Heilveil J S, Berlocher S H
Department of Entomology, University of Illinois 320 Morrill Hall, Urbana, 61801, USA.
Mol Ecol. 2006 May;15(6):1627-41. doi: 10.1111/j.1365-294X.2006.02876.x.
We have examined the effects of post-Wisconsinan glacial range expansion on the phylogeography of the saw-combed fishfly, Nigronia serricornis Say (Megaloptera: Corydalidae) because aquatic insects are under-represented in postglacial studies (and in phylogeography in general), and because the effects of ecological degradation on the population genetics of environmental indicator species like N. serricornis cannot be measured unless the underlying phylogeography is understood. Sequence data from a 630-base fragment of the mitochondrial cytochrome oxidase I (COI) gene were subjected to amova and nested clade analysis for 30 populations (n = 344) of N. serricornis. Both the amova and nested clade analysis revealed substantial population structure; 44.4% of the variance occured among populations. Three northward migrations are apparent: one from Tennessee into Illinois, Indiana, Wisconsin, Michigan and Ontario, a second that radiated eastward from Pennsylvania, and a third that moved along the coast from North Carolina into Connecticut, Massachusetts, Maine and then into New York. The latter two of these migrations were the result of contiguous range expansions, while the former expansion, out of Tennessee, appears to have been rapid with little gene flow from the source population. Additional clades included a group of haplotypes in central Kentucky that appear to have expanded along preglacial drainages, and clades in North Carolina and Georgia that have remained centrally located. Haplotype diversity decreased from south to north, a pattern that has been widely reported for animal and plant populations that expanded with the retreat of the Wisconsinan glaciation.
我们研究了威斯康星冰期后冰川范围扩张对锯缘鱼蛉（Nigronia serricornis Say，广翅目：齿蛉科）系统地理学的影响，原因如下：水生昆虫在冰期后研究（以及一般的系统地理学研究）中代表性不足；而且，除非了解其潜在的系统地理学情况，否则无法衡量生态退化对锯缘鱼蛉这类环境指示物种种群遗传学的影响。我们对锯缘鱼蛉的30个种群（n = 344）的线粒体细胞色素氧化酶I（COI）基因的630个碱基片段的序列数据进行了分子变异分析（AMOVA）和嵌套分支分析。AMOVA和嵌套分支分析均揭示了显著的种群结构；44.4%的变异发生在种群之间。明显存在三次向北的迁移：一次是从田纳西州迁入伊利诺伊州、印第安纳州、威斯康星州、密歇根州和安大略省；第二次是从宾夕法尼亚州向东辐射；第三次是沿海岸从北卡罗来纳州迁入康涅狄格州、马萨诸塞州、缅因州，然后进入纽约州。后两次迁移是连续范围扩张的结果，而从田纳西州向外的首次扩张似乎很迅速，源种群几乎没有基因流动。其他分支包括肯塔基州中部一组似乎沿着冰期前排水系统扩张的单倍型，以及位于北卡罗来纳州和佐治亚州且一直处于中心位置的分支。单倍型多样性从南向北降低，这种模式在随着威斯康星冰川消退而扩张的动植物种群中已被广泛报道。
