Colonization history of the Canary Islands endemic Lavatera acerifolia, (Malvaceae) unveiled with genotyping‐by‐sequencing data and niche modelling

Abstract

Aim Differentiation of island lineages from mainland relatives and radiation after initial colonization are two important processes generating island diversity. Both of these processes are influenced by colonization dynamics and contemporary connections between island species and their source populations. The classic island progression rule model, that is dispersal from mainland to older islands and subsequently to younger islands, can be considered a null hypothesis, particularly for islands that are geographically aligned perpendicular to the mainland coast with ages inversely proportional to distance from the mainland. Alterations to this pattern have been reported, particularly in archipelagos that are geographically closely adjacent to mainland source populations. Here we aim to integrate genomic and environmental niche data to infer the colonization history of a Canary endemic species and to understand its current diversity patterns. Location Canary Islands. Taxon Lavatera acerifolia (Malvaceae). Methods We used high‐throughput genotyping‐by‐sequencing (GBS) combined with species distribution modelling (SDM) projected onto past conditions. Genetic structure (clustering methods), relatedness (coalescent and ML trees), nucleotide diversity and differentiation (population genetics) were assessed based on SNPs obtained from three alternative bioinformatics pipelines. The influence of environmental variables over time was assessed with a generalized linear model in which the response variable was amount of heterozygous sites per individual. Results Four genetic groups were identified arranged along a longitudinal gradient, and the earliest diverging coincides with the older, and easternmost, islands (Lanzarote and Fuerteventura). Genetic diversity is reduced in the westernmost islands, which are more distant from the mainland, host few populations and yet apparently offer more suitable habitats. Main conclusions The inferred colonization scenario generally fits the progression rule model, but suggests a more complex pattern for the central islands. For the westernmost islands, the contrast between high availability of suitable habitats and reduced genetic diversity and number of populations suggests a colonization front moving at a slow pace, rather than local extinctions, as an explanation for the scarcity of populations in those islands. Historical projections of SDM lend support to this interpretation.

Evolution and conservation genetics of an insular hemiparasitic plant lineage at the limit of survival: the case of Thesium sect. Kunkeliella in the Canary Islands

“…The lowest values were found for T. palmense. This low genetic diversity in the youngest island (2 my) is a common pattern and has been detected previously in Phoenix canariensis (Saro et al, 2015) and Lavatera acerifolia (Villa-Machío et al, 2020). However, it is remarkable that we found heterozygosity excess in all populations because it is uncommon in restricted and endangered taxa.…”

The Radiation of Darwin’s Giant Daisies in the Galápagos Islands

“…In any case, lack of progression patterns in extant lineages does not preclude an occurrence of progression patterns in past lineages that has been erased by extinction and turnover. A growing number of studies of plant and animal lineages support the progression rule in several archipelagos (Hawaii, Canary Islands, and Gala ´pagos) [14,15,17,35,36], including plant radiations, such as Hawaiian silverswords [4]. Interestingly, several animal lineages follow the rule in the Gala…”

Phylogeography at the crossroad: Pleistocene range expansion throughout the Mediterranean and back‐colonization from the Canary Islands in the legume Bituminaria bituminosa

“…The distribution of genetic diversity across the archipelago suggested that the north massif on the island of Lanzarote (Famara), with relatively high levels of haplotype and nuclear diversity (Table S7), may have acted as a refuge area for the CAN1 sublineage (see Villa‐Machío et al, 2020 for a similar interpretation). The CAN2 sublineage, in contrast, typically displayed smaller levels of within‐population genetic diversity, particularly on the island of Fuerteventura.…”