Scale-specific correlations between habitat heterogeneity and soil fauna diversity along a landscape structure gradient

Habitat heterogeneity contributes to the maintenance of diversity, but the extent that landscape-scale rather than local-scale heterogeneity influences the diversity of soil invertebrates—species with small range sizes—is less clear. Using a Scottish habitat heterogeneity gradient we correlated Collembola and lumbricid worm species richness and abundance with different elements (forest cover, habitat richness and patchiness) and qualities (plant species richness, soil variables) of habitat heterogeneity, at landscape (1 km²) and local (up to 200 m²) scales. Soil fauna assemblages showed considerable turnover in species composition along this habitat heterogeneity gradient. Soil fauna species richness and turnover was greatest in landscapes that were a mosaic of habitats. Soil fauna diversity was hump-shaped along a gradient of forest cover, peaking where there was a mixture of forest and open habitats in the landscape. Landscape-scale habitat richness was positively correlated with lumbricid diversity, while Collembola and lumbricid abundances were negatively and positively related to landscape spatial patchiness. Furthermore, soil fauna diversity was positively correlated with plant diversity, which in turn peaked in the sites that were a mosaic of forest and open habitat patches. There was less evidence that local-scale habitat variables (habitat richness, tree cover, plant species richness, litter cover, soil pH, depth of organic horizon) affected soil fauna diversity: Collembola diversity was independent of all these measures, while lumbricid diversity positively and negatively correlated with vascular plant species richness and tree canopy density. Landscape-scale habitat heterogeneity affects soil diversity regardless of taxon, while the influence of habitat heterogeneity at local scales is dependent on taxon identity, and hence ecological traits, e.g. body size. Landscape-scale habitat heterogeneity by providing different niches and refuges, together with passive dispersal and population patch dynamics, positively contributes to soil faunal diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Elevational gradients in bird diversity in the Eastern Himalaya: an evaluation of distribution patterns and their underlying mechanisms

Background

Understanding diversity patterns and the mechanisms underlying those patterns along elevational gradients is critically important for conservation efforts in montane ecosystems, especially those that are biodiversity hotspots. Despite recent advances, consensus on the underlying causes, or even the relative influence of a suite of factors on elevational diversity patterns has remained elusive.

Methods and Principal Findings

We examined patterns of species richness, density and range size distribution of birds, and the suite of biotic and abiotic factors (primary productivity, habitat variables, climatic factors and geometric constraints) that governs diversity along a 4500-m elevational gradient in the Eastern Himalayan region, a biodiversity hotspot within the world''s tallest mountains. We used point count methods for sampling birds and quadrats for estimating vegetation at 22 sites along the elevational gradient. We found that species richness increased to approximately 2000 m, then declined. We found no evidence that geometric constraints influenced this pattern, whereas actual evapotranspiration (a surrogate for primary productivity) and various habitat variables (plant species richness, shrub density and basal area of trees) accounted for most of the variation in bird species richness. We also observed that ranges of most bird species were narrow along the elevation gradient. We find little evidence to support Rapoport''s rule for the birds of Sikkim region of the Himalaya.

Conclusions and Significance

This study in the Eastern Himalaya indicates that species richness of birds is highest at intermediate elevations along one of the most extensive elevational gradients ever examined. Additionally, primary productivity and factors associated with habitat accounted for most of the variation in avian species richness. The diversity peak at intermediate elevations and the narrow elevational ranges of most species suggest important conservation implications: not only should mid-elevation areas be conserved, but the entire gradient requires equal conservation attention.     

Habitat availability does not explain the species richness patterns of European lentic and lotic freshwater animals

Aim In Europe, the relationships between species richness and latitude differ for lentic (standing water) and lotic (running water) species. Freshwater animals are highly dependent on suitable habitat, and thus the distribution of available habitat should strongly influence large‐scale patterns of species richness. We tested whether habitat availability can account for the differences in species richness patterns between European lentic and lotic freshwater animals. Location Europe. Methods We compiled occurrence data of 1959 lentic and 2445 lotic species as well as data on the amount of lentic and lotic habitats across 25 pre‐defined biogeographical regions of European freshwaters. We used the range of elevation of each region as a proxy for habitat diversity. We investigated the relationships between species richness, habitat availability and habitat diversity with univariate and multiple regression analyses. Results Species richness increased with habitat availability for lentic species but not for lotic species. Species richness increased with elevational range for lotic species but decreased for lentic species. For both groups, neither habitat availability nor diversity could account for previously reported latitudinal patterns in species richness. For lotic species, richness declined with latitude, whereas there was no relationship between habitat availability and latitude. For lentic species, richness showed a hump‐shaped relationship with latitude, whereas available habitat increased with latitude. Main conclusions Habitat availability and diversity are poor predictors of species richness of the European freshwater fauna across large scales. Our results indicate that the distributions of European freshwater animals are probably not in equilibrium and may still be influenced by history, namely the recurrent European glaciations and possible differences in post‐glacial recolonization. The distributions of lentic species appear to be closer to equilibrium than those of lotic species. This lends further support to the hypothesis that lentic species have a higher propensity for dispersal than lotic species.     

