Global biodiversity and biogeography of mangrove crabs: Temperature,the key driver of latitudinal gradients of species richness

Mangroves are ideal habitat for a variety of marine species especially brachyuran crabs as the dominant macrofauna. However, the global distribution, endemicity, and latitudinal gradients of species richness in mangrove crabs remains poorly understood. Here, we assessed whether species richness of mangrove crabs decreases towards the higher latitudes and tested the importance of environmental factors such as Sea Surface Temperature (SST) in creating the latitudinal gradients in species richness of mangrove crabs. A total of 8262 distribution records of 481 species belonging to six families of mangrove crabs including Camptandriidae, Dotillidae, Macrophthalmidae, Ocypodidae, Sesarmidae, and Oziidae were extracted from open-access databases or collected by the authors, quality controlled, cleaned, and analyzed. Species richness was plotted against 5° latitudinal bands in relation to environmental factors. The R software and ArcGIS 10.6.1 were used to analyze the species latitudinal range and richness as well as to map the distribution of mangrove forest, endemic species, species geographical distribution records, and biogeographic regions. The Indo-West Pacific showed the highest species richness of mangrove crabs where more than 65% of species were found in the Indian Ocean and along the western Pacific Ocean. Our results showed that there are 11 significantly different biogeographic regions of mangrove crabs. The highest endemicity rate was observed in the NW Pacific Ocean (29%). Latitudinal patterns of species richness in Macrophthalmidae, Ocypodidae, and Sesarmidae showed an increasing trend from the poles toward the intermediate latitudes including one dip near the equator. However, latitudinal gradients in Camptandriidae, Dotillidae, and Oziidae were unimodal increasing from the higher latitudes towards the equator. Species richness per 5° latitudinal bands significantly increased following mean SST mean (°C), calcite, euphotic depth (m), and mangrove area (km²) across all latitudes, and tide average within each hemisphere. Species richness significantly decreased with dissolved O₂ (ml l⁻¹) and nitrate (μmol l⁻¹) over all latitudes and in the southern hemisphere. The climax of global latitudinal species richness for some mangrove was observed along latitudes 20° N and 15°–25° S, not at the equator. This can suggest that temperature is probably the key driver of latitudinal gradients of mangrove crabs’ species richness. Species richness and mangrove area were also highly correlated.     

Does life history predict past and current connectivity for rocky intertidal invertebrates across a marine biogeographic barrier?

The southeast Australian coast potentially includes a complex biogeographic barrier, largely lacking exposed rocky shore that may limit the dispersal of rocky intertidal taxa and contribute to the maintenance of two biogeographic regions. Surprisingly, within the 300-km barrier region, several species considered exposed rocky shore specialists occurred within sheltered sites. We analysed COI sequence variation for 10 rocky intertidal invertebrate species, with a range of life histories, to test the hypotheses that larval type and habitat specificity are strong predictors of gene flow between biogeographic regions. Our data revealed that the southeast corner of Australia includes a strong barrier to gene flow for six of eight species with planktonic larvae, and a coalescence analysis of sequence differentiation (IM model) suggests that a barrier has existed since the Pleistocene. In contrast, two direct developers were not affected by the barrier. Our comparative approach and data from earlier studies (reviewed here) do not support the hypothesis that larval type predicts gene flow across this barrier, instead we found that the ability to utilize sheltered habitat provides a clearer explanation of the phylogeographic break. Indeed, the species that displayed little or no evidence of a phylogeographic break across the barrier each displayed unexpectedly relaxed habitat specificity.     

Environmental and geometric drivers of small mammal diversity along elevational gradients in Utah

The mechanisms shaping patterns of biodiversity along spatial gradients remain poorly known and controversial. Hypotheses have emphasized the importance of both environmental and spatial factors. Much of the uncertainty about the relative role of these processes can be attributed to the limited number of comparative studies that evaluate multiple potential mechanisms. This study examines the relative importance of six variables: temperature, precipitation, productivity, habitat heterogeneity, area, and the mid-domain effect on patterns of species richness for non-volant small mammals along four neighboring mountain ranges in central Utah. Along each of these elevational gradients, a hump-shaped relationship of richness with elevation is evident. This study evaluates whether the processes shaping this common pattern are also common to all gradients. Model selection indicates that no one factor or set of factors best explains patterns of species richness across all gradients, and drivers of diversity may vary seasonally. These findings suggest that commonality in the pattern of species richness, even among elevational gradients with a similar biogeographic history and fauna, cannot be attributed to a simple universal explanation.     

