Stable Isotopic Studies of Earthworm Feeding Ecology in Tropical Ecosystems of Puerto Rico

Hendrix, PF, SL Lachnicht, MA Callaham, and XM Zou. 1999. Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of puerto rico. Rapid Communications in Mass Spectrometry 13 (13): 1295-9.

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used 13C and 15N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less 15N enrichment (delta 15N = 3–6%) than exotic Pontoscolex corethrurus (15N = 7–9%) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in 15N enrichment (delta15N = 6–9%), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in 15N than those in the forest sites, but more highly enriched in 13C suggesting assimilation of C from the predominant C4 grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright # 1999 John Wiley & Sons, Ltd.