Influence of habitat type and climatic variables on spider assemblages in rainforest and derived Savannah regions of Southwestern Nigeria

Spiders are important ecological indicators and natural predators that play vital roles in terrestrial ecosystems. This study assessed the abundance, diversity, and distribution of spider species across two ecological zones—rainforest and derived savannah—in Ogun State, southwestern Nigeria. Sampling was conducted using systematic random sampling across various habitats: grassland, fallow bush, agro-ecosystem, and residential areas within Ogun State, Nigeria. A total of 60m × 120m plots were demarcated in each habitat, and spiders were collected using three standard techniques: hand picking, sweep netting, and pitfall trapping. Specimens were preserved in 70% ethanol and identified to family and species levels using established taxonomic keys and reference manuals. Results showed that spider species composition was relatively similar across habitats, but species abundance varied significantly. Families such as Lycosidae, Araneidae, and Salticidae were the most dominant across both zones, while families like Hersiliidae, Amblypygi, and Sparassidae were the least represented. Hogna spp., Pardosa injucunda, Hippasa spp., and Ocyale neatalanta exhibited high abundance, particularly in the rainforest zone. Climatic factors influenced spider activity, with a statistically significant positive correlation between species abundance and temperature (p < 0.01), and a weak, negative, non-significant correlation with rainfall. Seasonal analysis further revealed that spider abundance, particularly of the family Lycosidae, was higher in both wet and dry seasons, with notable declines in other families during the dry season. Despite ecological and climatic differences, the similarity in spider abundance between the two zones was relatively high (80.5%). However, residential habitats showed distinct patterns, with little similarity to other habitat types. The study concludes that habitat complexity, prey availability, and climatic factors are major determinants of spider distribution and abundance. These findings underscore the need for ongoing biodiversity monitoring and the conservation of habitat heterogeneity to sustain arthropod diversity in tropical landscapes.