Patterns of diversity and habitat relationships in terrestrial mollusc communities of the Pukeamaru Ecological District, northeastern New Zealand

Aim The New Zealand terrestrial mollusc fauna is among the most speciose in the world, with often remarkably high richness at lowland forest sites. We sought to elucidate general explanations for patterns of richness in terrestrial mollusc communities by analysis of species coexistence and habitat relationships within a New Zealand district fauna. Location Pukeamaru Ecological District, eastern North Island, New Zealand. Methods We sampled molluscs using qualitative methods at twenty-three sites and quantitatively by frame sampling of scrubland-forest floor litter at sixteen of these sites and analysed patterns of species richness and turnover in relation to regional species pools and local habitat attributes. We then tested for nonrandom assemblage of taxa along diversity and habitat gradients. Results Ninety-four indigenous mollusc species were recorded from a district fauna estimated at 102 indigenous species: only two species were endemic. From the presumptive geological history of the district, the low endemism, and Brooks parsimony and indicator species analyses of faunal relationships, the communities were indicated to have resulted by accumulation of colonists from other New Zealand districts since the Miocene. Richness ranged from two or three indigenous species in dune habitats to fifty-nine species in a floristically rich forest. Beta diversity was high and site occupancy per species was low, indicating communities structured by successive replacement of ecological equivalents. Sites differing in vegetation had characteristic species assemblages, indicating a degree of habitat specialization. Canonical correspondence analysis indicated that canopy tree species, canopy height, floristic diversity, altitude, litter mass, and litter pH were important determinants of species assemblage in scrubland and forest. Richness was strongly associated with site floristic diversity and, for litter-dwelling species, the pH of litter substrate. High richness occurred at those sites supporting molluscs in high abundance. Shell-shape distributions were essentially Cainian unimodal, with communities dominated by snail species with subglobose to discoidal shells. Mean and variance of shell size increased with mollusc species richness and floristic diversity at sites, indicating dominance of communities by small-shelled species at early successional or floristically poor sites, and increased richness resulting from addition of larger snails into vacant niches. Shifts in shell form were associated with sympatry in several congeneric taxa. Main conclusions The underdispersion of shell shape, relative to faunas elsewhere in the world, indicates that community structure in New Zealand land snail faunas has been constrained by limited phylogenetic diversity and/or by convergence upon successful adaptations. The remarkably high richness that characterizes these communities indicates special conditions allow coexistence of numerous species. The relationship between floristic diversity at sites and the richness, diversity, and shell-size distributions of the molluscs suggests assemblages structured around niche partitioning among competing species. While there is an element of congruence between vegetation and mollusc pattern, this study indicates that assembly rules will be defined, and spatial pattern predicted, only through a better understanding of the linkage between regional species pool, organism traits, environment, and local community assemblage.     

Distribution patterns of land snails in Ugandan rain forests support the existence of Pleistocene forest refugia

Aim We investigated whether the biogeographical patterns expected if the East African fauna was affected by cycles of contraction to refugia and expansion of ranges, as has been previously hypothesized, can be found in the land snail fauna of rain forests in Uganda. Location The Albertine Rift region and the Lake Victoria forest belt in Uganda. Methods Snails and slugs were sampled in 60 plots in 13 rain forests, and small species were extracted from 5‐L leaf litter samples. Relative species richness was calculated by rarefaction. The influence of putative determinants of species richness was examined by bivariate correlation and multiple regression. Clustering and nestedness were tested by Monte Carlo simulations with a null model that considers the range size distribution, the species richness distribution of the forests, and the spatial autocorrelation of the occurrences of each species. Biotic elements were determined by model‐based Gaussian clustering. Results A total of 169 land snail species were recorded from 13 Ugandan rain forests. Relative species richness increases with rainfall and altitude, and decreases with evaporation and distance from the putative East Congolian refugia. Mean annual rainfall and distance from the putative East Congolian refugia were included in the best multiple regression model. The distribution areas of the Ugandan land snails are significantly clustered. Two montane, two lowland and a northern biotic element were found. The mean range extension increases with increasing distance from the putative East Congolian refugia. Moreover, the ranges of the Ugandan land snails are significantly nested. The centre of the sets of nested subsets is in the Virunga Mountains, close to the putative East Congolian refugia. Main conclusions The decrease of diversity with increasing distance from the putative East Congolian refugia, the clustering and nestedness of ranges, and the range size increase with increasing distance from the refugia indicate that the East African land snail fauna was affected by cycles of contraction to refugia and expansion of ranges. The significant clustering and nestedness cannot be explained by current environmental conditions. Given the environmental history, it can be supposed that the lowland elements expanded post‐glacially, whereas the ranges of the montane species are probably currently contracting.     

