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.