Species richness and diversity across rocky intertidal elevation gradients in Helgoland: testing predictions from an environmental stress model

Environmental stress affects species richness and diversity in communities, but the precise form of the relationship is unclear. We tested an environmental stress model (ESM) that predicts a unimodal pattern for total richness and diversity in local communities across the full stress gradient where a regional biota can occur. In 2008, we measured richness and diversity (considering all macrobenthic species) across the entire intertidal range on three rocky shores on Helgoland Island, Germany. Intertidal elevation is known to be positively related to abiotic stress. Since Helgoland is between the northern and southern biogeographic boundaries for the cold-temperate NE Atlantic intertidal biota, it exhibits low stress levels for this biota at low elevations and high stress at high elevations because of long (>6 h) emersion times. Thus, we predicted a unimodal trend for richness and diversity across elevation. On all three shores, richness increased from high to middle elevations, but remained similar between middle and low elevations. Diversity followed the same trend on one shore and different trends (although also non-unimodal) on the other two. Evenness explained the trend differences between richness and diversity. Overall, our study yielded little support for the ESM. Reasons for richness and diversity not decreasing at low elevations may be related to influences of mostly subtidal species, Helgoland’s intertidal range, or sampling resolution. Our study also suggests that the ESM must be developed further to differentiate between richness and diversity. We offer recommendations to improve future ESM research using intertidal systems.     

Biogeographic patterns of soil diazotrophic communities across six forests in the North America

Soil diazotrophs play important roles in ecosystem functioning by converting atmospheric N₂ into biologically available ammonium. However, the diversity and distribution of soil diazotrophic communities in different forests and whether they follow biogeographic patterns similar to macroorganisms still remain unclear. By sequencing nifH gene amplicons, we surveyed the diversity, structure and biogeographic patterns of soil diazotrophic communities across six North American forests (126 nested samples). Our results showed that each forest harboured markedly different soil diazotrophic communities and that these communities followed traditional biogeographic patterns similar to plant and animal communities, including the taxa–area relationship (TAR) and latitudinal diversity gradient. Significantly higher community diversity and lower microbial spatial turnover rates (i.e. z‐values) were found for rainforests (~0.06) than temperate forests (~0.1). The gradient pattern of TARs and community diversity was strongly correlated (r² > 0.5) with latitude, annual mean temperature, plant species richness and precipitation, and weakly correlated (r² < 0.25) with pH and soil moisture. This study suggests that even microbial subcommunities (e.g. soil diazotrophs) follow general biogeographic patterns (e.g. TAR, latitudinal diversity gradient), and indicates that the metabolic theory of ecology and habitat heterogeneity may be the major underlying ecological mechanisms shaping the biogeographic patterns of soil diazotrophic communities.     

Marine reserves indirectly affect fine‐scale habitat associations,but not overall densities,of small benthic fishes

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.     

Deconstructing the mammal species richness pattern in Europe – towards an understanding of the relative importance of climate,biogeographic history,habitat heterogeneity and humans

