RELICTOAK · The genetics of enduring isolation: diversity, gene flow and offspring performance in glacial relict tree populations

The response of species to changing environments is likely to be determined largely by population responses at range margins. In contrast to the expanding edge, the low-latitude limit of species ranges remains understudied, and the critical importance of its populations as long-term stores of species’ genetic diversity and foci of speciation has been little acknowledged. Here we propose to study a set of 23 low-latitude marginal populations of the widespread European forest tree Quercus robur (Pedunculate oak) in central Spain in order to elucidate how these were able to sustain their genetic diversity and viability through multiple glacial cycles. For this purpose, we investigate how genetic diversity is distributed and transmitted across populations. Because gene dispersal plays a central role in this process, we examine patters of historical and contemporary gene flow involving three levels: within populations, among populations, and between species. Finally, germination and growth experiments under controlled conditions will be used to assess whether low levels of genetic variation actually result in reduced fitness and resistance to abiotic stress. This study should help improve our understanding of how glacial relict populations manage to persist under adverse conditions and provide valuable background information for developing appropriate strategies for their conservation and management in a changing climate.