Understanding the legacy of widespread population translocations on the post-glacial genetic 2 structure of the European beech, Fagus sylvatica L.

Abstract

Aim  Human impacts have shaped species ranges throughout the Holocene. The putative native range of beech, Fagus sylvatica, in Britain was obscured by its late post-glacial arrival and subsequent extensive management. We sought to differentiate the interacting effects of post-glacial colonization and anthropic impacts on the current genetic structure and diversity of beech by contrasting phylogeographic signals from putatively natural and translocated populations.  Location  Samples were obtained from 42 sites throughout Great Britain.  Methods  Chloroplast and nuclear microsatellite marker data were interpreted alongside palynological, historical and anecdotal evidence. Genetic structure was analysed using individual-based Bayesian assignment methods and colonization history was analysed using an approximate Bayesian computation framework.  Results  Phylogeographic patterns suggested contemporary forests originated from putative native south-eastern populations. High haplotypic diversity was found near the entry point of beech into Britain. Cryptic signals of isolation-by-distance persisted in the putative native range, together with higher levels of gene diversity in nuclear markers. Weak regional nuclear genetic structure suggested high levels of contemporary gene flow throughout the country.  Main conclusions  Genetic patterns driven by natural colonization persist despite widespread anthropic intervention. Forests in northerly regions were established from forests in the putative native range, diminishing the credibility of any present boundary between the native and non-native range of beech in Britain.