Evolutionary relevance of lineages in the European black pine (Pinus nigra) in the transcriptomic era

Abstract

European black pine (Pinus nigra J.F.Arnold) is an ecologically and economically important conifer growing across southern Europe and the Mediterranean Basin in a variety of habitats. Its morphological and ecological variabilities as well as geographic origin are the basis for subspecies level taxonomic identification and forestry practice recommendations. Yet, no true consensus exists and genomic resources are lacking for resolving the taxonomy of P. nigra and assessing its adaptive potential. To provide genetic tools for further research, we generated novel genomic resources using six de novo transcriptomic assemblies representing major biogeographic regions where the species is growing naturally. Using two closely related species, Pinus sylvestris and Pinus halepensis, as outgroups, we identified a set of 2200 nuclear, putatively orthologous, single-copy genes. In addition, we identified a set of 405,624 polymorphic SNPs for P. nigra. Based on these resources, we were able to confirm the division of P. nigra into two wide geographical population groups and to provide new insights into evolutionary dynamics of the species.