科尔沁沙地植物物种丰富度格局及其与环境的关系

能量、水分和生境异质性是物种丰富度分布格局的重要因素。本文以特殊环境科尔沁沙地为对象,通过植物区域物种丰富度数据和对应气候数据统计,结合生境异质性分析,对科尔沁沙地物种丰富度格局及其主导因素进行研究。结果显示:(1)科尔沁沙地植物共计有115科1030种,呈现显著的空间异质分布,随着经度的增加物种丰富度呈先下降后上升的趋势,而受纬度影响较小。(2)水热动态假说最适合用于解释科尔沁沙地植物物种丰富度格局。说明水资源可利用性是科尔沁沙地植物物种丰富度的主要影响因素。     

Relationships between species richness of vascular plants and terrestrial vertebrates in China: analyses based on data of nature reserves

The relationship between plant diversity and animal diversity on a broadscale and its mechanisms are uncertain. In this study, we explored this relationship and its possible mechanisms using data from 186 nature reserves across China on species richness of vascular plants and terrestrial vertebrates, and climatic and topographical variables. We found significant positive correlations between species richness in almost all taxa of vascular plants and terrestrial vertebrates. Multiple regression analyses indicated that plant richness was a significant predictor of richness patterns for terrestrial vertebrates (except birds), suggesting that a causal association may exist between plant diversity and vertebrate diversity in China. The mechanisms for the relationships between species richness of plants and animals are probably dependent on vertebrate groups. For mammals (endothermic vertebrates), this relationship probably represents the integrated effects of plants on animals through trophic links (i.e. providing foods) and non-trophic interactions (i.e. supplying habitats), whereas for amphibians and reptiles (ectothermic vertebrates), this may be a result of the non-trophic links, such as the effects of plants on the resources that amphibians and reptiles require.     

Water-energy dynamics,habitat heterogeneity,history, and broad-scale patterns of mammal diversity

Numerous hypotheses on diversity patterns are often presented as if they were mutually exclusive. However, because of multicollinearity, correlational analyses are not able to distinguish the causal effects of different factors on these patterns. For this reason, we examine the interrelationships among current climate, habitat heterogeneity and evolutionary history by partitioning the variation in both total and non-volant mammal species richness in the Iberian Peninsula. Thus, it is possible to determine the variation accounted for by each one of these three components that is not shared by the others, and the respective overlaps. More specifically, we hypothesize that (H₁) in warm temperate zones, a small increase in the available energy has strong negative effects on mammal richness if water availability is limiting; (H₂) there are functional relationships between woody plant species richness (WOOD) and the richness of mammal species; (H₃) there is a signal of evolutionary history in contemporary patterns of species richness, and (H₄) mammal richness and the historical variable mean root distance (MRD) respond to the same driving forces. Additionally, we also test for spatial autocorrelation. We found a sharp nonlinear decrease in mammal richness with increasing energy and a monotonic increase with increasing water availability. Moreover, an interaction term between these two climate factors appeared to be statistically significant, so H₁ could not be rejected. WOOD remained significant after partialling out both current climate and MRD at the family level (MRDf), supporting H₂. The relationship between mammal diversity and MRD averaged by species richness was found to be spurious, but there appeared a significant historical signal using MRDf (this supports H₃). The overlaps among these factors are consistent with H₄ and suggest that water-energy dynamics have probably been active drivers throughout evolutionary history with habitat heterogeneity, and biotic interactions playing an important role.     

新疆开都河流域水生植物多样性及其影响因素

河流是一个连续的、流动的、独特而完整的系统,研究河流生态系统中水生植物的多样性分布格局及其影响因素对河流生态学研究具有重要意义。本文通过野外调查,研究了新疆开都河流域水生植物多样性、主要水生植物群落特征及与环境因子之间的关系,并利用水分-能量动态假说和栖息地异质性假说对该流域水生植物物种多样性的地理格局进行解释。结果表明: 开都河流域共有水生植物71种,隶属于24科39属;聚类分析可将开都河流域水生植物群落划分为10个主要群落类型,其中芦苇群落物种丰富度最高,狭叶香蒲群落和金鱼藻群落物种丰富度最低;流域水生植物群落Shannon指数与pH呈显著负相关,Simpson指数与pH、经度呈显著负相关,与海拔呈显著正相关;流域水生植物群落类型主要受海拔、水深及水温的影响;流域水生植物物种多样性随经纬度无明显变化规律。水分-能量动态假说和栖息地异质性假说共解释开都河流域水生植物多样性格局变量的31.4%,表明这两个假说对于该流域水生植物多样性格局的解释力并不高。     

