Global tests of regional effect on species richness of vascular plants and terrestrial vertebrates

Determining the effects of regional and contemporary factors on large-scale patterns in species richness has been a fundamental question in modern ecology and biogeography. However, few studies have examined effects of historical and regional factors on species richness at the global scale, and conclusions are often inconsistent or controversial. Here, I use a comprehensive dataset to examine regional effects on species richness of vascular plants and four taxa of terrestrial vertebrates (mammals, birds, reptiles, and amphibians) in the same set of sample units (ecoregions) in seven biogeographic realms across the globe. The same spatial scale and the same set of environmental variables, which are thought to influence large-scale patterns in species richness of vascular plants and terrestrial vertebrates, are used for all the five taxa. Species richness of each taxon is compared across biogeographic realms. Regional effect on species richness has been found for all the five taxa. Of the 90 realm-pair comparisons for the five taxa between observed richness of a region and the richness of the region predicted by the richness–environment relationship derived from the data of another region, 74 (82.2%) showed significant differences between observed and predicted species richness, indicating that a species richness–environment relationship developed for one region cannot accurately predict species richness in other regions of similar environments.     

The global distribution of frugivory in birds

Aim To examine patterns of avian frugivory across clades, geography and environments. Location Global, including all six major biogeographical realms (Afrotropics, Australasia, Indo‐Malaya, Nearctic, Neotropics and Palaearctic). Methods First, we examine the taxonomic distribution of avian frugivory within orders and families. Second we evaluate, with traditional and spatial regression approaches, the geographical patterns of frugivore species richness and proportion. Third, we test the potential of contemporary climate (water–energy, productivity, seasonality), habitat heterogeneity (topography, habitat diversity) and biogeographical history (captured by realm membership) to explain geographical patterns of avian frugivory. Results Most frugivorous birds (50%) are found within the perching birds (Passeriformes), but the woodpeckers and allies (Piciformes), parrots (Psittaciformes) and pigeons (Columbiformes) also contain a significant number of frugivorous species (9–15%). Frugivore richness is highest in the Neotropics, but peaks in overall bird diversity in the Himalayan foothills, the East African mountains and in some areas of Brazil and Bolivia are not reflected by frugivores. Current climate explains more variance in species richness and proportion of frugivores than of non‐frugivores whereas it is the opposite for habitat heterogeneity. Actual evapotranspiration (AET) emerges as the best single climatic predictor variable of avian frugivory. Significant differences in frugivore richness and proportion between select biogeographical regions remain after differences in environment (i.e. AET) are accounted for. Main conclusions We present evidence that both environmental and historical constraints influence global patterns of avian frugivory. Whereas water–energy dynamics possibly constrain frugivore distribution via indirect effects on food plants, regional differences in avian frugivory most likely reflect historical contingencies related to the evolutionary history of fleshy fruited plant taxa, niche conservatism and past climate change. Overall our results support an important role of co‐diversification and environmental constraints on regional assembly over macroevolutionary time‐scales.     

Relative role of contemporary environment versus history in shaping diversity patterns of China's woody plants

What determines large‐scale patterns of species diversity is a central and controversial topic in biogeography and ecology. In this study, we compared the effects of contemporary environment and historical contingencies on species richness patterns of woody plants in China, using fine‐resolution geographic databases of the distributions of 11 405 woody species and climate, topography, and vegetation information. Residuals of species richness‐environment generalized linear models were significantly different from 0 in the majority of seven biogeographical regions, and also differed significantly between these regions, indicating significant deviation from the predicted species richness based on contemporary environment. Additionally, species richness of a given biogeographical region deviated substantially from the predictions of species richness‐environment models developed for the remaining regions combined. This suggests different richness‐environment relationships among regions. These results indicate important historical signals in the species richness patterns of woody plants across China. The signals are especially pronounced in the eastern Himalayas, the Mongolian Plateau, and the Tibetan Plateau, perhaps reflecting their special geological features and history. Nevertheless, partial regression indicated that historical effects were less important relative to contemporary environment. In conclusion, contemporary environment (notably climate) determines the general trend in woody‐plant species richness across China, while historical contingencies generate regional deviations from this trend. Our findings imply that both species diversity and regional evolutionary and ecological histories should be taken into account for future nature conservation.     

