Human development has impacted the genetic diversity of lions. Human activities have notably damaged the genetic diversity of lions in the last century. Experts at the Texas A&M University College of Veterinary Medicine & Biomedical Sciences have found clear genetic changes in lion populations that are tied to habitat fragmentation.
When groups of the same species are isolated from each other, there is a lack of genetic flow that can have long-term consequences for the overall health of the species.
“I was surprised at what we found – surprised and disappointed, because it’s not what I wanted to see,” said study co-author Dr. James Derr. “I really wanted to be able to tell everyone that the management we’ve been doing for the last 100 years is perfect and to keep doing what we’ve been doing and everything will be fine. But that’s not the take-home lesson; unfortunately, that’s not the story we can tell.”
The researchers set out to examine whether the genetic structure of lion populations has changed over the last 100 years.
The study was focused on existing DNA data from modern lions that lived between 1990 and 2012. To obtain genetic data from historical populations, study co-author Dr. Caitlin Curry used DNA extracted from the preserved remains of 143 lions that lived between 1880 and 1949.
Both the modern and historical DNA datasets represent the same geographical range from India to Southern Africa. This type of analysis, which compares data from the same region at different times, is called a spatiotemporal study.
Female lions tend to stay close to where they were born, while male lions travel great distances to find new prides. This means that males are responsible for the movement of genes in the population, which promotes a high level of genetic diversity within the species.
The rapid growth of human development across Africa has increasingly limited the movement of lions through barriers such as cities, fences, and farms. These barriers prevent male lions from traveling over the great distances they once freely roamed.
According to study co-author Dr. Curry, while lions are still genetically diverse right now, the results in the DNA were more pronounced than she expected.
“In the historical population, you couldn’t easily identify where a lion was from based on its nuclear DNA. This is due to high historical levels of gene flow across the population,” said Dr. Curry. “But in the modern population, you can determine the general area, or sub-population, for most of the lions. But, even with sub-populations being more isolated, the overall level of genetic diversity is still considered high across all lion populations.”
However, the restricted movement of lions could gradually lead to much lower levels of genetic diversity, which comes along with health consequences.
“Over the last 100 years or so, we have restricted the natural movements of many species,” said Dr. Derr. “This isolation leads to reduced gene flow and ultimately may result in reducing genetic diversity to a level that threatens the survival of local populations.”
The African cheetah serves as an example of what happens with a lack of genetic diversity. Based on DNA evidence, scientists believe that cheetahs have suffered two large bottleneck events that have rapidly shrunk the gene pool. Today’s cheetah population has difficulty breeding, faces serious health issues, and struggles to fight off new diseases.
For lions, however, this fate can still be avoided in lions. The study findings provide clear evidence of the genetic consequences of habitat fragmentation and isolation, and this evidence can be used to protect lions.
“This should not be a disheartening story but rather one of hope,” said Dr. Curry. “Yes, we see a decrease in genetic diversity across lion populations over the past century. But, currently, compared with other mammalian species, lion genetic diversity is still considered high across all lion populations.”
“With responsible management focused on giving prides enough space to breed and allowing males to move more freely between isolated pockets, it is possible to increase the genetic diversity and reduce population subdivision across lion populations.”
Multiple projects have begun reintroducing lions back to areas they once roamed, and wildlife conservation programs are increasingly focused on coexistence strategies.
“The positive take-home message is now that we’ve documented this and we understand it, policies can be tailored to manage these populations differently,” said Dr. Derr. “We know now that you can’t treat all lions the same. Now we have the responsibility to manage these animals, and many other managed wildlife species, in ways that better reflects their current biology.”
The study is published in the journal Molecular Biology and Evolution.