Elevational Gradient in Species Richness Pattern of Epigaeic Beetles and Underlying Mechanisms at East Slope of Balang Mountain in Southwestern China

We report on the species richness patterns of epigaeic beetles (Coleoptera: Carabidae and Staphylinidae) along a subtropical elevational gradient of Balang Mountain, southwestern China. We tested the roles of environmental factors (e.g. temperature, area and litter cover) and direct biotic interactions (e.g. foods and antagonists) that shape elevational diversity gradients. Beetles were sampled at 19 sites using pitfall traps along the studied elevational gradient ranging from 1500 m–4000 m during the 2004 growing season. A total of 74416 specimens representing 260 species were recorded. Species richness of epigaeic beetles and two families showed unimodal patterns along the elevational gradient, peaking at mid-elevations (c. 2535 m), and the ranges of most beetle species were narrow along the gradient. The potential correlates of both species richness and environmental variables were examined using linear and second order polynomial regressions. The results showed that temperature, area and litter cover had strong explanatory power of beetle species richness for nearly all richness patterns, of beetles as a whole and of Carabidae and Staphylinidae, but the density of antagonists was associated with species richness of Carabidae only. Multiple regression analyses suggested that the three environmental factors combined contributed most to richness patterns for most taxa. The results suggest that environmental factors associated with temperature, area and habitat heterogeneity could account for most variation in richness pattern of epigaeic beetles. Additionally, the mid-elevation peaks and the small range size of most species indicate that conservation efforts should give attention to the entire gradient rather than just mid-elevations.     

Elevational gradient analyses and the use of historical museum specimens: a cautionary tale

Aim The value of biodiversity informatics rests upon the capacity to assess data quality. Yet as these methods have developed, investigating the quality of the underlying specimen data has largely been neglected. Using an exceptionally large, densely sampled specimen data set for non‐flying small mammals of Utah, I evaluate measures of uncertainty associated with georeferenced localities and illustrate the implications of uncritical incorporation of data in the analysis of patterns of species richness and species range overlap along elevational gradients. Location Utah, USA, with emphasis on the Uinta Mountains. Methods Employing georeferenced specimen data from the Mammal Networked Information System (MaNIS), I converted estimates of areal uncertainty into elevational uncertainty using a geographic information system (GIS). Examining patterns in both areal and elevational uncertainty measures, I develop criteria for including localities in analyses along elevational gradients. Using the Uinta Mountains as a test case, I then examine patterns in species richness and species range overlap along an elevational gradient, with and without accounting for data quality. Results Using a GIS, I provide a framework for post‐hoc 3‐dimensional georeferencing and demonstrate collector‐recorded elevations as a valuable technique for detecting potential errors in georeferencing. The criteria established for evaluating data quality when analysing patterns of species richness and species range overlap in the Uinta Mountains test case reduced the number of localities by 44% and the number of associated specimens by 22%. Decreasing the sample size in this manner resulted in the subsequent removal of one species from the analysis. With and without accounting for data quality, the pattern of species richness along the elevational gradient was hump‐shaped with a peak in richness at about mid‐elevation, between 2300 and 2600 m. In contrast, the frequencies of different pair‐wise patterns of elevational range overlap among species differed significantly when data quality was and was not accounted for. Main conclusions These results indicate that failing to assess spatial error in data quality did not alter the shape of the observed pattern in species richness along the elevational gradient nor the pattern of species’ first and last elevational occurrences. However, it did yield misleading estimates of species richness and community composition within a given elevational interval, as well as patterns of elevational range overlap among species. Patterns of range overlap among species are often used to infer processes underlying species distributions, suggesting that failure to account for data quality may alter interpretations of process as well as perceived patterns of distribution. These results illustrate that evaluating the quality of the underlying specimen data is a necessary component of analyses incorporating biodiversity informatics.     

