Oecologia (2003) 135:422–430 DOI 10.1007/s00442-003-1193-8 COMMUNITY ECOLOGY Bernhard Stadler · Pavel Kindlmann · Petr milauer · Konrad Fiedler A comparative analysis of morphological and ecological characters of European aphids and lycaenids in relation to ant attendance Received: 18 November 2002 / Accepted: 20 January 2003 / Published online: 11 March 2003 # Springer-Verlag 2003 Abstract Ants are a major environmental factor for many insect species. For example, aphids and lycaenids have evolved an array of associations with ants ranging from obligate myrmecophily to the avoidance of contact. Here we (1) analyze the predictive power of different ecolog- ical and morphological traits for explaining the strength of the association between ants and aphids/lycaenids and (2) contrast different taxonomic levels with respect to the variance explained by ant attendance. Data come from a literature survey including 112 species of aphids and 103 species of lycaenids from Europe. For aphids, feeding on woody plant parts is positively associated with ant attendance, while a high degree of mobility, feeding in isolation, and the possession of wings in the adult stage are negatively associated with ant attendance. In ly- caenids, feeding on inflorescences and feeding on Fabaceae host plants is closely associated with ant attendance, while living in forests bears a smaller likelihood to establish mutualistic relationships. Body size always appeared to be a poor predictor for the degree of ant attendance. Overall, in both insect groups less than 10% of the variation in the ecological traits recorded is explained by the different modes of ant association. When decomposing the variance in traits explained by ant attendance at different taxonomic levels, aphids and lycaenids show contrasting results. In aphids, most variance in the degree of ant attendance is explained at the subfamily level and least at the species level. The opposite is true for lycaenids, where most variance is explained at the lowest taxonomic level. Possible mech- anisms explaining these different patterns of associations with ants are suggested. Keywords Aphids · Lycaenids · Ant–myrmecophile interactions · Mutualism · Comparative analysis Introduction Ants have developed close associations with very differ- ent organisms from different kingdoms. For example, they have developed mutualistic interactions with more than 465 plant species from over 52 families (Jolivet 1996), with fungi cultivated in gardens (Mueller et al. 1998), and with insects from which the ants may collect honeydew or nectar (Hölldobler and Wilson 1990). Frequently, however, closely related species within each of these groups of organisms exhibit quite different degrees of associations with ants. The reasons for these divergent developments are still largely unknown. Among homopteran species, which feed on the same host plant and even on the same plant organ, some species may be closely attended, while others are never visited by ants. For example, different aphid species of the genus Cinara feeding on spruce, pine or larch have developed different associations ranging from obligate myrmecophily to the absence of any interactions on each of their respective host plants (Scheuer 1964). Closely related lycaenid species usually show a less pronounced variability (Fiedler 1991a), although exceptions exist (Drupadia/ Cheritra group, Seufert and Fiedler 1996; Ogyris, Braby 2000). These different degrees of associations with ants indicate that there are many solutions to respond to an omnipresent predacious group of organisms like ants. B. Stadler ( ) ) Bayreuth Institute for Terrestrial Ecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany e-mail: bernhard.stadler@bitoek.uni-bayreuth.de Fax: +49-921-555799 B. Stadler Harvard University, Harvard Forest, P.O. Box 68, Petersham, MA 01366, USA P. Kindlmann · P. milauer Faculty of Biological Sciences, University of South Bohemia, BraniÐovskµ 31, 370 05 C ˇ eskØ Bude ˇjovice, Czech Republic K. Fiedler Department of Animal Ecology I, University of Bayreuth, 95440 Bayreuth, Germany