Amphibian richness patterns in Atlantic Forest areas invaded by American bullfrogs

The relationship between invasion success and native biodiversity is central to biological invasion research. New theoretical and analytical approaches have revealed that spatial scale, land‐use factors and community assemblages are important predictors of the relationship between community diversity and invasibility and the negative effects of invasive species on community diversity. In this study we assess if the abundance of Lithobates catesbeianus, the American bullfrog, negatively affects the richness of native amphibian species in Atlantic Forest waterbodies in Brazil. Although this species has been invading Atlantic Forest areas since the 1930s, studies that estimate the invasion effects upon native species diversity are lacking. We developed a model to understand the impact of environmental, spatial and species composition gradients on the relationships between bullfrogs and native species richness. We found a weak positive relationship between bullfrog abundance and species richness in invaded areas. The path model revealed that this is an indirect relationship mediated by community composition gradients. Our results indicate that bullfrogs are more abundant in certain amphibian communities, which can be species‐rich. Local factors describing habitat heterogeneity were the main predictors of amphibian species richness and composition and bullfrog abundance. Our results reinforce the important role of habitats in determining both native species diversity and potential invasibility.     

Species richness, environmental heterogeneity and area: a case study based on land snails in Skyros archipelago (Aegean Sea, Greece)

Aim To test the performance of the choros model in an archipelago using two measures of environmental heterogeneity. The choros model is a simple, easy‐to‐use mathematical relationship which approaches species richness as a combined function of area and environmental heterogeneity. Location The archipelago of Skyros in the central Aegean Sea (Greece). Methods We surveyed land snails on 12 islands of the archipelago. We informed the choros model with habitat data based on natural history information from the land snail species assemblage. We contrast this with habitat information taken from traditional vegetation classification to study the behaviour of choros with different measures of environmental heterogeneity. R² values and Akaike's information criterion (AIC) were used to compare the choros model and the Arrhenius species–area model. Path analysis was used to evaluate the variance in species richness explained by area and habitat diversity. Results Forty‐two land snail species were recorded, living in 33 different habitat types. The choros model with habitat types had more explanatory power than the classic species–area model and the choros model using vegetation types. This was true for all islands of the archipelago, as well as for the small islands alone. Combined effects of area and habitat diversity primarily explain species richness in the archipelago, but there is a decline when only small islands are considered. The effects of area are very low both for all the islands of the archipelago, and for the small islands alone. The variance explained by habitat diversity is low for the island group as a whole, but significantly increases for the small islands. Main conclusions The choros model is effective in describing species‐richness patterns of land snails in the Skyros Archipelago, incorporating ecologically relevant information on habitat occupancy and area. The choros model is more effective in explaining richness patterns on small islands. When using traditional vegetation types, the choros model performs worse than the classic species–area relationship, indicating that use of proxies for habitat diversity may be problematic. The slopes for choros and Arrhenius models both assert that, for land snails, the Skyros Archipelago is a portion of a larger biogeographical province. The choros model, informed by ecologically relevant habitat measures, in conjunction with path analysis points to the importance of habitat diversity in island species richness.     

