Genomic Study of Eastern Massasauga Rattlesnakes Suggests Old School Genetics Still Works

Snakes are among the most diverse and fascinating animals on the planet, with over 3,000 species that exhibit a wide range of colors, patterns, sizes, and behaviors.

But how do snakes cope with changing environmental conditions and threats? How do they maintain their genetic health and diversity in small and isolated populations?

A new study by researchers from Ohio State University and other institutions sheds some light on these questions by using genomic analysis to explore the link between neutral and functional genetic diversity in snakes.

Neutral vs functional genetic diversity

(Photo : YURI CORTEZ/AFP via Getty Images)

Genetic diversity is the variation in DNA sequences among individuals of a species or a population. It is important for the survival and evolution of species, as it allows them to adapt to new challenges and opportunities.

However, not all DNA sequences are equally important for adaptation. Some DNA regions are involved in protein-coding genes, which determine the traits and functions of an organism.

These are called functional genetic diversity.

Other DNA regions are not related to protein-coding genes and have no apparent effect on the phenotype or fitness of an organism. These are called neutral genetic diversity.

Traditionally, genetic diversity has been estimated by measuring the variation in neutral DNA regions, which are easier and cheaper to obtain than functional DNA regions.

The assumption is that a higher level of neutral genetic diversity reflects a higher level of functional genetic diversity, and thus a higher potential for adaptation.

However, this assumption has been challenged by the genomic revolution, which allows scientists to sequence entire genomes and compare them across individuals and populations.

By doing so, scientists can directly assess the variation in functional DNA regions, and test whether they correlate with the variation in neutral DNA regions

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A case study of Eastern massasauga rattlesnakes

The researchers, including senior author and professor of evolution, ecology and organismal biology at The Ohio State University, H. Lisle Gibbs, conducted such a genomic analysis on 90 Eastern massasauga rattlesnakes, a threatened species that lives in wetlands across North America.

The Eastern massasauga rattlesnake was listed as threatened under the Endangered Species Act in 2016 because of loss and fragmentation of its habitat.

Gibbs' lab was the first to sequence the genome of this species.

The researchers compared the variation in both neutral and functional DNA regions across the 90 individuals, representing 11 populations from different geographic locations.

They found that the functional genetic diversity they detected by analyzing gene variations in fully sequenced genomes correlated nicely with the neutral genetic diversity seen across broad sections of those same genomes containing no protein-coding genes.

This means that measuring neutral genetic diversity can give a good indication of the genetic health and adaptive potential of this species.

The researchers also found that some populations had lower levels of both neutral and functional genetic diversity than others, suggesting that they are more vulnerable to inbreeding and genetic drift.

These populations may require more conservation efforts to prevent further loss of genetic variation and increase their chances of survival.

Implications for Snake Conservation

The study suggests that making a transition from "old school" genetics to "new school" genomics for species conservation purposes probably isn't necessary in all cases.

For small and isolated species like the Eastern Massasauga rattlesnake, neutral genetic diversity measured using traditional techniques can provide important information about their genetic health.

However, for larger and more complex species, such as humans or elephants, genomic analysis may be more informative and accurate.

The study also highlights the importance of preserving snake biodiversity, as snakes play vital roles in ecosystems as predators and prey.

Snakes are also valuable sources of biomedical research, as their venom contains molecules that can be used to develop drugs for various diseases.

By understanding how snakes adapt to their environment through their genes, scientists can better protect them from threats and appreciate their beauty and diversity.

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