Spatial distribution of genetic diversity in populations of Hagenia abyssinica (Bruce) J.F. Gmel from Ethiopia

Abstract

Genetic variation among 596 individuals from 22 natural and 3 planted populations of Hagenia abyssinica (Rosaceae) sampled from the montane forests of Ethiopia was investigated at amplified fragment length polymorphism (AFLP) loci. We observed 106 unequivocally scorable AFLP markers out of which 91.5 percent were polymorphic. Populations harbored varying genetic diversities (He = 0.139-0.362), and showed low but significant genetic differentiation among them (FST = 0.077). Significant differentiation was observed even though previous paleoecological studies indicated that Hagenia abyssinica recolonized Ethiopia only after the Last Glacial Maximum, and our earlier analyses of maternally inherited chloroplast DNA revealed low mixing of recolonizing lineages through seeds and rare long distance seed dispersal. Genetic diversity did not decrease along recolonization routes, confirming effective gene flow, most likely through pollen, among populations. The observed variation at putatively neutral AFLPs does not reflect clinal variation patterns. As expected, population differentiation is lower at anonymous, mostly biparentally inherited, AFLPs than at maternally inherited chloroplast haplotypes. Despite presumably efficient seed and pollen dispersal of H. abyssinica by wind, a significant non-random fine-scale spatial genetic structure was observed up to 80 m in some populations. Due to significant pair-wise differentiation observed between populations, as many populations as possible should be considered for conservation, tree improvement and forestation programs.