Novel Post-Glacial Haplotype Evolution in Birch—A Case for Conserving Local Adaptation

Abstract

Despite constituting the western-most edge of the population distributions for several native European plants, Ireland has largely been left out of key Europe-wide phylogeographic studies. This is true for birch (Betula pubescens Ehrh. and Betula pendula Roth), for which the genetic diversity has yet to be mapped for Ireland. Here we used eight cpDNA markers (two Restriction Fragment Length Polymorphism (RFLP) and six Simple Sequence Repeat (SSR)) to map the genetic diversity of B. pubescens, B. pendula, and putative hybrid individuals sampled from 19 populations spread cross most of the island of Ireland. Within Ireland, 11 distinct haplotypes were detected, the most common of which (H1) was also detected in England, Scotland, France, and Norway. A moderate level of population structuring (GST = 0.282) was found across Ireland and the genetic diversity of its northern populations was twice that of its southern populations. This indicates that, unlike other native Irish trees, such as oak and alder, post-glacial recolonization by birch did not begin in the south (i.e., from Iberia). Rather, and in agreement with palynological data, birch most likely migrated in from eastern populations in Britain. Finally, we highlight Irish populations with comparatively unique genetic structure which may be included as part of European genetic conservation networks.

Molecular characterisation of Pinus sylvestris (L.) in Ireland at the western limit of the species distribution

“…Only one population (Derrybawn – Glendalough) harboured trees which appear to be of continental origin, although this was mixed. These results are the first to describe the genetic diversity of a native Irish conifer in a European context and complement recent descriptions of the same for several broadleaf species [ 47 , 82 , 119 , 120 ]. This forms part of an inventory of Ireland’s forest genetic resources [ 121 ], which is an important step in determining population selection for both in situ and ex situ forest conservation approaches [ 122 ].…”

“…More recent genetic evidence also suggests at least some post-LGM migration from Britain into Ireland for downy birch ( Betula pubescens Ehrh.) [ 47 ] and common ash ( Fraxinus excelsior L.) [ 82 ]. This corroborated the direction of travel which had previously been inferred from isochrone maps based on radiocarbon-dated pollen for both species [ 21 ].…”

“…The four Scottish genotypes came from a breeding programme and neither them nor the Norwegian samples were collected from discrete sampling populations. DNA was extracted as described in Belton et al [ 47 ].…”