Intergeneric Phylogenetic Relationships of Swallows Estimated by Dna-dna Hybridization

--The phylogeny of the subfamily Hirundininae was estimated by hybridizing single-copy nuclear DNAs of 21 swallow species, representing 19 former and current genera, and a Tufted Titmouse (Parus bicolor) as outgroup. The phylogeny, which was unusually well resolved, consisted of three fundamental clades: Hirundo and allies, core martins, and African sawwings. The clade of Hirundo and allies comprised Hirundo rustica, Ptyonoprogne fuligula, Delichon urbica, Cecropis emirufa, Petrochelidon pyrrhonota, and P. spilodera. The sister-group of Hirundo and allies was the core martin clade, which consisted largely of endemic New World taxa (Pygochelidon cyanoleuca, Neochelidon tibialis, Atticora fasciata, Phaeoprogne tapera, Progne chalybea, Haplochelidon andecola, Stelgidopteryx ruficollis, and Tachycineta bicolor) and some basally branching Old World groups (Riparia riparia, R. cincta, Phedina borbonica, Pseudhirundo griseopyga, and Cheramoeca leucosternus). The African sawwings (represented by Psalidoprocne holomelas) formed the sister group of the core martins and Hirundo and allies. Among some interesting discoveries, we found a close relationship between the monotypic African and Australian genera Pseudhirundo and Cheramoeca. We also found that Delichon, which has persisted in the nomenclature as a genus separate from Hirundo, is monophyletic with taxa that are commonly considered to be members of Hirundo. On the other hand, Haplochelidon andecola, which is often considered to be a Hirundo or Petrochelidon, is not closely related to those genera, but instead lies among the New World members of the core martin clade. Received 1 July 1992, accepted 25 November 1992. PERHAPS NO FAMILY of passerines is as uniform morphologically and diverse generically as the swallows (Hirundinidae). All swallow species conform to a fundamental body plan that includes long and pointed wings, medium length tails, short legs, and bills that are short and wide. This uniformity is the likely result of adaptation to a strictly aerial insectivorous lifestyle. Apparently because of this uniformity, systematists have been loath to attempt a phylogenetic reconstruction of the swallow family as a whole. While there have been many classifications of the Hirundinidae (e.g. Sharpe 1885, Peters 1960, Turner and Rose 19•9, Sibley and Monroe 1990) and many discussions of the systematics of individual species or small groups of taxa, only one published paper has considered the familywide relationships of swallows based on evolutionary or phylogenetic logic. This is the 50-year-old study of Mayr and Bond (1943). At the time of Mayr and Bond's (1943) study, some 30 to 35 generic names had been applied to the 75 to 80 species of swallows. This multitude of small, seemingly equally divergent genera had been defined mainly on the basis of external morphological characters (e.g. plumage color, nasal form, fusion of skin between toes, tarsal feathering, and size). To bring some order and logic to this confusing array of names, Mayr and Bond grouped swallow genera into units using what they considered to be conservative, phylogenetically informative characteristics, in particular those of nesting habits and plumage color patterns. In the process, they outlined a rough scenario of swallow evolution based on nesting strategy and to a lesser extent geography. They postulated that the most "primitive" species were those that nested in natural cavities or on ledges. These were followed in evolutionary sequence by species that excavated nest holes and finally species that built nests from mud. Old World groups were judged to be more primitive than New World taxa because Africa, as the continent with the most swallow species, was perceived as the center of their origin. In addition to behavioral and geographic criteria, some features of exter-