Speciation and genetic diversity in Centaurea subsect. Phalolepis in Anatolia

Abstract

Mountains of Anatolia are one of the main Mediterranean biodiversity hotspots and their richness in endemic species amounts for 30% of the flora. Two main factors may account for this high diversity: the complex orography and its role as refugia during past glaciations. We have investigated seven narrow endemics of Centaurea subsection Phalolepis from Anatolia by means of microsatellites and ecological niche modelling (ENM), in order to analyse genetic polymorphisms and getting insights into their speciation. Despite being narrow endemics, all the studied species show moderate to high SSR genetic diversity. Populations are genetically isolated, but exchange of genes probably occurred at glacial maxima (likely through the Anatolian mountain arches as suggested by the ENM). The lack of correlation between genetic clusters and (morpho) species is interpreted as a result of allopatric diversification on the basis of a shared gene pool. As suggested in a former study in Greece, post-glacial isolation in mountains would be the main driver of diversification in these plants; mountains of Anatolia would have acted as plant refugia, allowing the maintenance of high genetic diversity. Ancient gene flow between taxa that became sympatric during glaciations may also have contributed to the high levels of genetic diversity.

Influence of the Quaternary Glacial Cycles and the Mountains on the Reticulations in the Subsection Willkommia of the Genus Centaurea

“…The high levels of historical gene flow detected in the present study are consistent with the low genetic differentiation observed between species (Table 2 and Supplementary Table 3), which are significant but much lower than those reported for both Greek, Italian, and Turkish Centaurea subsect. Phalolepis ( F ST = 0.243, 0.232, and 0.198, respectively; López-Vinyallonga et al, 2015; López-Pujol et al, 2016; Garcia-Jacas et al, 2019). Moreover, we have not detected isolation by distance (except among C. gadorensis populations of Sierra de Gádor), suggesting that the lineage distribution is the result of historical phylogeography.…”

“…Similar levels of genetic variability were found in species of Centaurea subsect. Phalolepis using almost the same set of microsatellite loci (mean H E = 0.587 and 0.504 for the Greek and Anatolian taxa, respectively; López-Vinyallonga et al, 2015; López-Pujol et al, 2016). For narrow endemic plants, the expected levels of genetic diversity are low, but in the Mediterranean mountains the endemisms appear to harbor moderate to high levels (cf.…”

“…Nm values for populations studied here are much higher than those reported for other endemic Centaurea species of the subsect. Phalolepis , phylogenetically close to Willkommia (Garcia-Jacas et al, 2006; Suárez-Santiago et al, 2007b) with disjunct areas in Greece (mean Nm = 0.534; López-Vinyallonga et al, 2015), Italy (mean Nm = 0.645; Garcia-Jacas et al, 2019), and Turkey (mean Nm = 0.466; López-Pujol et al, 2016). The high levels of historical gene flow detected in the present study are consistent with the low genetic differentiation observed between species (Table 2 and Supplementary Table 3), which are significant but much lower than those reported for both Greek, Italian, and Turkish Centaurea subsect.…”

“…At lower altitudes, secondary contacts between vicariant lineages occurred over the course of different glacial maxima, facilitating gene flow, hybridization, and hybrid speciation, resulting in complex evolutionary patterns (Thompson, 2005; Nieto Feliner, 2011, 2014). The reticulate evolution pattern linked to altitudinal shifts has been documented in several Mediterranean genera (e.g., Fuertes Aguilar et al, 1999; Albaladejo and Aparicio, 2007; Suárez-Santiago et al, 2007a; Alarcón et al, 2012; Maguilla and Escudero, 2016) including Centaurea (Suárez-Santiago et al, 2007b; Garcia-Jacas et al, 2009; López-Vinyallonga et al, 2015; López-Pujol et al, 2016).…”

The impact of Pleistocene sea-level oscillations on plant genetic diversity: the case of the western Mediterranean endemic Carduncellus dianius (Asteraceae)

“…As ecological niche modelling may be problematic for cases with occurrence records < 25, we applied the methodological approach developed by Pearson et al (2007) to confirm an accurate predictive performance of models, as described in López-Pujol et al (2016). Selected layers were used to build the definitive SDM models for the present time.…”