The Impact of Anthropogenic Disturbance on Assembly Patterns of Termite Communities

Intensification of land‐use threatens biodiversity, especially in tropical ecosystems that harbor the planet's highest species richness. This negative impact of anthropogenic disturbance on species numbers is well established, but the mechanisms underlying the community assembly processes are less well understood. Termites are of fundamental importance in tropical ecosystems where they are critical for nutrient recycling and species diversity. We tested the impact of anthropogenic disturbance on termite species diversity and assembly processes in a West African savanna applying the newest techniques of phylogenetic community analyses. Species richness dropped in areas of intensive land‐use and compositional similarity between intensive land‐use areas was high. This contrasted with a protected National Park where communities were characterized by high species richness and intermediate species turnover between sites. Slightly disturbed areas in the buffer zone surrounding the park were intermediate, they still had high species richness but similarity between sites increased. Strikingly, the assembly pattern also changed with disturbance from more phylogenetic overdispersion to more clustering (coexisting species became phylogenetically more similar), but only when the fungus‐growing termite Macrotermes bellicosus was absent. Our data suggest that the major forces structuring termite communities depend: (1) on the presence of this dominant mound‐building termite; and (2) that they change to more environmental filtering with disturbance. Anthropogenic disturbance seems to function as a filter that allows only a specific subset of species to occur. Such an effect might be widespread in ecology but it is difficult to document quantitatively. Phylogenetic community analyses can help to contribute such evidence.     

Floristic richness of three perhumid New Zealand alpine plant communities in comparison with other regions

Abstract Results are presented on vascular species richness in three representative alpine plant communities at 1040–1410 m on Mt Burns in the perhumid Fiordland region, a hotspot of alpine plant diversity, in south‐western South Island, New Zealand. Overall species richness was not dissimilar between the three communities in any of the eight plot sizes (mean values of 20.8–24.4 species in the largest plots of 100 m²), even though coefficients of floristic similarity were small (17.9; 23.5) between both low‐alpine communities (snow tussock‐shrubland and snow tussock grassland) and the high‐alpine cushion fellfield. Vascular species richness was generally similar to that in the few other oceanic New Zealand alpine communities for which data are available. The decline in richness from the low‐alpine to high‐alpine zones, revealed in more comprehensive records from two other regions with generally similar oceanic environments, was not recorded, indeed was reversed, on Mt Burns. Whether the recognized biodiversity hotspot of Fiordland has a generally richer high‐alpine flora than other regions in New Zealand needs further examination. The general pattern of alpine floristic richness in relation to elevation, in New Zealand, also prevails in most alpine regions abroad, usually under much more extreme continental environments. This pattern is usually ascribed to the associated decrease in temperature. Both the small size of the land mass and/or associated environmental conditions may be implicated but clarification awaits further data, preferably collected with standardized procedures.     

Diversity of the Western Carpathian flysch grasslands: Do extremely species-rich plant communities coincide with a high diversity of snails?

Upland fringes of the White Carpathians (Czech Republic) are known to support grasslands with the world’s highest local plant species richness. We investigated whether this unusually high plant richness has a parallel in snail communities, whether patterns of species composition of snail and plant communities in grasslands co-vary and how they are affected by local environment and landscape history. We compared plant and snail communities of dry to mesic grasslands in three neigh bouring regions: (1) hilly lowland of the Central Moravian Carpathians, (2) upland fringes and (3) upland of the White Carpathians. Both snail and plant communities exhibited a strong gradient in species composition associated with altitude, annual temperature and precipitation, soil calcium and pH. However, there was no correlation between local species richness of plants and snails in individual plots. The upland fringes of the White Carpathians were richest in snail species, probably due to intermediate environmental conditions, supporting the occurrence of species with contrasting environmental requirements. The highest local numbers of plant species were also recorded there, although differences among regions were not significant. The regional species richness of plants was also highest in the upland fringes, whereas that of snails was highest in the hilly lowland. Similarities in the diversity patterns of plants and snails among regions suggest the importance of regional factors for local richness, although local abiotic factors, which are partly correlated with the three regions, also influence local species composition and richness.     