Elevational gradient and human effects on butterfly species richness in the French Alps

We examined how butterfly species richness is affected by human impact and elevation, and how species ranges are distributed along the elevational gradient (200–2700 m) in the Isère Department (French Alps). A total of 35,724 butterfly observations gathered in summer (May–September) between 1995 and 2015 were analyzed. The number of estimated species per 100‐m elevational band was fitted to the elevational gradient using a generalized additive model. Estimations were also performed on a 500 m × 500 m grid at low altitude (200–500 m) to test for the human impact on species richness using generalized least squares regression models. Each species elevational range was plotted against the elevational gradient. Butterfly richness along the elevational gradient first increased (200–500 m) to reach a maximum of 150 species at 700 m and then remained nearly constant till a sharp decrease after 1900 m, suggesting that after some temperature threshold, only few specialized species can survive. At low elevation, urbanization and arable lands had a strongly negative impact on butterfly diversity, which was buffered by a positive effect of permanent crops. Butterfly diversity is exceptionally high (185 species) in this alpine department that represents less than 5% of the French territory and yet holds more than 70% of all the Rhopalocera species recorded in France. Both climate and habitat shape the distribution of species, with a negative effect of anthropization at low altitude and strong climatic constraints at high altitude.     

Small mammal species richness and turnover along elevational gradient in Yulong Mountain,Yunnan, Southwest China

Understanding the species diversity patterns along elevational gradients is critical for biodiversity conservation in mountainous regions. We examined the elevational patterns of species richness and turnover, and evaluated the effects of spatial and environmental factors on nonvolant small mammals (hereafter “small mammal”) predicted a priori by alternative hypotheses (mid‐domain effect [MDE], species–area relationship [SAR], energy, environmental stability, and habitat complexity]) proposed to explain the variation of diversity. We designed a standardized sampling scheme to trap small mammals at ten elevational bands across the entire elevational gradient on Yulong Mountain, southwest China. A total of 1,808 small mammals representing 23 species were trapped. We observed the hump‐shaped distribution pattern of the overall species richness along elevational gradient. Insectivores, rodents, large‐ranged species, and endemic species richness showed the general hump‐shaped pattern but peaked at different elevations, whereas the small‐ranged species and endemic species favored the decreasing richness pattern. The MDE and the energy hypothesis were supported, whereas little support was found for the SAR, the environmental stability hypothesis, and the habitat complexity. However, the primary driver(s) for richness patterns differed among the partitioning groups, with NDVI (the normalized difference vegetation index) and MDE being the most important variables for the total richness pattern. Species turnover for all small mammal groups increased with elevation, and it supported a decrease in community similarity with elevational distance. Our results emphasized for increased conservation efforts in the higher elevation regions of the Yulong Mountain.     

Distribution Patterns and Conservation Perspectives of the Endemic Flora of Peloponnese (Greece)

An inventory of the endemic vascular plants of the Peloponnese (395 species and subspecies) has been created based on literature, herbarium and field data. Endemics?? distribution patterns, altitudinal distribution and habitat specificity were investigated. A rarity score for each endemic has been calculated based on its population size, geographic range and habitat specificity. The main mountainous areas of the Peloponnese are largely congruent to the hotspots of endemism. Altitudinal range and niche breadth of the endemics were positively correlated to their range size. The elevational gradient of the endemic species richness showed a hump-shaped pattern, in contrast to the monotonically decreasing pattern of total species richness. Endemic species were found to support boundary theory, while total species richness distribution followed the Rapoport??s elevational rule. The elevational distribution of the average rarity score and the average weighted threat of the endemics resulted in low values for mid-elevation intervals and increased values for low and high altitude areas, indicating that conservation efforts should focus on the two extremes of the elevational gradient. Area prioritization methods were applied using a rarity/complementarity based algorithm with two species weighting schemes. Their results were largely congruent confirming the significance of the main mountainous areas for the conservation of the endemics. Spatial overlap among selected grid cells using the rarity/complementarity analysis and Natura 2000 network was found to be low. Our results revealed the conservation importance of at least one new area located on Kythera Island.     

