Causes of the genetic architecture of south-west European high mountain disjuncts

Abstract

Background: Postglacial climatic warming in south-western Europe and the retreat of cold-adapted species into higher elevations, starting in the Sierra Nevada and proceeding northwards to the Pyrenees and Alps, should have resulted in a pattern of 'successive vicariance'. Alternatively, long-distance dispersal might explain the extant distribution pattern of mountain species in this region. Aims: Here, we report an investigation of two alpine plants, Saxifraga oppositifolia and S. stellaris, which co-occur in the Sierra Nevada, the Pyrenees, and the south-western Alps/Massif Central. Our aim was to distinguish between (successive) vicariance and long-distance dispersal as alternative explanations for their present-day geographical distribution across these high mountain ranges. The patterns found in these two species were compared to those of four other mountain species previously studied by us. Methods: Samples of 378 individuals from 21 populations were surveyed for amplified fragment length polymorphism (AFLP) variation. Results: We found that vicariance best explains the phylogeographic pattern of S. oppositifolia, while in S. stellaris, Sierra Nevada samples fell within the group of non-monophyletic Pyrenean populations. Together with genetic diversity evidence, this latter pattern is hypothesised to reflect incomplete lineage sorting following range fragmentation rather than longdistance dispersal from the Pyrenees to the Sierra Nevada. Additionally, in S. stellaris, a distinct genetic cluster from the Massif Central was observed. Levels of among-region and among-population differentiation were higher in S. stellaris than in S. oppositifolia. This may be taken as evidence of a more strongly disrupted glacial distribution of the former species, and also accords with its preference for more specialised and patchily distributed habitats when compared to those of the 'pioneering' S. oppositifolia. Conclusions: In conjunction with our previous investigation, we conclude that vicariance is the predominant, but not sole process shaping the genetic architecture of south-west European high mountain disjuncts. Furthermore, 'successive vicariance' was only observed in three previously studied species but not in the two Saxifrages analysed here, possibly due to the persistence of past patterns of population substructuring.

Genetic and morphological diversity in <i>Armeria</i> (Plumbaginaceae) is shaped by glacial cycles in Mediterranean refugia

“…Most of the phylogeographic and genetic research on European refugia has focused on extinction and recolonization processes in the arctic-alpine flora of northern and central glaciated areas (Abbott & Comes, 2004;Ronikier & al., 2008), the identification of central and southern European refugia (Tribsch & Schönswetter, 2003;Schönswetter & al., 2005), and the pathways of recolonization from such refugia into deglaciated areas (Petit & al., 2003). However, little work has been done on how glaciationdeglaciation cycles affected the plants within the refugia of southern Europe (Kropf & al., 2006(Kropf & al., , 2008Petit & al., 2002;Nieto Feliner, 2011).…”

On the origins of Balkan endemics: the complex evolutionary history of theCyanus napulifergroup (Asteraceae)

“…Kropf et al, 2008Kropf et al, , 2012Bardy et al, 2010;Hilpold et al, 2011;Alarc on et al, 2012;Dobe s et al, 2013;Kuzmanovi c et al, 2013;Manafzadeh et al, 2014). Spatial isolation is considered one of the crucial mechanisms of speciation in homoploid plant groups (Watanabe, 1986;Gross and Rieseberg, 2005;Mart ın-Bravo et al, 2010), especially as members of the C. napulifer group are unlikely to be reproductively isolated (cf.…”

Glacial survival, phylogeography, and a comparison of microsatellite evolution models for resolving population structure in two species of dwarf yams (Borderea, Dioscoreaceae) endemic to the central Pyrenees

“…Although the number of such studies is increasing on plants occurring in the Alps and Carpathians (e.g. Tribsch and Schönswetter 2003;Schönswetter et al 2005;Mráz et al 2007;Ronikier et al 2008), very few studies involving a detailed genetic analysis of historical events have been conducted on alpine plants in the Pyrenees (Kropf et al 2006(Kropf et al , 2008. This is so despite the fact that the Pyrenees harbour a considerable amount of endemic and disjunctly distributed mountain plants that likely speciated there (Villar 1977).…”