Variation in ground dwelling insect assemblages within a fragmented agricultural landscape at Sebele content farm, Gaborone, Botswana

A study was conducted at Sebele Content Farm in Gaborone, Botswana to investigate the effects of fragmented agricultural landscape on species richness, diversity and abundance of ground dwelling insects. The agricultural landscape mosaic consisted of a mature orchard, crop field, irrigated fodder field (pasture land), fenced grazing land, and a natural forest. The ground dwelling insects were sampled 31st January to 18 March 2010 using passive pitfall traps placed on the five habitats. The results showed significant differences in ground dwelling insect species richness, diversity and abundance among five habitats, indicating that fragmentation influenced insect assemblages within the farm. The data showed higher variation in species richness and abundance over the sampling period of the study. The most abundant species were from the family, Tenebrionidae with a total of 251 individuals. The highest species richness was obtained from grazing land and crop field. A significantly lower insect diversity was obtained from forest and pasture land. Cluster analysis revealed similarities in ground dwelling insect assemblage of sites mostly used for agriculture. This was confirmed by principal component analysis and correspondence analysis which separated crop field, orchard and grazing land from forest land. The species richness from all five habitats was generally lower suggesting a possible decline in insect species diversity within Sebele Content Farm.