Hidalgo-Galiana Amparo, Sánchez-Fernández David, Bilton David T, Cieslak Alexandra, Ribera Ignacio
BMC Evol Biol. 2014 Sep 4;14:187. doi: 10.1186/s12862-014-0187-y.
Species thermal requirements are one of the principal determinants of their ecology and biogeography, although our understanding of the interplay between these factors is limited by the paucity of integrative empirical studies. Here we use empirically collected thermal tolerance data in combination with molecular phylogenetics/phylogeography and ecological niche modelling to study the evolution of a clade of three western Mediterranean diving beetles, the Agabus brunneus complex.
The preferred mitochondrial DNA topology recovered A. ramblae (North Africa, east Iberia and Balearic islands) as paraphyletic, with A. brunneus (widespread in the southwestern Mediterranean) and A. rufulus (Corsica and Sardinia) nested within it, with an estimated origin between 0.60-0.25 Ma. All three species were, however, recovered as monophyletic using nuclear DNA markers. A Bayesian skyline plot suggested demographic expansion in the clade at the onset of the last glacial cycle. The species thermal tolerances differ significantly, with A. brunneus able to tolerate lower temperatures than the other taxa. The climatic niche of the three species also differs, with A. ramblae occupying more arid and seasonal areas, with a higher minimum temperature in the coldest month. The estimated potential distribution for both A. brunneus and A. ramblae was most restricted in the last interglacial, becoming increasingly wider through the last glacial and the Holocene.
The A. brunneus complex diversified in the late Pleistocene, most likely in south Iberia after colonization from Morocco. Insular forms did not differentiate substantially in morphology or ecology, but A. brunneus evolved a wider tolerance to cold, which appeared to have facilitated its geographic expansion. Both A. brunneus and A. ramblae expanded their ranges during the last glacial, although they have not occupied areas beyond their LGM potential distribution except for isolated populations of A. brunneus in France and England. On the islands and possibly Tunisia secondary contact between A. brunneus and A. ramblae or A. rufulus has resulted in introgression. Our work highlights the complex dynamics of speciation and range expansions within southern areas during the last glacial cycle, and points to the often neglected role of North Africa as a source of European biodiversity.
物种的热需求是其生态学和生物地理学的主要决定因素之一，尽管我们对这些因素之间相互作用的理解因综合实证研究的匮乏而受到限制。在此，我们结合实证收集的热耐受性数据、分子系统发育学/系统地理学和生态位建模，来研究西地中海三种潜水甲虫（Agabus brunneus复合体）的一个分支的进化。
首选的线粒体DNA拓扑结构显示，A. ramblae（分布于北非、伊比利亚东部和巴利阿里群岛）是并系群，A. brunneus（广泛分布于地中海西南部）和A. rufulus（科西嘉岛和撒丁岛）嵌套其中，估计起源于0.60 - 0.25百万年前。然而，使用核DNA标记时，这三个物种均被恢复为单系群。贝叶斯天际线图表明，在上一个冰川周期开始时，该分支的种群数量出现了扩张。这三个物种的热耐受性差异显著，A. brunneus能够耐受比其他分类群更低的温度。这三个物种的气候生态位也有所不同，A. ramblae占据更干旱和季节性更强的区域，最冷月份的最低温度更高。在末次间冰期，A. brunneus和A. ramblae的估计潜在分布范围最受限，在末次冰期和全新世期间范围越来越广。
A. brunneus复合体在更新世晚期发生了分化，最有可能是在从摩洛哥殖民后在伊比利亚南部。岛屿形态在形态学或生态学上没有显著分化，但A. brunneus进化出了更广泛的耐寒性，这似乎促进了其地理扩张。A. brunneus和A. ramblae在末次冰期都扩大了它们的分布范围，尽管除了法国和英国的A. brunneus孤立种群外，它们尚未占据超出末次盛冰期潜在分布范围的区域。在岛屿上，可能在突尼斯，A. brunneus与A. ramblae或A. rufulus之间的二次接触导致了基因渗入。我们的研究突出了末次冰川周期内南部地区物种形成和范围扩张的复杂动态，并指出了北非作为欧洲生物多样性来源这一经常被忽视的作用。
