Alpine lakes and ponds – a promising source of high genetic diversity in metapopulations of aquatic insects

Alpine lakes and ponds are unique and vulnerable aquatic habitats inhabited by specific species assemblages. In contrast to alpine streams, the genetic diversity and population structure of the organisms found in alpine standing waters are almost completely unknown. Here we present a population genetic study of a macroinvertebrate species from alpine lakes, the diving beetle Agabus bipustulatus (Linnaeus, 1767). We used partial cytochrome b (Cyt b) mtDNA gene of 560 specimens from 43 lakes and ponds distributed across 20 mountain valleys of the Tatra Mountains (Western Carpathians) and their foothills. The aims of this study were to provide detailed genetic metapopulation analysis of A. bipustulatus within a geographically small mountain system, to explore the role of ridges in isolating lake populations, and to test for the applicability of Cyt b in insect population genetic studies. We detected high genetic variability (42 haplotypes), comparable to many large spatial scale studies. There was a star-shaped genetic structure with few dominant haplotypes, which confirmed recent origin, rapid expansion of metapopulation, and multiple colonization of the Tatra Mountain region by A. bipustulatus. The populations within the mountain system differed from each other, suggesting that the Tatra Mountain lakes and ponds were colonized through multiple colonization events, and also that colonization of the region and evolution of metapopulations are to a certain extent influenced by ridge barriers.高山湖泊与池塘是独特且脆弱的水生生境，栖息着特有的物种组合。与高山溪流不同，目前学界对高山静水水体中生物的遗传多样性与种群结构几乎完全未知。本研究针对高山湖泊中的一类大型无脊椎动物——龙虱Agabus bipustulatus（Linnaeus, 1767）开展种群遗传学研究。我们对采自西喀尔巴阡山脉塔特拉山脉及其山麓20个山谷的43个湖泊与池塘的560份标本的线粒体DNA细胞色素b（cytochrome b, Cyt b）部分基因片段进行了分析。本研究的目标在于：其一，对地理尺度较小的山地系统内的A. bipustulatus开展精细的遗传集合种群（metapopulation）分析；其二，探究山脊对湖泊种群的隔离作用；其三，验证Cyt b基因在昆虫种群遗传学研究中的适用性。研究检测到较高的遗传变异水平（共42个单倍型（haplotype）），该结果与诸多大空间尺度研究的结果相当。种群呈现星状遗传结构，仅存在少量优势单倍型，这证实了A. bipustulatus起源时间较近、集合种群快速扩张，且该物种曾多次殖民塔特拉山脉区域。该山地系统内的各湖泊种群彼此存在遗传分化，这表明塔特拉山脉的湖泊与池塘曾经历多次独立殖民事件，同时也说明该区域的殖民过程与集合种群演化在一定程度上受到山脊屏障的影响。