Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic Canarina canariensis (Campanulaceae)

Abstract

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.

Genetic structure of Micromeria (Lamiaceae) in Tenerife, the imprint of geological history and hybridization on within‐island diversification

“…As in M. varia , the divergence between Teno and Anaga populations has been observed in at least two other plant species, Hypericum canariense (Clusiaceae; Dlugosch and Parker 2007) and Canarina canariensis (Campanulaceae, Mairal et al. 2015), and also in studies of mitochondrial haplotype diversity in several animal groups (e.g., Gübitz et al. 2000; Brown et al.…”

“…The floristic differences between the paleo‐island regions might have been further intensified by additional volcanic activity and catastrophic landslide events that might have reisolated parts of the island thus disconnecting existing populations (i.e., Mairal et al. 2015; Otto et al. 2016).…”

“…2014; Mairal et al. 2015). It had been postulated that this high divergence and patterns of genetic structure are not only explained by the geomorphological history such as secondary contact and reisolation by landslides and lava streams.…”

“…2006; Mairal et al. 2015). Codominant markers are the method of choice to investigate genetic structure, gene flow and differentiation between populations because they allow determining the heterozygote state at one locus.…”

Historical volcanism and within-island genetic divergence in the Tenerife skink (Chalcides viridanus)

“…While several insular regions offer good examples of within-island diversity, including arthropods on Hawaii, reviewed by Roderick and Gillespie (1998), Anole lizards in the Caribbean, e.g., Malhotra and Thorpe (2000) and giant tortoises from the Galápagos (Ciofi et al, 2006), the Canary Island archipelago has become a key area for these studies. Research has addressed quite a broad range of taxonomic groups (Rees et al, 2001;Moya et al, 2004;Macías-Hernández et al, 2013;Mairal et al, 2015), including several lizards (Thorpe & Baez, 1987;Thorpe et al, 1996;Gübitz et al, 2000;Bloor et al, 2008;.…”