长白山溪流河岸带森林木本植物多样性沿海拔梯度分布规律

采用样带网格调查方法和α、β多样性指数分析方法,研究了长白山河岸带原始林和次生林群落木本植物多样性沿海拔梯度分布规律及其对采伐干扰的响应.结果表明：不同海拔区域河岸带原始林群落均由11～13个树种组成,其在群落中的地位随海拔升高而发生变化,阔叶树种优势地位逐步被针叶树种所取代,采伐干扰不仅改变了群落树种丰富度及其在群落中的地位,而且使针叶树种取代阔叶树种的趋势有所增强;河岸带原始林群落物种多样性沿海拔梯度呈现出中、低海拔区域相对较高且比较恒定(2.454～2.544),高海拔区域(2.250)下降的分布规律,采伐干扰改变了其沿海拔梯度分布格局(波动型),加大了不同海拔区域群落间的波动性(2.174～2.692);河岸带原始林群落树种沿海拔梯度的变动速率相对较低(1.5～3.5),且群落相似性较高(0.85～0.94),采伐干扰使次生林群落树种沿海拔梯度的变动幅度增大(0.5～6.0),群落相似性下降(0.68～0.91),但次生林群落沿海拔梯度分布仍具有较高连续性.     

Biodiversity surrogate effectiveness in two habitat types of contrasting gradient complexity

Enormous and increasing loss of biodiversity requires evaluation of surrogate taxa as a tool for conservation biology and new reserve selection, in spite of the fact that this approach has become questionable. The aim of this study was to assess the effect of gradient complexity on species richness and community composition among three taxonomic groups. We compared efficiency of vascular plants to indicate diversity of cryptogams (bryophytes, lichens) and snails in two contrasting habitat types (treeless fens and forests) within the same geographic region. We examined correlation of their species richness (Spearman rank correlation), community composition (Bray–Curtis similarity, Mantel test) and their responses to environmental variables (detrended and canonical correspondence analysis). We also focused on Red List species. We found that spatial congruence among studied taxa was affected by habitat type, however vascular plants were good indicator of snail biodiversity in both habitats. Nevertheless, all significant positive correlations of species richness were associated with the congruence in main environmental gradients. Although there was a consistency in significantly positive cross-taxon correlation in community similarity, the congruence was insufficient for conservation purposes. Furthermore we confirmed the necessity of integration of at-risk species in conservation planning as Red List species were poor indicators for total species richness and vice versa. We suggest the complementation of existing reserve network with small-scale protected areas focused on conservation of at-risk ecosystems, communities or species. In this study vascular plants were not found as a sufficient indicator for fine-filter conservation of other taxa.     

云南沾益中度退化天坑草地植物群落水平空间分布特征

规模最为宏大的地表负地形——喀斯特天坑不仅是世界罕见的地质奇观,圈闭化地形而形成的独特生境更是探索植物物种多样性及其空间分布特征最为理想的地域。以云南沾益天坑群中的中度退化天坑——"巴家陷塘"坑底草地植物群落为研究对象,通过α多样性指数与β相似性系数的应用,对"巴家陷塘"中度退化天坑坑底草地植物群落物种多样性的水平空间分布特征展开探讨,并对其近邻退化漏斗和"大毛寺"原生天坑坑外草地植物群落的相似性进行对比分析,研究结果发现:(1)中度退化天坑坑底草地植物群落物种丰富度和多样性从中心到边缘呈现出"中心高边缘低"的"逆洼地效应"特征;(2)相较于土壤资源,喀斯特天坑植物群落的生长与空间分布对光照资源的响应更为明显,且四周坑壁高度差异造成的坑内光照资源的空间异质性,也使坑底草地植物物种多样性存在一定的"圈层效应";(3)喀斯特天坑独特的圈闭化地形对植物群落的"隔离"、庇护作用即使在退化天坑中也有明显体现,且对喜阴、耐湿的物种更具庇护性。因而在全球气候变化下,即使是退化天坑,也应成为区域小尺度生态避难所的重要保护对象。     

Genetic and community similarities are correlated in endemic-rich springs of the northern Chihuahuan Desert

