Rapid and recent diversification patterns in Anseriformes birds: Inferred from molecular phylogeny and diversification analyses

Abstract

The Anseriformes is a well-known and widely distributed bird order, with more than 150 species in the world. This paper aims to revise the classification, determine the phylogenetic relationships and diversification patterns in Anseriformes by exploring the Cyt b, ND2, COI genes and the complete mitochondrial genomes (mito-genomes). Molecular phylogeny and genetic distance analyses suggest that the Dendrocygna species should be considered as an independent family, Dendrocygnidae, rather than a member of Anatidae. Molecular timescale analyses suggests that the ancestral diversification occurred during the Early Eocene Climatic Optimum (58 ~ 50 Ma). Furthermore, diversification analyses showed that, after a long period of constant diversification, the median initial speciation rate was accelerated three times, and finally increased to approximately 0.3 sp/My. In the present study, both molecular phylogeny and diversification analyses results support that Anseriformes birds underwent rapid and recent diversification in their evolutionary history, especially in modern ducks, which show extreme diversification during the Plio-Pleistocene (~ 5.3 Ma). Therefore, our study support that the Plio-Pleistocene climate fluctuations are likely to have played a significant role in promoting the recent diversification for Anseriformes.

Fig 1. Phylogram showing the phylogenetic relationship in Anseriformes based on the mito-genomes.

The values on nodes include four parts. The first two values indicate the split time and Bayesian posterior probabilities which were calculated by BEAST 1.7.4. The third values were the Bayesian posterior probabilities calculated by MrBayes 3.2.2, and the last values were the Bayesian posterior probabilities calculated by RAxML version 8. Blue bars at nodes show 95% highest posterior density (HPD) of divergence times.

Fig 2. Phylogram showing the phylogenetic relationship in Anseriformes based on two mitochondrial genes.

The values on nodes indicate the split time and Bayesian posterior probabilities which were calculated by BEAST 1.7.4, “-” indicated that the value was less than 70. Blue bars at nodes show 95% HPD of divergence times.

Fig 3. Lineage-through-time (LTT) plots for Anseriformes birds.

The colored lines represent the results of 1000 trees randomly selected from the BEAST analysis. The ref line shows the MCC tree.

Fig 4. Visualizations of diversification rate shifts within Anseriformes.

(a) Speciation-through-time plots utilizing BAMM. Curved red lines represent the median values with the 95% confidence intervals shown in blue. Arrows point to the three significant shifts in rates of speciation; (b) Posterior distribution of the number of rate shifts.