Fine‐scale determinants of butterfly species richness and composition in a mountain region

Aim Global patterns of species richness are often considered to depend primarily on climate. We aimed to determine how topography and land cover affect species richness and composition at finer scales. Location Sierra de Guadarrama (central Iberian Peninsula). Methods We sampled the butterfly fauna of 180 locations (89 in 2004, 91 in 2005) at 600–2300 m elevation in a region of 10800 km². We recorded environmental variables at 100‐m resolution using GIS, and derived generalized linear models for species density (number of species per unit area) and expected richness (number of species standardized to number of individuals) based on variables of topoclimate (elevation and insolation) or land cover (vegetation type, geology and hydrology), or both (combined). We evaluated the models against independent data from the alternative study year. We also tested for differences in species composition among sites and years using constrained ordination (canonical correspondence analysis), and used variation partitioning analyses to quantify the independent and combined roles of topoclimate and land cover. Results Topoclimatic, land cover and combined models were significantly related to observed species density and expected richness. Topoclimatic and combined models outperformed models based on land cover variables, showing a humped elevational diversity gradient. Both topoclimate and land cover made significant contributions to models of species composition. Main conclusions Topoclimatic factors may dominate species richness patterns in regions with pronounced elevational gradients, as long as large areas of natural habitat remain. In contrast, both topoclimate and land cover may have important effects on species composition. Biodiversity conservation in mountainous regions therefore requires protection and management of natural habitats over a wide range of topoclimatic conditions, which may assist in facilitating range shifts and alleviating declines in species richness related to climate change.     

Exploring anthropogenic and natural processes shaping fern species richness along elevational gradients

Aim (1) To explore the impact of land use, climate and environmental heterogeneity on fern species richness along a complete elevational gradient, and (2) to evaluate the relative importance of the three groups of variables within different elevational intervals. Location A temperate mountain region (55,507 km²) of Italy on the southern border of the European Alps divided into a regular grid of 1476 cells (grain 35.7 km²). Methods We applied multiple regression (spatial and non‐spatial) to determine the relative influence of the three groups of variables on species richness, including variation partitioning at two scales. We considered the whole gradient (all 1476 cells) to explain the overall elevational pattern of species richness, and we grouped the cells into elevational intervals of 500 m in order to evaluate the explanatory power of the predictors within different zones along the gradient. Results Species richness showed a hump‐shaped pattern with elevation, forming a plateau between 800 and 1500 m. The lowest species richness was found in warm and relatively dry disturbed lowlands. Moving upwards, the greatest species richness was found in forest‐dominated mid‐elevations with high environmental heterogeneity. At high elevations dominated by open natural habitats, where temperature and precipitation were relatively low, species richness declined but less sharply than in the lowlands. Although it was impossible to separate the effects of the three groups of predictors along the whole gradient, the analysis of separate elevational intervals shed light on their relative importance. The decline of species richness within lowlands was mainly related to a combined effect of deforestation and low environmental heterogeneity. In the middle part of the gradient, habitat heterogeneity and topographic roughness were positively associated with species richness. The richness decline within high‐elevation areas was related mostly to climatic constraints. Main conclusions Human impact due to land‐use modifications strongly affects the elevational pattern of species richness. It is therefore increasingly important to adopt a multiple‐hypothesis approach, taking anthropogenic effects explicitly into account when describing ecological processes along elevational gradients.     

Constant tree species richness along an elevational gradient of Mt. Bokor,a table-shaped mountain in southwestern Cambodia

Some previous studies along an elevational gradient on a tropical mountain documented that plant species richness decreases with increasing elevation. However, most of studies did not attempt to standardize the amount of sampling effort. In this paper, we employed a standardized sampling effort to study tree species richness along an elevational gradient on Mt. Bokor, a table-shaped mountain in southwestern Cambodia, and examined relationships between tree species richness and environmental factors. We used two methods to record tree species richness: first, we recorded trees taller than 4 m in 20 uniform plots (5 × 100 m) placed at 266–1048-m elevation; and second, we collected specimens along an elevational gradient from 200 to 1048 m. For both datasets, we applied rarefaction and a Chao1 estimator to standardize the sampling efforts. A generalized linear model (GLM) was used to test the relationship of species richness with elevation. We recorded 308 tree species from 20 plots and 389 tree species from the general collections. Species richness observed in 20 plots had a weak but non-significant correlation with elevation. Species richness estimated by rarefaction or Chao1 from both data sets also showed no significant correlations with elevation. Unlike many previous studies, tree species richness was nearly constant along the elevational gradient of Mt. Bokor where temperature and precipitation are expected to vary. We suggest that the table-shaped landscape of Mt. Bokor, where elevational interval areas do not significantly change between 200 and 900 m, may be a determinant of this constant species richness.     

