Systematic studies of giamensis and hanneae complexes (Homalomena : Homalomeneae : Araceae)

Hoe, Yin Chen (2012) Systematic studies of giamensis and hanneae complexes (Homalomena : Homalomeneae : Araceae). Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Homalomena Schott is one of the most abundant, speciose, least understood aroid genera in Tropical Southeast Asian. Taxonomy, pollination investigations, floral odour analyses and phylogeny of six Homalomena species in Hanneae and Giamensis Complexes were investigated in this study. Three new species- Homalomena gastrofructa sp. nov. ined. Y. C. Hoe, S. Y. Wong & P. C. Boyce, H. velutipedunculata sp. nov. ined. Y. C. Hoe, S. Y. Wong & P. C. Boyce and H. baangongensis sp. nov. ined. L. S. Tung & Y. C. Hoe were discovered The main pollinator for all the seven Homalomena species is Parastasia spp. (Scarabaeidae: Rutelinae). Chrysomelids (Chaleonus schawalleri, Chaleonus spp. & Deceptina sp. (Coleoptera: Chrysomelidae) are the opportunist pollinators. Colocasiomyia (Diptera: Drosophilidae), Trigona sp. (Apinae: Meliponini), unidentified earwigs (Dermaptera), unidentified pale yellow and orange chrysomelids (Coleoptera: Chrysomelidae), unidentified Nitidulidae and Staphylinidae are merely visitors. The food reward interpistillar staminode is the main pollinator attraction. Pollinator Parastasia spp. that consumed the interpistillar staminode is regarded as highly mutualistic between Parastasia-Homalomena. During pistillate anthesis (Hanneae Complex) floral odour serves to attract and retain insect pollinator until the end of the anthesis by remitting second less intensified odour during staminate anthesis. Floral odour serves to attract insect pollinator only in pistillate anthesis (Giamensis Complex) but did not or weakly remitted flora odour during staminate anthesis. Gas chromatography-mass spectrometry (GC-MS) analyses reveal three compounds: Cyclohexane, 2-ethenyl-l, l-dimethyl-3-methylene-, Cyclohexane, 4- methyl-2-methylene-l-(1-methylethylidene)- and Cyclohexene, 4-methyl-3-(1- methylethylidene)- and these have never been reported in Araceae. Hanneae Complex species can be represented by 1) majorly produce Terpenoid compounds especially alpha-pinene). Whereelse Giamensis Complex species can be differentiated by 1) emitting majority compound of Acetic Acetic acid, butyl ester and Furan, 3-(4-methyl-3-pentenyl)- but absent during staminate anthesis. Phylogeny was constructed for 17 taxa of all the complexes in Cyrtocladon, Homalomena, Punctulata and Chamaecladon Supergroups based on the nuclear internal transcribed spacer. The aligned sequences were analysed in PAUP* 4.0blO for maximum parsimony and `Advanced Mode' analyses for maximum likelihood. The tree supported delimitation of Hanneae and Giamensis Complexes from taxonomy, pollination, floral odour were mapped onto the phylogenetic tree to provide further evidences on the separation of both Complexes. This study provided an indepth investigation to explain the high level of biodiversity in the genus Homalomena in Borneo.

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