Species radiations, despite immense phenotypic variation, can be difficult to resolve phylogenetically when genetic change poorly matches the rapidity of diversification. Genomic potential furnished by palaeopolyploidy, and relative roles for adaptation, random drift and hybridisation in the apportionment of genetic variation, remain poorly understood factors. Here, we study these aspects in a model radiation, Syzygium, the most species-rich tree genus worldwide. Genomes of 182 distinct species and 58 unidentified taxa are compared against a chromosome-level reference genome of the sea apple, Syzygium grande. We show that while Syzygium shares an ancient genome doubling event with other Myrtales, little evidence exists for recent polyploidy events. Phylogenomics confirms that Syzygium originated in Australia-New Guinea and diversified in multiple migrations, eastward to the Pacific and westward to India and Africa, in bursts of speciation visible as poorly resolved branches on phylogenies. Furthermore, some sublineages demonstrate genomic clines that recapitulate cladogenetic events, suggesting that stepwise geographic speciation, a neutral process, has been important in Syzygium diversification.

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Holme et al., 2015). At higher elevations increased temperature may increase diversity but with limits imposed by available area as mountains taper (Dullinger et al., 2012;Elsen & Tingley, 2015). In addition,

Biogeographic patterns are underpinned by which species from the regional source pool are found in local communities (Zobel, 2016). Species have to overcome the spatial distance required to reach the community (dispersal limitation) and cope with the environmental variables found there (environmental filtering). In southeast Asia, there is a western source pool (Sunda), an eastern source pool (Sahul) and a region in between known as Wallacea (Figure 1a, b). Sunda, part of the Asian continental plate, and Sahul, the Australian, were historically more distant until they collided c. 26 million years ago, causing the uplift of Wallacea (Hall, 2017). The communities of Wallacea then assembled via dispersal from the two adjacent source pools (Pärtel & Zobel, 1999). Wallacean uplift also increased dispersal between Sunda and Sahul (Sniderman & Jordan, 2011; Crayn et al., 2015). Dispersal is referred to herein as both movement of a propagule between areas and establishment in the novel area. Evidence suggests current distributions of species may be a result of dispersal being limited by the past spatial separation of the two source pools (Schuster, 1972). However, Wallacea's environment is potentially more stressful than that in Sunda and Sahul. This is important because successful dispersal between Sunda and Sahul is

The genus Bauhinia sens. lat. formerly accommodated numerous species that have now been transferred to one of several segregate genera. One of those genera, Schnella, includes all neotropical liana species with tendrils. This study comprises a summary of the taxonomic and nomenclatural history of Schnella, and presents a list of names accepted under Schnella, including 12 new combinations. We recognise here a total of 53 taxa including 47 species. Distribution details for each taxon are given, illustrated with a map showing numbers of taxa within the TDWG regions of the neotropics. Within Schnella, there exist two morphologically and palynologically distinguishable groups of species. Further work, including a molecular-based study, will be needed to discover whether those two species groups are congeneric.