Testing the water-energy theory on American palms (Arecaceae) using geographically weighted regression

Water and energy have emerged as the best contemporary environmental correlates of broad-scale species richness patterns. A corollary hypothesis of water-energy dynamics theory is that the influence of water decreases and the influence of energy increases with absolute latitude. We report the first use of geographically weighted regression for testing this hypothesis on a continuous species richness gradient that is entirely located within the tropics and subtropics. The dataset was divided into northern and southern hemispheric portions to test whether predictor shifts are more pronounced in the less oceanic northern hemisphere. American palms (Arecaceae, n = 547 spp.), whose species richness and distributions are known to respond strongly to water and energy, were used as a model group. The ability of water and energy to explain palm species richness was quantified locally at different spatial scales and regressed on latitude. Clear latitudinal trends in agreement with water-energy dynamics theory were found, but the results did not differ qualitatively between hemispheres. Strong inherent spatial autocorrelation in local modeling results and collinearity of water and energy variables were identified as important methodological challenges. We overcame these problems by using simultaneous autoregressive models and variation partitioning. Our results show that the ability of water and energy to explain species richness changes not only across large climatic gradients spanning tropical to temperate or arctic zones but also within megathermal climates, at least for strictly tropical taxa such as palms. This finding suggests that the predictor shifts are related to gradual latitudinal changes in ambient energy (related to solar flux input) rather than to abrupt transitions at specific latitudes, such as the occurrence of frost.     

Relative importance of water, energy, and heterogeneity in determining regional pteridophyte and seed plant richness in China

Environmental variables, such as ambient energy, water availability, and environmental heterogeneity have been frequently proposed to account for species diversity gradients. How taxon-specific functional traits define large-scale richness gradients is a fundamental issue in understanding spatial patterns of species diversity, but has not been well documented. Using a large dataset on the regional flora from China, we examine the contrast spatial patterns and environmental determinants between pteridophytes and seed plants which differ in dispersal capacity and environmental requirements. Pteridophyte richness shows more pronounced spatial variation and stronger environmental associations than seed plant richness. Water availability generally accounts for more spatial variance in species richness of pteridophytes and seed plants than energy and heterogeneity do, especially for pteridophytes which have high dependence on moist and shady environments. Thus, pteridophyte richness is disproportionally affected by water-related variables; this in turn results in a higher proportion of pteridophytes in regional vascular plant floras (pteridophyte proportion) in wet regions. Most of the variance in seed plant richness, pteridophyte richness, and pteridophyte proportion explained by energy is included in variation that water and heterogeneity account for, indicating the redundancy of energy in the study extent. However, heterogeneity is more important for determining seed plant distributions. Pteridophyte and seed plant richness is strongly correlated, even after the environmental effects have been removed, implying functional linkages between them. Our study highlights the importance of incorporating biological traits of different taxonomic groups into the studies of macroecology and global change biology.     

Disentangling vegetation and climate as drivers of Australian vertebrate richness

Determining drivers of species richness is recognised as highly complex, involving many synergies and interactions. We examine the utility of newly available remote sensing representations of vegetation productivity and vegetation structure to examine drivers of species richness at continental and regional scales. We related richness estimates derived from stacked species distribution models for birds, mammals, amphibians, and reptiles to estimates of actual and potential evapotranspiration (AET and PET), forest structure, and forest productivity across Australia as a whole as well as by bioclimatic zones. We used structural equation modeling to partition correlations between climate energy and vegetation attributes and their subsequent associations with species richness. Continentally, vertebrate richness patterns were strongly related to patterns of energy availability. Richness of amphibians, mammals, and birds were positively associated with AET. However, reptile richness was most strongly associated with PET. Regionally, forest structure and productivity associations with bird, mammal, and amphibian richness were strongest. Again, reptile richness associated most strongly with PET. Our results suggest that a hierarchy of drivers of broad‐scale vertebrate richness patterns exist (reptiles excluded): 1) climate energy is most important at the continental scale; next, 2) vegetation productivity and vegetation structure are most important at the regional scale; except 3) at low extremes of climate energy when energy becomes limiting.     