Aim We deconstructed the mammal species richness pattern in Europe to assess the importance of large‐scale gradients in current macroclimate relative to biogeographic history, habitat heterogeneity and human influence (HHH variables) as richness determinants for total species, and for widespread and endemic species separately. Location Europe, west of 30° E. Methods We deconstructed total species richness (50‐km resolution) into its widespread and endemic species richness components. We used simultaneous autoregressive modelling (SAR) with information‐theoretic model selection and variation partitioning to assess the importance of macroclimate and HHH variables. The HHH variables included two historical factors, estimated by novel methodologies: (1) ice‐age‐driven dynamics, represented by accessibility to recolonization from hindcasting‐estimated glacial refugia, and (2) biogeographic peninsular dynamics, represented by distance to the entry region for the main European faunal source in western Asia. Results A large fraction of explained variation was shared between macroclimate and HHH in the SAR models. For total species richness, more variation could be uniquely attributed to macroclimate than to HHH, whereas for the deconstructed patterns (widespread and endemic species) the opposite was the case. Considering the individual factors, there was a strong peninsula effect on both widespread and endemic species richness but not on total richness. Main conclusions Both macroclimate and HHH variables (history, habitat heterogeneity and human influence) proved important predictors of species richness, but also difficult to disentangle. Notably, biogeographic history, in particular peninsular dynamics, is an important determinant of widespread and endemic species richness.     

Biodiversity and biogeography of Southern Ocean pycnogonids

The pycnogonids of the Southern Ocean have been studied for almost two centuries and have played a key role in shaping previous biogeographic regions for the Antarctic benthos. The aim of this study was to assess the biogeographic patterns derived from the most current sample records of pycnogonids from the Southern Ocean and neighbouring areas. 332 species of pycnogonids from 1837 sample locations were analysed using 279 3° by 3° grid cells. We investigated richness patterns and the effect of sampling intensity at both local and regional scales, and used multivariate analysis of distribution patterns and species assemblages to define biogeographic trends. These analyses identified a distinct and isolated Antarctic pycnogonid shelf fauna which was different to that of the deep‐sea around Antarctica, the Sub‐Antarctic islands, South America or New Zealand. Within the Antarctic, we found the South Shetland Islands to be the most speciose region and a probable center of radiation for the pycnogonids. No latitudinal gradients in species richness were detected. We note that the distribution patterns observed are based upon classical taxonomy and discuss the potential for changes to these patterns with new insights from molecular techniques. We conclude that, even with the potential for cryptic species, the large‐scale biogeographic trends observed in the pycnogonids should hold true.     

Habitat-specific size structure variations in periwinkle populations (<Emphasis Type="Italic">Littorina littorea)</Emphasis> caused by biotic factors

Shell size distribution patterns of marine gastropod populations may vary considerably across different environments. We investigated the size and density structure of genetically continuous periwinkle populations (Littorina littorea) on an exposed rocky and a sheltered sedimentary environment on two nearby islands in the south-eastern North Sea (German Bight). On the sedimentary shore, periwinkle density (917 ± 722 individuals m⁻²) was about three times higher than on the rocky shore (296 ± 168 individuals m⁻²). Mean (9.8 ± 3.9 mm) and maximum (22 mm) shell size of L. littorea on the sedimentary shore were smaller than on the rocky shore (21.5 ± 4.2 and 32 mm, respectively), where only few small snails were found. Additionally, periwinkle shells were thicker and stronger on the rocky than on the sedimentary shore. To ascertain mechanisms responsible for differences in population structures, we examined periwinkles in both environments for growth rate, predation pressure, infection with a shell boring polychaete (Polydora ciliata) and parasitic infestation by trematodes. A crosswise transplantation experiment revealed better growth conditions on the sedimentary than on the rocky shore. However, crab abundance and prevalence of parasites and P. ciliata in adult snails were higher on the sedimentary shore. Previous investigations showed that crabs prefer large periwinkles infested with P. ciliata. Thus, we suggest that parasites and shell boring P. ciliata in conjunction with an increased crab predation pressure are responsible for low abundances of large periwinkles on the sedimentary shore while high wave exposure may explain low densities of juvenile L. littorea on the rocky shore. We conclude that biotic factors may strongly contribute to observed differences in size structure of the L. littorea populations studied on rocky and sedimentary shores.     