Patterns in species richness and endemism of European freshwater fish

Aim  To analyse the patterns in species richness and endemism of the native European riverine fish fauna, in the light of the Messinian salinity crisis and the Last Glacial Maximum (LGM).
Location  European continent.
Methods  After gathering native fish faunistic lists of 406 hydrographical networks, we defined large biogeographical regions with homogenous fish fauna, based on a hierarchical cluster analysis. Then we analysed and compared the patterns in species richness and endemism among these regions, as well as species–area relationships.
Results  Among the 233 native species present in the data set, the Cyprinidae family was strongly dominant (> 50% of the total number of species). Seven biogeographical regions were defined: Western Peri-Mediterranea, Central Peri-Mediterranea, Eastern Peri-Mediterranea, Ponto-Caspian Europe, Northern Europe, Central Europe and Western Europe. The highest regional species richness was observed for Central Peri-Mediterranea and Ponto-Caspian Europe. The highest endemic richness was found in Central Peri-Mediterranea. Species–area relationships were characterized by high slope values for Peri-Mediterranean Europe and low values for Central and Western Europe.
Main conclusions  The results were in agreement with the 'Lago Mare' hypothesis explaining the specificity of Peri-Mediterranean fish fauna, as well as with the history of recolonization of Central and Western Europe from Ponto-Caspian Europe following the LGM. The results also agreed with the mechanisms of speciation and extinction influencing fish diversity in hydrographical networks. We advise the use of the seven biogeographical regions for further studies, and suggest considering Peri-Mediterranean Europe and Ponto-Caspian Europe as 'biodiversity hotspots' for European riverine fish.     

Global richness patterns of venomous snakes reveal contrasting influences of ecology and history in two different clades

Recent studies addressing broad-scale species richness gradients have proposed two main primary drivers: contemporary climate and evolutionary processes (differential balance between speciation and extinction). Here, we analyze the global richness patterns of two venomous snake clades, Viperidae and Elapidae. We used ordinary least squares multiple regression (OLS) and partial regression analysis to investigate to what extent actual evapotranspiration (AET; summarizing current environmental conditions) and biogeographical regions (representing evolutionary effects) were associated with species richness. For viperids, AET explained 45.6% of the variance in richness whereas the effect of this variable for elapids was almost null (0.5%). On the other hand, biogeographic regions were the best predictors of elapid richness (56.5%), against its relatively small effect (25.9%) in viperid richness. Partial regressions also revealed similar patterns for independent effects of climate and history in both clades. However, the independent historical effect in Elapidae decreased from 45.2 to 17.8% when we excluded Australia from the analyses, indicating that the strong historical effect that had emerged for the global richness pattern was reflecting the historical process of elapid radiation into Australia. Even after excluding Australia, the historical signal in elapid richness in the rest of the globe was still significant and much higher than that observed in viperid richness at a global scale (2.7% after controlling for AET effects). Differences in the evolutionary age of these two clades can be invoked to explain these contrasting results, in that viperids probably had more time for diversification, generating richness responses to environmental gradients, whereas the pattern of distribution of elapid richness can be more directly interpreted in an evolutionary context. Moreover, these results show the importance of starting to adopt deconstructive approaches to species richness, since the driving factors of these patterns may vary from group to group according to their evolutionary history. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biogeographical patterns of algal communities in the Mediterranean Sea: Cystoseira crinita‐dominated assemblages as a case study

Aim The aim of this study was to describe the composition, community structure and biogeographical variation of subtidal algal assemblages dominated by the brown alga Cystoseira crinita across the Mediterranean Sea. Location The Mediterranean coast, from Spain (1°25′ E) to Turkey (30°26′ E). Methods Data on the species composition and structure of assemblages dominated by the species C. crinita were collected from 101 sites in nine regions across the Mediterranean Sea. Multivariate and univariate statistical tools were used to investigate patterns of variation in the composition of the assemblages among sites and regions, and to compare these with previously defined biogeographical regions. Linear regressions of species richness versus longitude and versus latitude were also carried out to test previously formulated hypotheses of biodiversity gradients in the Mediterranean Sea. Results The main features characterizing C. crinita‐dominated assemblages across the Mediterranean included a similar total cover of species, a similar cover of C. crinita, and consistency in the presence of the epiphyte Haliptilon virgatum. Biogeographical variation was detected as shifts in relative abundances of species among regions, partly coinciding with previously described biogeographical sectors. A significant positive correlation was found between species richness and latitude, while no significant correlation was detected between species richness and longitude. Main conclusions The patterns of variation in community structure detected among the studied regions reflected their geographical positions quite well. However, latitude seemed to contribute more to the explanation of biological patterns of diversity than did geographical distances or boundaries, which classically have been used to delimit biogeographical sectors. Moreover, the positive correlation between species richness and latitude reinforced the idea that latitude, and possibly temperature as a related environmental factor, plays a primary role in structuring biogeographical patterns in the Mediterranean Sea. The lack of correlation between species richness and longitude contradicts the notion that there is a decrease in species richness from west to east in the Mediterranean, following the direction of species colonization from the Atlantic.     

