Abstract:

In natural ecosystem, species assemblages in fragmented habitats frequently exhibit a nested subset pattern. Although nestedness has been documented for a wide range of taxa, it is rarely tested in butterfly assemblages in oceanic archipelago ecosystems. We surveyed the butterfly occupancy and abundance on 28 islands using a line-transect method in the Zhoushan Archipelago, China from July to August 2013. We determined island geographical factors (area, isolation) based on the literature and obtained species life-history traits (area requirement, wingspan and body weight) in the laboratory. The recently developed metric WNODF was used to examine the nestedness. Partial Spearman rank correlation was used to evaluate the associations of nestedness and island geographical factors as well as life-history traits related to species extinction and immigration tendencies. We found that the community composition of butterflies in the Zhoushan Archipelago was significantly nested. Island area and species’ area requirements were significantly correlated with nestedness after synthesis for all independent variables. In contrast, according to the null-model random test, nestedness of butterflies might not result from passive sampling or selective colonization. Our results indicate that selective extinction is the main driver of nestedness of butterflies in our system. From a conservation perspective, we suggest that large islands and species with large area requirements should be paid more attention in order to maximize the total number of species preserved.

Key words: habitat fragmentation, nestedness, selective extinction, butterfly, Zhoushan Archipelago