Higher genetic diversity in recolonized areas than in refugia of Alnus glutinosa triggered by continent‐wide lineage admixture

Abstract

Genetic admixture is supposed to be an important trigger of species expansions because it can create the potential for selection of genotypes suitable for new climatic conditions. Up until now, however, no continent-wide population genetic study has performed a detailed reconstruction of admixture events during natural species expansions. To fill this gap, we analysed the postglacial history of Alnus glutinosa, a keystone species of European swamp habitats, across its entire distribution range using two molecular markers, cpDNA and nuclear microsatellites. CpDNA revealed multiple southern refugia located in the Iberian, Apennine, Balkan and Anatolian Peninsulas, Corsica and North Africa. Analysis of microsatellites variation revealed three main directions of postglacial expansion: (i) from the northern part of the Iberian Peninsula to Western and Central Europe and subsequently to the British Isles, (ii) from the Apennine Peninsula to the Alps and (iii) from the eastern part of the Balkan Peninsula to the Carpathians followed by expansion towards the Northern European plains. This challenges the classical paradigm that most European populations originated from refugial areas in the Carpathians. It has been shown that colonizing lineages have met several times and formed secondary contact zones with unexpectedly high population genetic diversity in Central Europe and Scandinavia. On the contrary, limited genetic admixture in southern refugial areas of A. glutinosa renders rear-edge populations in the Mediterranean region more vulnerable to extinction due to climate change.

Genetic diversity and genetic structure of black alder (Alnus glutinosa [L.] Gaertn) in the Belgium-Luxembourg-France cross-border area

“…However, Belgium and northern France were represented by only six trees in their study. In contrast, Havrdová et al (2015), using another marker system of cpDNA, revealed the existence of 43 haplotypes on the European scale, of which only one covered the area of our study. Using the same marker system as King and Ferris (1998), we found the same two haplotypes, F and G, in the area concerned.…”

“…This model has recently been challenged by a continentwide population genetic study (Havrdová et al 2015), suggesting that multiple refugia served as sources for the postglacial colonization of Europe by A. glutinosa, central Europe being an area of genetic admixture between western and eastern lineages originating from the northern part of the Iberian Peninsula and the Carpathians, respectively. Using SSR markers, Lepais et al (2013) showed a strong distinctiveness of Moroccan populations of A. glutinosa in the rear-edge distribution margins of the species.…”

Panmixia and dispersal from the Mediterranean Basin to Macaronesian Islands of a macrolichen species

“…Several studies on different organisms (e.g. refs 31,41, 42, 43) have shown that peripheral populations that are migration-dependent may exhibit lower diversity and smaller population sizes than core populations. Therefore, migration-dependent peripheral populations have been shown to be more vulnerable to the detrimental effects of genetic drift (e.g.…”

Species Delimitation and Lineage Separation History of a Species Complex of Aspens in China

“…STRUCTURE simulations were run, using the admixture model separately with each of correlated allele frequencies and independent allele frequencies (Miao et al, 2013; Havrdová et al, 2015; Zeng et al, 2015), under K -values from 1 to 8. Each simulation had 20 independent repeats, and comprised a burn-in of 500,000 steps followed by 1,500,000 MCMC (Monte Carlo Markov Chain) steps.…”