Karanovic Ivana, Sitnikova Tatiana Ya
Department of Life Science College of Natural Science Hanyang University Seoul South Korea.
Institute for Marine and Antarctic Studies University of Tasmania Hobart Tas Australia.
Ecol Evol. 2017 Aug 1;7(17):7091-7103. doi: 10.1002/ece3.3159. eCollection 2017 Sep.
With 104 endemic species family Candonidae is one of the most diverse crustacean groups in Lake Baikal, yet their phylogenetic relationships and position in the family have not been addressed so far. Here, we study the phylogenetic position of Baikal candonids within the family and their evolutionary history using molecular markers for the first time since their original description. We choose 10 Baikal and 28 species from around the world, and three ribosomal RNA-s (18S, 28S, and 16S), and analyze individual and concatenated datasets using Bayesian Inference in MrBayes and BEAST. For molecular divergence time estimates, four fossil records are used to calibrate the root and three internal nodes. The 28S dataset is tested under the strict molecular clock, while for other data we use relaxed clocks. Resulting trees show incongruence between molecular and fossil divergence time estimates, with the former suggesting older ages. Strict molecular clock analysis results in narrower node age confidence intervals and younger time estimates than other analysis. All trees support at least two candonid lineages in Baikal, with two independent colonization events, and 28S suggests a major radiation between 12 and 5 Mya. This divergence time estimate mostly agrees with another, unrelated, ostracod group in the lake and other lake animals as well. Baikal candonid clades show a close phylogenetic relationship with Palearctic lineages, but their deep divergence is indicative of separate genera. Results also suggest a monophyly of tribes that today live exclusively in subterranean waters, and we offer several hypotheses of their evolutionary history.
在贝加尔湖，坎东科有104个特有物种，是甲壳类动物中最多样化的类群之一，但它们的系统发育关系以及在该科中的地位至今尚未得到研究。在此，自贝加尔湖坎东科物种最初被描述以来，我们首次使用分子标记研究其在该科中的系统发育位置及其进化历史。我们选取了10种贝加尔湖物种和28种来自世界各地的物种，以及三种核糖体RNA（18S、28S和16S），并使用MrBayes和BEAST中的贝叶斯推理分析单个数据集和串联数据集。为了估计分子分歧时间，我们使用了四个化石记录来校准根部和三个内部节点。28S数据集在严格分子钟下进行测试，而其他数据则使用宽松分子钟。所得树状图显示分子分歧时间估计与化石分歧时间估计不一致，前者表明时间更久远。严格分子钟分析得出的节点年龄置信区间比其他分析更窄，时间估计也更年轻。所有树状图都支持贝加尔湖至少有两个坎东科谱系，存在两次独立的定殖事件，并且28S表明在1200万至500万年前发生了一次主要的辐射分化。这种分歧时间估计与该湖中另一个不相关的介形纲动物类群以及其他湖泊动物的情况大多一致。贝加尔湖坎东科分支与古北区谱系显示出密切的系统发育关系，但其深度分歧表明它们分属不同的属。结果还表明，如今仅生活在地下水域的族类是单系的，我们提出了几个关于它们进化历史的假设。