气候假说对内蒙古草原群落物种多样性格局的解释

物种丰富度的地理格局是宏观生态学和生物地理学的中心议题之一。本文基于内蒙古草原192个野外样地的调查数据, 结合各样地年平均气温、年降水量等9个气候因子, 探讨内蒙古草原物种丰富度格局及其主导因素, 以确定气候假说在该区的适用性。结果表明: (1)内蒙古草原物种丰富度经度格局显著, 呈现沿经度升高而增加的趋势, 同时由于经纬度的共线性, 也呈现出沿纬度升高而增加的趋势。(2)方差分解显示, 能量单独解释率为2.7%, 水分单独解释率为11.4%, 水分和能量共同解释率为46.3%, 未解释部分为39.6%, 可见能量与水分的共同作用在物种丰富度格局形成中占主导地位, 支持水热动态假说。这说明水热动态假说适用于解释内蒙古草原物种丰富度 格局。     

Patterns of species diversity and phylogenetic structure of vascular plants on the Qinghai‐Tibetan Plateau

Large-scale patterns of species richness and the underlying mechanisms regulating these patterns have long been the central issues in biogeography and macroecology. Phylogenetic community structure is a result of combined effects of contemporary ecological interactions, environmental filtering, and evolutionary history, and it links community ecology with biogeography and trait evolution. The Qinghai-Tibetan Plateau provides a good opportunity to test the influence of contemporary climate on shaping species richness because of its unique geological history, cold climate, and high biodiversity. In this study, based on high-resolution distributions of ˜9000 vascular plant species, we explored how species richness and phylogenetic structure of vascular plants correlate with climates on the highest (and species rich) plateau on the Earth. The results showed that most of the vascular plants were distributed on the eastern part of the plateau; there was a strong association between species richness and climate, even after the effects of habitat heterogeneity were controlled. However, the responses of richness to climate remarkably depended on life-forms. Richness of woody plants showed stronger climatic associations than that of herbaceous plants; energy and water availability together regulated richness pattern of woody plants; whereas water availability predominantly regulated richness pattern of herbaceous plants. The phylogenetic structure of vascular species clustered in most areas of the plateau, suggesting that rapid speciation and environment filtering dominated the assembly of communities on the plateau. We further propose that biodiversity conservation in this area should better take into account ecological features for different life-forms and phylogenetic lineages.     

Spatial patterns of woody plant and bird diversity: functional relationships or environmental effects?

Aim To understand cross‐taxon spatial congruence patterns of bird and woody plant species richness. In particular, to test the relative roles of functional relationships between birds and woody plants, and the direct and indirect environmental effects on broad‐scale species richness of both groups. Location Kenya. Methods Based on comprehensive range maps of all birds and woody plants (native species > 2.5 m in height) in Kenya, we mapped species richness of both groups. We distinguished species richness of four different avian frugivore guilds (obligate, partial, opportunistic and non‐frugivores) and fleshy‐fruited and non‐fleshy‐fruited woody plants. We used structural equation modelling and spatial regressions to test for effects of functional relationships (resource–consumer interactions and vegetation structural complexity) and environment (climate and habitat heterogeneity) on the richness patterns. Results Path analyses suggested that bird and woody plant species richness are linked via functional relationships, probably driven by vegetation structural complexity rather than trophic interactions. Bird species richness was determined in our models by both environmental variables and the functional relationships with woody plants. Direct environmental effects on woody plant richness differed from those on bird richness, and different avian consumer guilds showed distinct responses to climatic factors when woody plant species richness was included in path models. Main conclusions Our results imply that bird and woody plant diversity are linked at this scale via vegetation structural complexity, and that environmental factors differ in their direct effects on plants and avian trophic guilds. We conclude that climatic factors influence broad‐scale tropical bird species richness in large part indirectly, via effects on plants, rather than only directly as often assumed. This could have important implications for future predictions of animal species richness in response to climate change.     

