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

We investigated the phylogeography and speciation of Drilus 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 (cox1–3′ and cox1–5′ 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 Drilus species from the Peloponnese, the Ionian islands and Crete did not form a monophylum. Drilus sp. E from the Peloponnese and Zakynthos was sister to D. mauritanicus Lucas from Spain in most cases. The remaining Greek Drilus 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 Drilus 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 Drilus 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 Drilus species in Crete (seven species in total, since the DNA sequences were not available for D. creticus Pic); however, we formally identified and (re)described only four which can be morphologically defined: D. creticus, D. longulus Kiesenwetter, D. horasfakionus sp. nov. and D. baenai 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地萤属（Drilus）的系统地理学与物种形成机制展开探究，重点聚焦爱琴海区域，尤以克里特岛为核心研究对象。研究共对12个物种的细胞色素c氧化酶亚基I基因（cytochrome c oxidase subunit I, cox1）的两段线粒体DNA（mtDNA）片段（cox1–3′与cox1–5′）进行测序，共获得1381个核苷酸位点。研究分别以最大似然准则（maximum likelihood criterion）与贝叶斯推断（Bayesian inference）对两段片段单独分析，并将其拼接为单一数据集开展联合分析。 结果显示，采自伯罗奔尼撒半岛、爱奥尼亚群岛以及克里特岛的地萤属物种并未形成单系群（monophylum）。在多数分析中，采自伯罗奔尼撒半岛与扎金索斯岛的未定种Drilus sp. E与西班牙命名的毛里塔尼亚地萤D. mauritanicus Lucas互为姊妹群。其余希腊本土地萤属物种在所有分析中均构成支持度较高的演化支，但克里特岛的地萤属物种似乎并非单系群。 利用BEAST软件估算物种分化时间后发现，西爱琴海地萤属系统地理学演化的关键时间节点包括：托尔顿期克里特岛与伯罗奔尼撒半岛的分离事件（12–9百万年前）、地中海盆地在墨西拿盐度危机期间的干涸过程（5.96–5.33百万年前），以及上新世与更新世期间克里特岛的反复碎片化事件。在地萤属类群中，本研究得到的碱基替换速率估算结果为每百万年2.75%的序列分化率，这一结果与既往相关研究高度吻合。 广义混合尤尔合并法（Generalized Mixed Yule Coalescent, GMYC）分析表明，克里特岛境内共存在6种地萤属物种；若将未获得DNA序列的克里特地萤D. creticus Pic计入，则总计7个物种。但本研究仅正式鉴定并重新描述了4个可通过形态学界定的物种：克里特地萤D. creticus、长形地萤D. longulus Kiesenwetter、horasfakionus新种D. horasfakionus sp. nov.以及baenai新种D. baenai sp. nov.。上述物种均为克里特岛及其周边小岛的特有种，文中对它们的鉴别特征进行了图解，并提供了该类群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，并对未来的研究方向提出了相关建议。相关数据可访问：http://zoobank.org/urn:lsid:zoobank.org:pub:F8DDBCC1-C2D1-48F7-BE99-55D9ED4C2234