Mesquita N, Hänfling B, Carvalho G R, Coelho M M
Universidade de Lisboa, Faculdade de Ciências, Departamento de Biologia Animal/Centro de Biologia Ambiental, Campo Grande, 1749-016 Lisboa, Portugal.
Mol Ecol. 2005 Jun;14(7):1939-54. doi: 10.1111/j.1365-294X.2005.02569.x.
The Iberian cyprinid fauna, characterized by the presence of numerous endemic species, has suffered from significant habitat degradation. The critically endangered Squalius aradensis is restricted to small drainages of southern Portugal, habitats that typically exhibit a characteristic Mediterranean-type heterogeneous hydrological system throughout the year, including alternation of flooding events during winter and complete drought in large river sections during summer. To assess the effect of historical and recent processes on genetic diversity in S. aradensis we examined within- and among-population variability in cytochrome b and six polymorphic microsatellite loci. Estimates of genetic diversity in time and space through the combined use of traditional Phi-/F-statistics, phylogenetic trees, ordination methods and nested clade analysis indicated significant and congruent structuring among populations. Data suggest that the Arade drainage represent the evolutionary centre of the species, with subsequent allopatric fragmentation across drainages. Factors other than isolation by distance strongly affected the within-drainage genetic differentiation observed in these Mediterranean-type drainages, including recent population expansion from a bottleneck event and restricted gene flow imposed by a long-term barrier (brackish water area). Significant correlation was found between S. aradensis allelic diversity and upstream drainage area. The relevance of findings for conservation issues is discussed in relation to local intermittent hydrological conditions, the highly restricted distribution and the critically endangered status of the species.
伊比利亚鲤科动物群以众多特有物种为特征，却遭受了严重的栖息地退化。极度濒危的阿拉德圆腹雅罗鱼仅分布于葡萄牙南部的小流域，这些栖息地通常全年呈现典型的地中海型异质水文系统，包括冬季洪水事件的交替以及夏季大河部分河段的完全干旱。为了评估历史和近期过程对阿拉德圆腹雅罗鱼遗传多样性的影响，我们检测了细胞色素b和六个多态微卫星位点的种群内和种群间变异性。通过联合使用传统的Phi-/F统计量、系统发育树、排序方法和嵌套分支分析对遗传多样性进行时空估计，结果表明种群间存在显著且一致的结构。数据表明，阿拉德河流域是该物种的进化中心，随后各流域出现了异域性片段化。除距离隔离外，其他因素强烈影响了在这些地中海型流域中观察到的流域内遗传分化，包括近期由瓶颈事件导致的种群扩张以及长期障碍（咸水区域）造成的基因流受限。阿拉德圆腹雅罗鱼等位基因多样性与上游流域面积之间存在显著相关性。结合当地间歇性水文条件、该物种高度受限的分布以及极度濒危的现状，讨论了研究结果对保护问题的相关性。
