沙冬青(Ammopiptanthus)的遗传结构与保育

Genetic Structure of Ammopiptanthus and Its Conservation Implications

沙冬青(Ammopiptanthus)是蒙新砾质荒漠中唯一常绿阔叶灌木孑遗,且已陷入濒临灭绝的境地。沙冬青属内分类争论已久。利用分子手段对国内沙冬青居群进行了遗传结构分析,以对其保护提供准确的遗传学信息。核序列和叶绿体间隔数据均表明,沙冬青属包含两个明显不同的分支,分别分布于塔里木荒漠与阿拉善荒漠,我们据此建议恢复分布于新疆的沙冬青居群的物种地位,即新疆沙冬青(A.nunas)。沙冬青属属下两个种遗传多样性均比较低,可能由于先天遗传不足及破碎化小居群的遗传漂变与近交作用。新疆沙冬青无明显的遗传结构。蒙古沙冬青(A.mongolicus)在阿拉善荒漠北部与南部出现了明显的遗传分歧,这可能是由于南北部居群由不同的避难所扩张而来。也为沙冬青的保护提出了建议。

Ammopiptanthus is an only evergreen shrub relics with broad leaves in Neimeng--Xinjiang des- ert. There has been long dispute about the classification of the genus Ammopiptanthus, and it is at risk of extinction. We investigate the genetic structure across its whole distribution range using modern molecular techniques to provide useful information for its conservation. Both the nuclear and chloroplast datasets showed that Ammopiptanthus comprised two lineages, distributed respectively in Tarim Desert and Alxa Desert. The molecular data give further support to the suggestion that populations in Tarim Desert should be given species rank, A. nunas. The level of genetic diversity in the two species are both low, might caused by origination from genetically depauperate populations, and increased genetic drift and selfing in small frag- mented populations. There is no significant genetic structure in A. nunas. However, there is a significant genetic divergence between north and south Alxa Desert in A. mongolicus. Origins from different refugia may be responsible for the genetic divergence between north and south of Alxa Desert. Based on these re- sults, we provide some reasonable advices for the conservation of Ammopiptanthus.