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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The plant diversity of Bukit Timah Nature Reserve (BTNR) is relatively well studied due to concerted effort over several decades, particularly as part of the worldwide system of ecological plots set up by the Center for Tropical Forest Science (CTFS), now called the Forest Global Earth Observatory. Publications arising from previous works have set baseline data for the species diversity, suggested that the forest resilience was greater than would be expected in such a small forest fragment, but that there was low recruitment of primary forest tree species into the secondary forest. In order to assess the overall vascular plant diversity, and to compare the diversity of the various forest types within BTNR to each other, 52 plots were set up, each 20 × 5 m, along nine different transects that covered the full range of topography and forest types, primary, old secondary and maturing secondary forests, within the reserve. The vascular plant diversity within each plot was recorded. In total, 1250 species in 148 families were recorded, including an additional 167 species newly listed for BTNR. The primary forest had the highest number of species not found in the other forest types. It nevertheless had a very large overlap with species in the old secondary forest but not with the maturing secondary forest.

Several new records of plant species previously unknown in Singapore are reported, along with records of species presumed to be nationally extinct which have been rediscovered. These reports are based on specimens collected during our recent surveys of the Bukit Timah Nature Reserve and previously unreported older specimens, all deposited in SING. Three species are reported as new records for Singapore: Scindapsus lucens Bogner & P.C.Boyce, Passiflora quadriglandulosa Rodschied and Tectaria nayarii Mazumdar. Scindapsus lucens is likely to be native and previously overlooked, whereas Passiflora quadriglandulosa and Tectaria nayarii are exotic species which have escaped from cultivation and become naturalised. Another 10 species are rediscoveries of taxa previously considered to be nationally extinct:

The city-state of Singapore continues to provide many new records and rediscoveries of plant species in its nature reserves, offshore islands and secondary forests. Eleven new records for Singapore and eight rediscoveries of species previously presumed nationally extinct are reported here along with national conservation assessments. The new records are Albertisia crassa Forman, Arcangelisia flava (L.) Merr., Chaetocarpus castanocarpus (Roxb.) Thwaites, Dendrokingstonia nervosa (Hook.f. & Thomson) Rauschert,