Bird Taxonomic,Phylogenetic And Functional Beta Diversity In Habitat Island Systems

Habitat fragmentation is defined as a process in which a large expanse of continuous habitat transforms into several smaller patches of smaller total area,surrounded by a matrix unlike the original.Habitat fragmentation is typically considered as one of the primary causes of declines in global biodiversity.Therefore,to explore the geographical distribution and assembly patterns of species in fragmented habitats and their determinants is one of the urgent topics in ecology and conservation biology,which can not only elucidate the underlying ecological processes of dissimilarities in community compositions,but can also provide a strong scientific basis for the protection of biodiversity.Currently,most biodiversity studies in fragmented habitats have been restricted to patch-level analyses.How beta diversity patterns are shaped by landscape-level processes remains unclear across habitat island systems.We compiled bird data in 22 habitat island systems around the globe.We focused on two spatial extents of landscapes（small and large habitat island systems）,and three dimensions（i.e.,taxonomic,phylogenetic and functional）of beta diversity for bird assemblages in theses habitat island systems,and investigated the patterns of bird beta diversity at three dimensions by partitioning beta diversity into their spatial turnover and nestedness-resultant components.Multiple linear models were performed to assess the potential influence of climate factors（mean annual temperature,temperature seasonality,annual precipitation,precipitation of the driest quarter,precipitation seasonality）and system characteristics（area scale,total area of habitat island and mean inter-island distance）in shaping landscape-level patterns of beta diversity at the three dimensions across the small and large habitat island systems.The main results are as follows:The multisite taxonomic beta diversity of birds was primarily driven by species turnover in all small habitat island systems（100.0%）and most large habitat island systems（75.0%）.For small habitat island systems,mean annual temperature（MAT）and temperature seasonality（TS）were the main drivers of bird taxonomic beta diversity and species turnover,while nestedness-resultant components were affected by the mean inter-island distance（MID）.For large habitat island systems,MAT and MID were the main drivers of bird taxonomic beta diversity,while the species turnover was affected by TS,annual precipitation（AP）and the precipitation of the driest quarter,and nestedness-resultant component was affected by the total area of habitat islands（AT）.The multisite phylogenetic beta diversity of bird was primarily driven by phylogenetic turnover in most small habitat island systems（71.4%）,while phylogenetic nestedness-resultant component dominated multisite phylogenetic beta diversity in most large habitat island systems（62.5%）.For small habitat island systems,phylogenetic nestedness-resultant component was affected by precipitation-related factors[annual precipitation（AP）,the precipitation of the driest quarter（PDQ）and precipitation seasonality（PS）],while phylogenetic turnover was affected by precipitation-related factors（PDQ and PS）across large habitat island systems.Specifically,by comparison,the standardized effect sizes（SES）of phylogenetic beta diversity measures（SES.PβS）for small habitat island systems were more prone to be strongly affected by climate factors and habitat island system characteristics than that for large habitat island systems.The multisite functional beta diversity of bird was primarily driven by spatial turnover in all（100.0%）small habitat island systems,while turnover dominated multisite functional beta diversity of bird in half（50.0%）of the large habitat island systems.For small habitat island systems,the functional beta diversity and turnover component were affected by temperature[mean annual temperature（AP）and temperature seasonality（TS）],while nestedness-resultant component was affected by AP,the precipitation of the driest quarter（PDQ）,precipitation seasonality（PS）and the mean inter-island distance（MID）.For large habitat island systems,the functional beta diversity was affected by mean annual temperature（MAT）,the total area of habitat islands（AT）and MID.Functional turnover component were affected by PS,while nestedness-resultant component was not affected by climate factors and system characteristics.In addition,the standardized functional turnover measures(SES.Fβ_SIM)for small habitat island systems were significantly related to precipitation-related factors（AP and PS）,while habitat island system characteristics（area scale and MID）best explained the standardized functional beta diversity(SES.Fβ_SOR).Moreover,explanatory variables explained a greater proportion of variance in SES.Pβs than what we did for functional equivalents（SES.Fβs）,with higher values of R_adj² for SES.Pβs than that for SES.Fβs.Our findings confirmed that landscape-level beta diversity patterns and their best landscape-level characteristics varied across beta diversity components(β_SOR vs.β_SIM vs.β_SNE),dimensions（taxonomic vs.phylogenetic vs.functional）,and spatial extent（small vs.large）.We found substantial incongruent responses of SES.Pβs and SES.Fβs to our landscape-level characteristics.Also,our results suggest the roles of deterministic processes through the interplay among differential functional traits and phylogenetic distances of species,climate factors,and system characteristics as well as spatial extent in driving bird communities across multiple habitat island systems at a landscape level.Our study appeals that studies of the landscape-level species distribution patterns across habitat island systems should incorporate multiple dimensions of biodiversity（i.e.,taxonomic,phylogenetic and functional）.This study offers a better understanding of the processes underlying macroecological patterns of isolated biological communities across habitat island systems.