Determinants of alpha and beta vascular plant diversity in Mediterranean island systems: the Ionian islands,Greece

The Ionian archipelago is the second largest Greek archipelago after the Aegean, but the factors driving plant species diversity in the Ionian islands are still barely known. We used stepwise multiple regressions to investigate the factors affecting plant species diversity in 17 Ionian islands. Generalized dissimilarity modelling was applied to examine variation in the magnitude and rate of species turnover along environmental gradients, as well as to assess the relative importance of geographical and climatic factors in explaining species turnover. The values of the residuals from the ISAR log₁₀‐transfomed models of native and endemic taxa were used as a measure of island floristic diversity. Area was confirmed to be the most powerful single explanatory predictor of all diversity metrics. Mean annual precipitation and temperature, as well as shortest distance to the nearest island are also significant predictors of vascular plant diversity. The island of Kalamos constitutes an important plant diversity hotspot in the Ionian archipelago. The recent formation of the islands, the close proximity to the mainland source and the relatively low dispersal filtering of the Ionian archipelago has resulted in islands with a flora principally comprising common species and a low proportion of endemics. Small islands keep a key role in conservation of plant priority sites.     

秦岭国家植物园蝴蝶群落结构与多样性

为了查明秦岭国家植物园蝴蝶资源和多样性状况, 本研究选取了5种生境, 利用样线法进行了3年的蝴蝶多样性观测。结果表明: 秦岭国家植物园蝴蝶共有5科76属134种; 物种丰富度指数、物种多样性指数、均匀度指数和优势度指数分别为1.3295、3.4616、0.7068和0.7656; 其中蛱蝶科属数及物种数最多(33属65种), 凤蝶科最低(5属10种); 蛱蝶科物种多样性指数及物种丰富度指数最高, 分别为2.8525及1.3622; 凤蝶科多样性指数最低(1.4936); 粉蝶科物种丰富度指数最低(0.2790)。5种生境中, 随着植被丰富度的增加, 蝴蝶多样性指数上升。     

千岛湖岛屿特征与节肢动物多样性的关系

采用栅格采样法,于2006年4、5、8和10月对千岛湖库区50个不同大小岛屿中节肢动物的种类与数量进行了调查,分析了岛屿面积、海拔、形状和距离等因素对岛屿节肢动物物种丰富度的影响.结果表明:岛屿上节肢动物总物种丰富度、高扩散力物种丰富度和低扩散力物种丰富度均随岛屿面积的增大而增加,且岛屿面积与物种丰富度之间的关系符合经典岛屿生物地理学模型;节肢动物物种丰富度受岛屿面积、海拔和形状的综合影响,距离对岛屿上物种的丰富度没有显著影响;总的物种丰富度与岛屿形状指数和海拔呈显著正相关,岛屿面积和海拔与高扩散力物种的物种丰富度显著相关,而低扩散力物种与岛屿各地理因素之间的相关性均不显著.     

岛屿生物地理学理论：模型与应用

前言岛屿有许多显著特征,如地理隔离,生物类群简单。这些特点为重复性研究和统计学分析奠定了基础,从而有利于许多深入而细致的生物学研究。因此,岛屿为发展和检验自然选择、物种形成及演化,以及生物地理学和生态学诸领域的理论和假设,提供了重要的自然实验室。岛屿生物地理学理论(MacArthurwilson学说)即为岛屿生物学研究中所产生的著名理论之一。该理论发展之     

The environmental determinants of the insular butterfly faunas of the British Isles

A multiple regression analysis was performed upon selected environmental variables for a series of islands in the British Isles, to establish their effects upon the size of the butterfly fauna, measured as he number of species regularly breeding, S_B .
So that the data be normally distributed, the regression analyses were performed upon log₁₀ transformed data only, with the data for outliers, mainland Britain and Ireland, the two largest islands, excluded.
Most highly correlated with the number of butterfly species breeding upon an island is the number breeding within a 25 km radius of the nearest point of the mainland, r ²=0.5941, followed by the correlations with the latitude of the mid-point of the island, r ²=0.5541, the number of plant species comprising the island Hora, r ²=0.5225, and the distance separating the island from the mainland, r ²=0.4514.
A partial correlation analysis confirms the importance of the parameters distance separating the island from the mainland, D ₁, and the size of the faunal source S _F , and rejects the importance of the size of the flora and the latitude of the island. This is further confirmed by the results of a step-wise regression analysis, the two variables D ₁ and S_F accounting for 66% of the variation of the butterfly fauna.
If an alternative measure of isolation, D ₂, which allows for the geographical clumping of islands, is combined with the variable S_F , then 69% of the variation of the butterfly fauna is accounted for.     