Random sampling, abundance–extinction dynamics and niche-filtering immigration constraints explain the generation of species richness gradients

Aim  The paradigm that species' patterns of distribution, abundance and coexistence are the result of adaptations of the species to their niches has recently been challenged by evidence that similar patterns may be generated by simple random processes. We argue here that a better understanding of macroecological patterns requires an integration of both ecological and neutral stochastic approaches. We demonstrate the utility of such an integrative approach by testing the sampling hypothesis in a species–energy relationship of forest bird species.
Location  A Mediterranean biome in Catalonia, Spain.
Methods  To test the sampling hypothesis we designed a metacommunity model that reproduces the stochastic sampling from a regional pool to predict local species richness variation. Four conceptually different sampling procedures were evaluated.
Results  We showed that stochastic sampling processes predicted a substantial part (over 40%) of the observed variation in species richness, but left considerable variation unexplained. This remaining variation in species richness may be better understood as the result of alternative ecological processes. First, the sampling model explained more variation in species richness when the probability that a species colonises a new locality was assumed to increase with its niche width, suggesting that ecological differences between species matter when it comes to explaining macroecological patterns. Second, extinction risk was significantly lower for species inhabiting high-energy regions, suggesting that abundance–extinction processes play a significant role in shaping species richness patterns.
Main conclusions  We conclude that species–energy relationships may not simply be understood as a result of either ecological or random sampling processes, but more likely as a combination of both.     

Global patterns and predictors of tropical reef fish species richness

In the marine realm, the tropics host an extraordinary diversity of taxa but the drivers underlying the global distribution of marine organisms are still under scrutiny and we still lack an accurate global predictive model. Using a spatial database for 6336 tropical reef fishes, we attempted to predict species richness according to geometric, biogeographical and environmental explanatory variables. In particular, we aimed to evaluate and disentangle the predictive performances of temperature, habitat area, connectivity, mid‐domain effect and biogeographical region on reef fish species richness. We used boosted regression trees, a flexible machine‐learning technique, to build our predictive model and structural equation modeling to test for potential ‘mediation effects’ among predictors. Our model proved to be accurate, explaining 80% of the total deviance in fish richness using a cross‐validated procedure. Coral reef area and biogeographical region were the primary predictors of reef fish species richness, followed by coast length, connectivity, mid‐domain effect and sea surface temperature, with interactions between the region and other predictors. Important indirect effects of water temperature on reef fish richness, mediated by coral reef area, were also identified. The relationship between environmental predictors and species richness varied markedly among biogeographical regions. Our analysis revealed that a few easily accessible variables can accurately predict reef fish species richness. They also highlight concerns regarding ongoing environmental declines, with region‐specific responses to variation in environmental conditions predicting a variable response to anthropogenic impacts.     

Latitudinal variation of diversity in European freshwater animals is not concordant across habitat types

Aim   We analysed the variation of species richness in the European freshwater fauna across latitude. In particular, we compared latitudinal patterns in species richness and β-diversity among species adapted to different habitat types.
Location   Europe.
Methods   We compiled data on occurrence for 14,020 animal species across 25 pre-defined biogeographical regions of European freshwaters from the Limnofauna Europaea . Furthermore, we extracted information on the habitat preferences of species. We assigned species to three habitat types: species adapted to groundwater, lotic (running water) and lentic (standing water) habitats. We analysed latitudinal patterns of species richness, the proportion of lentic species and β-diversity.
Results   Only lentic species showed a significant species–area relationship. We found a monotonic decline of species richness with latitude for groundwater and lotic habitats, but a hump-shaped relationship for lentic habitats. The proportion of lentic species increased from southern to northern latitudes. β-Diversity declined from groundwater to lentic habitats and from southern to northern latitudes.
Main conclusions   The differences in the latitudinal variation of species richness among species adapted to different habitat types are in part due to differences in the propensity for dispersal. Since lentic habitats are less persistent than lotic or groundwater habitats, lentic species evolved more efficient strategies for dispersal. The dispersal propensity of lentic species facilitated the recolonization of central Europe after the last glaciation. Overall, we stress the importance of considering the history of regions and lineages as well as the ecological traits of species for understanding patterns of biodiversity.     

