How venom can be used to study phylogeny and evolution

This time last year I was studying for my final year as an undergraduate Zoology student. The vast majority of that year was spent in a lab trying to figure out how to use various computer software for my dissertation on theropod locomotion. Amongst other topics, one of the new areas of Zoology that I studied was Venomics, the study of venom. At first, I was slightly intimidated by this topic, mainly due to the wide use of chemistry to analyse venom properties, however, as I looked deeper into it, I found that venomics can be used to study evolution and phylogenetics, which as a natural history nerd, made me suddenly much more invested.

So what did I find?

Snake venom, as an example, can contain over 200 proteins and peptides, and is known to show rapid rates of evolution. This makes it an excellent tool for phylogenetic studies, and gives insights into their genotypes, allowing us to look at the evolution of venom, thus the animals themselves.

Venom properties have been seen to differ between populations of the same species, and have been shown to be influenced by variation in diet and geographic variation. An example of this is seen in separate populations of the Timber Rattlesnake (Crotalus horridus). Individuals that live along the southern edge of the population range express highly lethal neurotoxic venom, compared to the hemorrhagic venom of other individual Timber Rattlesnakes that live in different areas. Evidence of different groups of the same species expressing different venoms gives an example of rapid evolution and suggests that over time, these groups may evolve into separate species.

It is not only the proprietors of venom that have had their phylogeny revealed using venomics, but also their prey. This has been studied in woodrats and squirrels, a common prey animal for the Southern Pacific Rattlesnake (Crotalus ruber). It has been found that these animals have developed inhibitors for the SVMP protein, a common protein found in the venom of venomous viperids. This helps to build immunity against snake venom, acting as a natural anti-venom. This triggers further evolution in the venomous snakes, showing an example of an evolutionary arms race between two species, studied using venomics.

California ground squirrel (Spermophilus beecheyi), an example of a mammal that has developed natural immunity to certain venoms.

How can this be applied to Palaeontology?

Venomics can also be applied to Palaeontology, to better understand certain animals that lived millions of years ago. Mosasaurs, a group of marine reptiles that lived during the Late Cretaceous period are classed as Squamates, a large order of reptiles that includes many species of snakes and monitor lizards that are alive today, and are known to be venomous. Although not all Squamates are venomous, and the Mosasaur lineage ended with the K-Pg extinction 66 million years ago, there is evidence to suggest that some Mosasaurs may have been venomous. Although there are still disagreements, it has been hypothesised that Mosasaurs are a basal clade to Monitor lizards, such as the infamous Komodo Dragon. This knowledge, paired with fossil evidence of venomous reptiles dating to the Mid-Jurassic Period, makes it plausible that Mosasaurs were some of the earliest venomous reptiles. These traits were inherited by their living relatives. As previously mentioned, the placement of Mosasaurs on the phylogenetic tree has long been a debated topic, however, the fact that we are able to have these discussions and ideas is an omen to study of venomics and how it can be used to study evolution and phylogeny.


Restored skull of Koronyosaurs nigeriensis, a Mosasaur that has been hypothesised to have a fork-shaped tongue, similar to venomous snakes and monitor lizards.


References

Margres, M. J., K. Aronow, J. Loyacano, and D. R. Rokyta, 2013 The venom-gland transcriptome of the eastern coral snake (Micrurus fulvius) reveals high venom complexity in the intragenomic evolution of venoms. BMC Genomics 14: 531.

Naish, D., 2009. Tongues, venom glands, and the changing face of Goronyosaurus | ScienceBlogs. [online] Scienceblogs.com. Available at: <https://scienceblogs.com/tetrapodzoology/2009/04/13/tongues-venom-goronyosaurus> [Accessed 9 October 2022].

Robinson, K., Holding, M., Whitford, M., Saviola, A., Yates, J. and Clark, R., 2021. Phenotypic and functional variation in venom and venom resistance of two sympatric rattlesnakes and their prey. Journal of Evolutionary Biology, 34(9), pp.1447-1465.




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