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.     

Patterns in diversity of anurans along an elevational gradient in the Western Ghats, South India

Aim To examine patterns in anuran species richness along an elevation gradient and identify factors that govern anuran species richness on a tropical elevational gradient. Location Sampling for anurans was carried out in Kalakad Mundanthurai Tiger Reserve (KMTR) in the southern Western Ghats, India. Methods Night‐time sampling for anuran species richness was carried out from 20 November 2004 to 20 April 2005, during the north‐east monsoon and dry seasons, using transects (50 × 2 m) and visual encounter surveys along the streams. The entire gradient was classified into thirteen 100‐m elevation zones. Sampling at the alpha (single drainage basin) level was carried out in the Chinnapul River drainage basin (40–1260 m a.s.l.) and at the gamma (landscape) level in four drainage basins. Additionally, published records were used to arrive at an empirical species richness (S) for the entire landscape. Mid‐Domain Null software was used to test for the possible influence of geometric constraints on anuran species at both the alpha and gamma levels. The influence of area under each elevation zone on empirical S was tested. The pattern in anuran species richness along the elevational gradient was investigated using: (1) species boundaries in each elevation zone and their habitat correlates, (2) abiotic factors as predictor variables, (3) mean snout vent lengths of anurans, and (4) correlation between the matrices of distance in the elevation zones based on microhabitat parameters and species composition. Cluster analysis on species presence–absence in the elevation zones was used to categorize the entire gradient into high, middle and low elevations. In these three elevation categories, pattern in composition of species was examined for endemism in Western Ghats–Sri Lanka biodiversity hotspot, uniqueness to an elevation zone, adaptations of adults and modes of breeding. Results Species richness at the alpha level increased linearly with elevation, while at the gamma level there were three peaks. Maximum species richness was observed at the highest elevation (1200 m) at both the alpha and the gamma levels. The observed patterns differed significantly from mid‐domain null predictions. The multi‐modal pattern in species richness was a consequence of overlapping species range boundaries. Soil temperature was the best single measure in explaining the majority of variation in species richness at the alpha level (r² = 0.846, P < 0.01). However, soil moisture was the best predictor when both the alpha and the gamma sites were pooled (r² = 0.774, P < 0.01). Anuran body size decreased with an increase in elevation. The highest proportions of endemic and unique species were found at high elevations (> 700 m). The proportion of arboreal anurans increased from low to high elevation. Anurans exhibiting direct development were predominantly found at high elevations. Main conclusions Geometric constraints did not influence anuran species richness along the elevational gradient. Overlapping range boundaries influenced species richness at the gamma level. Abiotic factors such as soil temperature and moisture influenced anuran species richness in the mountain range. The ‘Massenerhebung effect’ could be responsible for range restriction and endemism of anurans, differences in guilds and mode of reproduction. These findings highlight the importance of cloud forests for endemic anurans.     

Elevational Gradient of Vascular Plant Species Richness and Endemism in Crete – The Effect of Post-Isolation Mountain Uplift on a Continental Island System

Understanding diversity patterns along environmental gradients and their underlying mechanisms is a major topic in current biodiversity research. In this study, we investigate for the first time elevational patterns of vascular plant species richness and endemism on a long-isolated continental island (Crete) that has experienced extensive post-isolation mountain uplift. We used all available data on distribution and elevational ranges of the Cretan plants to interpolate their presence between minimum and maximum elevations in 100-m elevational intervals, along the entire elevational gradient of Crete (0–2400 m). We evaluate the influence of elevation, area, mid-domain effect, elevational Rapoport effect and the post-isolation mountain uplift on plant species richness and endemism elevational patterns. Furthermore, we test the influence of the island condition and the post-isolation mountain uplift to the elevational range sizes of the Cretan plants, using the Peloponnese as a continental control area. Total species richness monotonically decreases with increasing elevation, while endemic species richness has a unimodal response to elevation showing a peak at mid-elevation intervals. Area alone explains a significant amount of variation in species richness along the elevational gradient. Mid-domain effect is not the underlying mechanism of the elevational gradient of plant species richness in Crete, and Rapoport''s rule only partly explains the observed patterns. Our results are largely congruent with the post-isolation uplift of the Cretan mountains and their colonization mainly by the available lowland vascular plant species, as high-elevation specialists are almost lacking from the Cretan flora. The increase in the proportion of Cretan endemics with increasing elevation can only be regarded as a result of diversification processes towards Cretan mountains (especially mid-elevation areas), supported by elevation-driven ecological isolation. Cretan plants have experienced elevational range expansion compared to the continental control area, as a result of ecological release triggered by increased species impoverishment with increasing elevation.     