Biogeography of Aphodiinae dung beetles based on the regional composition and distribution patterns of genera

Aim  To examine current biogeographical patterns of Aphodiinae dung beetles (Coleoptera: Scarabaeoidea: Scarabaeidae) in order to reveal relationships among regions and their potential impact on the diversification of this group.
Location  Worldwide.
Methods  Information about all Aphodiinae genera was obtained from the literature. An occurrence matrix was built for the six worldwide biogeographical regions, and their faunas were characterized through simple statistics. Regional variations and similarities were further explored using co-occurrence and nestedness analyses, sequential agglomerative, hierarchical and nested clustering (SAHN), and a parsimony analysis of endemicity (PAE). Mantel tests were also employed to assess the relationships between several characteristics of the regions and their faunas.
Results  The Palaearctic and Palaeotropical regions showed the highest total numbers of Aphodiinae genera and the greatest generic endemism. Both these regions and the Oriental also showed higher numbers of genera than would be expected according to their size. Co-occurrence and nestedness analyses confirmed the non-randomness of the distribution of genera. Clustering and PAE showed that the Palaearctic and Oriental regions are the most similar, followed by the Palaeotropical region. Regional dissimilarity in genera composition was related to biological and historical traits, but not to ecoregions.
Main conclusions  A structured geographical pattern for Aphodiinae was confirmed. Land continuity and proximity in the long term could have played a unifying role in regional faunas. We suggest that the different biogeographical regions have acted as either macroevolutionary sources (basically the Palaearctic and the Palaeotropical regions) or sink regions, according to their role as diversification centres. We review the processes and events that could account for current patterns of Aphodiinae diversity.     

Regional and environmental effects on the species richness of mammal assemblages

Aim Variation in species richness has been related to (1) environmental conditions (water, energy and habitat characteristics) and (2) regional differences (contingent historical events and regional particularities that result in differences between regional faunas acting at broad extents). Whereas climatic factors have been widely studied, the effects of regional differences are less often quantified. This work aims to characterize global trends in the species richness of mammal assemblages with respect to both current and historical influences. Location All terrestrial biogeographical realms except Antarctica. Methods Species richness in checklists from 224 sites distributed worldwide were investigated by partitioning the variation between a general set of habitat/climate factors, biogeographical regions, and their overlaps. Additional analyses studied the specific overlaps of region, water and energy. Data were also divided according to area to determine if the strength of these effects varies according to the size of sites. Results Environmental effects explained 38% of richness variation across all sites, whereas environmentally independent regional effects explained 11% and the overlap between region and environment explained 13%. Results were similar when only larger sites (between 1000 km² and 10,000 km²) were considered. However, the importance of the overlap between region and all environmental variables was greater in smaller sites (between 100 km² and 1000 km²). In contrast, the specific importance of water and energy variables and their overlap with region was greater in larger sites. The strength of the independent effect of region remained almost invariant regardless of the size of the sites studied. Main conclusions The relationship between species richness and climate varies with scale and among regions. Although environmental variables are the strongest correlates of richness, the unique history and physiographic characteristics of a region produce differences between the richness of mammal assemblages and their response to environmental gradients. The importance of environmental variables varies with scale: climatic gradients are more important at coarse grain (larger sites), possibly as a result of their effects on species ranges, whereas habitat type is more important at the smaller sites, where the importance of ecological interactions increases. Therefore, regional differences and the scale at which richness is measured should be taken into account when evaluating species richness–energy hypotheses.     

Explaining global termite diversity: productivity or history?

A map of termite generic richness worldwide shows that the Ethiopian biogeographical region is most genus-rich, while the Neotropical and Indo-Malayan regions are less rich. Net primary productivity (NPP) has been postulated as a possible explanation for some diversity patterns (energy-diversity theory). We reject this as the primary explanation for termite generic richness patterns because the Ethiopian region has low NPP and a high generic richness while the Neotropical and Indo-Malayan regions have high NPP and low generic richness. We explore an alternative historical hypothesis, that differing levels of Quaternary climatic disturbance are responsible for the differences in termite generic richness between the three tropical regions.     

