Natural history and behavioural homology

Although similarities and differences among animals have long inspired ethologists, three misconceptions haunt the literature on behavioural evolution: the absence of 'ethofossils' seriously hampers detection of behavioural homology; behaviour is more variable and subject to experiential modification than morphology; and behaviour is especially subject to convergence. As a backdrop to address these issues, I briefly survey parental care by amniotes and antipredator mechanisms is non-avian reptiles. Although those behaviours remain inadequately sampled taxonomically, they clearly vary at several cladistic levels; they are conservative across some major groups, innovative within subclades, and exhibit apparent homoplasy among and within groups. These behavioural examples also illustrate contextual influences on the expression of traits, as well as how behavioural context can shape other aspects of development. Enhanced understanding of behavioural evolution will follow from greater emphasis on how developmental context, including behaviour itself, shapes phenotypes; from integration of data for fossil and recent organisms; and from much denser ethological sampling among taxa. Phylogenetic analyses of behavioural similarity should in turn provide exciting insights into the evolutionary roles of behavioural shifts and constraints, as well as inform our aesthetic appreciation for the richness of nature.