The Population Dynamics Of Taxus Cuspidata

Habitat fragmentation can in principle reduce genetic diversity,limit gene flow and eventually lead to strong genetic structure.However,the genetic consequences of recent habitat fragmentation of long-lived tree species remain unclear.Taxus cuspidata,which has extremely small populations mainly distributed in Changbai Mountains in Northeast(NE)China,Russia,Japan and Korea,has recently endured severe habitat fragmentation.The species now is endangered and listed as one of the plant species with extremely small populations.We selected 265 individuals from 26 populations based on a large-scale field survey of the existing populations throughout their range in China for population genetic study,using paternally inherited chloroplast DNA(cpDNA)fragments,mitochondrial DNA(mtDNA)fragments and biparentally inherited nuclear microsatellite markers(nSSRs).We aim to investigate the pattern of genetic diversity and structure,identify risk factors,predict the potential distribution in the future and finally provide guidelines for the conservation and management of the species.The main findings of this study were as followed:(1)Three cpDNA fragments(2431 bp),two mtDNA fragments(830 bp)and seven nSSRs markers showed high genetic diversity,low genetic differentiation and extensive gene flow among both natural and transplanted populations of T.cuspidata over the entire geographical range of NE China(cpDNA:Hd=0.87,FST=0.06;mtDNA:Hd=0.66,FST=0.07;nSSRs:HO=0.31,HE=0.36,FST=0.08).(2)The most populations of T.cuspidata survived in multiple microrefugia in NE China and the stability of effective population size during the demographic history of the species,demonstrating past climatic oscillations had not severely affected population viability.However,ecological niche modeling suggests the species may be exposed to severe threats from future environmental change because of a decline in the area of suitable habitat by the years 2050 and 2070.(3)Our results suggest the size of natural populations in T.cuspidata has substantially decreased,mainly because of the habitat fragmentation caused by overexploitation of the forest resources.Thus,conservation and management strategies should be implemented in order to protect all extant fragmented natural and transplanted populations in situ,repair the degraded habitats,limit human disturbance,appropriately exploite the yew resources while coping with future climatic threats and invoke the public consciousness of conservation.Our study integrated sequence variation derived from cytoplasmic and nuclear genome fragments markers with ENM to investigate population genetic and the demographic history in T.cuspidata,which provides a basic theory for comprehensive understanding of the endangerment mechanisms and the corresponding conservation technologies of T.cuspidata.