Effects Of Habitat Fragmentation On Population Genetic Composition Of Three Fagaceae Trees

Habitat fragmentation is the phenomenon that large and continuous habitats are changed into multiple small and spatially isolated remnants.Mating system and seeddispersal modes play an important role in the responses of plant species to habitat fragmentation.Theoretical predictions indicate that species with similar life history characteristics will show similar responses to habitat fragmentation.However,this prediction has yet not been tested.In this paper,we chose the island habitats of Thousand-island Lake as the study system and used microsatellite markers to analyze genetic composition of three windpollinated and gravity seed-dispersed trees of Fagaceae,i.e.,Quercus fabri,Q.serrata var.brevipetiolata and Castanopsis sclerophylla.The main conclusions are as follows:1)In general,habitat fragmentation has not significantly changed genetic composition the three species.We found no significant relationship between genetic diversity and habitat size or isolation extent,except positive relationship between allelic richness and habitat size in Q.fabri populations and negative relationship between expected heterozygosity and the distance to the nearest island in Q.serrata var.brevipetiolata.Habitat size and isolation showed no interaction effect on genetic diversity of each species.The trend in response to habitat fragmentation was similar,and genetic diversity showed no significant interspecific difference on the whole,except allelic richness among populations of Q.fabri and Q.serrata var.brevipetiolata.2)Genetic differentiation among populations of three related species was not significantly influenced by habitat fragmentation.Population genetic differentiation of each species was at moderate levels but showed no genetic clusters phenomenon or isolation by distance pattern in this region.In summary,habitat fragmentation influences genetic diversity and differentiation of three species in a similar way,though decreased habitat size and increased isolation have a negative impact in few genetic parameters of Q.fabri and Q.serrata var.brevipetiolata.