Vertebrate metacommunity structure along an extensive elevational gradient in the tropics: a comparison of bats,rodents and birds

Aim We evaluated the structure of metacommunities for each of three vertebrate orders (Chiroptera, Rodentia and Passeriformes) along an extensive elevational gradient. Using elevation as a proxy for variation in abiotic characteristics and the known elevational distributions of habitat types, we assessed the extent to which variation in those factors may structure each metacommunity based on taxon‐specific characteristics. Location Manu Biosphere Reserve in the Peruvian Andes. Methods Metacommunity structure is an emergent property of a set of species distributions across geographic or environmental gradients. We analysed elements of metacommunity structure (coherence, range turnover and range boundary clumping) to determine the best‐fit structure for each metacommunity along an elevational gradient comprising 13 250‐m elevational intervals and 58 species of rodent, 92 species of bat or 586 species of passerine. Results For each taxon, the environmental gradient along which the metacommunity was structured was highly correlated with elevation. Clementsian structure (i.e. groups of species replacing other such groups along the gradient) characterized rodents, with a group of species that was characteristic of rain forests and a group of species that was characteristic of higher elevation habitats (i.e. above 1500 m). Distributions of bats were strongly nested, with more montane communities comprising subsets of species at lower elevations. The structure of the passerine metacommunity was complex and most consistent with a quasi‐Clementsian structure. Main conclusions Each metacommunity exhibited a different structure along the same elevational gradient, and each structure can be accounted for by taxon‐specific responses to local environmental factors that vary predictably with elevation. The structures of rodent and bird metacommunities suggest species sorting associated with habitat specializations, whereas structure of the bat metacommunity is probably moulded by a combination of species‐specific tolerances to increasingly cold, low‐productivity environs of higher elevations and the diversity and abundance of food resources associated with particular habitat types.     

The mid‐domain effect and habitat complexity applied to elevational gradients: Moss species richness in a temperate semihumid monsoon climate mountain of China

The utility of elevational gradients as tools to test either ecological hypotheses and delineate elevation‐associated environmental factors that explain the species diversity patterns is critical for moss species conservation. We examined the elevational patterns of species richness and evaluated the effects of spatial and environmental factors on moss species predicted a priori by alternative hypotheses, including mid‐domain effect (MDE), habitat complexity, energy, and environment proposed to explain the variation of diversity. Last, we assessed the contribution of elevation toward explaining the heterogeneity among sampling sites. We observed the hump‐shaped distribution pattern of species richness along elevational gradient. The MDE and the habitat complexity hypothesis were supported with MDE being the primary driver for richness patterns, whereas little support was found for the energy and the environmental factors.     

Mammals of the northern Philippines: tolerance for habitat disturbance and resistance to invasive species in an endemic insular fauna

Aim Island faunas, particularly those with high levels of endemism, usually are considered especially susceptible to disruption from habitat disturbance and invasive alien species. We tested this general hypothesis by examining the distribution of small mammals along gradients of anthropogenic habitat disturbance in northern Luzon Island, an area with a very high level of mammalian endemism. Location Central Cordillera, northern Luzon Island, Philippines. Methods  Using standard trapping techniques, we documented the occurrence and abundance of 16 endemic and two non‐native species along four disturbance gradients where habitat ranged from mature forest to deforested cropland. Using regression analysis and AIC_c for model selection, we assessed the influence of four predictor variables (geographic range, elevational range, body size and diet breadth) on the disturbance tolerance of species. Results Non‐native species dominated areas with the most severe disturbance and were rare or absent in mature forest. Native species richness declined with increasing disturbance level, but responses of individual species varied. Elevational range (a measure of habitat breadth) was the best predictor of response of native species to habitat disturbance. Geographic range, body size and diet breadth were weakly correlated. Main conclusions The endemic small mammal fauna of northern Luzon includes species adapted to varying levels of natural disturbance and appears to be resistant to disruption by resident alien species. In these respects, it resembles a diverse continental fauna rather than a depauperate insular fauna. We conclude that the long and complex history of Luzon as an ancient member of the Philippine island arc system has involved highly dynamic ecological conditions resulting in a biota adapted to changing conditions. We predict that similar responses will be seen in other taxonomic groups and in other ancient island arc systems.     

