Species Richness and Diversity Reveal that Human-Modified Environments are not Wastelands

Abstract

Urbanization is often associated with the loss of habitats for many species but the pattern of invertebrate abundance in increasingly human-dominated urban areas is less well documented particularly for the expanding urban Africa. This study investigated the composition and community structure of spiders in relation to human activities at the foot of the Uluguru Mountains in Morogoro city, Tanzania. Three different sampling methods: pitfall trapping, sweep netting and active searching were used to collect spiders in the study area and to allow comparison between structurally different habitat sites. Spider abundance differed significantly
between habitat types and was influenced by the sampling methods used. Family diversity and richness showed no significant differences across the sites. The spider species consisted of primarily three functional groups: ground wanderers, web builders and plant wanderers, and showed no within-group differences in abundance between sites. Similarity index between the study sites revealed a considerable overlap in the spider families present. No correlation between habitat variables: tree shade, herbaceous cover and ground cover and spider functional groups were found, suggesting that habitat alteration has minimal effect on the abundance of these invertebrate taxa. Further, cluster analysis at the family level revealed that spiders formed clusters on the basis of their hunting strategies, suggesting the avoidance of competition among spider guilds. This study provides insight into the importance of human-dominated areas on invertebrate biodiversity and serves as a basis for future work.