Population Structure, Genetic Diversity, and Evolutionary History of Kleinia neriifolia (Asteraceae) on the Canary Islands

Abstract

Kleinia neriifolia Haw. is an endemic species on the Canarian archipelago, this species is widespread in the coastal thicket of all the Canarian islands. In the present study, genetic diversity and population structure of K. neriifolia were investigated using chloroplast gene sequences and nuclear SSR (simple sequence repeat). The differentiation among island populations, the historical demography, and the underlying evolutionary scenarios of this species are further tested based on the genetic data. Chloroplast diversity reveals a strong genetic divergence between eastern islands (Gran Canaria, Fuerteventura, and Lanzarote) and western islands (EI Hierro, La Palma, La Gomera, Tenerife), this west–east genetic divergence may reflect a very beginning of speciation. The evolutionary scenario with highest posterior probabilities suggests Gran Canaria as oldest population with a westward colonization path to Tenerife, La Gomera, La Palma, and EI Hierro, and eastward dispersal path to Lanzarote through Fuerteventura. In the western islands, there is a slight decrease in the effective population size toward areas of recent colonization. However, in the eastern islands, the effective population size increase in Lanzarote relative to Gran Canaria and Fuerteventura. These results further our understanding of the evolution of widespread endemic plants within Canarian archipelago.

How repeatable is microevolution on islands? Patterns of dispersal and colonization-related plant traits in a phylogeographical context

“…Under an IBD model of differentiation, genetic drift is predicted to be pronounced in areas distant from source populations (Nistelberger et al, 2015). In our study, the higher occurrence of fixed haplotypes in populations on peripheral islands, in addition to lower levels of heterozygosity than those reported for central islands (García-Verdugo et al, 2015;Sun and Vargas-Mendoza, 2017), point towards genetic drift as a relevant evolutionary force on peripheral islands. Rare events of inter-island dispersal therefore allow successful colonization across the archipelago, but may also have set the stage for allopatric differentiation driven by random processes (Jordan and Snell, 2008).…”

“…In addition to similar habitat preferences and island distribution, both species produce diaspores with morphological traits typically related to wind dispersal: while K. neriifolia achenes are attached to a plumose pappus, seeds of P. laevigata are comose (Figure 1). Previous population-level studies have reported significant levels of population structure within these island taxa (García-Verdugo et al, 2015, 2017Sun and Vargas-Mendoza, 2017), which is suggestive of ongoing processes of within-species differentiation. Kleinia anteuphorbium and Periploca angustifolia are the sister mainland species of the two island taxa, and their populations are abundant in (and restricted to, in the former case) south-west Morocco (Halliday, 1986;Venter, 1997).…”

“…For Periploca, a broad-scale study on Macaronesian lineages identified the populations on the island of Gran Canaria as the oldest within the Canarian archipelago, whereas those on La Palma (at the western limit) and Lanzarote and Fuerteventura (at the eastern limit) were inferred as the youngest (García-Verdugo et al, 2017). A recent paper focusing on the population genetics of Kleinia island populations (Sun and Vargas-Mendoza, 2017) tested different scenarios of inter-island colonization applying a Bayesian approach with nuclear microsatellite data. Although the results varied substantially depending on the model selected, the authors chose as the most likely scenario a pattern of bidirectional colonization of westernmost and easternmost islands from Gran Canaria.…”

“…We hypothesize that factors related to stochastic colonization provide a more plausible explanation. For instance, as a likely consequence of recent island colonization by a limited number of colonists, Kleinia populations on El Hierro display significant levels of inbreeding (Sun and Vargas-Mendoza, 2017), a trait that has been linked to loss of dispersal potential in anemochorous plants (Mix et al, 2006). Alternatively, lack or scarcity of efficient pollinators on this island may have selected for shifts in mating system (selfing) and reduced dispersal (Cheptou, 2012).…”

Pleistocene extinctions as drivers of biogeographical patterns on the easternmost Canary Islands

“…The central area of Mahan probably served as a dispersal corridor between both areas during favourable conditions in the Pleistocene , but geographically intermediate populations went extinct, probably due to Quaternary climate fluctuations and, more recently, to human‐related pressures, including intense browsing by domestic herbivores. Such a biogeographical pattern has been supported by species displaying signatures of Quaternary population expansion on these islands (Juan, Ibrahim, Oromi, & Hewitt, ; Sun & Vargas‐Mendoza, ). This pattern ultimately reinforces the view of the north and south massifs of the ECI acting as efficient refugia, and underscores geographical isolation as a recent driver of speciation between eastern disjunct island populations.…”