Up to 1988 When Conifers W

MALESIA Geography Malesia in this Atlas is the region in tropical SE Asia covered by Flora Malesiana (up to 1988 when conifers were treated), with one addition, the island of Bougainville, which is geographically part of the Solomon Islands but politically belongs to Papua New Guinea. This region includes the following countries: Brunei, East Timor, Indonesia, Malaysia, Papua New Guinea, Philippines and Singapore. The total land area is 3,021,630 km² and is made up of a vast archipelago extending on either side of the Equator from the Malay Peninsula in the west to Bougainville in the east and from islands in the Luzon Strait between Taiwan and the Philippines in the north to the island of Timor in the south. The only area in the region connected to the mainland of Asia is Peninsular Malaysia which forms the southernmost part of the Malay Peninsula. The largest islands are New Guinea, Borneo, Sumatera, Jawa, Sulawesi, Luzon and Mindanao. Islands in a second size class are situated in the Philippines, the Moluccas and the Lesser Sunda Islands. The seas around the islands of the archipelago are significant in the interpretation of the distribution of conifers, due to the fact that large parts of the Sunda Shelf fell dry during glacial maxima of the Pleistocene, connecting the Malay Peninsula with Sumatra, Java and Borneo, while deep sections of ocean kept other islands and archipelagos isolated. Similarly, New Guinea became connected with Australia across the Sahul Shelf and while sea straits remained between the Philippines and Taiwan and mainland China, they became narrower. These colder periods lasted longer than the interglacials with high sea levels as at present and therefore these ‘bridges’ with adjacent floral regions may have influ- enced distribution patterns recognized today. Van Steenis (1950) found that the ‘bridges’ despite their relatively recent history of connections still form principal floristic ‘demarcation knots’ setting the flora of Malesia apart from adjacent regions. The deep sea sections and straits that maintained divisions between islands and archipelagos have caused internal divisions of biodiversity, princi- pally separating West Malesia from East Malesia along different ‘lines’. The best known of these is Wallace’s Line which separates the Philippines, Borneo and the Greater Sunda Islands + Bali from Sulawesi, the Lesser Sunda Islands (– Bali), Maluku and New Guinea. There are mountain ranges and systems on all the major islands and the Malay Peninsula and many of these are volcanic in origin. Mt. Kinabalu in Sabah, Borneo (4094 m) is the highest summit between Yunnan in China and New Guinea (Mt. Jaya, 5030 m). Extensive lowlands are situated in E Sumatra, S Borneo and S New Guinea, in many places with swamps and slow rivers. The climate is monsoonal throughout, but most markedly so in E Jawa and the Lesser Sunda Islands, while the highest mountains in the Philippines, Mt. Kinabalu and New Guinea are wet throughout the year. Conifers in Malesia Families Genera Species Species + infra Countries with Area of occupancy Endemic taxa conifers in km² 6/8 13/70 80/615 85/794 7/7 26,850/3,021,630 63 Numbers after ‘/’ are global or continent totals. 294 malesia Conifers occur naturally throughout Malesia, with species present on the Malay Peninsula and all the major islands and many of the smaller islands as well. Map MA-1. Distribution of conifer species in Malesia. Most species occur in mountains and consequently a greater density of dots on the map is found where the land is mountainous, while the major lowland areas mentioned above have very few conifer species, with large areas apparently without any conifers. The map has to be interpreted with some caution, as there is certainly a collection bias against some areas. For instance, the density of dots in the western (Indonesian) part of New Guinea is less than in the eastern (Papua New Guinean) part, not because there are necessarily fewer conifers but because that half of the island has not been as intensively surveyed botanically as PNG. Similarly, the Indonesian part of Borneo (Kalimantan) may be as diverse in conifers as Sarawak to the N of it, especially in the borderlands, but fewer herbarium collections have been made there. A similar bias may exist for parts of the Philippines, but here a long history of deforestation could have caused the low density of dots in e.g. Mindanao, Panay and Leyte. The Lesser Sunda Islands E of Flores, including Sumba to the south, are also poor in conifers or do not have them at all. This is genuine, caused by climate; these islands are closest to Australia from which a high pressure cell during July–August intensifies the dry season from June to September. All Malesian conifers are adapted to humidity and not to dryness. The lack of conifers on these islands is matched in the tropical zone of the Northern Territory in Australia (map AU-4 on p. 345) just 400 km across the Timor and Arafura Seas. The two principal ‘bridge’ areas for conifers are the Malay Peninsula, with species extending into mainland SE Asia and S China, and Bougainville/Solomon Islands connecting with the SW Pacific islands. The other ‘bridge’ across Torres Strait to Australia has resulted in only one taxon occurring on both sides, Sundacarpus amarus. The land on either side of the strait has no conifers for hundreds of km, so the gap at least at present is wider than it would seem. Malesia is therefore relatively isolated and being so extensive and topographically diverse naturally has a high level of endemism, 74% of conifer taxa occur only here. Distributions vary from across the region and beyond to a single mountain. In the latter category, Mt. Kinabalu stands out with four species endemic to that mountain. The long and high ‘backbone’ of mountains in New Guinea has many conifer species not present elsewhere or only on the nearest islands on either end. Conifer diversity in Malesia is substantial with 80 species but not high compared to Australasia with 119 species. While isolation may have played its part in speciation, none of the islands are as .

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