EVOLUTIONARY TRANSITIONS IN PARENTAL CARE IN SHOREBIRDS

This study examines historical changes in the relative contributions o f each sex to parental care in shorebirds, part of the infraorder Char adriides, which exhibits one of the highest diversities of parental ca re patterns of any comparably aged taxon. Specifically, we test two hy potheses for directions of change and compare our results with paralle l studies of fishes. Biparental care was ancestral in shorebirds, base d 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 b y the male. This was followed by numerous independent reductions in ca re by males, whereas female care was more evolutionarily labile, with as many evolutionary increases as reductions. The commonest sequence o f parental care has been from predominately male to either biparental or predominately female care. These findings are similar to the patter n suggested for fishes. The numerous evolutionary changes in sex diffe rences 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 mal es.