EVOLUTIONARY ASSOCIATIONS OF BROOD PARASITIC FINCHES (VIDUA) AND THEIR HOST SPECIES - ANALYSES OF MITOCHONDRIAL-DNA RESTRICTION SITES

The species-specific associations of the African brood parasitic finch es Vidua with their estrildid finch host species may have originated b y cospeciation with the host species or by later colonizations of new hosts. Predictions of these alternative models were tested in two spec ies groups of brood parasites (indigobirds, paradise whydahs) and thei r hosts. Phylogenetic analyses suggested that the brood parasites and their hosts did not speciate in parallel. The parasitic indigobirds sh are mitochondrial haplotypes with each other, and species limits in bo th indigobirds and paradise whydahs do not correspond with their gene trees. Different parasite species within a region are more closely rel ated to each other than any is to parasites that are associated with i ts same host species in other regions of Africa. There is little genet ic difference between parasite species (D) over cap(i,j) < 0.001 in th e indigobirds. (D) over cap(i,j) = 0.01 in the whydahs). Genetic dista nces (D) over cap(i,j) between the parasite species are less than the genetic distances between their corresponding host species in all para site-host comparisons, and average only 7.2% as large in the indigobir ds as in their hosts and 42% as large in the paradise whydahs as in th eir hosts. A phylogenetic model that allows ancestral haplotype polymo rphisms to be retained in descendant species was compared to a constra int model of species monophyly requiring all but the one ancestral hap lotype to be independently derived within each species. The constraint model increases the length of the indigobird tree by 50% over that of the model of retained ancestral polymorphisms; the difference is stat istically significant. Both phylogenetic and distance analyses indicat e that the brood parasites have become associated with their host spec ies through host switches and independent colonizations of the hosts, rather than through parallel cospeciation with them. The molecular gen etic results are supported by recent discoveries of additional host sp ecies that are associated with the indigobirds in the field and by var iation in the species-specific song behaviors of the brood parasites.