Tempo and mode of hummingbird evolution

Abstract

Lack of adequate historical data has hindered understanding of the evolutionary tempo and mode of many ecologically well-characterized avian radiations. DNA hybridization distances among 28 hummingbirds (Trochilidae) were used to establish a timescale for this family's radiation into more than 330 species. Under a variety of analytical assumptions, genetic distances calibrated with a fossil divergence date corrected for incompleteness in the geologic record indicated that all extant hummingbird lineages began to diverge in the Early Miocene, approximately 40 Myr (million years) after the Paleocene date estimated for the divergence of hummingbirds and swifts. The long period prior to the radiation of living forms provides ample time for divergent evolution to produce the large morphological gap that has tended to obscure thr sister-relationship of hummingbirds and swifts. The Miocene radiation of extant hummingbird lineages itsclf began with the divergence of the hermit and nonhermit SllbFdmilieS approximately I7 Ma (million years ago), followed by the rapid divergence of two Andean and one principally Central and North American clade at approximately 12 Ma.Younger subsidiary lineages, including ones found mainly in the Andes or in North America, date to the later Mioceiieeearlier Pliocene, approximately 6 Ma. The DNA hybridizationbased chronology thus indicates a protracted, rather than strictly rapid, radiation. Evidence from a broader spectrum of organisms supports the general pattern that higher taxonomic structure within many extant continental families evolved in the Miocene, suggesting that a common environmental pacemaker initiated radiation in unrelated groups. Compared to those in the Pleistocene, radiations tracing to the Miocene may have depended less on rapid climate cycling than on creation of new habitats by major geologic and climatic upheavals. For extant hummingbirds, a principal cause for their Miocene diversification probably was the ability of the ecologically generalized subfamily of nonhermits to radiate in montane arcas created by the Andean and other orogenies. Similar interactions between new habitats and their exploitation by ecological generalists may explain, at least in part, the contemporaneous radiation of Passeriformes, the most diverse avian order. 0 1998 T l i t -1,itiiwati Siirirty 01' London

Evolution of sexual dimorphism in bill size and shape of hermit hummingbirds (Phaethornithinae): a role for ecological causation

“…Hermits dominate the lowland understory curved-flower niche, which suggests that this niche may have been unoccupied when they entered it. This hypothesis is supported by molecular data placing the emergence of hermits and Heliconia at approximately the same time, 18-22 Myr ago (Bleiweiss 1998;Kress & Specht 2005).…”

Adaptive radiation, correlated and contingent evolution, and net species diversification in Bromeliaceae

“…These origins occurred at about the same time as the uplift of the northern Andes and the initial origin of two main Andean lineages of hummingbirds (Bleiweiss, 1998), although McGuire et al (2007) recently argued suggested that these clades represent one invasion of montane sites. No comparably large lineages of hummingbirds evolved in the Serra do Mar or the Guayana Shield (Bleiweiss, 1998). Hummingbirds in these areas appear to represent eclectic and not especially diverse mixes of taxa with various geographic affinities (R. Bleiweiss, pers.…”

Joint effects of feeding and breeding behaviour on trophic dimorphism in hummingbirds

“…Zink 1989, 1998Gill & Gerwin 1989;Sibley & Ahlquist 1990;Bleiweiss et al 1994Bleiweiss et al , 1997. Branch lengths were not available for most regions of the tree, and were speci¢ed under a speciational model that set all branch lengths equal to 1.…”