Ana García Moreno

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

Abstract The structure and seasonal changes of earthworm communities were evaluated in a natural savanna and in a improved grass-legume pasture in a Colombian oxisol over a period of 18 months. One plot of 90×90 m was isolated in each of the systems and each month five samples of 1 m2×0.5 m and ten of 20×20×20 cm were randomly selected from a stratified block design. Species richness was similar in the two evaluated plots (seven species), whereas diversity measured by the index, H (Shannon and Weaver 1949) was clearly different, i.e. H=2.89 in natural savanna and H=1.29 in pasture. This is explained by differences in earthworm community structure. The average annual density in the savanna was 49.8, ranging from 10.8 to 135.8 individuals (ind) m–2, and biomass was 3.3 g m–2 (hand-sorting method), ranging from 0.9 to 11.5 g m–2. In the man-made pasture, density was 80.1 ind m–2 on average, ranging from 24 to 215.8 ind m–2 and biomass was more than tenfold higher, ranging from 29.2 to 110.4 g m–2. This was especially due to the presence of a large glossoscolecid anecic species, Martiodrilus carimaguensis Jiménez and Moreno, which has been greatly favoured by conversion of savanna to pasture. Endogeic species were dominant in the natural savanna whereas the anecic species accounted for 88% of total earthworm biomass in the pasture. Total earthworm density and biomass were significantly different in the two systems studied (t-test). The results indicate a clearly positive response of earthworm communities to improved pastures, a type of land use that is being increasingly adopted in moist neotropical savannas.

Population dynamics and adaptive strategies of Martiodrilus carimaguensis (oligochaeta, glossoscolecidae), a native species from the well-drained savannas of Colombia

Abstract Martiodrilus carimaguensis (Oligochaeta, Glossoscolecidae) is a large, anecic native earthworm species which was found in natural and disturbed savannas in the Oxisols of the Colombian Llanos. Its population dynamics were studied in a native savanna, and in a 17 years old grazed grass-legume pasture where density and biomass were higher. Monthly cast deposition on the soil surface in the improved pasture was 38.4×103 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 the dry season were observed for adults and juveniles. Adults are active for eight months whereas juveniles enter diapause 3–4 months earlier. The vertical distribution pattern of the earthworm population also shows marked seasonal changes.

The status of Gilberto Righi's earthworm collection at the museum of Sao Paulo, Righi memorial: Tropical ecology

Dr. Gilberto Righi devoted all his life to the study of the worms of South America. The oligochaete material gathered throughout his professional life (more than 1600 containers) has been deposited in the collections of Oligochaeta of the Museu de Zoologia Universidad do Sao Paulo and the INPA in Manaus, both in Brazil. Together with the collection of specimens, the bibliography compiled by Dr. Righi is stored at the Museum of Sao Paulo. Both specimens and literature collections are computerized.

Contribution to the knowledge of Spanish Lumbricidae: II.Dendrobaena alvaradoin. sp.

Abstract A new species is recorded, Dendrobaena alvaradoi, from Galapagar (Madrid, Spain). Its morphology is described and the soil examined in which it was found. Similarities and differences with related species are discussed.