*Corresponding author. E-mail: christophe.lucas@ibaic.u-psud.fr Biological Journal of the Linnean Society, 2002, 75, 249–259. With 5 figures INTRODUCTION Phenotypic variation among sympatric insects may confound the correct identification of some species and further characterization in therefore needed. This is true for the ponerine ant, Pachycondyla villosa, described by Fabricius in 1804. P. villosa is one of the most common ants of the genus in the Neotropical Region. In recent years, P. villosa has been intensively studied in a number of biological fields including: his- tology and morphology (Camargo-Mathias & Caetano, 1991; Camargo-Mathias et al., 1991; 1992b; 1992b; 1992b; Camargo-Mathias & Caetano, 1992a, 1992b; 1995a; 1995b; 1996; Mariano et al., 2000); regula- tion of reproduction (Heinze et al., 1996; Trunzer et al., 1998); foraging behaviour (Lachaud et al., 1984; Hölldobler, 1985; Lachaud & Fresneau, 1985; Dejean & Corbara, 1990a, 1990b; Dejean et al., 1990; Valenzuela-Gonzalez et al., 1994; Dejean & Corbara, 1998); and ecology (Pérez-Bautista et al., 1985; Dejean, 1990). Discrepancies in behaviour and ecology between the mentioned studies, suggest some heterogeneity. For example, in Yucatan, Mexico, where P. villosa invari- ably lives with epiphytes, Dejean (1990) observed a strong tendency of young queens to nest in Bromelia epiphytes of the genus Aechmea. A number of other papers refer to a similar mode of nesting (Dejean & Corbara, 1990a, 1990b; Dejean et al., 1990; Camargo- Mathias & Caetano, 1991; 1992a; 1992b; 1995a; 1995b; 1996). Conversely, other studies refer to hollow branches of living or dead trees, abandoned preexist- ing nests, or rotten cocoa pods as the most character- istic nesting places (Lachaud et al., 1984; Hölldobler, 1985; Pérez-Bautista et al., 1985; Valenzuela- Gonzalez et al., 1994; Heinze et al., 1996; Trunzer et al., 1998). During our current study on colonies identified as P. villosa, consistent morphological differences were ob- © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 249–259 249 A multidisciplinary approach to discriminating different taxa in the species complex Pachycondyla villosa (Formicidae) CHRISTOPHE LUCAS 1 *, DOMINIQUE FRESNEAU 2 , KERSTIN KOLMER 3 , JURGEN HEINZE 3 , JACQUES H. C. DELABIE 4 and DANG B. PHO 1 1 Mécanismes de communication, Université Paris Sud, CNRS-UMR 8620, 91405 Orsay Cedex, France 2 LEEC, Université Paris Nord, CNRS-UPRESA no. 7025, F-93430 Villetaneuse, France 3 Biologie I, Universität Regensburg, D-93040 Regensburg, Germany 4 Mirmecologia, Convênio UESC/CEPLAC, C.P. 7, 45600–000, Itabuna, Bahia, Brazil Received 23 May 2001; accepted for publication 12 October 2001 A multidisciplinary approach provides new evidence that strongly supports the differentiation of three taxa previ- ously confounded in a single species, Pachycondyla villosa. All specimens studied were collected in the same loca- tion at Ilhéus, Bahia, Brazil. Bivariate plots of petiole heights vs. petiole lengths and isozyme patterns clearly differentiate the three taxa. Chain lengths and chemical structures of cuticular hydrocarbons are characteristic of each taxon. This congruent evidence shows that there are three different valid species. Ecological hypotheses are discussed to explain the benefits of these species remaining sympatric. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 249–259. ADDITIONAL KEYWORDS: ants – cuticular hydrocarbons – isozymes – morphometry – Pachycondyla inversa – Pachycondyla subversa – Pachycondyla villosa – Ponerinae – sympatry – taxonomy.