Systematics of New World cuckoos (Aves, Cuculidae) and the evolution of brood parasitism

grantor: University of TorontoMonophyly of the cuckoos (Cuculidae) was demonstrated through the description of 14 osteological synapomorphies. Only three apparent synapomorphies united the otherwise anatomically divergent turacos (Musophagidae), Hoatzin (Opisthocomus hoazin), and Cuculidae. Therefore, I recommended their placement in separate, but adjacent orders. Cuckoo phylogeny reconstructed using 135 osteological characters differed markedly from currently accepted classifications. All brood parasitic cuckoos, including New World obligate parasites Tapera and Dromococcyx and facultative parasites Coccyzus, formed a clade. This implies that the ancestral Coccyzus was an obligate parasite, and is consistent with many behavioral adaptations to parasitism exhibited by this genus. Tribe Saurotherini (Phaenicophaeinae) was erected to house all nonparasitic, arboreal, solitarily breeding New World cuckoos. The Old World genus Carpococcyx was removed from the New World Neomorphinae. Three subfamilies, comprised of nonparasitic, terrestrial cuckoos of Old World and New World distribution, occupied basal positions on the phylogeny. A new classification of the Cuculidae was proposed. I demonstrated that two species of facultative brood parasites, the Black-billed (Coccyzus erythopthalmus) and Yellow-billed (C. americanus) cuckoos, produce eggs that fully or nearly match the eggs of over 70% of their reported host species, a proportion significantly greater than if hosts were being selected at random from a potential host pool. This supports an hypothesis of egg mimicry, and implies an historically intense relationship between parasite and host. Factors responsible for the loss of obligate parasitism in this genus may also have contributed to the general paucity of obligate parasitism in New World cuckoos. Competitive exclusion or resistance to invasion by parasitic cowbirds (Molothrus spp.) should be considered. The phylogeny of the genus Coccyzus was reconstructed using skeletal characters, cytochrome b gene sequences, and external morphology. The optimal topology supports a Neotropical origin for the genus. Several vicariant and colonization events were responsible for the current distribution of South American endemic species. The Mangrove Cuckoo (C. minor) had two major northward routes out of South America. Yellow-billed and Black-billed cuckoos are highly divergent, and each represents a separate invasion of North America from South America.Ph.D