POPULATION-DYNAMICS AND ADAPTIVE STRATEGIES OF MARTIODRILUS-CARIMAGUENSIS (OLIGOCHAETA, GLOSSOSCOLECIDAE), A NATIVE SPECIES FROM THE WELL-DRAINED SAVANNAS OF COLOMBIA

Martiodrilus carimaguensis (Oligochaeta, Glossoscolecidae) is a large, anecic native earthworm species which was found in natural and distur bed savannas in the Oxisols of the Colombian Llanos. Its population dy namics were studied in a native savanna, and in a 17 years old grazed grass-legume pasture where density and biomass were higher. Monthly ca st deposition on the soil surface in the improved pasture was 38.4x10( 3) fresh casts ha(-1), eleven times more than in the native savanna. A strong relationship was found between numbers of M. carimaguensis and numbers of fresh surface casts. Different patterns of adaptation to t he dry season were observed for adults and juveniles. Adults are activ e for eight months whereas juveniles enter diapause 3-4 months earlier . The vertical distribution pattern of the earthworm population also s hows marked seasonal changes. (C) 1998 Elsevier Science B.V.