The morphology and taxonomy of invasive weeds from various habitats in the Ashanti Region, Ghana

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Weed invasion presents a serious threat to Ghana’s agriculture, forestry and ecotourism, which are the mainstay of the country’s fragile economy. Aquatic weeds, in particular, have become a nightmare for most Ghanaians as these have not only succeeded in invading numerous water bodies but also, threaten the energy sector as well as interfere with vital water supply systems. These notwithstanding, very little is known about invasive weeds in Ghana notably diversity, modes of introduction, and ecosystems they have invaded. The present study sought to determine the diversity and distribution of invasive species in the humid forest environment of Ashanti. This involved 12 months of field surveys and specimen collections. Keys and herbarium specimens from University of Ghana, Kwame Nkrumah University of Science and Technology and sometimes from Kew Botanic Garden aided in the identification. A total of 43 species were identified belonging to 19 families and 41 genera, which also comprised six life/growth forms. The species were found in five different habitats namely: cultivated, degraded, ruderal, forested and aquatic habitats. The greatest number of species was recorded in degraded habitat (31) while cultivated and forested habitats had the least numbers of 24 and 22 species respectively. However, the differences in the species distribution were not statistically significant (p > 0.05, Appendix 2A) supporting the view that the weeds thrive in all types of habitats. The most common invasive weeds in the region were Chromolaena odorata, Centrosema pubescens and Rottboellia cochinchinensis recording overall relative frequencies of 12.8, 10.4 and 6.4 respectively. Others were Euphorbia heterophylla (4.9), Calopogonum mucunoides (4.5), Mimosa pudica (4.4), Digitaria insularis (3.7), Ageratum conyzoides (3.5) and Leucaena leucocephala (3.2). These results reveal highly compromised ecosystems in the region and the growing menace of alien weed invasion in Ghana as a whole. Mitigation efforts require awareness creation, capacity building and large-scale inventories of these ecological miscreants. A dichotomous key was constructed to ease identification.
A thesis submitted to the Department of Theoretical and Applied Biology, College of Science in partial fulfilment of the requirements for the degree of Master of Science, 2004