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

Sérgio L Pereira,Anita Wajntal

doi:10.1590/s1415-47572008005000021

Abstract

Most Neotropical birds, including Pteroglossus aracaris, do not have an adequate fossil record to be used as time constraints in molecular dating. Hence, the evolutionary timeframe of the avian biota can only be inferred using alternative time constraints. We applied a Bayesian relaxed clock approach to propose an alternative interpretation for the historical biogeography of Pteroglossus based on mitochondrial DNA sequences, using different combinations of outgroups and time constraints obtained from outgroup fossils, vicariant barriers and molecular time estimates. The results indicated that outgroup choice has little effect on the Bayesian posterior distribution of divergence times within Pteroglossus, that geological and molecular time constraints seem equally suitable to estimate the Bayesian posterior distribution of divergence times for Pteroglossus, and that the fossil record alone overestimates divergence times within the fossil-lacking ingroup. The Bayesian estimates of divergence times suggest that the radiation of Pteroglossus occurred from the Late Miocene to the Pliocene (three times older than estimated by the “standard” mitochondrial rate of 2% sequence divergence per million years), likely triggered by Andean uplift, multiple episodes of marine transgressions in South America, and formation of present-day river basins. The time estimates are in agreement with other Neotropical taxa with similar geographic distributions.

Highlights

Toucans, aracaris and toucanets (Aves, Piciformes, Ramphastidae) are a group of Neotropical birds recognized by their colorful bills that are light and several times bigger than their head, bright-colored feathers and long tails sometime making up half of the body length
The following gamma priors were used: for taxon sets 1 and 3, which had the same root and Galloanserae as the most distant outgroup, we set the expected time between tip and root ± standard deviation (SD) = 122.2 ± 20 million years ago (Mya), based on Bayesian estimates of divergence times derived from a mitogenomic data for vertebrates using multiple fossil constraints spread throughout the tree (Pereira and Baker, 2006), rate of the root node = 0.00327 substitutions per site per million years (s/s/Myr), as estimated from the data set as the median of the tip-to-root branch lengths for all genes
We could only set time constraints based on fossil data available for outgroups, geological events assumed to have been a vicariant barrier for other avian and non-avian groups with similar geographic distribution as Pteroglossus, or molecular time estimates derived from other studies

Summary

Introduction

Aracaris and toucanets (Aves, Piciformes, Ramphastidae) are a group of Neotropical birds recognized by their colorful bills that are light and several times bigger than their head, bright-colored feathers and long tails sometime making up half of the body length. The following gamma priors were used: for taxon sets 1 and 3, which had the same root and Galloanserae as the most distant outgroup, we set the expected time between tip and root (rttm) ± standard deviation (SD) = 122.2 ± 20 Mya, based on Bayesian estimates of divergence times derived from a mitogenomic data for vertebrates using multiple fossil constraints spread throughout the tree (Pereira and Baker, 2006), rate of the root node (rtrate) = 0.00327 substitutions per site per million years (s/s/Myr), as estimated from the data set as the median of the tip-to-root branch lengths for all genes.

Results

Conclusion