An intercontinental comparison of dung beetle diversity between two mediterranean-climatic regions: local versus regional and historical influences

The species richness of biological communities is influenced by both local ecological, regional ecological, and historical factors. The relative importance of these factors may be deduced by comparison between communities in climatically and ecologically equivalent, but geographically and historically separate regions of the world. This claim is based on the hypothesis that community processes driven by similar local ecological factors lead to convergence in species richness whereas those driven by differing regional or historical factors lead to divergence. An intercontinental comparison between the winter rainfall regions of South Africa and the Iberian Peninsula showed that overall species richness of dung beetles was dissimilar at local, subregional and regional scales in Scarabaeidae s. str. but similar at all scales in Aphodiinae. Removal of species widespread in the summer rainfall region of Africa or the temperate region of Europe (regional component) resulted in dissimilarity in species richness of mediterranean endemics at all scales in both dung beetle taxa. However, the lines joining each set of species richness values were parallel which may indicate similarities in processes between different mediterranean climatic regions despite slight differences in latitudinal range. The dominant pattern of dissimilarity or non-convergence may be related primarily to intercontinental differences in regional biogeographical and evolutionary history (faunal dispersal, glaciation effects in relation to geographical barriers to dispersal, speciation history, long-term disturbance history). The limited pattern of similarity or convergence in overall species richness of Aphodiinae may be a chance result or primarily related to intercontinental similarities in local ecological factors.     

Regional variation in the historical components of global avian species richness

Aim Using a global data base of the distribution of extant bird species, we examine the evidence for spatial variation in the evolutionary origins of contemporary avian diversity. In particular, we assess the possible role of the timing of mountain uplift in promoting diversification in different regions. Location Global. Methods We mapped the distribution of avian richness at four taxonomic levels on an equal‐area 1° grid. We examined the relationships between richness at successive taxonomic levels (e.g. species richness vs. genus richness). We mapped the residuals from linear regressions of these relationships to identify areas that are exceptional in the number of lower taxa relative to the number of higher taxa. We use generalized least squares models to test the influence of elevation range and temperature on lower‐taxon richness relative to higher‐taxon richness. Results Peaks of species richness in the Neotropics were congruent with patterns of generic richness, whilst peaks in Australia and the Himalayas were congruent with patterns of both genus and family richness. Hotspots in the Afrotropics did not reflect higher‐taxon patterns. Regional differences in the relationship between richness at successive taxonomic levels revealed variation in patterns of taxon co‐occurrence. Species and genus co‐occurrence was positively associated with elevational range across much of the world. Taxon occurrence in the Neotropics was associated with a positive interaction between elevational range and temperature. Conclusions These results demonstrate that contemporary patterns of richness show different associations with higher‐taxon richness in different regions, which implies that the timing of historical effects on these contemporary patterns varies across regions. We suggest that this is due to dispersal limitation and phylogenetic constraints on physiological tolerance limits promoting diversification. We speculate that diversification rates respond to long‐term changes in the Earth's topography, and that the role of tropical mountain ranges is implicated as a correlate of contemporary diversity, and a source of diversification across avian evolutionary history.     

Biogeographical patterns of Chinese spiders (Arachnida: Araneae) based on a parsimony analysis of endemicity

Aim  The distributions of Chinese spiders are used to form biotic regions and to infer biogeographical patterns.
Location  China.
Methods  China was initially divided into 294 quadrats of 2° latitude by 2° longitude. The distributions of 958 species of spiders were summarized for each quadrat. Subsequently, these quadrats were pooled into 28 areas based on topographical characteristics and to a lesser extent on the distributions of spiders. Parsimony analysis of endemicity (PAE) was used to classify the 28 areas based on the shared distributional patterns of spiders.
Results  China was found to have seven major biogeographical regions based on the distributional patterns of spiders: Western Northern region (clade B₂: Tibetan Plateau and Inner Mongolia-Xinjiang subregions), Central Northern region (clade B₃), Eastern Northern region (clade B₄), Central region (clade C₂), Eastern Southern region (clade C₃), Western Southern region (clade C₄), and Central Southern region (clade C₅).
Main conclusions  The distributional patterns of Chinese spiders correspond broadly to geological provinces. A comparison of the geological provinces and the distributional patterns of spiders reveals that the spiders occur south of the geological provinces. Furthermore, a general biogeographical classification with five natural areas is suggested as follows: Tibetan Plateau, Central Northern, Eastern Northern, Western Northern (excluding Tibetan Plateau), and Southern regions.     

