Department of Biology and Biotechnology "Charles Darwin", Sapienza University of Rome, Viale dell'Università 32, 00186 Roma, Italy.
Department of Biology and Biotechnology "Charles Darwin", Sapienza University of Rome, Viale dell'Università 32, 00186 Roma, Italy.
Mol Phylogenet Evol. 2021 Oct;163:107243. doi: 10.1016/j.ympev.2021.107243. Epub 2021 Jul 3.
Marine rockpools are isolated patches of habitat in the supratidal environment (the so-called splash zone), at the transition between sea and land, found along the rocky shores worldwide and characterized by harsh conditions for life. Nonetheless, few specialized invertebrates successfully colonized this peculiar environment. Among them several members of the water beetles Ochthebius Leach, 1815, subgenus Cobalius Rey (1886), which are found almost exclusively in supratidal and upper-most intertidal marine rockpools from the eastern Atlantic Ocean (Cape Verde, Canary Islands and Morocco, Madeira, Azores) throughout the whole Mediterranean basin. The subgenus Cobalius before 2020 was considered to include ten valid species, based on morphological differences. In late 2020, four additional new species were described. However, recent molecular phylogenetic studies have uncovered further cryptic diversity suggesting the presence of multiple undetected species within this group, highlighting that the species boundaries remain unclear and systematics and taxonomy are in need of revision. In this study we provide a molecular phylogeny based on DNA sequence data from mitochondrial and nuclear genes obtained from ten described species belonging to the subgenus Cobalius, and extensive taxon sampling, in order to better understand the phylogenetic relationships within this genus and to infer the biogeographic processes behind its diversification. We also used a molecular clock to define a time window for diversification of distinct clades within the subgenus, and explore aspects of its evolutionary history. Finally, we used three species delimitation methods (PTP, GMYC and ABGD) to clarify taxonomy and validate species boundaries. Our phylogenetic and biogeographic results identified sixteen independent lineages grouped in four main clades and the possible origin of Cobalius was estimated to be in the Early Miocene (~22 Mya) in W Mediterranean area. Moreover, species delimitation methods suggest there are between 16 and 24 putative species, most of them diverged during the Late Miocene, Pliocene and Pleistocene (6.0-0.11 Mya).
海洋岩礁池是潮间带环境（所谓的飞溅区）中的孤立栖息地斑块，位于海洋和陆地之间的过渡地带，分布在全球的多岩石海岸上，其特点是生命条件恶劣。尽管如此，仍有少数特化的无脊椎动物成功地在这个特殊的环境中殖民。其中，几种水生甲虫 Ochthebius Leach, 1815，亚属 Cobalius Rey（1886），几乎只存在于东大西洋（佛得角、加那利群岛和摩洛哥、马德拉群岛、亚速尔群岛）的潮间带和最高潮间带海洋岩礁池中，遍布整个地中海盆地。2020 年之前，基于形态差异，亚属 Cobalius 被认为包括十个有效物种。2020 年底，又描述了四个新物种。然而，最近的分子系统发育研究揭示了更多的隐种多样性，表明该组内存在多个未被发现的物种，这突显了物种界限仍不清楚，系统学和分类学需要修订。在这项研究中，我们提供了一个基于来自亚属 Cobalius 十个描述物种的线粒体和核基因 DNA 序列数据的分子系统发育，以及广泛的分类群采样，以便更好地了解该属内的系统发育关系，并推断其多样化背后的生物地理过程。我们还使用分子钟来定义亚属内不同分支的多样化时间窗口，并探索其进化历史的各个方面。最后，我们使用了三种物种界定方法（PTP、GMYC 和 ABGD）来阐明分类学和验证物种界限。我们的系统发育和生物地理结果确定了 16 个独立的谱系，分为四个主要分支，Cobalius 的可能起源被估计在早中新世（约 2200 万年前）的西地中海地区。此外，物种界定方法表明存在 16 到 24 个可能的物种，其中大多数在晚中新世、上新世和更新世（600 万至 110 万年前）分化。