The environmental determinants of the insular butterfly faunas of the British Isles

A multiple regression analysis was performed upon selected environmental variables for a series of islands in the British Isles, to establish their effects upon the size of the butterfly fauna, measured as he number of species regularly breeding, S_B. So that the data be normally distributed, the regression analyses were performed upon log₁₀ transformed data only, with the data for outliers, mainland Britain and Ireland, the two largest islands, excluded. Most highly correlated with the number of butterfly species breeding upon an island is the number breeding within a 25 km radius of the nearest point of the mainland, r²=0.5941, followed by the correlations with the latitude of the mid-point of the island, r²=0.5541, the number of plant species comprising the island Hora, r²=0.5225, and the distance separating the island from the mainland, r²=0.4514. A partial correlation analysis confirms the importance of the parameters distance separating the island from the mainland, D₁, and the size of the faunal source S_F, and rejects the importance of the size of the flora and the latitude of the island. This is further confirmed by the results of a step-wise regression analysis, the two variables D₁ and S_F accounting for 66% of the variation of the butterfly fauna. If an alternative measure of isolation, D₂, which allows for the geographical clumping of islands, is combined with the variable S_F, then 69% of the variation of the butterfly fauna is accounted for.     

Latitudinal and altitudinal diversity patterns and Rapoport effects in north-west European land snails and their causes

The latitudinal and altitudinal range sizes of north-west European land-snail species increase with increasing latitude/altitude. These Rapoport effects are not caused by northern/high-altitude species with wider latitudinal/altitudinal ranges and southern/low-altitude species with narrower latitudinal/altitudinal ranges, as predicted by the climatic variability hypothesis. They are instead caused mainly by different northern/upper borders of species occurring in the south part of the study area or at low and intermediate altitudes, respectively. This pattern indicates that the observed Rapoport effects are the result mainly of differential northward/upward expansion of species that were restricted to southern/low or intermediate altitude refugia during the glacials. Although all species occurring in a refugium experienced the same climatic conditions, there is stochastic variation in their climatic tolerance. Species with broader climatic tolerance were able to expand farer northwards/upwards postglacial. The altitudinal distribution of species richness in the analysed alpine faunas cannot be explained by the Rapoport-rescue hypothesis, because species richness peaks at intermediate altitudes and because there is no negative correlation between the number of range borders and altitude. The Rapoport-rescue hypothesis alone is probably also insufficient to explain the decrease in species richness with increasing latitude.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 309–323.     

温州沿海小型海岛植物丰富度和β多样性及其影响因子

于2012-2015年调查了温州沿海20个小型无居民海岛的植物组成,共记录到维管束植物366种,隶属于95科244属,其中草本植物226种木本植物140种。拟合了5个种-面积关系模型,采用赤池信息量AIC对模型进行选择,发现种-面积-生境类型关系模型SAH_nR权重系数最大,为40.26%,两种断点回归种-面积关系模型BR-SAR权重系数分别仅为6.94%和0.43%,表明基于这20个海岛拟合的种-面积关系不存在小岛屿效应。岛屿植物物种丰富度主要受面积A影响,离大陆距离,I_m对丰富度无显著作用;偏相关分析表明除A外,周长/面积比PAR和岛屿生境多样性指数H_d显著影响了植物丰富度,其逐步回归方程分别为:植物总丰富度S=76.714+1.696A-0.046PAR,R~2=0.839;木本植物丰富度S_(-woody)=6.525+0.455A+24.544H_d,R~2=0.697;草本植物丰富度S_(-herbaceous)=66.899+1.285A-0.04PAR-23.434H_d,R~2=0.865。偏最小二乘回归PLS分析中岛屿空间特征参数对岛屿物种相似性指数重要性排序为:I_m(0.61)I_i(0.56)PAR(0.49)A(0.20)岸线长度Per(0.14)生境类型H(0.072)岛屿高程E(0.065)岛屿形状指数SI(0.05)。由此可见,近岸的小型海岛植物丰富度并不总是由岛屿面积来决定;隔离度对岛屿植物β多样性影响较大。     

Geographical,anthropogenic and climatic determinants of bryophyte species composition and richness in the Shengsi archipelago,East China Sea

Introduction. Few attempts have been made to assess the comparative contributions of different environmental factors on species composition (SC) and richness (SR) of bryophytes on continental islands.

