Format: ORAL

Mikko Paajanen1, Quentin Cronk1

1. Department of Botany, University of British Columbia, Vancouver, Canada

The genera Commidendrum (4 spp.) and Melanodendron (1 sp.) from St Helena (South Atlantic Ocean) form a single clade whose ancestor reached the island in the early Pliocene. All species have highly divergent morphologies linked to ecology. Commidendrum and Melanodendron are known to form an intergeneric hybrid and Commidendrum is known to form interspecific hybrids. Plant genomics can untangle evolutionary history as well as complex histories of hybridization on islands. Genomic evidence is presented that hybridization has occurred in the Commidendrum/Melanodendron clade due to recent conservation efforts due to planting species in proximity. Furthermore there is genomic evidence that hybridization events may be ancient, with the species forming a syngameon, so raising the genetic effective population sizes (Ne) of species. A syngameon is here defined as: a group of otherwise distinct species interconnected by limited gene exchange, i.e. the most inclusive interbreeding evolutionary unit (Suarez-Gonzalez et al., Adaptive introgression: a plant perspective Biology Letters 2017). Such hybridization events are postulated to be a continual source of background evolutionary rescue of species from any small population size impacts over geological time, a phenomenon of particular importance and impact on islands. Genomic studies are an essential tool for the study of plant evolution on islands, and for endemic plant conservation.