Food plant diversity as broad-scale determinant of avian frugivore richness

The causes of variation in animal species richness at large spatial scales are intensively debated. Here, we examine whether the diversity of food plants, contemporary climate and energy, or habitat heterogeneity determine species richness patterns of avian frugivores across sub-Saharan Africa. Path models indicate that species richness of Ficus (their fruits being one of the major food resources for frugivores in the tropics) has the strongest direct effect on richness of avian frugivores, whereas the influences of variables related to water-energy and habitat heterogeneity are mainly indirect. The importance of Ficus richness for richness of avian frugivores diminishes with decreasing specialization of birds on fruit eating, but is retained when accounting for spatial autocorrelation. We suggest that a positive relationship between food plant and frugivore species richness could result from niche assembly mechanisms (e.g. coevolutionary adaptations to fruit size, fruit colour or vertical stratification of fruit presentation) or, alternatively, from stochastic speciation-extinction processes. In any case, the close relationship between species richness of Ficus and avian frugivores suggests that figs are keystone resources for animal consumers, even at continental scales.     

Patterns, determinants and models of woody plant diversity in China

What determines large-scale patterns of species richness remains one of the most controversial issues in ecology. Using the distribution maps of 11 405 woody species in China, we compared the effects of habitat heterogeneity, human activities and different aspects of climate, particularly environmental energy, water-energy dynamics and winter frost, and explored how biogeographic affinities (tropical versus temperate) influence richness-climate relationships. We found that the species richness of trees, shrubs, lianas and all woody plants strongly correlated with each other, and more strongly correlated with the species richness of tropical affinity than with that of temperate affinity. The mean temperature of the coldest quarter was the strongest predictor of species richness, and its explanatory power for species richness was significantly higher for tropical affinity than for temperate affinity. These results suggest that the patterns of woody species richness mainly result from the increasing intensity of frost filtering for tropical species from the equator/lowlands towards the poles/highlands, and hence support the freezing-tolerance hypothesis. A model based on these results was developed, which explained 76-85% of species richness variation in China, and reasonably predicted the species richness of woody plants in North America and the Northern Hemisphere.     

Latitudinal diversity gradients in bryophytes and woody plants: Roles of temperature and water availability

It remains unclear whether the latitudinal diversity gradients of micro- and macro-organisms are driven by the same macro-environmental variables. We used the newly completed species catalog and distribution information of bryophytes in China to explore their spatial species richness patterns, and to investigate the underlying roles of energy availability, climatic seasonality, and environmental heterogeneity in shaping these patterns. We then compared these patterns to those found for woody plants. We found that, unlike woody plants, mosses and liverworts showed only weakly negative latitudinal trends in species richness. The spatial patterns of liverwort richness and moss richness were overwhelmingly explained by contemporary environmental variables, although explained variation was lower than that for woody plants. Similar to woody plants, energy and climatic seasonality hypotheses dominate as explanatory variables but show high redundancy in shaping the distribution of bryophytes. Water variables, that is, the annual availability, intra-annual variability and spatial heterogeneity in precipitation, played a predominant role in explaining spatial variation of species richness of bryophytes, especially for liverworts, whereas woody plant richness was affected most by temperature variables. We suggest that further research on spatial patterns of bryophytes should incorporate the knowledge on their ecophysiology and evolution.     

Energy, range dynamics and global species richness patterns: reconciling mid-domain effects and environmental determinants of avian diversity

Spatial patterns of species richness follow climatic and environmental variation, but could reflect random dynamics of species ranges (the mid-domain effect, MDE). Using data on the global distribution of birds, we compared predictions based on energy availability (actual evapotranspiration, AET, the best single correlate of avian richness) with those of range dynamics models. MDE operating within the global terrestrial area provides a poor prediction of richness variation, but if it operates separately within traditional biogeographic realms, it explains more global variation in richness than AET. The best predictions, however, are given by a model of global range dynamics modulated by AET, such that the probability of a range spreading into an area is proportional to its AET. This model also accurately predicts the latitudinal variation in species richness and variation of species richness both within and between realms, thus representing a compelling mechanism for the major trends in global biodiversity.     

