EVOLUTIONARY TRANSITIONS IN PARENTAL CARE IN SHOREBIRDS

This study examines historical changes in the relative contributions of each sex to parental care in shorebirds, part of the infraorder Charadriides, which exhibits one of the highest diversities of parental care patterns of any comparably aged taxon. Specifically, we test two hypotheses for directions of change and compare our results with parallel studies of fishes. Biparental care was ancestral in shorebirds, based on either of two outgroups and two independent phylogenies, and this has remained the dominant form of care in one clade, the Charadriida (plovers and allies). In the other clade, the Scolopacida (sandpipers and allies) there was an early change to care provided predominately by the male. This was followed by numerous independent reductions in care by males, whereas female care was more evolutionarily labile, with as many evolutionary increases as reductions. The commonest sequence of parental care has been from predominately male to either biparental or predominately female care. These findings are similar to the pattern suggested for fishes. The numerous evolutionary changes in sex differences in care shown here complement studies of contemporary selection, and suggest that biparental incubation and freedom from feeding the young may facilitate early abandonment by either sex, particularly males.