School of Biological Sciences, University of East Anglia, Norwich, NR4 7J, UK.
BMC Evol Biol. 2011 Jun 17;11:170. doi: 10.1186/1471-2148-11-170.
The Iberian Peninsula is recognized as an important refugial area for species survival and diversification during the climatic cycles of the Quaternary. Recent phylogeographic studies have revealed Iberia as a complex of multiple refugia. However, most of these studies have focused either on species with narrow distributions within the region or species groups that, although widely distributed, generally have a genetic structure that relates to pre-Quaternary cladogenetic events. In this study we undertake a detailed phylogeographic analysis of the lizard species, Lacerta lepida, whose distribution encompasses the entire Iberian Peninsula. We attempt to identify refugial areas, recolonization routes, zones of secondary contact and date demographic events within this species.
Results support the existence of 6 evolutionary lineages (phylogroups) with a strong association between genetic variation and geography, suggesting a history of allopatric divergence in different refugia. Diversification within phylogroups is concordant with the onset of the Pleistocene climatic oscillations. The southern regions of several phylogroups show a high incidence of ancestral alleles in contrast with high incidence of recently derived alleles in northern regions. All phylogroups show signs of recent demographic and spatial expansions. We have further identified several zones of secondary contact, with divergent mitochondrial haplotypes occurring in narrow zones of sympatry.
The concordant patterns of spatial and demographic expansions detected within phylogroups, together with the high incidence of ancestral haplotypes in southern regions of several phylogroups, suggests a pattern of contraction of populations into southern refugia during adverse climatic conditions from which subsequent northern expansions occurred. This study supports the emergent pattern of multiple refugia within Iberia but adds to it by identifying a pattern of refugia coincident with the southern distribution limits of individual evolutionary lineages. These areas are important in terms of long-term species persistence and therefore important areas for conservation.
伊比利亚半岛被认为是第四纪气候循环中物种生存和多样化的重要避难所。最近的系统地理学研究表明，伊比利亚半岛是多个避难所的复合体。然而，大多数这些研究要么集中在该地区分布狭窄的物种上，要么集中在分布广泛但通常具有与第四纪前分支事件相关的遗传结构的物种群上。在这项研究中，我们对分布范围涵盖整个伊比利亚半岛的蜥蜴物种 Lacerta lepida 进行了详细的系统地理学分析。我们试图确定该物种的避难所区域、再殖民路线、次要接触区和人口动态事件的日期。
结果支持存在 6 个进化谱系（系统发育群），遗传变异与地理之间存在很强的关联，表明在不同避难所经历了异域分化的历史。谱系内的多样化与更新世气候振荡的开始相一致。与北部地区高频率的近期衍生等位基因相比，几个谱系的南部地区显示出高频率的祖先等位基因。所有的系统发育群都显示出近期人口和空间扩张的迹象。我们还确定了几个次要接触区，在这些区带有分歧的线粒体单倍型发生在狭窄的同域区。
谱系内检测到的空间和人口扩张的一致模式，以及几个谱系南部地区高频率的祖先单倍型，表明在不利的气候条件下，种群收缩到南部避难所的模式，随后发生了北部扩张。这项研究支持了伊比利亚半岛多个避难所的新兴模式，并通过确定与个别进化谱系南部分布极限一致的避难所模式对其进行了补充。这些地区对物种的长期生存具有重要意义，因此是保护的重要区域。
