International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Effects of Anthropogenic Activities on Distribution and Abundance of the Epiphytic Orchid, Polystachya fusiformis (Thou.) Lindl. in the Manga Range Ecosystem, Kisii, Kenya Mageto Evans1, Abel Kamweya2, John Ochora3, Samson Maobe4 Corresponding Author: Jomo Kenyatta University of Agriculture and Technology, Department of Zoology, P.O. Box 3026-040200 Kisii, Kenya, Jomo Kenyatta University of Agriculture and Technology, Department of Zoology, P.O. Box 62000-00200, Nairobi, Kenya Jomo Kenyatta University of Agriculture and Technology, Department of Botany, P.O. Box 62000-00200, Nairobi, Kenya Senior Principal Research Officer, Kenya Agricultural Research Institute, Kisii, Kenya
Abstract: It has been observed that anthropogenic activities namely, farming, tree harvesting, seasonal fire regimes, introduction of exotic tree species like Eucalyptus and Greviella, and collection of herbs for medicinal use are going on and form a major threat for the orchid Polystachya fusiformis (Thou.) Lindl. This study determined the relative abundance and distribution of the species Polystachya fusiformis (Thou.) Lindl. in the Manga range ecosystem of Kisii, Western Kenya during two flowering seasons. Other results of the present study were analyzed with SPSS version 17 for paired sample correlations, OriginPro7 t-Test and ANOVA, Minitab 16 chi-square test. From the analysis there is a significant correlation between altitude and number of orchid population clusters with a p-value of 0.008 in the distribution of Polystachya fusiformis (Thou.) Lindl. which led to rejection of the null hypothesis. The Levene’s test for equal variance shows that at α 0.05 there is a significant difference between altitude and number of clusters as indicated by the P value of 0.00004. Of the 88 sites sampled, only 41sites had orchid clusters. Principal component analysis using Unscrambler 9.7 indicated that many of the orchid population clusters fell within the range of one or two orchid population clusters. The score plots from the two Hoteling’s outputs show how well data is distributed including sample patterns, groupings, similarities and differences during the study. The two analyses illustrated how fire affects the orchid population on fire prone sites of the range. Orchid population clusters progressively increased with increase with altitude range (from 1800m to 1850m) above sea level, but number of orchid population clusters decreased towards 1950m. Sites with minimal anthropogenic disturbances (1796m, 1830m, 1854m, 1886m, and 1890m) had a higher number of orchid population clusters.
Keywords: Orchidaceae, Polystachya fusiformis, mycorrhiza, pollinia, herbivory.
1. Introduction and Literature Review 1.1 Introduction Orchids are nonvascular perennial plants having simple leaves, parallel venation with flowers which display a variety of colours and fragrances. Leaves may be ovate lanceolate or orbiculate with varying sizes. Leaves are normally alternately positioned while the structure of the leaf depends on habitat conditions. Orchids have complex life cycles often involving a fungal partner in mycorrhiza and seed germination, and specific pollinators. Some have single bilaterally symmetrical flowers but most including Polystachya fusiformis (Thou.) Lindl. have a racemose inflorescence with a large number of flowers. Pollen is released in the form of pollinia which is a waxy mass of pollen grains held together by a glue-like viscin. Orchids tend to have highly specialized pollination systems which reduces chances of being pollinated and as such, orchid flowers remain receptive for 2-3 weeks before shriveling. The possible pollinators are lured by shape, fragrance, nectar and colour of labellum. Orchids are cosmopolitan plants which occur in all habitats except glaciers, with the highest concentration being found in the tropics especially in Asia, South America, Central America, and Africa. Terrestrial orchids form rhizomes, corms or tubers used as food reserves and as perenating organs. Epiphytic orchids have
modified aerial roots made up of spongy velamen which absorbs humidity. A majority of orchids are perennial epiphytes or lithophytes which grow anchored on trees, shrubs or on rocks. They are very sensitive to environmental change and are a subject of great concern at present. Threats facing orchids can be narrowed down to human activities including land clearance for agriculture, mining and urban development, weed invasion, introduction of exotic plant species, grazing, altered environmental conditions and collection of plants for horticulture and ethnobotanical uses. The family (orchidaceae) has a considerable economic value in horticulture, floristry, pharmaceutical and fragrance industries becoming a major source of income in some countries in Asia. All types of orchids are being sought by collectors such as Sutherlandshire orchid society and the American orchid society who encourage cultivation, collection of orchids, conservation and research. Orchids offer alot in the study of interaction of plants, fungi and animals (pollinators). 1.2 Orchidaceae Orchidaceae is an insect pollinated plant family composed of five monophyletic clades, which correspond with the currently recognized Subfamilies: Apostasioideae, Cypripedioideae, Orchidoideae, Epidendroideae, Vanilloideae[1]- [2]. Polystachya fusiformis (Thou.) Lindl.
Volume 2 Issue 8, August 2013 www.ijsr.net
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