Diversification of Ramphastinae (Aves, Ramphastidae) prior to the Cretaceous/Tertiary boundary as shown by molecular clock of mtDNA sequences

Abstract

Partial cytochrome b and 12S rDNA mitochondrial DNA sequences of eight representatives of the Ramphastidae family were analyzed. We applied the linearized tree method to identify sequences evolving at similar rates and estimated the divergence times among some of the taxa analyzed. After excluding Ramphastos tucanus and Capito dayi from our data set, the remaining taxa presented a constant rate of DNA substitution, and branch lengths could be re-estimated with a clock constraint using the maximum likelihood method. Branch lengths were calibrated assuming that Galliformes and Piciformes split around 100 million years ago (mya). Our results indicate that Ramphastinae, and probably Capitoninae, diverged from other Piciformes in the Late Cretaceous (~82 mya), suggesting that Piciformes is another avian order that survived the mass extinction event occurred 65 mya at the Cretaceous/Tertiary (K/T) boundary. The divergence times estimated within the Ramphastinae genera cover the period from the Middle Eocene (around 47 mya) through the Late Miocene (9.5 mya). Our estimate of divergence time is coincidental with the split of the African and the South American continents and other intense geologic activities and modifications of the areas which correspond to the current Neotropics. These events might have influenced the diversification of Ramphastinae in South America.

Evolution of bill size in relation to body size in toucans and hornbills (Aves: Piciformes and Bucerotiformes)

“…1) was derived from a combination of published DNA sequencebased phylogenies. The relationships among the ramphastid genera were based on NAHUM et al (2003); see also PATANÉ et al (2009). Relationships within the genus Ramphastos were based on PATANÉ et al (2009); see also WECKSTEIN (2005).…”

The historical biogeography of Pteroglossus aracaris (Aves, Piciformes, Ramphastidae) based on Bayesian analysis of mitochondrial DNA sequences

“…Eberhard and Bermingham (2005) estimated that the viridis group separated from other groups of Pteroglossus around 3 Mya, which is three times younger than the age proposed by Nahum et al (2003). These differences can be explained in light of different calibration approaches taken in both studies.…”

“…However, he later reformulated his hypothesis, suggesting that these vegetational changes may have also occurred prior to the Pleistocene (reviewed in Haffer, 1997). Nahum et al (2003) estimated that genus diversification within Ramphastidae occurred from about 47 million years ago (Mya) in the Middle Eocene to about 9.5 Mya in the Late Miocene, based on partial sequences of the mitochondrial cytochrome (cyt) b and the ribosomal small subunit (12S rDNA) genes of one species of each genus. Eberhard and Bermingham (2005) obtained cyt b, ATPase subunits 8 and 6 (ATPase8/6) and cytochrome oxidase subunit I (COI) sequences for all but one species of Pteroglossus and estimated that the radiation within Pteroglossus initiated around 3 Mya in the Late Pliocene, and only few divergences occurred into the Pleistocene.…”

“…Considering Baillonius bailloni as Pteroglossus bailloni (Kimura et al, 2004), this species is part of the viridis superspecies group (sensu Haffer, 1974), and the split of viridis from the other superspecies groups is the only common node in Nahum et al (2003) and Eberhard and Bermingham (2005). Eberhard and Bermingham (2005) estimated that the viridis group separated from other groups of Pteroglossus around 3 Mya, which is three times younger than the age proposed by Nahum et al (2003).…”

“…These differences can be explained in light of different calibration approaches taken in both studies. Nahum et al (2003) applied a strict molecular clock, excluding taxa that evolved at a significantly higher or lower rate than the average, and calibrated the clock assuming the split between Galliformes and Piciformes to have occurred 100 Mya (Nahum et al, 2003). Given the lack of fossil or other reasonable molecular calibration data for the Ramphastidae, Eberhard and Bermingham (2005) applied the "standard" avian mitochondrial molecular clock rate of 2% sequence divergence per million years (Myr) (Shields and Wilson, 1987) to estimate divergence times for major nodes within Pteroglossus, based on uncorrected genetic distances.…”