Methods. The bryophyte flora and the impact of seven environmental variables (island area, elevation, isolation, human disturbance, rainfall, vegetation cover, and exposed rock area) on 18 continental islands of the Shengsi archipelago in the East China Sea were investigated. Redundancy Analysis and Canonical Correspondence Analysis were used to determine to what extent the environmental variables could explain variation in species richness and species composition on these islands.

Key results & Conclusions. Island elevation, isolation, area and human disturbance intensity all significantly influenced bryophyte SC at island level, accounting for 12.7%, 9.9%, 8.8% and 7.8% of the total SC variation, respectively. Island area was the most important determinant of bryophyte SR (P?=?0.002), accounting for 58.3% of the total variation (9.7% by area per se and 48.6% confounded with other variables); elevation and human disturbance intensity also significantly influenced species richness, accounting for 10.5% and 6.9% of the total SR variation (conditional effects), respectively. Elevation and area had a positive interaction effect on SR while isolation exerted no significant effects (P?>?0.05). The relationships of bryophyte species number (S) with area (A) follow log₁₀ (S)?=?c?+?z?×?log₁₀ (A), with z values from 0.28 to 0.38. The effects of human disturbance on bryophyte SR followed the Gaussian model, supporting the ‘intermediate disturbance hypothesis’ to some extent.     

Seasonal variation of black fly (Diptera: Simuliidae) species diversity and community structure in tropical streams of Thailand

Seasonal variation of the physicochemical conditions of streams plays an important role in aquatic insect diversity and community structure. Asian tropical streams profoundly change between seasons due to the effects of monsoons. However, little is known about how these changes affect aquatic insect diversity and community structure. The objectives of this study are to examine seasonal variations of the physicochemical conditions in tropical streams in Thailand and to assess the effects of these changes on black fly community structure and diversity. Black flies were sampled and physicochemical conditions recorded at eight sites between December 2007 and December 2008. A total of 10 black fly species were found. Comparisons of the streams between seasons revealed that physical conditions related to rainfall rate were significantly different. Canonical correspondence analysis differentiated sampling sites from each season. Streams in the rainy season were faster and deeper, with higher discharge and conductivity than those of the cold and dry seasons. Species richness was significantly higher in the rainy season than in the cold and dry seasons ( F  = 6.23, P  = 0.004). Community structure profoundly changed between the low-flow season (cold and dry) and high-flow season. Black fly species found predominantly in the low-flow season ( Simulium siamense "cytoform A", S. aureohirtum ) decreased dramatically during the high-flow season. In contrast, species found at high frequency during the high-flow season ( S. nakhonense , S. angulistylum ) disappeared in the low-flow season. The study demonstrates the importance of seasonal variation of stream conditions on black fly community structure and diversity.     

The effects of archipelago spatial structure on island diversity and endemism: predictions from a spatially‐structured neutral model

Islands are particularly suited to testing hypotheses about the ecological and evolutionary mechanisms underpinning community assembly. Yet the complex spatial arrangements of real island systems have received little attention from both empirical studies and theoretical models. Here, we investigate the extent to which the spatial structure of archipelagos affects species diversity and endemism. We start by proposing a new spatially structured neutral model that explicitly considers archipelago structure, and then investigate its predictions under a diversity of scenarios. Our results suggest that considering the spatial structure of archipelagos is crucial to understanding their diversity and endemism, with structured island systems acting both as “museums” and “cradles” of biodiversity. These dynamics of diversification may change the traditionally expected pattern of decrease in species richness with distance from the mainland, even potentially leading to increasing patterns for taxa with high speciation rates in archipelagos off species‐poor continental areas. Our results also predict that, within spatially structured archipelagos, metapopulation dynamics and evolutionary processes can generate higher diversity on islands more centrally placed than at the periphery. We derive from our results a set of theoretical predictions, potentially testable with empirical data.     

Animal community structure as a function of stream size

The species-area relationship of the island biogeography theory was calculated for macroinvertebrates in 22 coastal, adjacent streams. A z-value of 0.19 was obtained. The low z-value was probably a consequence of the short distances between streams as well as high dispersal rates. In addition, a cluster analysis based on the dissimilarity of species assemblages showed that stream size was of prime importance in categorizing the streams. To a smaller extent water quality affected the community structure in the streams.     

Subsidized Island Biogeography Hypothesis: another new twist on an old theory

We present a new hypothesis for predicting and describing patterns of species diversity on small islands and habitat fragments. We have modified the traditional island biogeography equilibrium theory to incorporate the influence of spatial subsidies from the surrounding matrix, which vary among islands and habitat fragments, on species diversities. The modification indicates three possible directions for the effects of spatial subsidies on diversity, which depend on where the focal community falls on the hypothesized unimodal curve of the productivity–diversity relationship. The idea is novel because no recent syntheses of productivity–diversity–area relationships examine the role of allochthonous resources on recipient communities’ diversity patterns.     