Aim Species diversity and genetic diversity within a taxon are intrinsic parts of global biodiversity. These two levels of biodiversity can show strong correlation due to a variety of reasons (i.e. parallel processes affecting both communities and populations, genotypes of a numerically or functionally dominant species affecting community composition, a species assemblage selecting for a particular genotype by affecting its selection regime). We examined correlations between species and genetic biodiversity in four isolated endemic‐rich spring systems in a hot desert and their potential link to environmental variables and physical isolation. Location Chihuahuan Desert spring systems in the Pecos River basin of New Mexico and Texas, USA. Methods We compared species richness of fish and benthic macroinvertebrate communities to within‐population allelic richness of amphipods (monophyletic Gammarus spp.) and Pecos gambusia (Gambusia nobilis) using Mantel tests. We also compared pairwise community similarities with pairwise genetic identities of populations among the same groups. We tested correlations among diversity, similarity and environmental variables after controlling for the effects of spatial distances using partial Mantel tests. We partitioned genetic and species diversity into three spatial scales (i.e. individual springs, individual spring systems, the entire region) using AMOVA and partition . Results We found strong correlations between invertebrate species richness and mosquitofish allelic richness. We found even stronger correlations of amphipod and gambusia genetic identities with fish and invertebrate community similarities; these were best explained by geographic distance rather than abiotic environmental factors. Most of the taxa and communities exhibited the largest proportion of diversity at the regional level. Main conclusions Our results suggest that drift and migration are the mechanisms that best explain our observations, and although α‐diversity among genes and species may not be strongly correlated, the pattern of species and allelic complementarity among these groups seems to be concordant at the regional level.     

Multi-scale altitudinal patterns in species richness of land snail communities in south-eastern France

Aim Species richness is an important feature of communities that varies along elevational gradients. Different patterns of distribution have been described in the literature for various taxonomic groups. This study aims to distinguish between species density and species richness and to describe, for land snails in south‐eastern France, the altitudinal patterns of both at different spatial scales. Location The study was conducted on five calcareous mountains in south‐eastern France (Etoile, Sainte Baume, Sainte Victoire, Ventoux and Queyras). Methods Stratified sampling according to vegetation and altitude was undertaken on five mountains, forming a composite altitudinal gradient ranging from 100 to 3100 m. Visual searching and analysis of turf samples were undertaken to collect land snail species. Species density is defined as the number of species found within quadrats of 25 m². Species richness is defined as the number of species found within an elevation zone. Different methods involving accumulation curves are used to describe the patterns in species richness. Elevation zones of different sizes are studied. Results Eighty‐seven species of land snails were recovered from 209 samples analysed during this study. Land snail species density, which can vary between 29 and 1 species per 25 m², decreases logarithmically with increasing altitude along the full gradient. However, on each mountain separately, only a linear decrease is observable. The climatic altitudinal gradient can explain a large part of this pattern, but the great variability suggests that other factors, such as heterogeneity of ground cover, also exert an influence on species density. The altitudinal pattern of species richness varies depending on the spatial resolution of the study. At fine resolution (altitudinal zones of 100 m) land snail species richness forms a plateau at altitudes below 1000 m, before decreasing with increasing altitude. At coarse resolution (altitudinal zones of 500 and 1000 m) the relationship becomes linear. Main conclusions This study reveals that land snail species density and land snail species richness form two different altitudinal patterns. Species density exhibits strong variability between sites of comparable altitude. A large number of samples seem necessary to study altitudinal patterns of species density. Species density decreases logarithmically with increasing altitude. Above a critical altitudinal threshold, this decrease lessens below the rate seen in the first 1500 m. Different methods exist to scale‐up species density to species richness but these often produce different patterns. In this study, the use of accumulation curves has yielded a pattern of species richness showing a plateau at low altitude, whereas simple plotting of known altitudinal ranges from single mountains would have produced stronger mid‐altitudinal peaks. This study shows that not only factors such as temperatures and habitat heterogeneity, but also an ecotone effect, are responsible for the observed patterns.     

