The origin and diversity of <i>Drilus</i> Olivier, 1790 (Elateridae: Agrypninae: Drilini) in Crete based on mitochondrial phylogeny

We investigated the phylogeography and speciation of <i>Drilus</i> in the Mediterranean, with focus on the Aegean and especially Crete. Altogether 12 species were sequenced for two fragments of the cytochrome c oxidase subunit I gene (<i>cox1–3′</i> and <i>cox1–5′</i> mtDNA) and provided 1381 nucleotides. Both fragments were analysed under the maximum likelihood criterion and Bayesian inference separately and concatenated as a single dataset. The <i>Drilus</i> species from the Peloponnese, the Ionian islands and Crete did not form a monophylum. <i>Drilus</i> sp. E from the Peloponnese and Zakynthos was sister to <i>D. mauritanicus</i> Lucas from Spain in most cases. The remaining Greek <i>Drilus</i> species formed a robustly supported clade in all analyses; however, the species from Crete do not seem to be monophyletic. Estimating species divergences using BEAST, we found out that the key dates in the west Aegean <i>Drilus</i> phylogeography appeared to be the Tortonian Crete–Peloponnese separation (12–9 Mya), the desiccation of the Mediterranean basin during the Messinian Salinity Crisis (5.96–5.33 Mya), and the repeated fragmentation of Crete during the Pliocene and Pleistocene. Within the <i>Drilus</i> lineages, we obtained a substitution rate estimate of 2.75% divergence per million years, which is in excellent agreement with previous studies. A Generalized Mixed Yule Coalescent (GMYC) analysis suggested the presence of six <i>Drilus</i> species in Crete (seven species in total, since the DNA sequences were not available for <i>D</i>. <i>creticus</i> Pic); however, we formally identified and (re)described only four which can be morphologically defined: <i>D</i>. <i>creticus</i>, <i>D. longulus</i> Kiesenwetter, <i>D. horasfakionus</i> sp. nov. and <i>D. baenai</i> sp. nov. These species are endemic to Crete and surrounding islets. Their diagnostic characters are illustrated and an identification key to males of these species is provided. The intraspecific variability, distribution and ecology of all species are discussed and suggestions for further research are given.http://zoobank.org/urn:lsid:zoobank.org:pub:F8DDBCC1-C2D1-48F7-BE99-55D9ED4C2234

本研究针对地中海地区的<i>Drilus</i>属开展系统地理学与物种形成机制研究，重点聚焦爱琴海区域，尤以克里特岛为核心。研究共对12个<i>Drilus</i>属物种的细胞色素c氧化酶亚基I基因（cytochrome c oxidase subunit I，简称cox1）的两段线粒体DNA（mtDNA）片段（<i>cox1–3′</i>与<i>cox1–5′</i>）进行扩增测序，共获得总长1381个核苷酸的序列。研究分别采用最大似然法与贝叶斯推断法对两段片段单独进行系统发育分析，并将其拼接为单数据集开展联合分析。采自伯罗奔尼撒半岛、爱奥尼亚群岛与克里特岛的<i>Drilus</i>属物种并未形成单系类群。在多数分析框架下，采自伯罗奔尼撒半岛与扎金索斯岛的<i>Drilus</i> sp. E类群与西班牙产的<i>D. mauritanicus</i> Lucas构成姐妹群关系。其余希腊本土的<i>Drilus</i>属物种在所有分析中均构成支持度较高的演化支；但克里特岛的<i>Drilus</i>属物种并未呈现单系起源特征。利用BEAST软件估算物种分化时间后，本研究发现西爱琴海<i>Drilus</i>属系统地理学演化的关键时间节点包括：中新世托尔通期克里特岛与伯罗奔尼撒半岛的分离事件（12–9百万年前，Mya）、地中海盆地在墨西拿盐度危机期间的干涸事件（5.96–5.33百万年前），以及上新世与更新世期间克里特岛的多次碎片化过程。在<i>Drilus</i>属演化支中，本研究得到的碱基替换速率估算结果为每百万年2.75%的序列分歧度，这与此前相关研究结果高度吻合。广义混合尤尔-合并模型（Generalized Mixed Yule Coalescent，简称GMYC）分析结果表明，克里特岛共存在6个<i>Drilus</i>属物种（若计入未获得DNA序列的<i>D. creticus</i> Pic，则全球总计7个物种）；但本研究仅正式鉴定并（重新）描述了4个可通过形态学特征界定的物种：<i>D. creticus</i>、<i>D. longulus</i> Kiesenwetter、<i>D. horasfakionus</i> 新种（sp. nov.）与<i>D. baenai</i> 新种（sp. nov.）。上述4个物种均为克里特岛及其周边小岛的特有种。本研究对各物种的鉴别特征进行了图示，并提供了针对这些物种雄性个体的分类检索表。本研究还讨论了所有物种的种内变异、分布范围与生态习性，并提出了后续研究方向与建议。本研究的官方注册信息可通过以下链接获取：http://zoobank.org/urn:lsid:zoobank.org:pub:F8DDBCC1-C2D1-48F7-BE99-55D9ED4C2234