THE INFLUENCE OF LARGE, VEGETATED TERMITARIA AND LARGE HERBIVORES ON SPIDER (ARANEAE) DIVERSITY IN MIOMBO WOODLANDS

Abstract

This study reports on spider species richness, abundance, and spider species community composition, in relation to differing herbivore impacts in miombo woodlands that have large vegetated termitaria. The chosen woodlands formed a gradient of herbivore impacts from Chizarira National Park that had high herbivore impacts mostly due to the presence of elephants, to Chivero Game Park that had intermediate herbivore impacts and no elephant population, and to the Chivero Bird Sanctuary that had minimal herbivore impacts. Pitfall traps were used to sample spiders on the large termite mounds and in the adjacent woodland matrix, and these spiders were consequently classified into morpho-species. In order to explain any differences in spider species richness, abundance, and spider species community composition the habitat structure was characterized through measuring ground cover, aerial cover, and woody plant species richness. The Welch two sample t-test revealed no significant differences in spider abundance between termite mounds and the woodland matrix in the Bird Sanctuary, a higher abundance in the woodland matrix in the Chivero Game Park, and a higher abundance on the termite mounds in the Chizarira National Park. The same results were observed with spider richness except for a higher richness in the woodland matrix in the Bird Sanctuary.

Generalized linear models showed that no single environmental variable was responsible for observed patterns in spider abundance and richness in all the study areas. Instead, it was established that various variable interactions (of different orders) of the aerial cover, ground cover, woody plant richness, and site (termite mounds/woodland matrix) influence spider richness and abundance differently, with the number of interactions increasing across the herbivore impact gradient, from the least impacted (the Bird Sanctuary) to the most impacted (Chizarira National Park). The importance of termite mounds in determining spider diversity also seemed to increase across this gradient. Non metric multi-dimensional scaling and hierarchical cluster analysis revealed different spider species community composition on termite mounds and in the surrounding woodland matrix, and this difference increased from the lowest herbivore impact area to the highest, with distinct spider assemblages being realized in the most impacted woodland. It was therefore concluded that termite mounds are not hotspots for the diversity of ground spiders as they are to other animals, but rather act as refugia for ground dwelling spiders in highly impacted miombo woodlands.