Physical effects of habitat‐forming species override latitudinal trends in temperature

Latitudinal and elevational temperature gradients (LTG and ETG) play central roles in biogeographical theory, underpinning predictions of large‐scale patterns in organismal thermal stress, species' ranges and distributional responses to climate change. Yet an enormous fraction of Earth's taxa live exclusively in habitats where foundation species modify temperatures. We examine little‐explored implications of this widespread trend using a classic model system for understanding heat stresses – rocky intertidal shores. Through integrated field measurements and laboratory trials, we demonstrate that thermal buffering by centimetre‐thick mussel and seaweed beds eliminates differences in stress‐inducing high temperatures and associated mortality risk that would otherwise arise over 14° of latitude and ~ 1 m of shore elevation. These results reveal the extent to which physical effects of habitat‐formers can overwhelm broad‐scale thermal trends, suggesting a need to re‐evaluate climate change predictions for many species. Notably, inhabitant populations may exhibit deceptive resilience to warming until refuge‐forming taxa become imperiled.     

Global patterns in the effects of predator declines on sea urchins

Latitudinal gradients in the strength of biotic interactions have long been proposed, but empirical evidence for the expectation of more intense predation, herbivory and competition at low latitudes has been mixed. Here, we use a meta‐analysis to test the prediction that predation pressure on sea urchins, a group of consumers with a particularly strong influence on community structure in the world's oceans, is strongest in the tropics. We then examine which biotic and abiotic factors best correlate with biogeographic and within habitat patterns in sea urchin responses to predation. Consistent with expectations, predator impacts on sea urchins were highest in tropical coral reefs and decreased towards the poles in rocky reef habitats (> 25° absolute latitude). However, latitude and temperature were weakly correlated with effect sizes, and the strongest predictor of predator impacts was sea urchin species. This suggests an important role of prey identity (i.e. traits including behaviour, physical, and chemical defences) rather than large scale abiotic factors in determining variation in interaction strengths. Ecosystem‐shaping sea urchins such as Tripneustes gratilla, Diadema savignyi and Centrostephanus rodgersii were strongly impacted by consumers, indicating a tight coupling between predators of these species and their boom and bust prey. Anthropogenic activities such as over‐fishing, climate change and habitat destruction are causing rapid environmental change, and understanding how predation pressure varies with temperature, across habitats and among prey species, will aid in predicting the likelihood of ecosystem wide effects (via trophic cascades).     

Latitudinal patterns and regionalization of plant diversity along a 4270‐km gradient in continental Chile

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270‐km north–south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence–absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270‐km latitudinal distribution curve, with a concentration of richness in central Chile (31–42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22–37°S) was especially high. This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18–22°S), north Mediterranean (23–28°S), central Mediterranean (29–32°S), south Mediterranean (33–37°S), north temperate (38–42°S), south temperate (43–52°S) and Austral (53–56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.     

Climatic niche conservatism and ecological opportunity in the explosive radiation of arvicoline rodents (Arvicolinae,Cricetidae)

Climatic niche conservatism shapes patterns of diversity in many taxonomic groups, while ecological opportunity (EO) can trigger rapid speciation that is less constrained by the amount of time a lineage has occupied a given habitat. These two processes are well studied, but limited research has considered their joint and relative roles in shaping diversity patterns. We characterized climatic and biogeographic variables for 102 species of arvicoline rodents (Arvicolinae, Cricetidae), testing the effects of climatic niche conservatism and EO on arvicoline diversification as lineages transitioned between biogeographic regions. We found that the amount of time a lineage has occupied a precipitation niche is positively correlated with diversity along a precipitation gradient, suggesting climatic niche conservatism. In contrast, shift in diversification rate explained diversity patterns along a temperature gradient. Our results suggest that an indirect relationship exists between temperature and diversification that is associated with EO as arvicoline rodents colonized warm Palearctic environments. Climatic niche conservatism alone did not fully explain diversity patterns under density‐dependence, highlighting the additional importance of EO‐related processes in promoting the explosive radiation in arvicoline rodents and shaping diversity pattern among biogeographic regions and along climatic gradients.     

