Data from: Postglacial expansion and not human persecution best explains the population structure in the endangered kea (Nestor notabilis)

Inferring past demography is a central question in evolutionary and conservation biology. It is however sometimes challenging to infer the processes that shaped the current patterns of genetic variation in endangered species. Population sub-structuring can occur as a result of survival in several isolated refugia and subsequent recolonization processes or via genetic drift following a population decline. The kea (Nestor notabilis) is an endemic parrot widely distributed in the mountains of the South Island of New Zealand that has gone through a major human-induced population decline during the 1860s-1970s. The aims of this study were to understand the glacial and post-glacial history of kea and to determine whether the recent population decline played a role in the shaping of the current genetic variation. We examined the distribution of genetic variation, differentiation and admixture in kea using 17 microsatellites and the mitochondrial control region. Mitochondrial data showed a shallow phylogeny and a genetic distinction between the North and South of the range consistent with the three genetic clusters identified with microsatellite data. Both marker types indicated an increase of genetic isolation by geographic distance. Approximate Bayesian Computation supported a scenario of recent divergence from a single ancestral glacial refugium, suggesting that the contemporary genetic structure is has resulted from post-glacial recolonization processes than from the recent population decline. The recent origin of this genetic structure suggests that each genetic cluster does not need to be considered as independent conservation units.

推断过往种群历史是进化生物学与保护生物学的核心研究议题。然而，针对濒危物种，解析塑造其当前遗传变异格局的演化进程往往颇具挑战。种群亚结构的形成，可源于多个孤立冰期避难所的存续与后续的再定植过程，亦或种群衰退后发生的遗传漂变。啄羊鹦鹉（kea, Nestor notabilis）是新西兰南岛山区广泛分布的特有鹦鹉类群，曾在1860年至1970年间经历过由人类活动主导的大规模种群衰退。本研究旨在阐明啄羊鹦鹉的冰期与冰期后种群历史，并探明近期的种群衰退是否参与塑造了其当前的遗传变异格局。本研究依托17个微卫星标记（microsatellites）与线粒体控制区（mitochondrial control region）序列，分析了啄羊鹦鹉的遗传变异分布、种群分化与遗传混合情况。线粒体数据显示出较浅的系统发育结构，且其分布区南北两侧存在显著遗传分化，这与微卫星数据所鉴定出的三个遗传聚类群结果高度一致。两类分子标记均检测到显著的距离隔离遗传分化模式。近似贝叶斯计算（Approximate Bayesian Computation, ABC）分析结果支持“从单一祖先冰期避难所发生近期分化”的演化场景，表明当代种群的遗传结构更多由冰期后的再定植过程塑造，而非近期的种群衰退。该遗传结构的近期起源提示，无需将每个遗传聚类群视作独立的保护单元。