Format: ORAL

Surabhi Ranavat1, Dieu-Merci Assumani1,2, Crispin Ilunga-Mulala3,4, Jean Pierre Ngongo1,5, Bonaventure Sonk 6, Nils Bourland 7, Jean-Franois Flot1, Olivier Hardy1

1 Ecology and Evolutionary Biology, Université Libre de Bruxelles, Brussels, Belgium 2 Faculty of Renewable Natural Resources Management, University of Kisangani, Kisangani, Democratic Republic of Congo 3 Gembloux Agro-Bio Tech, Forest Is Life, TERRA Teaching and Research Centre, University of Liège, Gembloux, Belgium 4 Department of Environment, Faculty of Sciences, Université du Cinquantenaire de Lwiro, Lwiro, Democratic Republic of Congo 5 Faculty of Sciences, University of Kisangani, Kisangani, Democratic Republic of Congo 6 Plant Systematic and Ecology Laboratory, University of Yaoundé I, Yaoundé, Cameroon 7 Service of Wood Biology, Royal Museum for Central Africa, Tervuren, Belgium

Pericopsis elata is a large, gregarious, and light demanding tree distributed in the Western and Central African tropics. Highly exploited for its excellent quality timber, it is listed as endangered on the IUCN Red List and included in the CITES Appendix II. It is a peculiar tropical tree as it has a mixed-mating system, with a high selfing rate, and a lack of regeneration throughout its natural distribution range. Previous results from Democratic Republic of Congo (DRC) showed a high proportion of inbred individuals, with 54% inbreeding in seeds and seedlings, and 20% in adults, indicating inbreeding depression. Recently, two highly differentiated gene pools (FST=0.53) were identified in DRC (Eastern gene pool), and Republic of Congo and Cameroon (Western gene pool). Along the Western gene pool, we observe a steep westward decay of heterozygosity, and we hypothesize that this is a recent range expansion into Cameroon with founder effects, possibly facilitated by selfing. Our aim is to assess inbreeding depression and mutation load along this westward expansion. Whole genome resequencing data of individuals along this gradient will be used to detect the runs of homozygosity (ROH), which will aid in inferring the demographic history and finding deleterious variants. To detect the mutation load, we will test if there is a westward decay of the ratio of synonymous to non-synonymous mutations, and the predicted effect of amino acid substitution on protein function based on sequence homology across closely related species. On the range expansion front, we expect longer ROHs, and an increase in inbreeding coefficient and mutation load towards the west. These analyses, combined with phenotypic data, will help in identifying the effects of inbreeding and informing sustainable management strategies for this threatened timber tree.