RESUMO
We use the small-bodied toucan genus Pteroglossus to test hypotheses about diversification in the lowlandNeotropics. We sequenced three mitochondrial genes and one nuclear intron from all Pteroglossus speciesand used these data to reconstruct phylogenetic trees based on maximum parsimony, maximumlikelihood, and Bayesian analyses. These phylogenetic trees were used to make inferences regarding boththe pattern and timing of diversification for the group. We used the uplift of the Talamanca highlands ofCosta Rica and western Panama as a geologic calibration for estimating divergence times on the Pteroglossustree and compared these results with a standard molecular clock calibration. Then, we used likelihoodmethods to model the rate of diversification. Based on our analyses, the onset of the Pteroglossus radiationpredates the Pleistocene, which has been predicted to have played a pivotal role in diversification in theAmazon rainforest biota. We found a constant rate of diversification in Pteroglossus evolutionary history,and thus no support that events during the Pleistocene caused an increase in diversification. We compareour data to other avian phylogenies to better understand major biogeographic events in the Neotropics.These comparisons support recurring forest connections between the Amazonian and Atlantic forests,and the splitting of cis/trans Andean species after the final uplift of the Andes. At the subspecies level, thereis evidence for reciprocal monophyly and groups are often separated by major rivers, demonstrating theimportant role of rivers in causing or maintaining divergence. Because some of the results presented hereconflict with current taxonomy of Pteroglossus, new taxonomic arrangements are suggested.
Assuntos
Animais , Genes Mitocondriais/genética , Íntrons/genética , ProbabilidadeRESUMO
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 ôstandardõ 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.