生境片段化对千岛湖岛屿上黄足厚结猛蚁遗传多样性的影响

Effects of habitat fragmentation on the genetic diversity of Pachycondyla luteipes on islands in the Thousand Island Lake,East China

利用相关序列扩增多态性(SRAP)分子标记法,对千岛湖片段化生境中14个岛屿上的黄足厚结猛蚁(Pachycondyla luteipes)种群遗传结构和多样性进行研究。利用5对SRAP引物对42份材料的基因组进行扩增,共得到大小在50—800 bp之间的71个可重复位点,其中63个为多态性位点,多态性比率达88.73%。AMOVA分析结果显示,65.03%的遗传变异存在于种群间,34.97%的遗传变异来自种群内(P<0.001)。利用PopGene Version 1.32软件对SRAP多态性数据进行分析,不同岛屿种群的多态位点比例和Nei's基因多样性指数变化范围分别介于35.21%—91.55%和0.2662—0.4905之间,平均值分别为58.25%和0.3729,其中多态位点比率最高的岛屿为面积最大的JSE岛。多态位点比例和Nei's基因多样性指数与岛屿面积、海拔均无显著相关性,但与隔离度呈显著正相关关系。种群间遗传分化指数介于0.0777—0.9328之间,平均值为0.4419,基因流值介于0.0360—5.9350之间,平均值为1.0451,种群间遗传分化程度较高,基因流较低。利用UPGMA聚类分析法对14岛屿上的42个个体进行遗传聚类分析,表明地理距离较近的个体和岛屿具有优先聚在一起的趋势。Mantel检验表明黄足厚结猛蚁各种群间地理距离与遗传距离间存在显著相关性(r=0.7757,P<0.01)。以上结果表明地理隔离是影响千岛湖黄足厚结猛蚁种群遗传结构和多样性的主要因素。

Habitat fragmentation caused by human activity poses a serious threat to biodiversity worldwide, with severe negative impacts on species genetic diversity. In recent years, many attentions have been paid to the genetic effects of anthropogenic habitat fragmentation on plants and animals, mainly focusing on terrestrial habitat islands created by agricultural development, deforestation and so on. However, the habitat islands have confused history, fuzzy boundary, and varied matrix which can cause confusion of results. Conversely, known-age land-bridge islands in artificial lakes are more ideal model systems to elucidate the ecological, genetic and evolutionary consequences of habitat fragmentation. The Thousand Island Lake （TIL） in East China （Chunan County, Zhejiang Province） is a large reservoir, which was formed in 1959 by the damming of the Xinanjiang River for constructing a hydroelectric power station. So far, the fragmented islands are formed around 50 years. Based on this superiority, we studied a dispersal-limited species of soil arthropod Pachycondyla luteipes at TIL to explore the genetic consequences of recent habitat fragmentation of this species.Sequence-related amplified polymorphism （SRAP） molecular markers were used to study the genetic diversity on population levels. Five SRAP primer combinations were used to measure 42 individuals of P. luteipes from 14 islands to estimate the genetic diversity and structure. The result showed that 5 SRAP primer combinations amplified 71 bands with 63 （88.73%） polymorphic. The percentage of polymorphic bands （PPB） at the population level ranged from 35.21% to 91.55%, with an average of 58.25%, and the largest JSE island owned the highest percentage of polymorphic bands. The Nei＇s gene diversity index （H） ranged from 0.2662 to 0.4905, with an average of 0.4753. The islands attributes such as area and elevation, had no significant correlation with PPB and H, but the isolation degree among different islands had significant correlation with them. The analysis of AMOVA showed that the main variance between populations was 65.03%, and 34.97% within populations. The genetic differentiation coefficient （Gst） among populations ranged from 0.0777 to 0.9328, with an average of 0.4419. Gene flow （Nm） among populations, based on the genetic differentiation coefficient, ranged from 0.0360 to 5.9350, with an average of 1.0451. The Nm and Gst value implied that the gene flow was at a low level and genetic differentiation was high. The dendrogram obtained by UPGMA cluster analysis showed that populations with nearest distance were clustered firstly. In addition, Mantel test （r=0.7757, P 〈 0.01） suggested that there was significant association between genetic distance and geographic distance.These results indicate that the P. luteipes populations in the TIL had gene drift mainly due to the isolation between islands. However, the gene flow is still high between some adjacent islands, because these islands could connect each other when the water level is enough low. In this context, the corridor may play an important role in affecting the genetic diversity in this fragmented landscape. We suggest that beside the island attributes, other factors such as the physical and chemical properties of soils should also be considered into the future studies.