Biogeography and relationships of the Abies taxa from the mediterranean and central Europe regions as revealed by nuclear DNA markers and needle structural characters

Abstract

The firs (genus Abies, Pinaceae) species are a diverse and ecologically and economically important forest trees. In the Mediterranean and Central Europe, the genus Abies comprises twelve taxa with only partially resolved systematic statuses, and it has been classically divided into the sections Piceaster (fir-type `ancestral¿ group) and Abies (fir-type `modern¿ group). We expected that the simultaneous use of nuclear microsatellite (nSSR) markers and a set of morphological and anatomical needle characteristics would clarify the taxonomy and biogeographical history of the genus. Additionally, the level of genetic diversity for particular taxa was estimated. The highest level of genetic diversity was observed in the Balkans. The hypothesis of a decreasing level of diversity from east to west was confirmed.

According to our results, the `ancestral¿ section Piceaster is well distinguished from the `modern¿ section Abies. The differentiation of `modern¿ Abies indicated the separation of A. alba, A. nebrodensis, A. cephalonica and A. cilicica, supporting the species status of these taxa. However, admixture between populations and taxa was detected, possibly because of crossbreeding between firs and ancient hybridization events. Anatolian A. equi-trojani, A. bornmuelleriana and A. nordmanniana were closely related and exhibited the highest level of admixture within populations, possibly because of intensive past migrations and crossing, supporting their subspecies taxonomic status. Gene exchange was also detected for some populations of A. cilicica, which are currently spatially isolated from taxa of the A. nordmanniana group. The differentiation detected within A. cilicica supported its subdivision into subsp. cilicica and subsp. isaurica. The same processes are responsible for differences between populations of A. cilicica subsp. cilicica from the Taurus and Lebanon Mountains.