Megapode phylogeny and the interpretation of incubation strategies

Among megapodes, several incubation stategies can be recognized. Eggs are incubated by heat generated from microbial decomposition, volcanism, or the sun. For a long time, controversy has existed whether these strategies represent primitive traits, inherited from reptilian ancestors, or have evolved from the 'regular' way of incubation in birds. In this paper these strategies are interpreted by superimposing them on the most recent phylogenetic hypotheses regarding the inter- and intrafamilial relationships of megapodes. We conclude that similarities shared with reptiles and kiwis are due to convergence. Arguments are put forward that mound-building represents the plesiomorphic condition in megapodes and that burrow-nesting has been derived from it. Furthermore, we infer that burrow-nesting at sun-exposed beaches has evolved from burrow-nesting in volcanically heated soils. René W.R.J. Dekker, National Museum of Natural History, P.O. Box 9517, 2300 RA Leiden, The Netherlands.