Mizuyama Masaru, Masucci Giovanni D, Reimer James D
Molecular Invertebrate Systematics and Ecology Laboratory, Graduate School of Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
Molecular Invertebrate Systematics and Ecology Laboratory, Department of Marine Sciences, Chemistry and Biology, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
PeerJ. 2018 Jul 4;6:e5132. doi: 10.7717/peerj.5132. eCollection 2018.
Zoantharians are sessile marine invertebrates and colonial organisms possessing sexual and asexual reproductive ability. The zooxanthellate zoantharian genus is widely distributed in coral reef ecosystems. In the Ryukyu Archipelago, Japan, sympatric and are the dominant species of this genus in the intertidal zone. Previous phylogenetic analyses have shown that these two species are closely related, and additionally revealed a putative sympatric hybrid species (designated as sp. yoron). In this study, we attempted to delineate species boundaries and to clarify the relationships among these three groups plus another additional putative sympatric species (. aff. ) by multiple independent criteria. The morphology of these four lineages was clearly different; for example the number of tentacles was significantly different for each species group in all pairwise comparisons. From observations of gonadal development conducted in 2010 and 2011, sp. yoron and . aff. appear to be reproductively isolated from . In the phylogenetic tree resulting from maximum likelihood analyses of the ITS-rDNA sequence alignment, and . sp. yoron formed a very well supported monophyletic clade (NJ = 100%, ML = 95%, Bayes = 0.99). This study demonstrates that despite clear morphological and/or reproductive differences, and . sp. yoron are phylogenetically entangled and closely related to each other, as are and . aff. . Additionally, no single molecular marker was able to divide these four lineages into monophyletic clades by themselves, and a marker that has enough resolution to solve this molecular phylogenetic species complex is required. In summary, the morphological and reproductive results suggest these lineages are four separate species, and that incomplete genetic lineage sorting may prevent the accurate phylogenetic detection of distinct species with the DNA markers utilized in this study, demonstrating the value of morphological and reproductive data when examining closely related lineages.
群体海葵是固着生活的海洋无脊椎动物和具有有性及无性繁殖能力的群体生物。虫黄藻共生的群体海葵属广泛分布于珊瑚礁生态系统中。在日本琉球群岛，同域分布的[物种名称1]和[物种名称2]是该属在潮间带的优势物种。先前的系统发育分析表明这两个物种亲缘关系密切，此外还揭示了一个假定的同域杂交物种（命名为[物种名称3] sp. yoron）。在本研究中，我们试图通过多个独立标准来界定[物种名称1]、[物种名称2]和[物种名称3]这三个类群以及另一个假定的同域物种（[物种名称4]. aff. [物种名称5]）之间的物种界限，并阐明它们之间的关系。这四个谱系的形态明显不同；例如，在所有两两比较中，每个物种组的触手数量都有显著差异。通过对2010年和2011年性腺发育的观察，[物种名称3] sp. yoron和[物种名称4]. aff. [物种名称5]似乎与[物种名称1]存在生殖隔离。在对ITS - rDNA序列比对进行最大似然分析得到的系统发育树中，[物种名称1]和[物种名称3] sp. yoron形成了一个得到很好支持的单系类群（NJ = 100%，ML = 95%，贝叶斯 = 0.99）。本研究表明，尽管[物种名称1]和[物种名称3] sp. yoron在形态和/或生殖方面存在明显差异，但它们在系统发育上相互纠缠且亲缘关系密切，[物种名称2]和[物种名称4]. aff. [物种名称5]也是如此。此外，没有单一的分子标记能够单独将这四个谱系划分为单系类群，需要一个具有足够分辨率来解决这个分子系统发育物种复合体问题的标记。总之，形态和生殖结果表明这些谱系是四个独立的物种，并且不完全的遗传谱系分选可能会妨碍用本研究中使用的DNA标记准确地进行系统发育检测来区分不同物种，这证明了在研究亲缘关系密切的谱系时形态和生殖数据的价值。
