Résumé
The threatened conifer Abies cilicica currently persists in Lebanon in
geographically isolated forest patches. The impact of demographic and
evolutionary processes on population genetic diversity and structure were
assessed using 10 nuclear microsatellite loci. All remnant 15 local
populations revealed a low genetic variation but a high recent effective
population size. FST-based measures of population genetic differentiation
revealed a low spatial genetic structure, but Bayesian analysis of
population structure identified a significant Northeast-Southwest
population structure. Populations showed significant but weak
isolation-by-distance, indicating non-equilibrium conditions between
dispersal and genetic drift. Bayesian assignment tests detected an
asymmetric Northeast-Southwest migration involving some long-distance
dispersal events. We suggest that the persistence and Northeast-Southwest
geographic structure of Abies cilicica in Lebanon is the result of at
least two demographic processes during its recent evolutionary history:
(1) recent migration to currently marginal populations and (2) local
persistence through altitudinal shifts along a mountainous topography.
These results might help us better understand the mechanisms involved in
the species response to expected climate change.