Commentary Where have all the trees gone? The declining use of phylogenies in animal behaviour journals J. Jordan Price a, * , Mary K. Clapp a , Kevin E. Omland b, 1 a Department of Biology, St Mary’s College of Maryland b Department of Biological Sciences, University of Maryland Baltimore County article info Article history: Received 16 September 2010 Initial acceptance 21 October 2010 Final acceptance 23 November 2010 Available online 6 January 2011 MS. number: AS-10-00616R Keywords comparative method ethology evolution literature phylogeny Tinbergen tree Phylogenetic comparative methods have a rich history in the study of animal behaviour (Brooks & McLennan 1991; Martins 1996; Owens 2006). For early ethologists, comparative studies of multiple species were an essential technique for reconstructing the processes and patterns of behavioural evolution (Lorenz 1941, 1958; Tinbergen 1951, 1959, 1963; McKinney 1965; van Tets 1965; also see Darwin 1872). Indeed, this approach was one of Niko Tinbergen’s four ‘levels of analysis’, the others being the functional significance, ontogenetic development and proximate mechanisms underlying such traits (Tinbergen 1963; Sherman 1988). To these researchers, phylogenetic relationships among species provided a fundamental framework upon which our understanding of the other processes responsible for animal behaviour may be derived (Brooks & McLennan 1991). Despite its early importance, however, the historical component of behaviour subsequently received relatively little attention in comparison to other research interests in the field (Brooks & McLennan 1991; Wenzel 1992; Ryan 1996; Owens 2006). This reduced attention was due in part to early scepticism that behav- ioural similarities between species due to homology could be distinguished from similarities due to convergent evolution (Atz 1970). Behavioural traits were often considered far too labile and homoplasious to be useful as characters in phylogenetic analyses (reviewed by Wenzel 1992). But this change in focus also coincided with a variety of exciting new approaches for understanding behavioural traits (e.g. Hamilton 1964; Maynard Smith 1974) and a general shift in interest towards current adaptive function (Ryan 1996; Owens 2006). Wenzel (1992, page 361) put it bluntly in his assessment that ‘ethology has made almost no advance with respect to a phylogenetic understanding of behavior since the late 1950s’. Yet, during this same time period, another science was flour- ishing. Hennig’s (1966) cladistic methods inspired a progression of new techniques for estimating phylogenetic relationships and comparing traits across taxa, which together revolutionized our abilities to reconstruct character evolution (Brooks & McLennan 1991; Harvey & Pagel 1991; Avise 2004; Freckleton 2009). For example, from a statistical perspective, accurate phylogenies are necessary to transform comparative data so that they do not violate the assumptions of statistical independence (Felsenstein 1985; Garland et al. 1992; Martins & Hansen 1997). Studies also * Correspondence: J. J. Price, Department of Biology, St Mary’s College of Maryland, 18952 E. Fisher Road, St Mary’s City, MD 20686, U.S.A. E-mail address: jjprice@smcm.edu (J.J. Price). 1 K. E. Omland is at the Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, U.S.A. Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav 0003-3472/$38.00 Ó 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.anbehav.2010.12.004 Animal Behaviour 81 (2011) 667e670