelling to identify important core habitats and corridors between patches. We also used a graph network analysis to quantify the importance of each core patch to landscape connectivity.

Results

Potential habitats of the studied carnivores appeared to be strongly influenced by prey density, annual precipitation, topographical roughness, shrubland density and anthropogenic factors. Most of the core patches were covered by protected areas and no‐hunting areas. This may be attributed to the relatively high resistance outside protected areas leading to isolated occupied patches. Patch importance to connectivity was significantly correlated with patch extent, density of dispersing individuals and probability of occurrence in the core patch.

Main conclusions

Our findings revealed that prey abundance in core habitat is critically important, and has higher influence than habitat area per se. In addition, our analysis provided the first map of landscape connectivity for multiple species in Iran and revealed that conserving these species requires integrated landscape‐level management to reduce mortality risk and protect core areas and linkages among them. These results will assist the development of multispecies conservation strategies to protect core areas for carnivores.

     

Species richness and phylogenetic diversity of native and non‐native species respond differently to area and environmental factors

Aim

To test whether native and non‐native species have similar diversity–area relationships (species–area relationships [SARs] and phylogenetic diversity–area relationships [PDARs]) and whether they respond similarly to environmental variables.

Location

United States.

Methods

Using lists of native and non‐native species as well as environmental variables for >250 US national parks, we compared SARs and PDARs of native and non‐native species to test whether they respond similarly to environmental conditions. We then used multiple regressions involving climate, land cover and anthropogenic variables to further explore underlying predictors of diversity for plants and birds in US national parks.

Results

Native and non‐native species had different slopes for SARs and PDARs, with significantly higher slopes for native species. Corroborating this pattern, multiple regressions showed that native and non‐native diversity of plants and birds responded differently to a greater number of environmental variables than expected by chance. For native species richness, park area and longitude were the most important variables while the number of park visitors, temperature and the percentage of natural area were among the most important ones for non‐native species richness. Interestingly, the most important predictor of native and non‐native plant phylogenetic diversity, temperature, had positive effects on non‐native plants but negative effects on natives.

Main conclusions

SARs, PDARs and multiple regressions all suggest that native and non‐native plants and birds responded differently to environmental factors that influence their diversity. The agreement between diversity–area relationships and multiple regressions with environmental variables suggests that SARs and PDARs can be both used as quick proxies of overall responses of species to environmental conditions. However, more importantly, our results suggest that global change will have different effects on native and non‐native species, making it inappropriate to apply the large body of knowledge on native species to understand patterns of community assembly of non‐native species.

     

Modelling the distribution and compositional variation of plant communities at the continental scale

Aim

We investigate whether (1) environmental predictors allow to delineate the distribution of discrete community types at the continental scale and (2) how data completeness influences model generalization in relation to the compositional variation of the modelled entities.

Location

Europe.

Methods

We used comprehensive datasets of two community types of conservation concern in Europe: acidophilous beech forests and base‐rich fens. We computed community distribution models (CDMs) calibrated with environmental predictors to predict the occurrence of both community types, evaluating geographical transferability, interpolation and extrapolation under different scenarios of sampling bias. We used generalized dissimilarity modelling (GDM) to assess the role of geographical and environmental drivers in compositional variation within the predicted distributions.

Results

For the two community types, CDMs computed for the whole study area provided good performance when evaluated by random cross‐validation and external validation. Geographical transferability provided lower but relatively good performance, while model extrapolation performed poorly when compared with interpolation. Generalized dissimilarity modelling showed a predominant effect of geographical distance on compositional variation, complemented with the environmental predictors that also influenced habitat suitability.

Main conclusions

Correlative approaches typically used for modelling the distribution of individual species are also useful for delineating the potential area of occupancy of community types at the continental scale, when using consistent definitions of the modelled entity and high data completeness. The combination of CDMs with GDM further improves the understanding of diversity patterns of plant communities, providing spatially explicit information for mapping vegetation diversity and related habitat types at large scales.

     

An integrated,spatio‐temporal modelling framework for analysing biological invasions

Aim

We develop a novel modelling framework for analysing the spatio‐temporal spread of biological invasions. The framework integrates different invasion drivers and disentangles their roles in determining observed invasion patterns by fitting models to historical distribution data. As a case study application, we analyse the spread of common ragweed (Ambrosia artemisiifolia).

Location

Central Europe.

Methods

A lattice system represents actual landscapes with environmental heterogeneity. Modelling covers the spatio‐temporal invasion sequence in this grid and integrates the effects of environmental conditions on local invasion suitability, the role of invaded cells and spatially implicit “background” introductions as propagule sources, within‐cell invasion level bulk‐up and multiple dispersal means. A modular framework design facilitates flexible numerical representation of the modelled invasion processes and customization of the model complexity. We used the framework to build and contrast increasingly complex models, and fitted them using a Bayesian inference approach with parameters estimated by Markov chain Monte Carlo (MCMC).

Results

All modelled invasion drivers codetermined the A. artemisiifolia invasion pattern. Inferences about individual drivers depended on which processes were modelled concurrently, and hence changed both quantitatively and qualitatively between models. Among others, the roles of environmental variables were assessed substantially differently subject to whether models included explicit source‐recipient cell relationships, spatio‐temporal variability in source cell strength and human‐mediated dispersal means. The largest fit improvements were found by integrating filtering effects of the environment and spatio‐temporal availability of propagule sources.

