Diversity and Species Composition of the Spider Fauna of the Aripo Savannas, Trinidad, W.I.

Abstract

Little attention has been placed on the biodiversity of natural savannas, which are declining worldwide. On the island of Trinidad, West Indies, many studies have been conducted on the flora in the Aripo Savannas Scientific Reserve, but none on the arachnid fauna it contains. This study aims to document and compare the biodiversity of the spiders found in the three main habitat types in the reserve: savanna, palm marsh and marsh forest. Three localities of each habitat were sampled for 15 hours each, utilising sweep-netting and visual search methods to collect spiders from a wide spectrum of microhabitats. The spider fauna was separated into three functional groups: plant wanderers, ground wanderers and web-builders. A total of 585 individuals belonging to 69 species distributed among 21 families were found on the reserve. Data were analysed using Analysis of Variance (ANOVA), species abundance models and multi-dimensional scaling plots. Habitat type was found to have no significant influence on species richness, diversity, evenness or dominance. All habitat types were dominated by web-builders; a smaller proportion of plant and ground wanderers were found as could be expected since most species in these groups are cryptic. However, the savanna possessed the most distinct spider species assemblage.