title: Processes Driving the Adaptive Radiation of a Tropical Tree (Diospyros, Ebenaceae) in New Caledonia, a Biodiversity Hotspot.
abstract: Due to its special geological history, the New Caledonian Archipelago is a mosaic of soil types, and in combination with climatic conditions this results in a heterogeneous environment across relatively small distances. A group of over 20 endemic species of Diospyros (Ebenaceae) has rapidly and recently radiated on the archipelago after a single long-distance dispersal event. Most of the Diospyros species in the radiating group are morphologically and ecologically well differentiated, but they exhibit low levels of DNA variability. To investigate the processes that shaped the diversification of this group we employed restriction site associated DNA sequencing (RADseq). Over 8400 filtered SNPs generally confirm species delimitations and produce a well-supported phylogenetic tree. Our analyses document local introgression, but only a limited potential for gene flow over longer distances. The phylogenetic relationships point to an early regional clustering among populations and species, indicating that allopatric speciation with respect to macrohabitat (i.e., climatic conditions) may have had a role in the initial differentiation within the group. A later, more rapid radiation involved divergence with respect to microhabitat (i.e., soil preference). Several sister species in the group show a parallel divergence in edaphic preference. Searches for genomic regions that are systematically differentiated in this replicated phenotypic divergence pointed to loci potentially involved in ion binding and cellular transport. These loci appear meaningful in the context of adaptations to soil types that differ in heavy-metal and mineral content. Identical nucleotide changes affected only two of these loci, indicating that introgression may have played a limited role in their evolution. Our results suggest that both allopatric diversification and (parapatric) ecological divergence shaped successive rounds of speciation in the Diospyros radiation on New Caledonia.
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria;
authors.forename: Ovidiu
authors.initials: O
authors.lastname: Paun
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria; barbara.turner@univie.ac.at.
authors.forename: Barbara
authors.initials: B
authors.lastname: Turner
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria;
authors.forename: Emiliano
authors.initials: E
authors.lastname: Trucchi
authors.affiliation: IRD, UMR AMAP, 34398 Montpellier, France;
authors.forename: Jérôme
authors.initials: J
authors.lastname: Munzinger
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens, Kew, TW9 3AB Surrey, UK; and School of Plant Biology, University of Western Australia, Crawley, WA 6009 Australia.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Chase
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, 1030 Vienna, Austria;
authors.forename: Rosabelle
authors.initials: R
authors.lastname: Samuel
mesh_terms: D000222:Adaptation, Physiological; D044822:Biodiversity; D018744:DNA, Plant / Q000235:genetics; D029788:Diospyros / Q000145:classification* / Q000502:physiology*; D049810:Genetic Speciation; D014644:Genetic Variation; D018745:Genome, Plant / Q000235:genetics*; D009510:New Caledonia; D012987:Soil / Q000737:chemistry; D014329:Tropical Climate
chemical_list: D018744:DNA, Plant; D012987:Soil
keywords: Adaptive radiation; Diospyros; New Caledonia; RAD-sequencing; hybridization; soil adaptation