in Sri Lanka - Ministry of Environment

Analysis of Seed Plants of Sri LankaSiril Wijesundara 1 , H. S. Kathriarachchi 2 , S. W. Ranasinghe 1 , G. Hapuarachchi 21Department of National Botanic Gardens2University of ColomboSeed-bearing plants or seed plants are perhaps the most obvious group of plants on earth.They include gymnosperms and angiosperms.In gymnosperms the seeds are not enclosed in a fruit. Gymnosperms can be further classifiedinto gnetophytes, cycads, ginkgo, and conifers. In Sri Lanka there are no native conifers,gnetophytes or ginkgo. There are only two gymnosperm species In Sri Lanka belongingto genus Cycas in the family Cycadaceae. They are Cycas nathorstii (madu) and Cycaszeylanica (Lindstrom & Hill, 2007). Of these two species, Cycas zeylanica (maha madu) is ahighly threatened species. The habitat of this species was damaged by tsunami in 2005 andit is believed that the population of this species was seriously affected (Lindstrom & Hill, 2007).Angiosperms are flowering plants that produce seeds enclosed in a fruit. They are the mostdiverse group of plants with an estimated number of 200,000 to 400,000 species (Thorne,2002). These species are classified into 415 families (APG, 2009)Sri Lanka’s angiosperm flora has been explored, studied and documented by many botanistssince the colonial times (Jayasuriya, 2007). Trimen’s Handbook to the Flora of Ceylon (Trimen,1893-1900), was considered as one of the most comprehensive floras of that time. Basedon Trimen’s Flora, Abeywickrama (1945) reported 1,065 genera and 2,855 species in 171families. Out of those 853 species were considered to be endemic to Sri Lanka.The revision of the Trimen’s Flora (Dassanayake et al., 1980-2000) described 3,771 speciesin 1,363 genera and that included many naturalized species. The total number of endemicspecies (including varieties and subspecies) was about 1,000 according to that revision.Compared to the other countries in South Asia, angiosperm diversity in Sri Lanka is remarkablyhigher due to multitudes of factors. Origin, affinities and biogeography of our flowering plantshave been discussed by several authors in the past (Trimen, 1885; Abeywickrama, 1945;Ashton and Gunatilleke, 1987).One of the striking features of our angiosperm flora is the high percentage of endemic species.Analyses done during the preparation of this Red List revealed that there are 894 endemicangiosperm species in Sri Lanka. These species are distributed mainly in the central andsouth west region of the island (The map preceding page). However, there may be moreendemic species in the north east and eastern areas of the country which were not botanizedas extensively as the south western regions.340