Quantification of climatic niches in birds: adding the temporal dimension

Quantification of the climatic niche from geographic occurrences is an increasingly important tool for studying species’ relationships to their environment, for example to predict responses to climate change. However, as the geographic distributions of birds are seasonally dynamic, they pose a challenge to carrying out comparable and appropriate quantification of climatic niches. In this review, we first assess how relevant seasonal dynamics are across birds as a whole by compiling a database of migratory behaviour for 10 443 bird species. Second, we examine how studies have quantified climatic niches of birds. Finally, using Australia as a case study, we investigate how well existing distribution datasets represent temporal dynamics by comparing seasonal patterns of species richness obtained from point‐occurrence data with those from range maps and assess the consequences for niche quantification. We provide a consistent classification of migratory behaviour across all birds, and find that a huge variety exists between and within species that should be considered when quantifying climatic niches. Despite this, our review of the literature revealed that seasonal dynamics have often not been accounted for. For future studies, we provide a framework for selecting appropriate occurrence data depending on migratory behaviour and data availability. Our comparison of seasonal species richness patterns obtained from extent‐of‐occurrence range maps and point‐occurrence data suggests that range maps are less able to detect temporal dynamics of bird distributions than point‐occurrence data. We conclude that seasonally explicit range maps combined with climatic data for the corresponding time period can be used to adequately quantify climatic niches for resident birds, but are not adequate to quantify the climatic niches of migratory and nomadic species. Therefore, consistent quantification of climatic niches across all birds requires temporally explicit occurrence points. As such, increasing the availability of occurrence data and methods correcting biases should be a priority.     

Partitioning sources of variation in vertebrate species richness

Aim To explore biogeographic patterns of terrestrial vertebrates in Maine, USA using techniques that would describe local and spatial correlations with the environment. Location Maine, USA. Methods We delineated the ranges within Maine (86,156 km²) of 275 species using literature and expert review. Ranges were combined into species richness maps, and compared to geomorphology, climate, and woody plant distributions. Methods were adapted that compared richness of all vertebrate classes to each environmental correlate, rather than assessing a single explanatory theory. We partitioned variation in species richness into components using tree and multiple linear regression. Methods were used that allowed for useful comparisons between tree and linear regression results. For both methods we partitioned variation into broad‐scale (spatially autocorrelated) and fine‐scale (spatially uncorrelated) explained and unexplained components. By partitioning variance, and using both tree and linear regression in analyses, we explored the degree of variation in species richness for each vertebrate group that could be explained by the relative contribution of each environmental variable. Results In tree regression, climate variation explained richness better (92% of mean deviance explained for all species) than woody plant variation (87%) and geomorphology (86%). Reptiles were highly correlated with environmental variation (93%), followed by mammals, amphibians, and birds (each with 84–82% deviance explained). In multiple linear regression, climate was most closely associated with total vertebrate richness (78%), followed by woody plants (67%) and geomorphology (56%). Again, reptiles were closely correlated with the environment (95%), followed by mammals (73%), amphibians (63%) and birds (57%). Main conclusions Comparing variation explained using tree and multiple linear regression quantified the importance of nonlinear relationships and local interactions between species richness and environmental variation, identifying the importance of linear relationships between reptiles and the environment, and nonlinear relationships between birds and woody plants, for example. Conservation planners should capture climatic variation in broad‐scale designs; temperatures may shift during climate change, but the underlying correlations between the environment and species richness will presumably remain.     

Water links the historical and contemporary components of the Australian bird diversity gradient

Aim To document the geographical structure of the historical signal in the continental species richness gradient of birds and evaluate the influences of contemporary and historical climatic conditions on the generation and maintenance of the richness pattern. Location Australia. Methods We used range maps of breeding birds to generate the spatial pattern of species richness at four grain sizes, and two molecular phylogenies to measure the level of evolutionary development of avifaunas at each grain size. We then used simple correlation and path analysis to generate a statistical model of species richness using environmental predictor variables and compared the spatial patterns of richness and mean evolutionary development to identify possible environmental links between richness and net diversification rates across the continent. Results The contemporary richness pattern is well explained statistically by actual evapotranspiration (a measure of water–energy balance), operating both directly and indirectly through plant production, and this is robust to the spatial resolution of the analysis. Further, species richness and the mean level of evolutionary development of faunas show a strong spatial correspondence, such that dry areas support both fewer species and species from more highly derived families, whereas wet areas support more species of both basal and derived families. The evolutionary pattern conforms to a similar pattern known for plants and is probably explained by the increase in aridity in western and central Australia arising in the Miocene. Main conclusion The contemporary bird richness gradient contains a historical signal and reflects the effects of both current levels of water availability as well as changes in rainfall patterns extending over evolutionary time. The historical signal persists even in the absence of obvious hard barriers to dispersal.     

