High genetic diversity and significant population structure in Cedrus brevifolia Henry, a narrow endemic Mediterranean tree from Cyprus

Abstract

Endemic island plant species with a narrow distribution are often, but not always, linked to low genetic variation within populations and a lack of differentiation among populations. Cedrus brevifolia is a narrow endemic island tree species of Cyprus. Its range is restricted to a single forest, divided into five neighbouring sites. This study, using biparentally inherited nuclear microsatellites and paternally inherited plastid (chloroplast) microsatellites, assessed the genetic variation of C. brevifolia within its sole population and the level of genetic differentiation among formed sites. The results from both markers showed high diversity (nuclear H T = 0.70; plastid H T = 0.93), strongly suggesting that the species did not experience severe bottleneck events or extensive genetic drift. Besides, the maintenance of a high genetic diversity in C. brevifolia may suggest that it originates from a widespread congener species. Significant genetic differentiation at nuclear (G ST = 0.052) and plastid (G ST = 0.119) markers was found among the formed sites. Remarkably, the relatively high genetic differentiation found at plastid markers was comparable to values observed in two widespread congener cedar species. The genetic differentiation probably occurred due to fragmentation of a previously uniform population. This would lead to the shaping of different genetic groups (Bayesian analysis) and to significant population substructure. Furthermore, significant values observed for both isolation by distance and large-scale spatial genetic structure could indicate ineffective gene flow among sites and the early geographical isolation of the more isolated sites from the core population.

Relationships among Cedrus libani, C. brevifolia and C. atlantica as revealed by the morphological and anatomical needle characters

“…When accepting this hypothesis, the Cypriote environmental conditions should influence the needle morphology, resulting in formation of different values of most of the characters (Tables 2, 3). The high level of genetic diversity detected within C. brevifolia can indicate the long-term presence of the species in the mountains of Cyprus (Bou Dagher-Kharrat et al 2007;Eliades et al 2011). The significant level of divergence among particular populations of the species is characteristic for the narrow endemics (e.g., Carrió et al 2010;Eliades et al 2011), and indicate their spatial isolation but also can be a signal of origin from a widespread ancestor (Eliades et al 2011).…”

“…The high level of genetic diversity detected within C. brevifolia can indicate the long-term presence of the species in the mountains of Cyprus (Bou Dagher-Kharrat et al 2007;Eliades et al 2011). The significant level of divergence among particular populations of the species is characteristic for the narrow endemics (e.g., Carrió et al 2010;Eliades et al 2011), and indicate their spatial isolation but also can be a signal of origin from a widespread ancestor (Eliades et al 2011). The historical events, which could allow for direct contact between populations of Cypriote and Anatolian cedars taking place during the Miocene Messinian Salt Crisis, when the level of the Mediterranean Sea subsided forming several land bridges between the Asiatic continent and Cyprus (Pons and Quézel 1985;Thompson 2005).…”

“…The historical events, which could allow for direct contact between populations of Cypriote and Anatolian cedars taking place during the Miocene Messinian Salt Crisis, when the level of the Mediterranean Sea subsided forming several land bridges between the Asiatic continent and Cyprus (Pons and Quézel 1985;Thompson 2005). The cedar seeds from the various regions of continent, transported during that time by animals were the source of the remnant C. brevifolia population on the Cyprus (Eliades et al 2011). The possible origin from different regions (Taurus, Antitaurus, Lebanon mountain ridges) can be also a reason for the high level of genetic variation of the species (Bou DagherKharrat et al 2007;Eliades et al 2011).…”

“…The cedar seeds from the various regions of continent, transported during that time by animals were the source of the remnant C. brevifolia population on the Cyprus (Eliades et al 2011). The possible origin from different regions (Taurus, Antitaurus, Lebanon mountain ridges) can be also a reason for the high level of genetic variation of the species (Bou DagherKharrat et al 2007;Eliades et al 2011).…”

“…The studies on genetic diversity and phylogeography of C. atlantica (Terrab et al 2006(Terrab et al , 2008, genetic diversity of C. libani (Semaan and Dodd 2008) and C. brevifolia (Eliades et al 2011) described the high level of genetic variation and significant differences among studied populations of compared species. The Mediterranean cedars differ in respect to the length, width and shape of the male and female cones and in the length of the needles (e.g., Gaussen 1964;Krüssmann 1985;Vidaković 1991;Farjon 2010).…”