This study tells us how the fragmentation of the distribution of a population of wild cats negatively impacts genetic diversity and survival. Small population numbers lead to a reduction in genetic diversity which in turn can lead to sterility due to inbreeding, which in turn again leads to a smaller population and a vicious cycle to the extinction of that small population.
In this study 32 bobcats were introduced to an island off the coast of Georgia more than 30 years ago. After the 30 years the Penn State researchers compared the genetic diversity of the population with those of a population of bobcats on Kiawah Island off the coast of South Carolina.
After the 32 bobcats were left alone as a group of 30 years, 24 of them were left. The island on which they were isolated, Cumberland Island, is separated from the mainland by open water.
The scientists checked the DNA from scats from which they were able to identify individual bobcats. They were then able to estimate the levels of inbreeding and survival rates.
They knew the DNA from the original bobcats and therefore they were able to measure the loss of genetic diversity. And they said that over the past 30 years the population “has lost about 15% of its genetic diversity. There appears to be some inbreeding, but generally it is low.”
They also assessed the DNA of the bobcat population on Kiawah Island. They’ve figured that “about every five years, a bobcat from the mainland contributes genes to the island population”. In other words, there was a means of travelling from the mainland to the island which allowed the odd bobcat to introduce fresh genes to that trapped population. As a consequence, the genetic diversity of the Kiawah Island bobcat population was slightly better than that of the Cumberland Island population.
They concluded that the probability of the Cumberland Island bobcats becoming extinct will continue to increase going forwards. They predicted that the risk of extinction will increase to about 20% by 2040 unless there is human intervention “to restore the loss of genetic diversity”. They would do this by introducing a bobcat from the mainland every four or five years.
They expect the information to help the conservation of endangered species. Their predictions of the loss of genetic diversity using computer modelling were accurate, they said.
The bobcats of Cumberland Island simulated an endangered species scenario. The fragmentation of already small overall populations of endangered wild cat species of any kind further endangers their survival as indicated by the study.
Penn State. “Unique study of isolated bobcat population confirms accuracy of extinction model: Genetic follow-up on offspring of felines brought to island 30 years earlier validates population viability analysis.” ScienceDaily. ScienceDaily, 22 February 2021.
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