The Underlying Mechanisms Of Diversity And Nestedness Pattern Of Ground-dwelling Spiders In The Thousand Island Lake

Under the scenario of increasing habitat fragmentation in global scale, more and more continuous habitats have degraded into small isolated patches, and this will lead to dramatic change of previous ecological process and biodiversity under the shift of area and isolation. Therefore, trying to elucidate the ecological process of animal and plant inhabit in fragmented habitats will help us understand the nature of fragmentation and also provide theoretical guidance for biodiversity conservation.Ground-dwelling spider has relative short life span and is sensitive to habitat fragmentation, thus providing an excellent system to elucidate the effects of fragmentation on biodiversity and community composition. However, few studies have described nested pattern in spiders under fragmented habitats. In this study, we examined species biodiversity and connection between patches of spider assemblages by using species-area relationship, species-isolation relationship and nestedness analysis under a fragmented land-bridge island system in the Thousand Island Lake (TIL), China.Pitfall traps were used to sample occupancy and abundance of ground-dwelling spiders from May 2013 to September 2014 on 31 islands in TIL. We used Spearman correlation analysis to explore the relationship between biodiversity of spider assemblages, community composition and island parameters. Two metrics NODF and WNODF were employed to quantify nestedness pattern. Spearman’s rank correlations and partial Spearman’s rank correlations were used to evaluate the associations of nestedness and geographic and ecological parameters of the islands (i.e. area, isolation, habitat diversity). All the analyses were conducted in R 3.1.3.We found that island area (P< 0.001) and isolation (P< 0.05) have significant effects on the distribution pattern of spiders, whereas habitat diversity and plant richness haven’t. Community composition of ground-dwelling spiders was significantly nested. Spearman’s rank correlations revealed that nested matrix rank was strongly correlated with ranks of both island area and isolation. However, we failed to detect significant association between nestedness and habitat diversity.