Evolution of termite functional diversity: analysis and synthesis of local ecological and regional influences on local species richness

Aim To (1) describe termite functional diversity patterns across five tropical regions using local species richness sampling of standardized areas of habitat; (2) assess the relative importance of environmental factors operating at different spatial and temporal scales in influencing variation in species representation within feeding groups and functional taxonomic groups across the tropics; (3) achieve a synthesis to explain the observed patterns of convergence and divergence in termite functional diversity that draws on termite ecological and biogeographical evidence to‐date, as well as the latest evidence for the evolutionary and distributional history of tropical rain forests. Location Pantropical. Methods A pantropical termite species richness data set was obtained through sampling of eighty‐seven standardized local termite diversity transects from twenty‐nine locations across five tropical regions. Local‐scale, intermediate‐scale and large‐scale environmental data were collected for each transect. Standardized termite assemblage and environmental data were analysed at the levels of whole assemblages and feeding groups (using components of variance analysis) and at the level of functional taxonomic groups (using correspondence analysis and canonical correspondence analysis). Results Overall species richness of local assemblages showed a greater component of variation attributable to local habitat disturbance level than to region. However, an analysis accounting for species richness across termite feeding groups indicated a much larger component of variation attributable to region. Mean local assemblage body size also showed the greater overall significance of region compared with habitat type in influencing variation. Ordination of functional taxonomic group data revealed a primary gradient of variation corresponding to rank order of species richness within sites and to mean local species richness within regions. The latter was in the order: Africa > south America > south‐east Asia > Madagascar > Australia. This primary gradient of species richness decrease can be explained by a decrease in species richness of less dispersive functional taxonomic groups feeding on more humified food substrates such as soil. Hence, the transects from more depauperate sites/regions were dominated by more dispersive functional taxonomic groups feeding on less humified food substrates such as dead wood. Direct gradient analysis indicated that ‘region’ and other large‐scale factors were the most important in explaining patterns of local termite functional diversity followed by intermediate‐scale geographical and site variables and, finally, local‐scale ecological variables. Synthesis and main conclusions Within regions, centres of termite functional diversity lie in lowland equatorial closed canopy tropical forests. Soil feeding termite evolution further down food substrate humification gradients is therefore more likely to have depended on the long‐term presence of this habitat. Known ecological and energetic constraints upon contemporary soil feeders lend support for this hypothesis. We propose further that the anomalous distribution of termite soil feeder species richness is partly explained by their generally very poor dispersal abilities across oceans. Evolution, radiation and dispersal of soil feeder diversity appears to have been largely restricted to what are now the African and south American regions. The inter‐regional differences in contemporary local patterns of termite species richness revealed by the global data set point to the possibility of large differences in consequent ecosystem processes in apparently similar habitats on different continents.     

Fish diversity in European lakes: geographical factors dominate over anthropogenic pressures

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Global diversity in light of climate change: the case of ants

Aim To use a fine‐grained global model of ant diversity to identify the limits of our knowledge of diversity in the context of climate change. Location Global. Methods We applied generalized linear modelling to a global database of local ant assemblages to predict the species density of ants globally. Predictors evaluated included simple climate variables, combined temperature × precipitation variables, biogeographic region, elevation, and interactions between select variables. Areas of the planet identified as beyond the reliable prediction ability of the model were those having climatic conditions more extreme than what was represented in the ant database. Results Temperature was the most important single predictor of ant species density, and a mix of climatic variables, biogeographic region and interactions between climate and region yielded the best overall model. Broadly, geographic patterns of ant diversity match those of other taxa, with high species density in the wet tropics and in some, but not all, parts of the dry tropics. Uncertainty in model predictions appears to derive from the low amount of standardized sampling of ants in Asia, in Africa and in the most extreme (e.g. hottest) climates. Model residuals increase as a function of temperature. This suggests that our understanding of the drivers of ant diversity at high temperatures is incomplete, especially in hot and arid climates. In other words, our ignorance of how ant diversity relates to environment is greatest in those regions where most species occur – hot climates, both wet and dry. Main conclusions Our results have two important implications. First, temperature is necessary, but not sufficient, to explain fully the patterns of ant diversity. Second, our ability to predict ant diversity is weakest exactly where we need to know the most, the warmest regions of a warming world. This includes significant parts of the tropics and some of the most biologically diverse areas in the world.