Global patterns of plant diversity

Summary Using 94 data sets from across the globe, we explored patterns of mean community species richness, landscape species richness, mean similarity among communities and mosaic diversity. Climate affected community species richness primarily through productivity while other climatic factors were secondary. Climatic equability affected species richness only in temperate regions where richness was greatest at high levels of temperature variability and low levels of precipitation variability. Landscape species richness correlated positively with community species richness. A global gradient in mean similarity existed but was uncorrelated with community species richness. Mean similarity was least and mosaic diversity was greatest between 25 and 30° latitude. The most diverse landscapes (low mean similarity) correlated with warm temperatures, high elevations, large areas and large seasonal temperature fluctuations. The most complex landscapes (high mosaic diversity) correlated with large areas, high productivity and warm winters. We compared diversity measures among continents and found only one significant difference: Australian landscapes have greater mosaic diversity than African landscapes. Based on our analyses we propose two hypotheses: (1) for plants, biotic interactions are more important in structuring landscapes in warmer climates and (2) longer isolated landscapes have more clearly differentiated ecological subunits.     

Spatial and environmental determinants of vascular plant species richness distribution in the Iberian Peninsula and Balearic Islands

Using an exhaustive data compilation, Iberian vascular plant species richness in 50 times 50 UTM grid cells was regressed against 24 explanatory variables (spatial, geographical, topographical, geological, climatic, land use and environmental diversity variables) using Generalized Linear Models and partial regression analysis in order to ascertain the relative contribution of primary, heterogeneous and spatially structured variables. The species richness variation accounted for by these variables is reasonably high (65% of total deviance). Little less than half of this variation is accounted for spatially structured variables. A purely spatial component of variation is hardly significant. The most significant variables are those related to altitude, and particularly maximum altitude, whose cubic response reflects the occurrence of the maximum number of species at the highest altitudes. This result highlighted the importance of Iberian mountains as hotspots of diversity and the relevance of large and small scale historical factors in contemporary plant distribution patterns. Climatic or energy-related variables contributed little, whereas geological (calcareous and acid rocks) and, to a lesser extent, environmental heterogeneity variables (land use diversity and altitude range) seem to be more important.     

井冈山鹿角杜鹃群落灌木层功能多样性及其随海拔梯度的变化

研究植物群落功能多样性沿环境梯度的变化可以揭示功能多样性与生态系统功能间的关系及维持机制。以井冈山地区鹿角杜鹃（Rhododendron latoucheae）群落为研究对象,通过调查不同海拔梯度群落灌木层植物的物种组成与结构特征,研究了该群落类型灌木层植物的物种多样性、功能多样性、环境因子的特征及其相互之间的关系。结果表明：1）群落类型灌木层植物物种多样性和功能多样性沿海拔梯度呈现不同的变化趋势。物种多样性指数均随着海拔的升高呈减小趋势,而功能多样性指数的变化却较为复杂。其中FRic、FEve和FDis随着海拔的升高显著减小,FDiv和Rao却随海拔的升高而增加;2）群落中物种多样性和功能多样性呈现复杂的相关性。FRic、FEve与丰富度指数呈显著正相关,而Rao、FDis、FDiv与Simpson优势度指数呈线性相关关系,且具有显著相关性;3）群落所分布的坡位及土壤氮与磷含量等环境因子对灌木植物的功能多样性有着重要的影响。鹿角杜鹃群落灌木层植物的物种多样性和功能多样性的相互关系及其对环境变化的响应共同决定了群落的生态系统功能。     

Plant diversity,biogeography and environment in Iberia: Patterns and possible causal factors

