Genetic variation in Tertiary relics: The case of eastern-Mediterranean Abies (Pinaceae).

Matúš Hrivnák,Diana Krajmerová,Irina Tvauri,Hakan Şevik,İbrahim Turna,Şemsettin Kulaç,Dušan Gömöry,Ladislav Paule

doi:10.1002/ece3.3519

Abstract

The eastern‐Mediterranean Abies taxa, which include both widely distributed species and taxa with minuscule ranges, represent a good model to study the impacts of range size and fragmentation on the levels of genetic diversity and differentiation. To assess the patterns of genetic diversity and phylogenetic relationships among eastern‐Mediterranean Abies taxa, genetic variation was assessed by eight nuclear microsatellite loci in 52 populations of Abies taxa with a focus on those distributed in Turkey and the Caucasus. Both at the population and the taxon level, the subspecies or regional populations of Abies nordmanniana s.l. exhibited generally higher allelic richness, private allelic richness, and expected heterozygosity compared with Abies cilicica s.l. Results of both the structure analysis and distance‐based approaches showed a strong differentiation of the two A. cilicica subspecies from the rest as well as from each other, whereas the subspecies of A. nordmanniana were distinct but less differentiated. ABC simulations were run for a set of scenarios of phylogeny and past demographic changes. For A. ×olcayana, the simulation gave a poor support for the hypothesis of being a taxon resulting from a past hybridization, the same is true for Abies equi‐trojani: both they represent evolutionary branches of Abies bornmuelleriana.

Highlights

Even though theoretical population-genetic models predict that range fragmentation and small population size generally result in low intrapopulation diversity and high differentiation (Kimura & Crow, 1964), empirical data show that the extent of the erosion of gene diversity and the levels of genetic divergence depends from the degree of fragmentation related to gene flow rate, dispersal mechanisms, demographic structure, and other factors
The genus itself is supposed to have originated in northern Eurasia in the late Cretaceous (Xiang, Cao, & Zhou, 2007), but the divergence of the extant taxa occurred much later: the sections of the Mediterranean firs diverged in the Miocene (Aguirre-Planter et al, 2012), whereas diversification of species within the section Abies occurred in the late Pliocene and early Pleistocene (Liu, 1971)
We focused on taxa within A. nordmanniana s.l. and A. cilicica s.l

Summary

Introduction

Even though theoretical population-genetic models predict that range fragmentation and small population size generally result in low intrapopulation diversity and high differentiation (Kimura & Crow, 1964), empirical data show that the extent of the erosion of gene diversity and the levels of genetic divergence depends from the degree of fragmentation related to gene flow rate, dispersal mechanisms, demographic structure, and other factors (Bialozyt, Ziegenhagen, &Petit, 2006; Ellstrand & Elam, 1993; Young, Boyle, & Brown, 1996). Differentiation patterns indicate a strong fragmentation in some species: in spite of a range size comparable to the other studied Abies species and subspecies, A. cilicica subsp.

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