Phylogeographic insights into Artemisia crithmifolia (Asteraceae) reveal several areas of the Iberian Atlantic coast as refugia for genetic diversity

Abstract

The study of fragmentation processes should be tackled using different approaches, in order to obtain solid and robust evidence that could help in identifying potential barriers and threats for species. In this study, we have evaluated the spatial fragmentation patterns in Artemisia crithmifolia (Asteraceae) along its current distribution along the Atlantic coastlines of Europe, from Portugal to the Netherlands and the UK. Niche modelling analyses considering current and past climatic conditions, combined with plastid markers, have been used to evaluate the disconnected distribution pattern of the species, genetic flow between populations and habitat suitability for present and past populations. Plastid markers showed very low variability, while suggesting that the westernmost populations from the Atlantic coast of the Iberian Peninsula are partially genetically isolated, due to the existence of a potential barrier for gene flow on the northern Spanish coast. However, niche models identify this area as a potential habitat for the species, even during the last glacial maximum (20,000 years ago). The combination of both techniques allows identification of potential refugia for the species, highlighting the most likely recolonisation routes and distribution patterns which resulted in the overall low levels of genetic diversity. Anthropogenic activities (urban sprawl, beach expansions, etc.) are most likely behind local extinctions, thus preventing the establishment and expansion of new populations.