Signature of mid-Pleistocene lineages in the European silver fir (Abies alba Mill.) at its geographic distribution margin.

Caroline Scotti-Saintagne,Thomas Boivin,Brigitte Musch,Bruno Fady,Marie Suez,Ivan Scotti

doi:10.1002/ece3.7886

Abstract

In a conservation and sustainable management perspective, we identify the ecological, climatic, and demographic factors responsible for the genetic diversity patterns of the European silver fir (Abies alba Mill.) at its southwestern range margin (Pyrenees Mountains, France, Europe). We sampled 45 populations throughout the French Pyrenees and eight neighboring reference populations in the Massif Central, Alps, and Corsica. We genotyped 1,620 individuals at three chloroplast and ten nuclear microsatellite loci. We analyzed within‐ and among‐population genetic diversity using phylogeographic reconstructions, tests of isolation‐by‐distance, Bayesian population structure inference, modeling of demographic scenarios, and regression analyses of genetic variables with current and past environmental variables. Genetic diversity decreased from east to west suggesting isolation‐by‐distance from the Alps to the Pyrenees and from the Eastern to the Western Pyrenees. We identified two Pyrenean lineages that diverged from a third Alpine–Corsica–Massif Central lineage 0.8 to 1.1 M years ago and subsequently formed a secondary contact zone in the Central Pyrenees. Population sizes underwent contrasted changes, with a contraction in the west and an expansion in the east. Glacial climate affected the genetic composition of the populations, with the western genetic cluster only observed in locations corresponding to the coldest past climate and highest elevations. The eastern cluster was observed over a larger range of temperatures and elevations. All demographic events shaping the current spatial structure of genetic diversity took place during the Mid‐Pleistocene Transition, long before the onset of the Holocene. The Western Pyrenees lineage may require additional conservation efforts, whereas the eastern lineage is well protected in in situ gene conservation units. Due to past climate oscillations and the likely emergence of independent refugia, east–west oriented mountain ranges may be important reservoir of genetic diversity in a context of past and ongoing climate change in Europe.

Highlights

| INTRODUCTIONAs the world's biodiversity continues to decline (Secretariat of the Convention on Biological Diversity, 2020), the Post-2020 Biodiversity Framework of the Convention on Biological Diversity (CBD) and the EU Biodiversity Strategy for 2030 have called for transformative changes that will halt biodiversity decline and maintain ecosystem, species, and genetic diversity for the benefit of people (Hoban et al, 2020)
As the world's biodiversity continues to decline (Secretariat of the Convention on Biological Diversity, 2020), the Post-2020 Biodiversity Framework of the Convention on Biological Diversity (CBD) and the EU Biodiversity Strategy for 2030 have called for transformative changes that will halt biodiversity decline and maintain ecosystem, species, and genetic diversity for the benefit of people (Hoban et al, 2020).Among these transformative changes is the need to better consider and protect genetic diversity
A significant number of phylogeographic studies have demonstrated the role of Holocene and the Last Glacial Maximum in the distribution of species, populations, and their genetic diversity in the world's temperate regions, emphasizing climate change and dispersal as the main drivers of observed and modeled patterns

Summary

| INTRODUCTION

As the world's biodiversity continues to decline (Secretariat of the Convention on Biological Diversity, 2020), the Post-2020 Biodiversity Framework of the Convention on Biological Diversity (CBD) and the EU Biodiversity Strategy for 2030 have called for transformative changes that will halt biodiversity decline and maintain ecosystem, species, and genetic diversity for the benefit of people (Hoban et al, 2020). Along the Pyrenees, the landscape changes from oceanic and lower elevation in the west to Mediterranean and variable elevation and geomorphology toward the east (Ninot et al, 2007) These longitudinally contrasted environments have led to a west-east genetic divergence attributed to secondary refugia in many animal species, such as the mountain ringlet butterfly Erebia epiphoron (Schmitt et al, 2006), the ground-dwelling spider Harpactocrates ravastellus (Bidegaray- Batista et al, 2016), the pine processionary moth Thaumetopoea pityocampa (Rousselet et al, 2010), and plant species such as snapdragons Antirrhinum sp. We addressed the following questions: other species does not demonstrate the existence of separate lineages on each side of the central high peak ridge of the Pyrenees

| METHODS

| DISCUSSION

Findings

| CONCLUSION