β diversity among ant communities on fragmented habitat islands: the roles of species trait, phylogeny and abundance

Habitat loss and fragmentation reduce biodiversity and alter species composition in local communities. β diversity describes the variation in species composition between or among communities in fragmented landscapes and has two components: species turnover and nestedness. In this study, we assessed β diversity of ant assemblages on 24 island fragments in the Thousand Island Lake, China. We constructed a species‐level phylogenetic tree and measured five morphological traits of all ant species captured. We then assessed taxonomic (both incidence‐based and abundance‐weighted), functional and phylogenetic β diversity and partitioned β diversity into turnover and nestedness (as well as the contributions of particular species and particular islands). Finally, we examined the relationships between β diversity and a suite of geographical variables (i.e. difference in island area, difference in isolation and inter‐island distance) using Mantel tests. We found taxonomic and phylogenetic turnover components dominated overall β diversity whereas the functional turnover and nestedness components contributed equally to overall β diversity. Overall β diversity increased with increasing difference in isolation and inter‐island distance; however, only abundance‐weighted overall β diversity decreased with increasing difference in island size. Our results indicate that species that were abundant on large islands were also abundant on small islands. We conclude that the dispersal limitation of ants likely shapes the pattern of β diversity along isolation and inter‐island distance gradients. Additionally, functional redundancy of species (i.e. different species share similar functional roles) could also explain β diversity patterns among fragmented habitat islands. Our results highlight the necessity of incorporating both incidence‐based and abundance‐weighted community data when examining β diversity in fragmented landscapes. By partitioning β diversity into the contributions of particular species and particular fragments, our study implies that small patches can be valuable for maintaining biodiversity among ant communities.