Besnard G, Christin P A, Baali-Cherif D, Bouguedoura N, Anthelme F
Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland.
Heredity (Edinb). 2007 Dec;99(6):649-57. doi: 10.1038/sj.hdy.6801051. Epub 2007 Sep 12.
The Laperrine's olive (Olea europaea subsp. laperrinei) is an emblematic species of the Sahelo-Saharan Mountains. Populations of this tree are locally threatened by extinction due to climatic vicissitudes and human activities, particularly in Niger and Algeria. In order to study the spatial genetic structure and the dynamics of O. e. laperrinei populations, we sampled trees in four isolated mountain ranges (Tassili n'Ajjer and Hoggar (Algeria), Tamgak and Bagzane (Niger)). A total of 237 genets were identified using nuclear microsatellites. Phylogenetic reconstruction based on plastid DNA data supported a maternal origin of O. e. laperrinei populations in South Algeria, where a higher allelic richness was observed. Based on nuclear microsatellite data, two levels of structure were revealed: first, individuals from Niger and Algeria were separated in two distinct groups; second, four less differentiated clusters corresponded to the four studied mountain ranges. These results give support to the fact that desert barriers have greatly limited long distance gene flow. Within populations, pairwise kinship coefficients were significantly correlated to geographical distance for Niger populations but not for Algerian mountains. Historical factors and habitat heterogeneity may explain the differences observed. We conclude that the Hoggar acts as an important genetic reservoir that has to be taken into account in future conservation programmes. Moreover, very isolated endangered populations (for example, Bagzane) displaying evident genetic particularities have to be urgently considered for their endemism.
拉佩林油橄榄（Olea europaea subsp. laperrinei）是萨赫勒 - 撒哈拉山脉的标志性物种。由于气候变迁和人类活动，特别是在尼日尔和阿尔及利亚，这种树的种群在当地面临灭绝威胁。为了研究拉佩林油橄榄种群的空间遗传结构和动态，我们在四个孤立的山脉（阿尔及利亚的塔西里阿杰尔和霍加尔，尼日尔的坦加克和巴扎内）采集了树木样本。使用核微卫星共鉴定出237个基因系。基于质体DNA数据的系统发育重建支持了阿尔及利亚南部拉佩林油橄榄种群的母系起源，在那里观察到更高的等位基因丰富度。基于核微卫星数据，揭示了两个层次的结构：第一，来自尼日尔和阿尔及利亚的个体被分为两个不同的组；第二，四个分化程度较低的聚类对应于四个研究的山脉。这些结果支持了沙漠屏障极大地限制了长距离基因流动这一事实。在种群内部，尼日尔种群的成对亲缘系数与地理距离显著相关，而阿尔及利亚山脉的则不然。历史因素和栖息地异质性可能解释了观察到的差异。我们得出结论，霍加尔山脉是一个重要的遗传库，在未来的保护计划中必须予以考虑。此外，非常孤立的濒危种群（例如巴扎内）因其特有性必须被紧急关注。
