A recent study combined molecular and morphological data.
In 2021, I published a short paper on hybridization patterns in tinamous, a group of Neotropical birds that together with several flightless ratites (e.g., ostriches and emus) form the Palaeognathae. My paper introduced a scoring scheme to assess the reliability of hybrid records. Applying this idea to the tinamous revealed one well-documented case and three doubtful records that require further investigation. In addition to the literature supporting certain hybrid records, I also took into account the distribution of the parental species and their divergence time. Surprisingly, I could not find reliable estimates for divergence times due to a lack of genetic studies. I had to rely on a maximum date that corresponds to the split between the subfamilies Nothurinae and Tinaminae (17 million years ago).
Recently, a study in the Zoological Journal of the Linnean Society attempted to fill this knowledge gap on divergence times. Francisca Almeida and her colleagues combined molecular and morphological data to determine the phylogenetic relationships within the tinamou family.
Two Major Groups
The researchers produced a molecular dataset of three mitochondrial and five nuclear genes, representing 32 of the 45 species. The morphological dataset included all species and comprised information on 249 characters. Analyses of both datasets – separately and combined – converged upon the same phylogenetic backbone, supporting the idea of two major groups within tinamous: the open-area Nothurinae (genera Tinamotis, Eudromia, Taoniscus, Nothura, Nothoprocta and Rhynchotus) and the forest-dwelling Tinaminae (genera Nothocercus, Tinamus, Crypturellus).
All genera were monophyletic with the exception of Nothoprocta and Nothura. The Dwarf Tinamou (Taoniscus nanus) was embedded with the genus Nothura, and the phylogenetic position of the Rhynchotus species rendered the genus Nothoprocta paraphyletic. A taxonomic revision might be warranted here.
Divergence Times
The phylogenetic relationships are quite clear, but what about the divergence times? The answer is not that straightforward. The authors “obtained four different estimates based on different calibration schemes and matrices.” Despite this uncertainty, it seems that the Tinamidae originated between 31 and 40 million years ago. The split between the two subfamilies appears to be older than the previous estimate of 17 million years. Their diversification started in the late Eocene (38–33 Mya) or the Oligocene (33-23 Mya) when the woodland savannahs spread in South America. Many questions remain, but we are slowly learning more about this mysterious group of birds.
References
Almeida, F. C., Porzecanski, A. L., Cracraft, J. L., & Bertelli, S. (2022). The evolution of tinamous (Palaeognathae: Tinamidae) in light of molecular and combined analyses. Zoological Journal of the Linnean Society, 195(1), 106-124.
Featured image: Pale-browed Tinamou (Crypturellus transfasciatus) © Nick Athanas | Flickr
Avian Hybrids 