Seasonal changes in earthworm diversity and community structure in Central Cote d'Ivoire

This study assessed the impact of seasonal variation in the structure and diversity of earthworm communities of a savanna protected for 27 years in the central region of Cote d'Ivoire. Earthworm species were sampled in 1995 at monthly intervals from January to December on a 95 x 50 m experimental plot, using direct hand-sorting techniques. Each month, 10 monoliths of 1 m(2) x 40 cm were randomly selected from a stratified bloc design. Ten earthworm species were collected over the study period. Chuniodrilus zielae from the Eudrilidae family was by far, the most important earthworm species in term of abundance. Although earthworm diversity varied significantly, the effect of seasonal variation was unclear. Sampling efficiency of species richness varied from 80% to 100% regardless of the rainfall variation. On a seasonal time scale the C-score was lower (0.139) than expected (0.154), showing that earthworm communities exhibit a random pattern of organization. There was no evidence of non-random seasonal niche overlap because the Czechanowski index (0.50) was not significantly larger than expected (0.49). (c) 2006 Elsevier Masson SAS. All rights reserved.