Evolutionary Studies of Heterochrony in Tropical Plants

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1. Various kinds of plant materials were collected from Malay Peninsula, Sarawak and Sabah, Malaysia, and Celebes, Seram (Moluccas) and Sumatra, Indonesia. Using those, the following studies were conducted.2. An analysis of molecular phylogenetic relationships among species of Monophyllaea (Gesneriaceae) based on matK sequences is going on. A comparative analysis will be made with previous classifications of the genus based on morphological characters.3. Morphogenetic and histochemical studies have been carried out of extremely unequal cotyledons of Monophyllaea horsfieldii and M.hirtella. Morphogenesis takes place at the base of one of two cotyledons, which grows into a common foliage leaf. A non-apical, intercalary meristem appears at the base of the cotyledon. Which cotyledon enlarges is due to competition between two cotyledons. In the annual species M.glabra, the meristem disappears during its reproductive phase much earlier than in most perennial species. However, in the presumably annual (or monocarpous) M.minima (nom.nud.), the meristem remains during the reproductive phase. In M.singularis with inflorescenses arising on the petiolode, the petiolode, meristem appears between two cotyledons, whereas in most other species, the meristem appears below two cotyledons.4. A molecular phylogenetic analysis of Matoniaceae showed that Matonia and Phanerosorus are closely related, through they are morphologically distinct. Observations of heteroblastic leaf morphology of the genera suggest that the pinnate, pendulous Phanerosorus leaves were derived from the pedate Matonia leaves.5. Field observations suggested that our collections include rheophytes that were recently derived from land species, and those that were speciated secondarily from rheophytes. They will be useful for further studies of speciation involving heterochrony.