Singapore (1°21'07.6"N 103°49'11.3"E) is a tropical island-state situated south of Peninsular Malaysia, and north of the Riau Archipelago. Similar to tropical areas elsewhere, Singapore's climate is characterised by abundant rainfall (mean annual: 2165.9 mm), and generally high temperature (diurnal range: 23-33°C) and humidity (mean annual relative: 83.9%) throughout the year (Meteorological Service Singapore, 2018). Singapore's terrain is generally low-lying, with about three quarters of the island below 15 m. The highest point is the summit of Bukit Timah, which is at 163.63 m elevation (Wong, 2011). In 1963, the land area was 581.5 km 2 , and by 2018 had increased to 724.2 km 2 through land reclamation (Singapore Land Authority, 2019). There are 62 offshore islands-the two largest (Pulau Ubin and Pulau Tekong) are located northeast of the main island, and the rest are mostly found south of the main island. Before the arrival of the British in 1819, Singapore was likely covered mostly by lowland mixed dipterocarp forest (Fig. 1), similar to the original forest that was dominant in this part of Southeast Asia (Corlett, 1991, 1992). Mangrove forest likely occurred near river mouths with the vegetation transiting into freshwater swamp forest further inland. Stretches of sandy beach and rocky shore would have lined parts of the coast. Early human settlements (fourteenth to eighteenth centuries) have been recorded at the mouths or estuaries of the Singapore River, Kallang River, Seletar River and Punggol River. Singapore underwent tremendous landscape and ecological transformation after British colonisation (see Corlett (1992) and O'Dempsey (2014) for detailed accounts). Large tracts of lowland dipterocarp rain forest were cleared for timber, then converted to plantations of various crops, including black pepper, gambier, and pineapple. By the early 1900s, most lowland dipterocarp rain forest had been cleared and the remaining few patches were mostly gazetted as forest reserves. Extensive black pepper and gambier plantations had rendered the soil infertile in many areas. After H.N. Ridley's arrival in Singapore in 1888 and his experiments with the excision method to tap rubber more effectively and sustainably, large areas were converted into rubber plantations (Wycherley, 1959; Wee & Corlett, 1986). Kampungs (traditional villages) also increased in number as the island became more developed. Mangrove habitats were also affected by over-exploitation although later, in 1939, Pandan and Kranji mangrove areas were gazetted as forest reserves to allow regeneration (Wee & Corlett, 1986). After Singapore became independent from Malaysia in 1965, the new island nation began to focus on its industrial infrastructure resulting in the discontinuation or down-scaling of many agriculture-based activities. The growth of public housing estates to cater to the basic needs of a growing population saw most residents of the rural kampungs eventually resettled to high-rise public housing by the 1990s. Plantations and kampungs were grad...

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:

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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,