Data from: Islands within an island: Population genetic structure of the endemic Sardinian newt, Euproctus platycephalus

The identification of historic and contemporary barriers to dispersal is central to the conservation of endangered amphibians, but may be hindered by their complex life history and elusive nature. The complementary information generated by mitochondrial (mtDNA) and microsatellite markers generates a valuable tool in elucidating population structure and the impact of habitat fragmentation. We applied this approach to the study of an endangered montane newt, Euproctus platycephalus. Endemic to the Mediterranean island of Sardinia, it is threatened by anthropogenic activity, disease, and climate change. We have demonstrated a clear hierarchy of structure across genetically divergent and spatially distinct subpopulations. Divergence between three main mountain regions dominated genetic partitioning with both markers. Mitochondrial phylogeography revealed a deep division dating to ca. 1 million years ago (Mya), isolating the northern region, and further differentiation between the central and southern regions ca. 0.5 Mya, suggesting an association with Pleistocene severe glacial oscillations. Our findings are consistent with a model of southward range expansion during glacial periods, with postglacial range retraction to montane habitat and subsequent genetic isolation. Microsatellite markers revealed further strong population structure, demonstrating significant divergence within the central region, and partial differentiation within the south. The northern population showed reduced genetic diversity. Discordance between mitochondrial and microsatellite markers at this scale indicated a further complexity of population structure, in keeping with male-biased dispersal and female philopatry. Our study underscores the need to elucidate cryptic population structure in the ecology and conservation strategies for endangered island-restricted amphibians, especially in the context of disease and climate change.

明确历史与当代扩散障碍是濒危两栖动物保护的核心要务，但这类动物复杂的生活史与隐匿特性往往会阻碍相关研究的推进。线粒体DNA（mitochondrial DNA, mtDNA）与微卫星标记（microsatellite markers）所产生的互补信息，为阐明种群结构与生境破碎化的影响提供了宝贵的研究手段。我们将该研究方法应用于一种濒危山地蝾螈——扁头真螈（Euproctus platycephalus）的相关研究中。该物种为地中海撒丁岛特有种，目前正受到人类活动、疫病以及气候变化的威胁。研究结果显示，在遗传分化显著且空间分隔的亚种群间，存在清晰的种群结构层级。两种标记均表明，三大山地种群间的分化主导了整体的遗传结构分区。线粒体系统地理学（mitochondrial phylogeography）分析揭示了一次可追溯至约100万年前（Mya）的深度分化事件，该事件将北部种群完全隔离；同时还发现中部与南部种群在约50万年前（Mya）进一步产生分化，这一结果暗示其与更新世（Pleistocene）时期的剧烈冰期旋回（glacial oscillations）存在关联。我们的研究结果与‘冰期时期种群向南方扩张，冰期结束后种群退缩至山地生境并随之产生遗传隔离’的模型相符。微卫星标记则进一步揭示了更为显著的种群结构：中部种群内部存在显著分化，南部种群内部则存在部分分化。北部种群的遗传多样性水平有所降低。在此尺度下，线粒体DNA与微卫星标记的结果不一致，这表明种群结构存在更为复杂的特征，这与‘雄性偏向扩散（male-biased dispersal）、雌性恋巢（female philopatry）’的模式相符。本研究强调，针对局限于岛屿生境的濒危两栖动物，阐明其隐蔽的种群结构，对于其生态学研究与保护策略制定至关重要，在疫病与气候变化的背景下这一点尤为突出。