Phylogenetic Analyses of Shorea sensu lato (Dipterocarpaceae) in Borneo

Nur Aina Afiqah, Binti Abdul Halid (2018) Phylogenetic Analyses of Shorea sensu lato (Dipterocarpaceae) in Borneo. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Dipterocarpaceae is a key family, both ecologically and commercially, in the forests of Southeast Asia. The distribution is pantropical, mostly confined to Asian tropics between the Seychelles Island and Southeast Asia to New Guinea with the greatest diversity and abundance in western Malesia. Members of the family are predominantly distributed in tropical lowland and hill forests within this region. The family consists of 17 genera with about 500 species in three subfamilies. Shorea Roxb. ex C.F.Gaertn. is the largest genus in the family, consisting of 196 species so far, 138 species are known in Borneo, of which 91 species are endemic and 130 species occur in Sabah and Sarawak. Previous studies showed that, Shorea is probably paraphyletic with the genera Hopea Roxb. and Neobalanocarpus (a monotypic genus), probably belonging within the genus Shorea. Neobalanocarpus were proposed to be derived via hybridization between Shorea and Hopea. Both genera possess many similarities and display continuous morphological variation at generic and specific levels. These two genera were regarded as closely related genera. Parashorea were clustered together with Shorea species as reported in previous study. The previous phylogenetic work on Shorea focused on Southeast Asia, but none of these studies were specifically focused on Borneo. There was still insufficient information for robust molecular classification and further sequence data were required, covering a greater range of species from various localities, especially to include more species from various groups in the genus Shorea. Therefore, this project was conducted to investigate the phylogeny of the genus Shorea in Borneo broadly focusing on the issue of their intrageneric delimitation. There were three objectives in this project: (1) to resolve the phylogeny of the genus Shorea species of Borneo with the emphasis on species from Sarawak; (2) to clarify the positions of different sections/groups within the genus Shorea; (3) to determine the monophyly or paraphyly of Shorea species. A total of 76 and 191 accessions of ITS and matK, respectively, covering 93 taxa of Shorea (231 accessions with ten sections included following Ashton classification) together with 23 taxa (36 accessions) from closely related genera (Anisoptera, Cotylelobium, Dipterocarpus, Dryobalanops, Hopea, Neobalanocarpus, Parashorea, Upuna, Vatica, Monotes) were included in this study. This made up to total of 116 taxa of Dipterocarpaceae included in this project. The analysis of matK region provided better topology than ITS region. In most of the trees, there were at least four groups within Shorea observed which were Rubroshorea (Red Meranti), Richetia (Yellow Meranti), Anthoshorea (White Meranti) and Shorea (Selangan Batu or Balau) respectively. There were two big clades found within the genus Shorea. One clade consists of Richetia (Yellow Meranti), Rubroshorea (Red Meranti) and Shorea (Selangan Batu/Balau) while the other one consists of Anthoshorea (White Meranti) and Doona. However, the eleven sections recognized by Ashton (1982) were not supported. Current delimitation of Shorea makes Shorea a paraphyletic genus as Parashorea, Neobalanocarpus, Dryobalanops and Hopea genera are embedded in the phylogeny of this study. Several taxa which are morphologically belonging to section Shorea (Selangan Batu/Balau) are not supported in the molecular phylogeny.

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