GENETIC VARIATION IN POPULATIONS OF GONYSTYLUS BANCANUS (RAMIN) FROM PEAT SWAMP FOREST ON THE ISLAND OF BORNEO(ABSTRACT)

摘要

The centre of diversity for the tree genus Gonystylus (Thymeleaeceae) is in Borneo (67 % of Gony stylus spp. are endemic to the island) and this is believed to be the origin of the subfamily Gonystyloideae. One species, G. bancanus (ramin), is more or less restricted to peatswamp forest and this tree was chosen for molecular phylogenetic study. The aims of the study were to explore intraspecific genetic variation and investigate whether this could be used to elucidate patterns of migration. A total of 29 leaf collections of Gony stylus bancanus (Thymeleaeceae) were collected from locations in Central Kalimantan, Sarawak and Brunei. Whole genomic DNA was isolated before being amplified by polymerase chain reaction (PCR) using the plant/ fungal-designed primers of ITS4 and ITS5 that allow amplification of the intergenic spacers (ITS) for the nuclear ribosomal DNA (rDNA). Amplified material was then subject to sequence analysis. Sequences were verifed, cleaned and aligned and phylogenetic analysis was performed using PAUP (Phylogenetic Analysis Using Parsimony). The resulting phylogenetic tree was 'rooted' using leaf material from the tree Aquilaria beccariana (Thymeleaeceae) as the outgroup taxon and reliability of the data was tested using bootstrap analysis. The phylogenetic tree revealed five clades or ribotypes of the G. bancanus samples. Three ribotypes were identified from one peatland dome in Central Kalimantan, with clear intraspecific differences between populations of three, contiguous phasic communities (mixed swamp forest, low pole forest and tall interior forest). The ribotype of the mixed swamp forest population was widely distributed elsewhere in Central Kalimantan and in Sarawak, whilst a separate ribotype was identified from the Brunei samples. The implications of these results for the development of peatlands on the island of Borneo will be discussed.