Community structure of land flatworms (Platyhelminthes, Terricola): comparisons between Araucaria and Atlantic forest in Southern Brazil

Land flatworms (Platyhelminthes: Terricola) are sensitive to environmental changes and might be used as biological indicators of the degree of disturbance of their habitats. Nevertheless, studies on the structure of land flatworm communities are rare. In the present study, we investigated the terrestrial flatworm communities in two types of ombrophilous forest, Atlantic forest and Araucaria forest, aiming to answer the following questions: (1) Is the community structure of the two types of ombrophilous forest different? (2) Are there differences, regarding community structure, among distinct fragments of Araucaria forest? (3) Are there indicators of edge effects in these communities? The study site, the National Park of Aparados da Serra, is mainly covered, at high altitudes, by fragments of Araucaria forest immersed in a matrix of open areas (grasslands) and, in low altitudes, by a continuous Atlantic forest. We conducted monthly surveys in the two types of forest with three replications per forest type over a period of 2 years. Results indicated that: (1) community structure is clearly distinct between the two types of forest, as well as among fragments of the Araucaria forest; (2) there are no apparent edge effects; (3) the diversity indices of the two types of ombrophilous forest are not significantly different (Atlantic forest-H'=2.87, Araucaria forest-H'=2.55; p > 0.05); and (4) there are significant differences in diversity indices between two fragments of Araucaria forest (H'=2.92 and 2.47; p < 0.001). The following factors could affect community structure: type of vegetation, degree of human disturbance, and abiotic factors, such as pH and temperature.