Conserving intraspecific diversification in a warmer world

Southern European mountain ranges harbor a remarkable plant biodiversity. For instance, the Pyrenees, the principal mountain range of southwestern Europe, are home to more than 4300 plant species of which c. 300 are endemic. Upslope migration of alpine plants caused by temperature increase conferred by climate change has the most dramatic consequences for relatively low ranges such as the Pyrenees. For a long time conservation efforts have targeted ecosystems or species; in recent years a new focus has been put on cryptic intraspecific diversity on the gene level. It is crucial to focus conservation strategies on areas, which do not only possess high levels of inter- and intraspecific diversity and endemism but also enable long-term survival of species by offering the possibility of niche tracking via upslope migration. To this end, we will integrate molecular data obtained from the next generation sequencing based technique restriction site associated DNA sequencing, species richness data and retrospective as well as prospective distribution modelling of species and intraspecific lineages. Our aims are to 1) identify glacial refugia for alpine plants endemic to the Pyrenees, 2) identify areas of high phylogenetic endemism for alpine plants endemic to the Pyrenees and compare them with the geographic distribution of alpine species richness, and 3) model the future distribution of alpine habitats and identify areas with high stability of climatic suitability under different climate change scenarios. Finally, priority areas for conservation of alpine plants will be defined where diversity and endemism indicators as well as future stability of climatic suitability are maximized. We will test the following hypotheses: (1) Glacial refugia for endemic alpine plants in the Pyrenees are found in their eastern and western margins, the southern Pre-Pyrenees and non- glaciated areas in the main chain. (2) Pyrenean endemics show a geographically structured distribution of intraspecific lineages. Areas of high phylogenetic endemism overlap with glacial refugia, but not necessarily with areas of high alpine species richness. (3) Areas of future stability of climatic suitability are found in the central Pyrenees, where mountains reach the highest altitude, thus allowing for future niche tracking. The proposed research would be the first comparative intraspecific phylogeographic study of alpine plants of the Pyrenees, with the added value of a direct application of the results towards prioritizing areas for conservation. The approach proposed here represents a novel, synthetic way to address mountain plant conservation under a climate change scenario in a regional context.

Alpine plants are strongly threatened by climate change. The aim of this project was to find priority areas to preserve their biodiversity at various levels, thus not only focussing on species richness but also on intraspecific genetic diversity. To do that we chose the Pyrenees, the principal mountain range of southwestern Europe, and nine endemic plant species to study how their intraspecific diversity is distributed and how it will respond to climate change. With this aim, we sequenced thousands of short DNA fragments (RADseq) of 903 samples from 159 sites in the Pyrenees. First, we identified the main genetic groups in each species, established how they are related to each other and estimated the population size of species and genetic groups over the last thousands of years. Second, we modelled the geographic distribution of the studied species under present, past (20,000 years ago at the Last Glacial Maximum, LGM) and future conditions (2080, two different emission rate scenarios). Combining both types of data we first studied the origin of the genetic groups and their refugial areas during glaciation, by assigning the genetic groups to geographically close refugia, which provided suitable areas during the LGM. Alpine plants survived glaciations in smaller populations than at present at the eastern and western extremities of the main chain, as well as in southern peripheral ranges. One of the strongest geographic barriers was the deep Cerdanya valley in the eastern Pyrenees, which usually delimited genetic groups on each side. The predictions under future conditions show a general decrease in the potential distribution of the studied species. The situation is especially alarming for strictly alpine species, while species able to occupy lower elevation habitats still have possibilities in many cases to track their niche by upslope migration, though the southernmost occurrences of such species will most likely disappear. In the same line, small areas harboring strongly differentiated lineages, such as the eastern-most Pyrenees, show strong reductions of the suitable area, causing significant losses in intraspecific diversity. These results will be more specifically investigated in the near future by modelling phylogenetic endemism (PE) for each species and projecting PE to future conditions. The PE informs us, how singular a genetic group is, by estimating how well differentiated it is from others, and to which extent it is restricted to a certain geographic area. Therefore, highly differentiated groups occurring in small areas will have a high PE, implying that they represent very unique parts of the genetic diversity of the species and this is where the strongest conservation effort should be targeted.