Connections Between Benthic Populations and Local Strandings of the Southern Bull Kelp Durvillaea Antarctica Along the Continental Coast of Chile1

Floating seaweeds are important dispersal vectors in marine ecosystems. However, the relationship between benthic populations and stranded seaweeds has received little attention. After detachment, a fraction of floating specimens returns to the shore, resulting in strandings that fluctuate in space and time. It has been hypothesized that the availability of stranded seaweeds is related to their benthic abundance on adjacent coasts. Using the large fucoid Durvillaea antarctica, we tested whether stranded biomasses are higher at sites with dense adjacent benthic populations. Benthic abundance of D. antarctica along the continental coast of Chile was estimated using three approximations: (i) availability of potentially suitable habitat (PSH), (ii) categorical visual abundance estimates in the field, and (iii) abundance measurements in the intertidal zone. Higher PSH for D. antarctica was observed between 31° S–32° S and 40° S–42° S than between 33° S and 39° S. Lowest benthic biomasses were estimated for the northern latitudes (31° S–32° S). Regression models showed that the association between stranded biomass and PSH was highest when only the extent of rocky shore 10 km to the south of each beach was included, suggesting relatively short-distance dispersal and asymmetrical transport of floating kelps, which is further supported by low proportions of rafts with Lepas spp. (indicator of rafting). The results indicate that stranded biomasses are mostly subsidized by nearby benthic populations, which can partly explain the low genetic connectivity among populations in the study region. Future studies should also incorporate other local factors (e.g., winds, currents, wave-exposure) that influence stranding dynamics.     

Forest vascular plants as indicators of plant species richness: A data analysis of a flora atlas from northwestern Germany

Abstract

Our study had the objective to examine whether the number of forest vascular plants in a forest-poor region may be indicative of total plant species richness and of the number of threatened plant species. We also related forest plant species richness to geological and soil variables. The analysis was based on a regional flora atlas from the Weser-Elbe region in northwestern Germany including incidence data of species in a total of 1109 grid cells (each ca. 2.8 × 2.8 km²). All taxa were classified either as forest or non-forest species. Total species richness in the grid cells ranged from 65 to 597, with a mean value of 308. The number of forest species varied between 20 and 309 (mean 176). Grid cells with or without particular geological units differed in total and forest species richness, with those containing peatland and marshland being particularly species-poor. Indicator value analysis showed that both total and forest species richness in the grid cells were related to soil acidity and nitrogen in a hump-backed manner, with the highest number of species found at moderately low values for nitrogen and at intermediate values of pH. Forest species richness was highly positively correlated with the number of non-forest species and threatened non-forest species. Indicators for high species richness were primarily those species that are confined to closed semi-natural forests with a varied topography and relatively base- and nutrient-rich soils. Grid cells including historically ancient forest exhibited a higher species richness than grid cells lacking ancient forest, indicating the importance of a long habitat continuity for a high phytodiversity. The “habitat coincidence” of high species richness is best explained by similar responses of forest species and species of other habitats to the main environmental gradients. It is suggested that the regional patterns found for the Weser-Elbe region can be transferred also to other forest-poor regions in Central Europe.     

Towards a biogeographic regionalization of the European biota

Aim To determine if it is possible to generate analytically derived regionalizations for multiple groups of European plants and animals and to explore potential influences on the regions for each taxonomic group. Location Europe. Methods We subjected range maps of trees, butterflies, reptiles, amphibians, birds and mammals to k‐means clustering followed by v‐fold cross‐validation to determine the pattern and number of regions (clusters). We then used the mean range sizes of species in each group as a correlate of the number of regions obtained for each taxon, and climate and species richness gradients as correlates of the spatial arrangement of the group‐specific regions. We also included the pattern of tree clusters as a predictor of animal clusters in order to test the ‘habitat templet’ concept as an explanation of animal distribution patterns. Results Spatially coherent clusters were found for all groups. The number of regions ranged from three to eight and was strongly associated with the mean range sizes of the species in each taxon. The cluster patterns of all groups were associated with various combinations of climate, underlying species richness gradients and, in the case of animals, the arrangement of tree clusters, although the rankings of the correlates differed among groups. In four of five groups the tree pattern was the strongest single predictor of the animal cluster patterns. Main conclusions Despite a long history of human disturbance and habitat modification, the European biota retains a discernable biogeographic structure. The primary driver appears to be aspects of climate related to water–energy balance, which also influence richness gradients. For many animals, the underlying habitat structure, as measured by tree distributions, appears to have a strong influence on their biogeographic structure, highlighting the need to preserve natural forest formations if we want to preserve the historical signal found in geographic distributions.     

