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Study of natural hybridisation in some tropical plants using amplified fragment length polymorphism analysis
Author
Teo, Lai Lai
Supervisor
Gan-Yap, Yik Yuen
Lee, Sing Kong
Abstract
A Hybrid is the product of breeding between different plant species. Most species do not hybridise under natural circumstances. In cultivation, where external reproductive barriers are removed, hybridization is common. In temperate regions, hybridization is not a rare phenomenon. In contrast, very few natural hybrids have been found in tropical regions. In Singapore and Peninsular Malaysia, where the number of species of flowering plants is estimated to be 8000-9000, less than 10 natural hybrids have been discovered. These include, the duku-langsat (Lansium domesticum), Mangifera odorata, hybrids of Nepenthes, Begonia decora x venusta, hybrids of Globba and hybrids of Rhododendron. Except for Globba, no detailed studies have been carried out on these hybrids. Their identification as hybrids was based mainly on alpha-taxonomy. In the present study, Mangifera odorata, hybrids of Nepenthes, Begonia decora x venusta, duku-langsat were included. A DNA-fingerprinting method (i.e. Amplified Fragment Length Polymorphism) was employed to study the hybrid status of these plants. Mangifera odorata was confirmed to be a hybrid between its putative parents, M. indica and M. foetida. The hybrid status of the three Nepenthes hybrids (N. x trichocarpa, N. x hookeriana and N. rafflesiana x gracilis) found in Singapore was confirmed. The results indicated that there is a lack of backcrossing between these Nepenthes hybrids and their parental species. The Begonia hybrid found at Cameron Highlands formed hybrid swarms, which lead to the breakdown of the species boundary between the two morphologically distinct parental species. AFLP analysis showed that duku-langsat is not a hybrid between duku and langsat because they shared all the langsat bands and none of the duku bands. In the phenogram, they are clustered with langsat and are therefore thought to be a lineage of langsat that obtained some characteristics of duku. Of the four groups of putative hybrid studied, Mangifera odorata and the hybrids of Nepenthes might be leading to speciation. However, hybrid speciation does not seem to be an important mechanism in the evolution of tropical rain forest. Very few of the tropical plant species studied are known to be of hybrid origin. In disturbed areas, such as Cameron Highlands, hybridization seemed to lead to breakdown of species boundaries and did not contribute to speciation.
Date Issued
2001
Call Number
QK982 Teo
Date Submitted
2001