The evolution of search modes: Ecological versus phylogenetic perspectives

Both theoretical and empirical studies, many of them on lizards, suggest that foraging behaviors often take one of two forms, sometimes called 'modes': active search or sedentary ambush. I tested this by expanding the database on lizard foraging behaviors and testing for the existence of modality in this much larger database. My findings did not support the validity of some previous analyses. Greatly expanded lizard data did not show a bimodal distribution of foraging behaviors. Phylogeny, however, was a strong predictor of behavior. One clade, Autarchoglossa, was characterized by a wide range of foraging behaviors, but closely related species tended to exhibit similar behaviors. Two other clades, Iguania and Gekkota, retain the ancestral sedentary behavior. This phylogenetic trend, combined with phylogenetically biased sampling, may have been responsible for the appearance of bimodality in previous studies. Thus, bimodality of search modes is rejected. Some previous generalizations regarding correlates of foraging 'mode' need to be reevaluated in this light.