Spatial distribution and abundance of <i>solanecio biafrae</i> (olive & heirne) c. Jeffrey and structure of weed communities in some Cocoa plots in Ekiti, Oyo And Cross River States, Nigeria

Abstract

Cocoa plots and cocoa agro-forests have served as sustainable land-use practice that conserve the biological diversity of the original tropical forests and remain the major source of Solanecio biafrae, a pot herb, and other useful tropical rainforest plants. The population of Solanecio biafrae may be endangered as its common sight in the local markets has been replaced by exotic vegetable species. This study determined the abundance of Solanecio biafrae and structure of weed communities in selected cocoa plots in Ekiti, Oyo and Cross-Rivers States with the aim of establishing the threat status and shift in species composition, and identifying possible invasive species. Enumeration of low-growing herbs was conducted in 19 cocoa plots following random sampling technique, with ten 1m wooden quadrats located within a 50m² area in each plot. The data were used to determine the Relative Importance Value (RIV) as a measure of abundance for each species. The Species Richness (R), Shannon-Wiener (H'), Equitability (J) and Dominance (D) and Jaccard indices were determined as measures of community structure. Seventy six (76) weed species belonging to 36 families were found. The species richness per plot ranged from 5 to 29. Of the 7 common weed species, Solanecio biafrae remained the most ubiquitous, being found in 15 plots. The RIV for S. biafrae ranged from 0.46 to 14.76 across plots. Most of the ubiquitous species were invasive plants, which included Chromolaena odorata, Asystasia gangetica, Oplismenus burmannii and Adenia cissampeloides. Across the plots in the three states, diversity indices ranged from 1.390 to 2.938 for Shannon-Wiener, 0.793 to 0.992 for Equitability and 0.057 to 0.271 for Dominance. These implied high species diversity, except in CR plots, and random distribution of the species. Jaccard index of similarity ranged from 0 to 90.91% across plots. The inter-state Jaccard index values ranged from 18.18 to 20.00%. The high values indicate less environmental heterogeneity and low values imply high environmental heterogeneity. The spread of Adenia cissampeloides in the cocoa plots may aggravate threat to S. biafrae populations.

Keywords: Cocoa plots, Invasive Plants, Solanecio biafrae, Species Diversity, Weed Communities.