Using potential distributions to explore determinants of Western Palaearctic migratory songbird species richness in sub-Saharan Africa

Aim  Although the breeding ranges of most Western Palaearctic migratory passerines are well documented in Europe, their overwintering ranges and patterns of species richness in Africa remain poorly understood. To illustrate potential patterns of species richness despite severely limited data, we extrapolated species ranges from a new and unique data bank of locality records that documents overwintering locations of these birds in Africa.
Location  Sub-Saharan Africa.
Methods  We predicted potential geographical distributions of 60 species of passerine birds based on overwintering records using bioclimatic models. We then combined these predictions to estimate potential species richness and explored response shapes using spatial linear regression. We also evaluated the evidence for a mid-domain effect using a one-dimensional null model.
Results  Spatial linear regression analyses of the species richness pattern revealed non-linear relationships to seasonality in precipitation, minimum net primary productivity, minimum average temperature, habitat heterogeneity, percentage of tree cover, distance from the Sahara Desert and inter-annual variability in net primary productivity. The explanatory power of these variables decreased with geographic range size. The one-dimensional null model of species richness based on distance from the Sahara Desert did not show evidence of a mid-domain effect.
Main conclusions  Distributions of migrants seem generally strongly determined by distance from the Sahara Desert working in concert with climatic effects, but this cannot adequately explain richness patterns of species with small ranges in Africa, many of which are of substantial conservation concern.     

Temporal turnover of common species in avian assemblages in North America

Aim We examine patterns of temporal turnover of common species in avian assemblages in North America to test the hypothesis that changes in avian diversity structure observed in these assemblages were associated with the colonization of common species. Location The contiguous United States and southern Canada. Methods We measured temporal turnover from 1968 to 2003 for 547 avian species at 1673 North American Breeding Bird Survey (BBS) routes. We used the Euclidian distance between expected and observed presence/absence vectors and randomization tests to place species into two categories, common and not‐common, and into three categories for common species: (1) always common, (2) common and colonizing, and (3) common and extirpated. We used these categories to identify species experiencing extreme colonization and extirpation events and to examine changes in species composition at BBS routes. We also determined how these patterns were associated with changes in species richness and changes in similarity in species composition. Results Nine of the 547 species represented outliers, where the number of BBS routes colonized greatly exceeded the number extirpated; no species showed extreme values for extirpation. The nine species colonized BBS routes primarily in the upper Midwest and north‐eastern United States. Presence of the nine species at BBS routes was correlated with increasing net gain in common species (difference between common colonized and common extirpated), higher levels of species richness and increasing species richness over time, more similar species compositions and increasing similarity over time, and a greater prevalence of common species over not‐common species. The literature indicates that all nine species experienced some form of geographical range expansion during the time of the survey involving four elements: (1) introduction and invasion; (2) the ability to use human‐altered environments, including habitats associated with agricultural, suburban, or urban areas; (3) intensive management activities, including habitat improvements and reintroductions and (4) the ability to use habitats formed through forest regeneration. These factors in combination point to anthropogenic activities and related land use histories as the primary drivers of change. One of the nine species colonized regions well outside its historic geographical range and the remaining eight species were native within the regions they colonized. Main conclusions Our results suggest that a combination of anthropogenic activities promoted, within certain regions of North America, the geographical expansion of a limited number of common species that were native to those regions. These colonization events were correlated with changes in diversity structure, implying that large‐scale diversity patterns were being influenced by anthropogenic activities. These changes can be characterized primarily by gains in species richness, an increased prevalence of common species, and more similar species compositions. Thus, using simple large‐scale measures of diversity could be problematic if recent biogeographical patterns of species diversity are not considered. Specifically, using species richness or an indicator species to assess diversity could bias assessments towards common species whose populations have recently benefited through anthropogenic activities.     

