Data from: A portrait of a sucker using landscape genetics: how colonization and life history undermine the idealized dendritic metapopulation

Dendritic metapopulations have been attributed unique properties by in silico studies, including an elevated genetic diversity relative to a panmictic population of equal total size. These predictions have not been rigorously tested in nature, nor has there been full consideration of the interacting effects among contemporary landscape features, colonization history, and life history traits of the target species. We tested for the effects of dendritic structure as well as the relative importance of life history, environmental barriers, and historical colonization on the neutral genetic structure of a longnose sucker (Catostomus catostomus) metapopulation in the Kogaluk watershed of northern Labrador, Canada. Samples were collected from eight lakes, genotyped with 17 microsatellites, and aged using opercula. Lakes varied in differentiation, historical and contemporary connectivity, and life history traits. Isolation by distance was detected only by removing two highly genetically differentiated lakes, suggesting a lack of migration-drift equilibrium and the lingering influence of historical factors on genetic structure. Bayesian analyses supported colonization via the Kogaluk’s headwaters. The historical concentration of genetic diversity in headwaters inferred by this result was supported by high historical and contemporary effective sizes of the headwater lake, T-Bone. Alternatively, reduced allelic richness in headwaters confirmed the dendritic structure’s influence on gene flow, but this did not translate to an elevated metapopulation effective size. A lack of equilibrium and upstream migration may have dampened the effects of dendritic structure. We suggest that interacting historical and contemporary factors prevent the achievement of the idealized traits of a dendritic metapopulation in nature.

计算机模拟（in silico）研究显示，树枝状集合种群（dendritic metapopulations）具备独特性状：相较于总规模相当的随机交配种群（panmictic population），其遗传多样性水平显著更高。但这类预测尚未在自然环境中得到严格验证，且学界尚未充分考量当代景观特征、定殖历史与目标物种生活史性状之间的交互效应。本研究以加拿大拉布拉多北部科加卢克（Kogaluk）流域的长鼻吸盘鱼（Catostomus catostomus）集合种群为研究对象，探究树枝状结构的影响，以及生活史、环境障碍、历史定殖事件对其中性遗传结构（neutral genetic structure）的相对重要性。研究团队从8个湖泊中采集样本，利用17个微卫星标记（microsatellites）进行基因分型，并通过鳃盖骨（opercula）开展年龄鉴定。各湖泊在遗传分化、历史与当代连通性以及生活史性状上均存在差异。仅在剔除2个遗传分化极高的湖泊后，才检测到距离隔离效应，这表明种群未达到迁移-漂变平衡，且历史因素对遗传结构仍存在持续影响。贝叶斯分析结果支持该种群通过科加卢克流域的上游源头完成定殖。该结果推断出的源头区域遗传多样性历史富集现象，得到了源头湖泊T-Bone较高的历史与当代有效种群大小（effective population size）的佐证。与之相对，源头区域的等位基因丰富度降低，证实了树枝状结构对基因流的影响，但这并未转化为集合种群有效种群大小的提升。种群未达到平衡以及向上游迁移的现象，可能削弱了树枝状结构的预期效应。本研究表明，历史与当代因素的交互作用，阻碍了自然环境中树枝状集合种群理想性状的实现。