Detalle de: Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic C anarina canariensis ( C ampanulaceae)

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 (cp DNA haplotypes) and the nuclear ( AFLP s) genomes to examine the patterns of genetic variation in C anarina canariensis , an iconic plant species associated with the endemic laurel forest of the C anary I slands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has T enerife as its central axis and divides C anarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo‐islands’ of A naga, T eno and R oque del C onde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within T enerife or the nearby islands using a B ayesian 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 T enerife, with the palaeo‐islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.