Biogeography of freshwater fishes of the Balkan Peninsula

Delineating biogeographical regions is a critical step towards the establishment and evaluation of conservation priorities. In the present study, we analysed the distribution patterns of the freshwater fish of an understudied European biodiversity hotspot, the Balkan Peninsula. Based on the most extensive available database of native freshwater fish species distributions, we performed a hierarchical clustering analysis to identify the major biogeographical regions of the Balkan Peninsula. We also highlighted the ‘hottest hotspots’ of freshwater fish diversity across the delimited biogeographical regions by describing the patterns of species richness, endemic and vulnerable species; indicator species were also determined. The bioregionalisation scheme consisted of eight groups of drainage basins that correspond to distinct regions of the Balkan Peninsula. Overall, the delineated biogeographical regions varied in terms of species richness, endemism, vulnerability (i.e. extinction threats) and indicator species composition. From a conservation perspective, this study emphasises the prioritisation of areas characterised by high levels of irreplaceability (endemism) and vulnerability (i.e. the Attikobeotia region, Ionian Sea and Prespa Lakes) and stresses the necessity of implementing a network of protected freshwater areas across the Balkan Peninsula.     

Can the tropical conservatism hypothesis explain temperate species richness patterns? An inverse latitudinal biodiversity gradient in the New World snake tribe Lampropeltini

Aim  A latitudinal gradient in species richness, defined as a decrease in biodiversity away from the equator, is one of the oldest known patterns in ecology and evolutionary biology. However, there are also many known cases of increasing poleward diversity, forming inverse latitudinal biodiversity gradients. As only three processes (speciation, extinction and dispersal) can directly affect species richness in areas, similar factors may be responsible for both classical (high tropical diversity) and inverse (high temperate diversity) gradients. Thus, a modified explanation for differential species richness which accounts for both patterns would be preferable to one which only explains high tropical biodiversity.
Location  The New World.
Methods  We test several proposed ecological, temporal, evolutionary and spatial explanations for latitudinal diversity gradients in the New World snake tribe Lampropeltini, which exhibits its highest biodiversity in temperate regions.
Results  We find that an extratropical peak in species richness is not explained by latitudinal variation in diversification rate, the mid-domain effect, or Rapoport's rule. Rather, earlier colonization and longer duration in the temperate zones allowing more time for speciation to increase biodiversity, phylogenetic niche conservatism limiting tropical dispersal and the expansion of the temperate zones in the Tertiary better explain inverse diversity gradients in this group.
Main conclusions  Our conclusions are the inverse of the predictions made by the tropical conservatism hypothesis to explain higher biodiversity near the equator. Therefore, we suggest that the processes invoked are not intrinsic to the tropics but are dependent on historical biogeography to determine the distribution of species richness, which we refer to as the 'biogeographical conservatism hypothesis'.     

Bird dietary guild richness across latitudes,environments and biogeographic regions

Aim To integrate dietary knowledge and species distributions in order to examine the latitudinal, environmental, and biogeographical variation in the species richness of avian dietary guilds (herbivores, granivores, frugivores, nectarivores, aerial insectivores, terrestrial/arboreal insectivores, carnivores, scavengers, and omnivores). Location Global. Methods We used global breeding range maps and a comprehensive dietary database of all terrestrial bird species to calculate guild species richness for grid cells at 110 × 110 km resolution. We assessed congruence of guild species richness, quantified the steepness of latitudinal gradients and examined the covariation between species richness and climate, topography, habitat diversity and biogeographic history. We evaluated the potential of current environment and biogeographic history to explain global guild distribution and compare observed richness–environment relationships with those derived from random subsets of the global species pool. Results While most guilds (except herbivores and scavengers) showed strong congruence with overall bird richness, covariation in richness between guilds varied markedly. Guilds exhibited different peaks in species richness in geographical and multivariate environmental space, and observed richness–environment relationships mostly differed from random expectations. Latitudinal gradients in species richness were steepest for terrestrial/arboreal insectivores, intermediate for frugivores, granivores and carnivores, and shallower for all other guilds. Actual evapotranspiration emerged as the strongest climatic predictor for frugivores and insectivores, seasonality for nectarivores, and temperature for herbivores and scavengers (with opposite direction of temperature effect). Differences in species richness between biogeographic regions were strongest for frugivores and nectarivores and were evident for nectarivores, omnivores and scavengers when present‐day environment was statistically controlled for. Guild richness–environment relationships also varied between regions. Main conclusions Global associations of bird species richness with environmental and biogeographic variables show pronounced differences between guilds. Geographic patterns of bird diversity might thus result from several processes including evolutionary innovations in dietary preferences and environmental constraints on the distribution and diversification of food resources.