Metacommunity patterns in larval odonates

The growth of metacommunity ecology as a subdiscipline has increased interest in how processes at different spatial scales structure communities. However, there is still a significant knowledge gap with respect to relating the action of niche- and dispersal-assembly mechanisms to observed species distributions across gradients. Surveys of the larval dragonfly community (Odonata: Anisoptera) in 57 lakes and ponds in southeast Michigan were used to evaluate hypotheses about the processes regulating community structure in this system. We considered the roles of both niche- and dispersal-assembly processes in determining patterns of species richness and composition across a habitat gradient involving changes in the extent of habitat permanence, canopy cover, area, and top predator type. We compared observed richness patterns and species distributions in this system to patterns predicted by four general community models: species sorting related to adaptive trade-offs, a developmental constraints hypothesis, dispersal assembly, and a neutral community assemblage. Our results supported neither the developmental constraints nor the neutral-assemblage models. Observed patterns of richness and species distributions were consistent with patterns expected when adaptive tradeoffs and dispersal-assembly mechanisms affect community structure. Adaptive trade-offs appeared to be important in limiting the distributions of species which segregate across the habitat gradient. However, dispersal was important in shaping the distributions of species that utilize habitats with a broad range of hydroperiods and alternative top predator types. Our results also suggest that the relative importance of these mechanisms may change across this habitat gradient and that a metacommunity perspective which incorporates both niche- and dispersal-assembly processes is necessary to understand how communities are organized. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Pattern of ant diversity in Korea: An empirical test of Rapoport's altitudinal rule

Two diversity patterns (hump-shaped and monotonic decrease) frequently occur along altitude or latitude gradients. We examined whether patterns of ant species richness along altitudes in South Korea can be described by these patterns and whether ranges of ant species follow Rapoport's altitudinal rule. Ants on 12 high mountains (> 1100 m) throughout South Korea (from 33° N to 38° N) were surveyed using pitfall traps at intervals of 200–300 m altitude. The temperatures at the sampling sites were determined from digital climate maps. Ant species richness decreased monotonically along the altitudinal gradient and increased along the temperature gradient. However, species richness of cold-adapted species (highland species) showed a hump-shaped pattern along altitude and temperature gradients. The altitude and temperature ranges of ant species followed Rapoport's rule. Sampling site temperature ranges were significantly correlated with coldness. Therefore, Rapoport's rule can be explained by high cold-tolerance of species inhabiting high altitudes or latitudes.     

The unusual suspect: Land use is a key predictor of biodiversity patterns in the Iberian Peninsula

Although land use change is a key driver of biodiversity change, related variables such as habitat area and habitat heterogeneity are seldom considered in modeling approaches at larger extents. To address this knowledge gap we tested the contribution of land use related variables to models describing richness patterns of amphibians, reptiles and passerines in the Iberian Peninsula. We analyzed the relationship between species richness and habitat heterogeneity at two spatial resolutions (i.e., 10 km × 10 km and 50 km × 50 km). Using both ordinary least square and simultaneous autoregressive models, we assessed the relative importance of land use variables, climate variables and topographic variables. We also compare the species–area relationship with a multi-habitat model, the countryside species–area relationship, to assess the role of the area of different types of habitats on species diversity across scales. The association between habitat heterogeneity and species richness varied with the taxa and spatial resolution. A positive relationship was detected for all taxa at a grain size of 10 km × 10 km, but only passerines responded at a grain size of 50 km × 50 km. Species richness patterns were well described by abiotic predictors, but habitat predictors also explained a considerable portion of the variation. Moreover, species richness patterns were better described by a multi-habitat species-area model, incorporating land use variables, than by the classic power model, which only includes area as the single explanatory variable. Our results suggest that the role of land use in shaping species richness patterns goes beyond the local scale and persists at larger spatial scales. These findings call for the need of integrating land use variables in models designed to assess species richness response to large scale environmental changes.     

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.