Abstract

Over the past two decades, behavioural biologists and ecologists have made effective use of the comparative method, but have often stopped short of adopting an explicitly phylogenetic approach. We examined 68 behaviour and life history (BLH) traits of 15 penguin species to: (i) infer penguin phylogeny, (ii) assess homology of behavioural characters, and (iii) evaluate hypotheses about character evolution and ancestral states. Parsimony analysis of the BLH dataset found either two shortest trees (characters coded as unordered) or a single shortest tree (characters coded as a combination of unordered and Dollo). The BLH data had significant structure. Kishino–Hasegawa tests indicated that BLH trees were significantly different from most previous estimates of penguin phylogeny. The BLH phylogeny generated from Dollo characters appeared to be less accurate than the tree derived from the completely unordered dataset. Dividing BLH data into display and non-display traits resulted in no significant differences in level of homoplasy and no difference in the accuracy of phylogeny. Tests for homology of BLH traits were performed by mapping the characters onto a molecular tree. Assuming that independent gains are less likely than losses of character states, 65 of the 68 characters were likely to be homologous across taxa, and at least several characters appeared to have been stable since the origin of modern penguins around 30 Myr. Finally, the likely BLH traits of the most recent common ancestor of extant penguins were reconstructed from character states along the internal branch leading to the penguins. This analysis suggested that the “proto-penguin” probably had a similar life history to current temperate penguins but few ritualized behaviours. A southern, cool-temperate origin of penguins is suggested.