Main conclusions

Our modelling framework provides a straightforward means to build integrated invasion models and address hypotheses about the roles and mutual relationships of different putative invasion drivers. Its statistical nature and generic design make it suitable for studying many observed invasions. For efficient invasion modelling, it is important to represent changes in spatio‐temporal propagule supply by explicitly tracking the species’ colonization sequence and establishment of new populations.

     

Unravelling the evolutionary origins of biogeographic assemblages

Aim

Floristic and faunal diversity fall within species assemblages that can be grouped into distinct biomes or ecoregions. Understanding the origins of such biogeographic assemblages helps illuminate the processes shaping present‐day diversity patterns and identifies regions with unique or distinct histories. While the fossil record is often sparse, dated phylogenies can provide a window into the evolutionary past of these regions. Here, we present a novel phylogenetic approach to investigate the evolutionary origins of present‐day biogeographic assemblages and highlight their conservation value.

Location

Southern Africa.

Methods

We evaluate the evolutionary turnover separating species clusters in space at different time slices to determine the phylogenetic depth at which the signal for their present‐day structure emerges. We suggest present‐day assemblages with distinct evolutionary histories might represent important units for conservation. We apply our method to the vegetation of southern Africa using a dated phylogeny of the woody flora of the region and explore how the evolutionary history of vegetation types compares to common conservation currencies, including species richness, endemism and threat.

Results

We show the differentiation of most present‐day vegetation types can be traced back to evolutionary splits in the Miocene. The woody flora of the Fynbos is the most evolutionarily distinct, and thus has deeper evolutionary roots, whereas the Savanna and Miombo Woodland show close phylogenetic affinities and likely represent a more recent separation. However, evolutionarily distinct phyloregions do not necessarily capture the most unique phylogenetic diversity, nor are they the most species‐rich or threatened.

Main conclusions

Our approach complements analyses of the fossil record and serves as a link to the history of diversification, migration and extinction of lineages within biogeographic assemblages that is separate from patterns of species richness and endemism. Our analysis reveals how phyloregions capture conservation value not represented by traditional biodiversity metrics.

     

Turnover and nestedness in subtropical dung beetle assemblages along an elevational gradient

Aim

We investigated changes in dung beetle β‐diversity components along a subtropical elevational gradient, to test whether turnover or nestedness‐related processes drive the dissimilarity of assemblages at spatial and temporal scales.

Location

An elevational gradient (200–1,600 m a.s.l.) of the Atlantic Forest in southern Brazil.

Methods

We investigated the extent to which β‐diversity varied along the elevational gradient (six elevations) at both spatial (among sites at different elevations) and temporal (different months at the same site) scales. We compared both the turnover and nestedness‐related dissimilarity of species and genera using multiple‐site or multiple‐month measures and tested whether these measurements were different from random expectations.

Results

A mid‐elevation peak in species richness along the elevational gradient was observed, and the lowest richness occurred at the highest elevations. We found two different groups of species, lowland and highland species, with a mixing of groups at intermediate elevations. The turnover component of β‐diversity was significantly higher for both spatial (i.e. elevational) and temporal changes in species composition. However, when the data for genera by site were considered, the elevational turnover value decreased in relative importance. Nestedness‐related processes are more important for temporal dissimilarity patterns at higher elevation sites.

Main conclusions

Spatial and temporal turnover of dung beetle species is the most important component of β‐diversity along the elevational gradient. High‐elevation assemblages are not subsets of assemblages that inhabit lower elevations, but this relationship ceases when β‐diversity is measured at the generic level. Environmental changes across elevations may be the cause of the differential establishment of distinctive species, but these species typically belong to the same higher taxonomic rank. Conservation strategies should consider elevational gradients in case‐specific scenarios as they may contain distinct species assemblages in lowlands vs. highlands.

     

Species traits suggest European mammals facing the greatest climate change are also least able to colonize new locations

Aim

The risk climate change poses to biodiversity is often estimated by forecasting the areas that will be climatically suitable for species in the future and measuring the distance of the “range shifts” species would have to make to reach these areas. Species’ traits could indicate their capacity to undergo range shifts. However, it is not clear how range‐shift capacity influences risk. We used traits from a recent evidence review to measure the relative potential of species to track changing climatic conditions.

Location

Europe.

Time period

Baseline period (1961–1990) and forecast period (2035–2064).

Major taxa studied

62 mammal species.

Methods

We modelled species distributions using two general circulation models and two representative concentration pathways (RCPs) to calculate three metrics of “exposure” to climate change: range area gained, range area lost and distance moved by the range margin. We identified traits that could inform species’ range‐shift capacity (i.e., potential to establish new populations and proliferate, and thus undertake range shifts), from a recent evidence‐based framework. The traits represent ecological generalization and reproductive strategy. We ranked species according to each metric of exposure and range‐shift capacity, calculating sensitivity to ranking methods, and synthesized both exposure and range‐shift capacity into “risk syndromes.”

Results

Many species studied whose survival depends on colonizing new areas were relatively unlikely to undergo range shifts. Under the worst‐case scenario, 62% of species studied were relatively highly exposed. 47% were highly exposed and had relatively low range‐shift capacity. Only 14% of species faced both low exposure and high range‐shift capacity. Both range‐shift and exposure metrics had a greater effect on risk assessments than climate models.

Main conclusions

The degree to which species’ potential ranges will be altered by climate change often does not correspond to species’ range‐shift capacities. Both exposure and range‐shift capacity should be considered when evaluating biodiversity risk from climate change.