Narrow endemics in European mountains: high genetic diversity within the monospecific genus Pseudomisopates (Plantaginaceae) despite isolation since the late Pleistocene

Abstract

Aim The evolutionary history of narrow endemic species has received little attention compared with that of more widely distributed species. Small effective population sizes and long-term isolation of many narrow endemic species make research on their genetic make-up important for their future conservation. In this study we investigated the genetic variation and historical distribution of an isolated plant, the monospecific genus Pseudomisopates, as an example of the phylogeographical history of narrow endemics.Location Central Range, Iberian Peninsula, Mediterranean Europe.Methods We used amplified fragment length polymorphisms (AFLPs), nuclear and plastid DNA sequences and species distribution modelling. Sequence data were analysed using statistical parsimony, molecular dating, and a coalescent-based Bayesian model of isolation with migration. Genetic diversity and differentiation analyses based on AFLP data were performed. We compared the detection of clones using AFLPs with the results of a previous study that used simple sequence repeats (SSRs).Results AFLP analysis revealed that SSRs underestimate clone number. The coalescent-based Bayesian model of isolation with migration suggested a late Pleistocene divergence between the populations of Pseudomisopates on two mountain massifs (Gredos and La Serrota), despite the presence of a large area suitable for population admixture. Moderate to high levels of genetic diversity and high effective population sizes were inferred.Main conclusions Our results imply that the levels of genetic diversity within narrow endemic species from Mediterranean mountains could primarily be driven by extrinsic historical factors, rather than by intrinsic species-specific factors depending on their own biological characteristics. Narrow endemics are widely believed to harbour low genetic diversity because of small effective population sizes. However, this study and others on narrow endemic angiosperms demonstrate that narrow endemism does not necessarily result in low genetic diversity.

Differentiation between two self-compatible cytotypes of Herbertia lahue (Iridaceae): evidence from genotypic and phenotypic variation

“…However, other factors may also influence within-population genetic diversity (i.e., population size, founder effect, genetic bottleneck and local adaptation). These characteristics may also induce inbreeding and subsequent reductions in genetic variability, though large population sizes generally buffer the potential effects of inbreeding, as well as other processes influencing genetic variation over time (Porcher and Lande 2005;Barringer 2007;Wright et al 2008Wright et al , 2013Jiménez-Mejías et al 2015). Natural populations of H. lahue occur in open grassland areas and usually consist of large number of plants, probably over 500 individuals (Stiehl-Alves pers.…”

Speciation and genetic diversity in Centaurea subsect. Phalolepis in Anatolia

“…Our results, as well as the growing number of studies reporting narrow endemic species with unexpectedly high levels of genetic polymorphism3334 suggest that the geographic range is not always a good predictor of genetic diversity in plant species. It is generally agreed that a complex network of factors shape genetic diversity in plant populations, which are usually classified into two categories35: (1) intrinsic biological properties of the species (i.e., life-history traits and ecological interactions) and (2) extrinsic dynamic processes which affect species (i.e., historical factors that may include occurrence of bottlenecks, divergence events, or Quaternary expansions/retreats).…”

“…These movements would have favored secondary contacts at the glacials and populations would have admixed, largely blurring the genetic differentiation produced by periods of isolation at the interglacials. This process was favored by the much longer duration of glacials compared to interglacials and has also been proposed for other plants from the Mediterranean mountains133444. Genetic connectivity is also present in Anatolian species of subsect.…”

Can the reproductive system of a rare and narrowly endemic plant species explain its high genetic diversity?

“…Clearly, the genetic dynamics of a species should not be predicted based on its geographical range alone: widely distributed species are not always characterised by high levels of genetic diversity ; conversely, genetic diversity levels are not necessarily low in species with a narrow distribution (Fernández-Mazuecos et al 2014;Jiménez-Mejías et al 2015;Forrest et al 2017). A great number of factors can influence diversity levels within and between populations.…”