Data from: Paleo-islands as refugia and sources of genetic diversity within volcanic archipelagos: The case of the widespread endemic Canarina canariensis (Campanulaceae)

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within-island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo-islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra-island levels of genetic diversity larger than those between-islands. We argue that volcanic eruptions and landslides after the merging of the palaeo-islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo-islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.

海洋屏障介导的地理隔离与气候稳定性，历来被视作驱动火山群岛内物种分化的核心因素之一。然而，目前鲜有研究关注灾难性火山事件在地质时间尺度上对岛内分化模式的影响。本研究采用叶绿体（cpDNA单倍型）与核基因组（扩增片段长度多态性，AFLPs）数据，对加那利风铃草（*Canarina canariensis*）——一种与加那利群岛特有月桂林密切关联的标志性植物类群——的遗传变异模式进行了探究。研究发现，该类群存在显著的地理种群结构：约0.8百万年前发生的首次分化以特内里费岛为核心轴，将加那利群岛的种群划分为东部与西部两个支系。遗传多样性最高的区域为地质环境稳定的阿纳加、特诺与孔德岩古岛；通过贝叶斯系统地理聚类方法推断，这些区域亦是向特内里费岛内其他受干扰区域或邻近岛屿传播迁移等位基因的祖先起源地。相较而言，海洋屏障对遗传变异结构的塑造作用相对有限，岛内遗传多样性水平显著高于岛间水平。我们认为，3.5百万年前古岛合并后发生的火山喷发与山体滑坡，是塑造特内里费岛内遗传分化边界的关键因素；古岛不仅作为抵御灭绝的避难所，同时亦是群岛内其他区域遗传多样性的起源与传播源。