Diversity,Nestedness And Genetic Diversity Of Butterfly Assemblages In The Zhoushan Archipelago

The authors surveyed the butterfly occupancy and abundance on 42 islands by line-transect method in the Zhoushan Archipelago,China from July to August,2014.Island geographical factors(area,isolation)and life-history traits(area requirement,wingspan and body weight)were obtained by literatures and laboratory works.Recently developed metric WNODF was used to examine nestedness.Partial Spearman rank correlation was used to evaluate the associations of nestedness and island geographical factors as well as life-history trait related to species extinction and immigration tendencies.The authors also studied the genetic diversity of Lycaena phlaeas by CO? gene.The main results are as follows:1 Species diversity A total of 8048 butterfly specimens belonged to 68 species,47 genera,and 7 families were collected during the study period.The number of species collected on each island varied between 1 and 41.Pseudozizeeria maha and Pieris rapae were the dominant species and accounted for 2.94% of total species and 35.36% of the total specimens;Lycaena phlaeas,Eurema hecabe,Pieris canidia,Papilio polytes were the common species and accounted for 5.88% of total species and 33.75% of the total specimens;62 specie were rare species and accounted for 91.18% of total species and 30.89% of the total specimens.Linear regression revealed that the butterfly species richness increased with increase in the size of islands,the regression equation was LnS = 0.3511 LnA + 2.8527(R2 = 0.4692,P < 0.001).Butterfly species richness was significantly correlating with the distance to the nearest mainland,but the fitting degree was lower than species-area regression linear;the distance to the nearest island had little influence on butterfly species richness.2 The distribution patterns of butterfly assemblages The community structures of butterfly assemblages in the Zhoushan archipelago were significantly nested.The whole butterfly-by-island incidence matrix exhibited a strong degree of nestedness than expected by assumed communities(WNODF = 40.39,P < 0.01).Species(WNODFr = 36.81,P < 0.01)and sites(WNODFc = 40.58,P < 0.01)were also significantly nested,respectively.Survey completeness for the 42 islands ranged from 68.86% to 100%(mean±SD: 0.82 ± 0.09).According to the expected species richness,on 37 of the 42 islands(88.1%),more than 75% of the species were collected.The nestedness of butterfly assemblages was not due to passive sampling.Only one of the observed data points lay within ±1 SD of the expected species-area cure,which indicated a directly rejection to the expectation from the random placement model.Those results reveal that nestedness of butterfly assemblages was on account of selective extinction.From a conservation viewpoint,this paper suggest that people should protect larger islands with richer species in order to maximize the number of species preserved.3 Genetic diversity Although the 344 Lycaena phlaeas came from different islands,but the overall evolutionary relationship was closer.There were tow subbranches with more than one Lycaena phlaeas.Members in the same subbrach had even more closer genetic relationship and might come from the same subspecies.