Ecological gradient of sexual selection: elevation and song elaboration in finches

Ecological gradients in natural and sexual selection often result in evolutionary diversification of morphological, life history, and behavioral traits. In particular, elevational changes in habitat structure and climate not only covary with intensity of sexual selection in many taxa, but may also influence evolution of mating signals. Here we examined variation in courtship song in relation to elevation of breeding across cardueline finches-a subfamily of birds that occupies the widest elevational range of extant birds and shows extensive variation in life histories and sexual selection along this range. We predicted that decrease in sexual selection intensity with elevation of breeding documented in this clade would result in a corresponding evolutionary reduction in elaboration of courtship songs. We controlled for the effects of phylogeny, morphology, and habitat structure to uncover a predicted elevational decline in courtship song elaboration; species breeding at lower elevations sang more elaborated and louder songs compared to their sister species breeding at higher elevations. In addition, lower elevation species had longer songs with more notes, whereas frequency components of song did not vary with elevation. We suggest that changes in sexual selection account for the observed patterns of song variation and discuss how elevational gradient in sexual selection may facilitate divergence in mating signals potentially reinforcing or promoting speciation.     

Nonlinear Distribution Pattern of Hibernating Bats in Caves along an Elevational Gradient in Mountain (Carpathians,Southern Poland)

Background

Thermal gradients along changes in elevation in mountainous environments are reflected by different biotas. Although there have been studies of elevation variation in bat assemblages in summer, winter changes in the same gradients remain unknown.

Methodology/Principal Findings

The objective of this study was to document changes in the species composition of bats hibernating in caves along a temperate elevational gradient. We studied 70 caves between from 300 m to 1,930 m altitude along a slope of the Carpathian Mountains in southern Poland. We recorded changes in bats, including species richness, abundance, altitudinal distribution and dominance during consecutive winters between 2003 and 2009. Similarity of dominance of faunal structure was assessed by using the Bray-Curtis similarity index. We used the generalised additive model and rarefaction to study the variation in species richness, and generalized additive mixed models to examine the effect of abiotic factors on the qualitative and quantitative structure of bat assemblages. During 351 surveys we recorded 13,856 hibernating bats from 15 species. Species richness peaked around mid-elevation (1,100–1,400 m a.s.l.) with richness declining at both higher and lower elevations. Based on the results of a cluster analysis, we could distinguish among four altitudinal zones that differed in species richness and dominance structure.

Conclusions/Significance

This is the first study documenting changes in species richness and variation of structure of bats hibernating in caves along an elevational gradient. The most surprising and key finding is the fact that changes in the structure of assemblages of hibernating bats along the altitudinal gradient occurred in jumps, forming zones similar to those observed in the vegetation zones. Moreover, species richness and dominance structure of assemblages of hibernating bats in the mountains depended not only on location above sea level, but also on local geomorphologic conditions which strongly affected the microclimate of the caves.     

Mammalian species richness and morphological complexity along an elevational gradient in the arid south-west

Aim We examined the relationship between species richness and morphological complexity of terrestrial mammal communities along an elevational gradient. Location The gradient is in the Sonoran Desert in Southern California and extends from a sand dune habitat near sea level to coniferous forest ending at >2600 m. Methods Morphological diversity, characterized by both size and shape of coexisting mammal species, was estimated within and between sites from projections of variables on principal components axes. Similarities among species were calculated as Euclidean distances. To tease apart size and shape, we constructed two principal component analyses: one based on log-transformed original measurements, the other on log-transformed proportional shape variables. To test whether species number accounted for the morphological diversity at each site we designed two null models. The models generated were random communities generated from the forty-two-species pool. Indices of morphological diversity for real communities were compared with the results of 500 simulations of each null model. Results Species richness varied along the gradient, peaking in the mid-elevation agave-ocotillo habitat. Morphological diversity of shapes and sizes correlated strongly with species richness. Locomotor, tooth, and skull traits were all important in distinguishing among species. Main conclusions Two important patterns emerged: (1) diversity of both sizes and of shapes of species within communities correlated positively with species number, and both sets of variables behaved similarly across this gradient; (2) the most species rich sites were not composed of specialists on these best places, but rather, a community of species derived from overlapping faunal groups.