University of L'Aquila, Department of Health, Life and Environmental Sciences, 67100 Coppito, L'Aquila, Italy; CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal.
CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal.
Mol Phylogenet Evol. 2021 Aug;161:107169. doi: 10.1016/j.ympev.2021.107169. Epub 2021 Mar 30.
Podarcis wall lizards are endemic to the Mediterranean Basin where they represent the predominant reptile group. Despite being extensively used as model organisms in evolutionary and ecological studies their phylogeny and historical biogeography are still incompletely resolved. Moreover, molecular clock calibrations used in wall lizard phylogeography are based on the assumption of vicariant speciation triggered by the abrupt Mediterranean Sea level rise at the end of the Messinian salinity crisis (MSC). However, the validity of this biogeographic calibration remains untested. In this study we inferred a robust time tree based on multilocus data and fossil calibrations using both gene concatenation and species-tree approaches and including models with gene-flow. We found five deeply divergent, geographically coherent, and well-supported clades comprising species from i) Iberian Peninsula and North Africa; ii) Western Mediterranean islands, iii) Sicilian and Maltese islands; and iv-v) Balkan region and Aegean islands. The mitochondrial tree shows some inconsistencies with the species tree that warrant future investigation. Diversification of main clades is estimated in a short time frame during the Middle Miocene and might have been associated with a period of global climate cooling with the establishment of a marked climatic zonation in Europe. Cladogenetic events within the main clades are scattered throughout the time tree, from the Late Miocene to the Early Pleistocene, suggesting that speciation events in wall lizards reflect a complex interplay between regional topography, climate and geological history rather than a shared major climatic or paleogeographic event. Our absolute time estimates, as well as a relative dating approach, demonstrate that the assumption of a causal link between sea-level rise at the end of the MSC and the diversification of many island endemics is not justified. This study reinforces the notion that multiple dispersal and vicariant events, at different time frames, are required to explain current allopatric distributions and to account for the historical assembly of Mediterranean biota, and cautions against the use of biogeographic calibrations based on the assumption of vicariance.
壁蜥是地中海盆地特有的蜥蜴，是该地区主要的爬行动物群体。尽管它们被广泛用作进化和生态学研究的模式生物，但它们的系统发育和历史生物地理学仍然没有得到完全解决。此外，壁蜥系统地理学中使用的分子钟校准是基于由米西尼盐度危机（MSC）末期地中海海平面突然上升引发的地理隔离物种形成的假设。然而，这种生物地理学校准的有效性尚未得到检验。在这项研究中，我们使用基因串联和种系树方法以及包括基因流模型的方法，基于多基因数据和化石校准，推断出一个稳健的时间树。我们发现了五个深度分歧、地理上一致且得到很好支持的分支，包括来自 i）伊比利亚半岛和北非；ii）西地中海岛屿；iii）西西里岛和马耳他岛；以及 iv-v）巴尔干地区和爱琴海岛屿的物种。线粒体树与种系树存在一些不一致之处，这需要进一步研究。主要分支的多样化是在中中新世的短时间内估计的，可能与全球气候变冷有关，在欧洲建立了明显的气候分带。主要分支内的分支事件散布在时间树上，从上新世晚期到更新世早期，这表明壁蜥的物种形成事件反映了区域地形、气候和地质历史之间的复杂相互作用，而不是共同的主要气候或古地理事件。我们的绝对时间估计以及相对约会方法表明，将 MSC 末期海平面上升与许多岛屿特有物种的多样化之间建立因果关系的假设是没有根据的。这项研究加强了这样一种观点，即需要多次扩散和地理隔离事件，在不同的时间框架内，以解释当前的异域分布，并解释地中海生物群的历史组装，同时警告不要使用基于地理隔离假设的生物地理学校准。