Abstract. We associated patterns of plant diversity with possible causal factors by considering 93 local regions in the Iberian Peninsula and Balearic Islands with respect to biogeography, environmental favourability, and environmental heterogeneity, and their relationship with measured species diversity at four different scales: mean local species richness standardized at a grain of 100 m², total species richness in a community type within a region (regional community richness), mean compositional similarity, and mosaic diversity. Local regions in biogeographic transition zones to the North African and Atlantic floras had higher regional community richness and greater mosaic diversity than did non‐transitional regions, whereas no differences existed in mean local species richness or mean compositional similarity. Mean local species richness was positively related to environmental favourability as measured by actual evapotranspiration, but negatively related to total precipitation and temporal heterogeneity in precipitation. Mean local species richness was greatest in annual grassland and dwarf shrubland communities, and on calcareous bedrock types. Regional community richness was similarly related to actual evapotranspiration and total precipitation, but in addition was positively related to spatial heterogeneity in topography and soil water holding capacity. Mean compositional similarity decreased with increasing spatial heterogeneity and temperature seasonality. Mosaic diversity, a measure of complexity, increased with increasing local and regional richness. We hypothesize that these relationships can be explained by four ecological and evolutionary classes of causal factors: numbers of individuals, intermediate environments, limits to adaptation, and niche variation. These factors operate at various scales and manifest themselves in various ways. For example, at the site level, apparently processes that increase the number of individuals increase mean local species richness, but at the level of the entire region no such effects were found.     

Host diversity begets parasite diversity: bird final hosts and trematodes in snail intermediate hosts

An unappreciated facet of biodiversity is that rich communities and high abundance may foster parasitism. For parasites that sequentially use different host species throughout complex life cycles, parasite diversity and abundance in 'downstream' hosts should logically increase with the diversity and abundance of 'upstream' hosts (which carry the preceding stages of parasites). Surprisingly, this logical assumption has little empirical support, especially regarding metazoan parasites. Few studies have attempted direct tests of this idea and most have lacked the appropriate scale of investigation. In two different studies, we used time-lapse videography to quantify birds at fine spatial scales, and then related bird communities to larval trematode communities in snail populations sampled at the same small spatial scales. Species richness, species heterogeneity and abundance of final host birds were positively correlated with species richness, species heterogeneity and abundance of trematodes in host snails. Such community-level interactions have rarely been demonstrated and have implications for community theory, epidemiological theory and ecosystem management.     

Effects of neutrality and productivity on mammal richness and evolutionary history in Australia

Explaining how heterogeneous spatial patterns of species diversity emerge is one of the most fascinating questions of biogeography. One of the great challenges is revealing the mechanistic effect of environmental variables on diversity. Correlative analyses indicate that productivity is associated with taxonomic, phylogenetic, and functional diversity of communities. Surprisingly, no unifying body of theory have been developed to understand the mechanism by which spatial variation of productivity affects the fundamental processes of biodiversity. Based on widely discussed verbal models in ecology about the effect of productivity on species diversity, we developed a spatially explicit neutral model that incorporates the effect of primary productivity on community size and confronted our model's predictions with observed patterns of species richness and evolutionary history of Australian terrestrial mammals. The imposed restrictions on community size create larger populations in areas of high productivity, which increases community turnover and local speciation, and reduces extinction. The effect of productivity on community size modeled in our study causes higher accumulation of species diversity in productive regions even in the absence of niche‐based processes. However, such a simple model is not capable of reproducing spatial patterns of mammal evolutionary history in Australia, implying that more complex evolutionary mechanisms are involved. Our study demonstrates that the overall patterns of species richness can be directly explained by changes in community sizes along productivity gradients, supporting a major role of processes associated with energetic constraints in shaping diversity patterns.     

Quantitative partitioning of regional and local processes shaping regional diversity patterns

Much recent research explaining plant community diversity has focused on comparing the relative impacts of regional and local processes. We employed a novel analysis to quantify the effects of multiple regional and local processes on species richness, and to make quantitative comparisons of those effects across two sites that differ in plot-level species richness, productivity and environmental conditions. While abiotic stress and competition limited richness within the communities at both sites, only differences in the overall pool of species at the site, likely resulting from long-distance dispersal and climate fluctuations, explained the differences in plot-level richness between sites. Patterns in local richness may be driven by a temporal storage effect, with greater richness in the site with greater climatic variability. By identifying both the factors that impact diversity within communities and those that vary systematically across communities, our integrated approach provides a better understanding of regional diversity patterns.