Does plant richness influence animal richness?: the mammals of Catalonia (NE Spain)

Although it has long been held that plant diversity must influence animal diversity, the nature of this relationship remains poorly understood at large spatial scales. We compare the species richness patterns of vascular plants and mammals in north‐eastern Spain using a 100‐km² grain size to examine patterns of covariation. We found that the total mammal richness pattern, as well as those of herbivores and carnivores considered separately, only weakly corresponded to the pattern of plants. Rather, mammal richness was best described by climatic variables incorporating water inputs, and after adding these variables to multiple regression models, plant and mammal richness were virtually independent. We conclude that the observed association, although weak, is explained by shared responses of both groups to climate, and thus, plant richness has no influence on the richness pattern of Catalan mammals.     

Ants and people: a test of two mechanisms potentially responsible for the large‐scale human population–biodiversity correlation for Formicidae in Europe

Aim: Recent coarse‐scale studies have shown positive relationships between the biodiversity of plants/vertebrates and the human population. Little is known about the generality of the pattern for invertebrates. Moreover, biodiversity and human population might correlate because they both covary with other factors such as energy availability and habitat heterogeneity. Here we test these two non‐mutually exclusive mechanisms with ant species‐richness data from the Fauna Europaea. Location Forty‐three European countries/regions. Methods We derived mixed models of total, native and exotic ant species richness as a function of human population size/density, controlling for country area, plant species richness (as a proxy for habitat heterogeneity), and mean annual temperature and precipitation (variables related to energy availability). Results Ant species richness increased significantly with increasing human population. This result was confirmed when controlling for variations in country area. Both for human population size/density and for ant species richness, there were positive correlations with temperature but not with precipitation. This finding is in agreement with the energy‐availability hypothesis. However, we observed a negative latitudinal gradient in ant and plant species richness, although not in human population size/density. Plant species richness was positively correlated with ant species richness but not with human population size/density. Thus, there is evidence that this type of habitat heterogeneity can play a role in the observed latitudinal gradient of ant species richness, but not in the positive correlation between ant species richness and human population. The results were confirmed for the 545 native and the 32 exotic ant species reported, and we observed a good correlation between exotic and native ant species richness. Main conclusions Ant species richness in European countries conforms to six macroecological patterns: (1) a negative latitudinal gradient; and a positive (2) species–energy relationship, (3) species–area relationship, (4) correlation with plant species richness, (5) exotic–native species richness correlation, and (6) species–people correlation. There is some evidence for the energy‐availability hypothesis, but little evidence for habitat heterogeneity as an explanation of the large‐scale human population–ant biodiversity correlation. This correlation has implications for the conservation of ant diversity in Europe.     

Evolutionary speed limited by water in arid Australia

The covariation of biodiversity with climate is a fundamental pattern in nature. However, despite the ubiquity of this relationship, a consensus on the ultimate cause remains elusive. The evolutionary speed hypothesis posits direct mechanistic links between ambient temperature, the tempo of micro-evolution and, ultimately, species richness. Previous research has demonstrated faster rates of molecular evolution in warmer climates for a broad range of poikilothermic and homeothermic organisms, in both terrestrial and aquatic environments. In terrestrial systems, species richness increases with both temperature and water availability and the interaction of those terms: productivity. However, the influence of water availability as an independent variable on micro-evolutionary processes has not been examined previously. Here, using methodology that limits the potentially confounding role of cladogenetic and demographic processes, we report, to our knowledge, the first evidence that woody plants living in the arid Australian Outback are evolving more slowly than related species growing at similar latitudes in moist habitats on the mesic continental margins. These results support a modified evolutionary speed explanation for the relationship between the water-energy balance and plant diversity patterns.