Data from: Genetic and paleomodelling evidence of the population expansion of the cattle egret Bubulcus ibis in Africa during the climatic oscillations of the Late Pleistocene

Increasing aridity during glacial periods produced the retraction of forests and the expansion of arid and semi-arid environments in Africa, with consequences for birds. Cattle egret (Bubulcus ibis) is a dispersive species that prefers semiarid environments and requires proximity to bodies of water. We expected that climatic oscillations led to the expansion of the range of the cattle egret during arid periods, such as the Last Maximum Glacial (LGM) and contraction of distribution during the Last Interglacial (LIG) period, resulting in contact of populations previously isolated. We investigated this hypothesis by evaluating the genetic structure and population history of 15 cattle egret breeding colonies located in West and South Africa using the mitochondrial DNA (mtDNA) control region, mtDNA ATPase 8 and 6, and an intron of nuclear gene transforming growth factor beta-2. Occurrence data and bioclimatic information were used to generate ecological niche models of three periods (present, LGM and LIG). We used the genetic and paleomodelling data to assess the responses of the cattle egret from Africa to the climatic oscillations during the late Pleistocene. Genetic data revealed low levels of genetic differentiation, signs of isolation-by-distance, as well as recent increases in effective population size that started during the LGM. The observed low genetic structure may be explained by recent colonization events due to the demographic expansion following the last glacial period and by dispersal capacity of this species. The paleomodels corroborated the expansion during the LGM, and a more restricted potential distribution during the LIG. Our findinds supports the hypothesis that the species range of the cattle egret expanded during arid periods and contracted during wet periods.

冰期时段干旱程度加剧，导致非洲地区森林退缩、干旱与半干旱环境扩张，这对鸟类种群产生了显著影响。
牛背鹭（Bubulcus ibis）是一种偏好半干旱环境且需邻近水体的扩散性鸟类。我们推测，气候振荡会使牛背鹭在末次盛冰期（Last Maximum Glacial, LGM）等干旱时段的分布范围扩张，而在末次间冰期（Last Interglacial, LIG）时段分布范围收缩，进而使此前隔离的种群产生接触。
本研究以非洲西部和南部的15个牛背鹭繁殖种群为研究对象，通过线粒体DNA（mitochondrial DNA, mtDNA）控制区、mtDNA ATP合酶8和6基因以及核基因转化生长因子β-2（transforming growth factor beta-2, TGF-β2）的内含子序列，对该假说进行验证。
研究人员结合物种出现记录数据与生物气候信息，构建了当前、末次盛冰期、末次间冰期三个时段的生态位模型。
我们结合遗传数据与古生态模型数据，分析了非洲牛背鹭对晚更新世气候振荡的响应。
遗传数据分析结果显示，种群间遗传分化程度较低，存在距离隔离信号，且有效种群数量自末次盛冰期以来呈持续增长趋势。
此次观测到的低遗传结构现象，可归因于末次冰期后种群扩张带来的近期定殖事件，以及该物种自身的扩散能力。
古生态模型结果证实，牛背鹭在末次盛冰期时分布范围扩张，而在末次间冰期时潜在分布范围更为局限。
本研究结果支持这一假说：牛背鹭的分布范围在干旱时段扩张，在湿润时段收缩。