Reconstructing biogeographic temporal events in the evolution of the livebearer fish genus <i>Jenynsia</i> based on total evidence analysis (<i>Cyprinodontiformes: Anablepidae</i>)

The current distribution of the Neotropical ichthyofauna has been widely affected by the main geological events that occurred in South and Central America. However, robust biogeographic information is still scarce or absent for most fish families. The biogeographic relationships of the most diverse anablepid genus, Jenynsia, are herein analysed, using temporal and spatial approaches based on a total evidence dataset, including 167 morphological characters and seven nuclear genes, totalling 6075 bp. A time calibrated analysis recovered the origin of Jenynsia at the Miocene and the diversification of its two subgenera between the Late Miocene and Early Pliocene. This result combined with the analysis of reconstruction of ancestral states indicates that the ancestor of Jenynsia colonized the Paranean Sea, and the current distribution of the species of the genus is probably a result of geological events, including: (1) ancient connections between Iguaçu and upper Uruguay River basins; (2) sea level variation along the Pliocene in the South American Atlantic coast; and (3) the decrease of the Paranean Sea along the Pliocene and Pleistocene.新热带区鱼类区系（Neotropical ichthyofauna）的现有分布格局，广泛受到南美与中美洲发生的主要地质事件影响。然而，绝大多数鱼类科属仍缺乏详实可靠的生物地理学研究数据。本研究基于包含167个形态性状与7个核基因（总长度6075 bp）的总证据数据集，采用时空分析方法，对物种多样性最高的四眼鱼科（Anablepidae）詹尼鱼属（Jenynsia）的生物地理学亲缘关系展开解析。时间校准分析结果显示，詹尼鱼属的起源时间为中新世，其两个亚属的物种分化发生于晚中新世至早上新世时段。结合祖先性状重建分析的结论，本研究证实詹尼鱼属的祖先类群曾定居于巴拉那海（Paranean Sea）；该属现有物种的分布格局，大概率由以下三类地质事件塑造：（1）伊瓜苏河与乌拉圭河上游流域的古水系连通事件；（2）上新世期间南美大西洋沿岸的海平面波动；（3）上新世至更新世时期巴拉那海的萎缩消退。