Irish oaks : characterising their biodiversity through molecular and morphological analysis

Abstract

Oak populations were sampled across Ireland to investigate the biodiversity of Irish oak. Two species are recognized as being native; Quercus petraea (Matt.) Liebl. and Q. robur L. Oak leaves were analysed for morphological variables and DNA was extracted for molecular analysis. The molecular analysis consisted of a chloroplast marker (cpDNA haplotype) and two nuclear- dominated markers (AFLP and SSR). Oak does form morphological species in Ireland, but analysis of the molecular markers shows the species lack distinction at the sub-microscopic level. The biological species concept is difficult to apply to Irish oak. While the morphological species can be distinguished, a level of 10 % hybridisation was estimated within Ireland based on morphological data. Very few (30 %) distinct species were recognised by the hybrid index method of morphological analysis. Quercus robur was, in general, more morphologically variable but also more distinct as putative hybrid and introgressed individuals grouped closer to Q. petraea individuals with the Neighbor-joining cluster analysis. There are a greater number of Q. petraea individuals across Ireland than Q. robur individuals and the species tend to occupy separate ecological niches. Populations are not homogenous, although most are dominated by one or other species.