Evolutionary Zoology Laboratory, Department of Organisms and Ecosystems Research, National Institute of Biology, Ljubljana, Slovenia.
Evolutionary Zoology Laboratory, Institute of Biology, Research Centre of the Slovenian Academy of the Sciences and Arts, Ljubljana, Slovenia.
Sci Rep. 2019 Jan 23;9(1):397. doi: 10.1038/s41598-018-36590-y.
Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus Cyrtognatha (Tetragnathidae) from the Caribbean, with the aims to reconstruct its evolutionary history, examine its biogeographic history in the archipelago, and to estimate the timing and route of Caribbean colonization. Specifically, we test if Cyrtognatha biogeographic history is consistent with an ancient vicariant scenario (the GAARlandia landbridge hypothesis) or overwater dispersal. We reconstructed a species level phylogeny based on one mitochondrial (COI) and one nuclear (28S) marker. We then used this topology to constrain a time-calibrated mtDNA phylogeny, for subsequent biogeographical analyses in BioGeoBEARS of over 100 originally sampled Cyrtognatha individuals, using models with and without a founder event parameter. Our results suggest a radiation of Caribbean Cyrtognatha, containing 11 to 14 species that are exclusively single island endemics. Although biogeographic reconstructions cannot refute a vicariant origin of the Caribbean clade, possibly an artifact of sparse outgroup availability, they indicate timing of colonization that is much too recent for GAARlandia to have played a role. Instead, an overwater colonization to the Caribbean in mid-Miocene better explains the data. From Hispaniola, Cyrtognatha subsequently dispersed to, and diversified on, the other islands of the Greater, and Lesser Antilles. Within the constraints of our island system and data, a model that omits the founder event parameter from biogeographic analysis is less suitable than the equivalent model with a founder event.
岛屿系统为检验与基因流和扩散受限生物多样性相关的进化假说提供了极好的场所。在这里，我们专注于加勒比地区的一种圆蛛属 Cyrtognatha（管巢蛛科），旨在重建其进化历史，研究其在群岛中的生物地理历史，并估计加勒比地区的殖民化时间和路线。具体来说，我们测试 Cyrtognatha 生物地理历史是否与古老的地理隔离情景（GAARlandia 陆桥假说）或水上扩散一致。我们基于一个线粒体（COI）和一个核（28S）标记构建了一个种级系统发育树。然后，我们使用这个拓扑结构来约束一个时间校准的 mtDNA 系统发育树，以便在随后的生物地理分析中，使用带有和不带有创始事件参数的模型，对超过 100 个原始采样的 Cyrtognatha 个体进行分析。我们的结果表明，加勒比海 Cyrtognatha 发生了辐射进化，包含 11 到 14 种，它们都是单一岛屿的特有种。尽管生物地理重建不能排除加勒比分支的地理隔离起源，可能是由于外群可用性稀疏的人为产物，但它们表明殖民化的时间太近，GAARlandia 无法发挥作用。相反，中中新世的水上殖民到加勒比地区更好地解释了数据。从海地岛开始，Cyrtognatha 随后扩散到大安的列斯群岛和小安的列斯群岛的其他岛屿，并在那里多样化。在我们的岛屿系统和数据的限制内，从生物地理分析中省略创始事件参数的模型不如具有创始事件参数的等效模型合适。
