Colonization history, phylogeography and conservation genetics of the gravely endangered tree species Hagenia abyssinica (Bruce) J. F. Gmel from Ethiopia

The monotypic tropical tree species Hagenia abyssinica (Rosaceae) is an anemogamous and anemochorous broad-leaved dioecious tree species native to Africa. Fossil pollen evidences suggest that it immigrated into Ethiopia from the south during the late Pleistocene. The chloroplast haplotypes identified in Hagenia are grouped into two lineages and demonstrated a strong pattern of congruence between their geographical distribution and genealogical relationships. Restricted gene flow through seeds, contiguous range expansion, mutation and rare long-distance dispersal shaped the genetic structure in the chloroplast genome of Hagenia. Populations showed moderate to high gene diversities and moderate but significant genetic differentiation at AFLP markers, reflecting high levels of post-colonization gene flow. Despite the dispersal of seed and pollen by wind, a significant fine-scale spatial genetic structure (SGS) was observed in some populations. A weighted-score population prioritization matrix (WS-PPM) that combines genetic, morphological and demographic criteria was developed and used for the first time to prioritize populations for conservation and domestication. Conservation and massive plantation programs should be launched to ensure the survival of the gravely endangered Kosso and to boost its economic and ecological values.