How genetic research can help to explain carnivoran (dog and cat) evolution

FGF gene family characterization provides insights into its adaptive evolution in Carnivora

Qinquo Wei, Yuehuan Dong, Guolei Sun, Xibao Wang, Xiaoyang Wu, Xiaodong Gao, Weilai Sha, Guang Yang, Honghai Zhang

Summarized by Kale Headings,  a senior at the University of South Florida. They are getting a dual degree in geology and environmental science and policy. They intend to study planetary geology or glaciology in graduate school next, and then work as a researcher or professor after they finish graduate school. In their free time they like to draw, play video games, and hang out with friends!

What data were used? The researchers looked at FGF genes, or fibroblast growth factors, from humans, domestic dogs and cats, mice, and other Carnivora genes from GenBank. FGFs affect a variety of biological functions including metabolism and development.

Methods: The researchers searched for Carnivora genetic sequences in GenBank, which is a database of genetic information of various species and confirmed that the genetic sequences they found were FGF genes. They did a phylogenetic analysis on the Carnivora species to determine their evolutionary relationships and the relationships of their FGF genes, using the FGF genes of mice and humans as an outgroup (outgroups ‘root’ the tree). In other words, comparing carnivoran FGF genes to human and mice FGF genes could help researchers determine which FGF genes are unique to carnivorans, and which are present across many groups and species, including mice and humans. Much of this analysis utilized various advanced computer programs and techniques. The researchers referenced preexisting phylogenetic trees for Carnivora and used Bayesian inference methods to create phylogenetic trees that included FGF genes alongside the Carnivora tree. Bayesian inference methods use Bayes theorem, an equation, to help infer which evolutionary relationships between species are most supported by the data. 

Results: The researchers found 660 new FGF genes in 30 different carnivora genomes. The phylogenetic trees created both with and without the FGF data were similar, and the FGF genes were able to be classified into 10 subfamilies (Figure 1) based on their locations on the phylogenetic tree. There were positive selection sites for two FGF genes that control metabolism and muscle development in Carnivora, which is significant because these features are important to these animals’ predatory habits. There was also a positive selection gene for FGF19 in the group of carnivora that was semiaquatic, and this is notable because it may indicate that FGF19 helps semiaquatic animals to regulate their body temperature and keep their balance in water. 

Alt text: Image of two concentric color-coded wheels, with the outer wheel containing text to label FGF subfamilies 19, 22, 5, 3, 7, 8, 1, 9, 4, and 11. The inner wheel shows individual FGF genes that are a part of each subfamily. Inside the space in the center of the two wheels is a tree-like diagram representing the phylogenetic families of Carnivora, with each section of the tree lined up with and color-coded to match the FGF gene and subfamily that it corresponds to.
Figure 1. The phylogenetic tree of Carnivora with the corresponding FGF subfamilies and specific genes, as determined by the researchers using Bayesian inference methods.

Why is this study important? The researchers concluded that the FGF gene family of Carnivora should be divided into 10 subfamilies. The researchers also found positive selection for several individual FGF genes that may be related to the diet and predator status of Carnivora animals, as these genes help to metabolize fats and develop muscles. They also found that habitat plays a role in what FGF genes are selected for, as notably FGF19 was selected for in semiaquatic carnivorans, and several other FGF genes also showed a strong relationship with the animals’ habitat types. These conclusions show how FGF genes can be used to further understand the evolutionary relationships and significance of specific evolutionary traits across a variety of species of mammals, since other groups of mammals besides Carnivora also have FGF genes. 

The big picture:  This study may help researchers better understand the evolutionary pathways taken by earlier carnivorans in the fossil record. In the specific case of FGF genes, these genes contain key physiological processes, just a few of which are metabolism and muscle development. Therefore, better understanding of the FGF genes and how they function across groups of mammals and how they vary due to evolutionary relationships may also help us to better understand our own FGF genes and how they work in our own human bodies.  

Citation: Wei, Q., Dong, Y., Sun, G., Wang, X., Wu, X., Gao, X., Sha, W., Yang, G., & Zhang, H. (2021). FGF gene family characterization provides insights into its adaptive evolution in Carnivora. Ecology and Evolution, 11, 9837– 9847.