Inbreeding Threatens Michigan’s Only Rattlesnake — What It Means for Conservation

The post Inbreeding threatens Michigan’s only rattlesnake — and what it means for conservation appeared first on AZ Animals.

Quick shot

• michiganonly rattlesnake Eastern Massasauga species, shown inbreeding depression.

• The two eastern Massauga populations with a higher number of inbred individuals had lower reproductive output and Survive.

• measure Restoring genetic fitness These populations may need to be protected to prevent local extinction.

• maintain habitat corridor Dispersal may benefit other snake species that may also be affected by inbreeding depression.

If you encounter a rattlesnake in Michigan, it is the eastern rattlesnake (chain loach), the state’s only venomous snake. They are relatively small for a rattlesnake, averaging two to three feet in length as adults. You’re lucky if you can spot one, as Eastern Massasaurs spend most of their time hiding in logs or brush near their wetland habitats and tend to flee when disturbed. Therefore, although the bite of Massasaurus is venomous, very few people are bitten.

Although they have a wide geographical range, found in several U.S. states from Michigan to Missouri, the population of the Eastern Masala has declined dramatically since the mid-1970s, according to monitoring by the U.S. Fish and Wildlife Service. In 2016, they were listed as a threatened species under the Endangered Species Act, and the reason for their decline is believed to be illegal harvesting and destruction of their habitat over the past 200 years.

As roads and human settlements develop, the eastern lizard’s habitat becomes smaller and smaller. In a recent paper, conservation biologists found that habitat fragmentation made it difficult for Massasaurus to reproduce successfully, reducing their chances of future survival.

Biologists at Michigan State University used genetics to trace the family history of two snake species. Through a long-term monitoring program with Grand Valley State University, West Virginia University and the Association of Zoos and Aquariums, researchers obtained DNA samples from more than 1,000 snakes captured and released in projects funded by the U.S. Fish and Wildlife Service.

Each captured snake is weighed, measured, assessed for sex and reproductive status, blood sampled, then released and given a unique PIT tag for individual identification. The DNA in the blood samples is used to build a family tree of the population, showing how individuals are related. Visits to both populations over 15 years yielded estimates of snake births and deaths.

“This long-term in-situ monitoring is the backbone of this study,” lead author Meaghan Clark, a graduate student at the time, said in a press release. “Having people out and catching these snakes every season makes this possible.”

Analysis of the data showed that massasaga inbreeding in the two populations was causing reproductive problems. By mating non-randomly with more closely related snakes, these massasaurs reduced their chances of producing viable offspring. Inbreeding reduces fitness by amplifying the expression of deleterious gene combinations. Massasaurs who mated with closest relatives were 3.5% less likely to have surviving offspring, and their annual survival rate was 11.6% lower. But why would these Eastern Massasaurs choose to mate with their relatives?

“Habitat loss and fragmentation hinders occasional migrations between eastern Massasaga populations, which over time increases relatedness within each population,” lead author Clark explained via email. Additionally, Masseurs naturally tend to move away from their parents, limiting the flow of genes from their birth stock. “In our data set, we found that the distance between a snake and its parent was smaller than the distance between pairs of unrelated individuals,” Clark added.

As a result, Michiganmassaurus, already a homebody, was squeezed further into closer proximity to their relatives due to habitat modification and loss. Genetically related parents can cause “inbreeding depression” – a known decrease in fitness and survival. Over time, you would expect inbreeding depression to reduce the population size in Massasaga, Michigan, leading to more inbreeding, creating a vicious cycle.

Other eastern Massasaugas tended to have smaller populations, and their movements were similarly restricted by roads, farms, and other obstacles. This is the first study to directly quantify the adaptive effects of inbreeding due to habitat fragmentation on the eastern Masala.

“These are fairly large and stable populations in the eastern Massasaugas,” senior author Sarah Fitzpatrick said in a press release. “The fact that we found inbreeding issues in these populations is worrisome is that many other populations in the Midwest are much smaller and more dispersed.”

Once a population of an organism becomes small and isolated, its likelihood of local extinction increases dramatically. A single natural event could wipe out these Massasaga populations because they lack the buffer of nearby rearing populations to replenish genetic diversity and individuals.

“The way to combat this decline is to increase population size and promote gene flow with other populations,” Clark said. [of massasaugas]. Research is currently underway on how best to do this. “Saving genetic diversity to limit harmful gene combinations may be key to protecting eastern Michigan’s massage snake population, and may even require moving the snakes away from other populations.

The study authors also recommend long-term monitoring of other snake populations to determine whether they are successfully maintaining their gene pools in the face of environmental changes that limit habitat connectivity. Implementing changes such as building underpasses for snakes to cross or creating openings in fences can improve connectivity and thus increase gene flow between populations.

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