Biodiversity and Conservation 11: 1091–1104, 2002.  2002 Kluwer Academic Publishers. Printed in the Netherlands. Terrestrial flatworm (Platyhelminthes: Tricladida: Terricola) diversity versus man-induced disturbance in an ombrophilous forest in southern Brazil 1, 1 * FERNANDO CARBAYO , ANA MARIA LEAL-ZANCHET and EMERSON 2 M. VIEIRA 1 ´ ˆ ´ Instituto de Pesquisas de Planarias, Centro de Ciencias da Saude – Universidade do Vale do Rio dos 2 ˜ ´ Sinos ( UNISINOS), Av. Unisinos 950, 93022-000 Sao Leopoldo-RS, Brazil; Laboratorio de Ecologia de ´ ˆ ´ Mamıferos, Centro de Ciencias da Saude – Universidade do Vale do Rio dos Sinos ( UNISINOS), Av. * ˜ Unisinos 950, 93022-000 Sao Leopoldo-RS, Brazil; Author for correspondence (e-mail: fernando@cirrus.unisinos.br; fax: 155-51-5908122) Received 30 January 2001; accepted in revised form 25 June 2001 Key words: Bioindicators, Fragmentation, Geoplanidae, Platyhelminthes, Reforestation, Subtropical rainforest Abstract. Terrestrial flatworms, or Terricola, are sensitive to environmental changes and therefore might be excellent indicators of the conservation status of natural habitats. The present study aimed to answer two main questions: (1) is terrestrial planarian diversity affected by human disturbances, and (2) is there ˜ any species or group of species that indicates such disturbance? The study site, National Forest of Sao Francisco de Paula, Brazil, was originally covered by a mixed ombrophilous forest, but successive reforestations and selective logging have modified the original landscape. We studied Terricola diversity in the four main habitats in the study area: mixed ombrophilous forest (NA), ombrophilous forest with selective Araucaria angustifolia logging (N), A. angustifolia reforestation (A), and reforestation of Pinus elliottii (P). According to an increasing degree of disturbance, the habitats might be ordered as follows: (NA),(N),(A),(P). We conducted 24 surveys in each habitat over a period of 1 year. Our results indicate that: (1) Terricola diversity is inversely related to the degree of habitat disturbance; (2) there are species (Geoplana franciscana, Geoplana sp. 5, and possibly Geoplanidae 3 and Notogynaphallia guaiana) that prefer habitats located on the extreme right along the main axis of a detrended corre- spondence analysis ordination and therefore can be considered as indicators of well preserved, natural habitats. On the other hand there are species (Xerapoa sp. 1, Choeradoplana iheringi, G. marginata sensu Marcus and Geoplana sp. 2) preferring more disturbed habitats, which may form biological indicators of such disturbances. Introduction Terrestrial flatworms (Platyhelminthes: Tricladida: Terricola) feed on a wide range of invertebrates, like earthworms, terrestrial leeches, isopods, snails, insect larvae, and termites (Du Bois-Reymond Marcus 1951; Jones et al. 1995; Ogren 1995; Sluys 1999). Some Terricola are necrophagic and others can even prey on other flatworms, at least under laboratory conditions (Winsor 1977; W. Santos, personal communica- tion). These animals are generally part of the soil cryptofauna (Winsor et al. 1998). They are stenohygric, depending strongly on the degree of humidity of its mi-