Genetic Structure and Diversity of the Endangered Fir Tree of Lebanon (Abies cilicica Carr.): Implications for Conservation

Abstract

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.

Effect of geographic range discontinuity on species differentiation—East-Mediterranean Abies cilicica: a case study

“…The increasing of AR, H E , and F IS ( Supplementary Fig. 1) with latitude, noted in our study reflects the lower genetic diversity noted in the Lebanese populations compared with Table 1) the Turkish stands, which agrees with the results obtained recently by Awad et al (2014). According to those authors, fragmentation has negatively affected the level of genetic diversity in populations of Cilician fir from Lebanon.…”

“…This study is one of the first attempts to describe diversity and differentiation of endangered East Mediterranean A. cilicica within the species' natural range and thus importantly supplements a recent study by Awad et al (2014), which was a regional analysis focused on remnant populations of A. cilicica occurring in Lebanon. Results of our investigations provide information regarding the influence of the structure of the geographic range of the species on the genetic composition of the species which may have practical importance.…”

“…Large deforestations in Lebanon began in ancient times when Lebanese forests supplied timber to Egypt (Talhouk et al 2001). More recently, Cilician fir forests became highly fragmented in Lebanon due to the logging that occurred during World Wars I and II and the expansion of agricultural activity, both of which have resulted in the degradation of the populations of most tree species in that region (Talhouk et al 2001;Fady et al 2008;Douaihy et al 2011;Awad et al 2014).…”

Population size, center–periphery, and seed dispersers’ effects on the genetic diversity and population structure of the Mediterranean relict shrub Cneorum tricoccon

“…According to hierarchical AMOVA, 57% of the variation was found among populations, and mean F ST value was 0.56, much higher than the average of F ST  = 0.24 for plant species with mixed breeding systems (Nybom, 2004). Concurrent with the strong population structure, we also found a pattern of IBD; that is, closer populations were genetically more similar than populations farther apart (see Awad et al., 2014; Eckstein et al., 2006). Spatial distribution of genetic variation in plants is the outcome of several factors such as mating system, gene flow, genetic drift, and natural selection (Petit & Hampe, 2006).…”

“…Relict species are generally expected to show low levels of genetic diversity and strong population structure (Awad, Fady, Khater, Roig, & Cheddadi, 2014; Bauert, Kalin, Baltisberger, & Edwards, 1998; Ge et al., 2005) because they are usually composed of small, geographically isolated populations (Dobrowski, 2011; Hampe & Petit, 2005). However, experimental evidence has not always supported this generalization (see Peakall, Ebert, Scott, Meagher, & Offord, 2003; Vanden‐Broeck et al., 2011).…”