Format: ORAL

Theodore S. Brook1,2, Kyle Macleod1, Martin Bidartondo1,2, Ian Hutton3, Sue Bower4, Alex Papadopulos5, Trevor Wilson6, Vincent Savolainen1

1 Department of Life Sciences, Imperial College London, London, UK 2 Ecosystem Stewardship, Royal Botanic Gardens, Kew, London, UK 3 LHI Museum, Lord Howe Island, Australia 4 Bower Bush Works, Sydney, Australia 5 Environment Centre of Wales, Bangor University, Bangor, UK 6 Botanic Gardens of Sydney, Sydney, Australia

Speciation with gene flow sympatric speciation has often been considered improbable. Recent evidence, which is becoming more readily available with next generation sequencing data, has revealed that it can occur and, in some scenarios, may be relatively common. The flora of Lord Howe Island (LHI) provides a unique system to study this process due to its isolation and small size, enabling us to rule out allopatry in many cases. A putative example of sympatric speciation on LHI is a small radiation of Coprosma (Rubiaceae), which has produced up to seven species across two independent colonisations. Alongside producing an integrated taxonomic revision of this genus, we are using a transcriptomic data to test the hypotheses that these species evolved in sympatry and that hybrid speciation has produced at least two of the (putative) species. The latter could provide some of the first substantial evidence for the syngameon hypothesis, the proposed role of elevated levels of hybridisation upon colonisation of a new environment in enabling rapid adaptive diversification under disruptive/divergent selection. This phylotranscriptomic approach involves constructing reference transcriptomes for each species, mapping RNA-seq reads from samples across each species range, and producing a phylogenetic tree and network of the genus on LHI. This is complimented by a range of population genetic analyses to determine the stage of speciation and transcriptomic regions associated with differentiation in this radiation. Given the strong evidence for sympatric speciation among other genera on LHI (Howea and Metrosideros), further study into Coprosma allows us to determine how general sympatric speciation is across the island and thus how relevant this process is generating biodiversity on LHI and beyond.