In response to targeting by trophy hunters, wild populations of bighorn sheep are now growing 10 per cent smaller horns than they did less than 20 years ago as a way to adapt and minimize the risk to their species.
That rapid evolutionary interplay between hunter and hunted is an example described in a recently accepted paper in the Journal of Molecular Ecology entitled “The Pace of Modern Life, Revisited,” co-authored by a research team at Brock University.
Such adaptations can be measured as phenotypic rates of change and allow scientists to predict patterns of ‘contemporary’ evolutionary change.
The research by the paper’s co-senior author, Brock University Assistant Professor of Biological Sciences Kiyoko Gotanda, along with colleagues at 10 institutions around the world, shows evolution can be seen within a lifetime.
“In some species, anywhere from two to 200 generations is enough to exhibit change,” Gotanda said, pointing out that for fruit flies, 200 generations is approximately six years.
“We have come a long way from the old view of evolution as a slow process to the point where we are now realizing that everything is evolving all around us all the time,” said co-senior author Andrew Hendry, Professor of Biology at McGill University.
Lead author Sarah Sanderson, a PhD candidate in Biology at McGill, says the big question now is “how this rapid phenotypic change matters for populations, communities, ecosystems and nature’s contribution to people.”
Gotanda’s team compiled many individual studies that have shown this type of evolution. They used the data to answer long-standing questions about how contemporary evolution works and provide a massive dataset of these changes so other investigators can answer related questions.
The team is responsible for adding 5,676 new estimates of phenotypic change to the list, representing a 77 per cent increase.
Key to their findings are how human disturbances such as trophy hunting influence change.
“We focused on human disturbances and found a small absolute difference in rates of change exists between human disturbed and natural populations,” Gotanda said.
Analyses of the expanded dataset also confirms previous studies showing: harvesting by humans results in larger rates of change than non-human disturbances; introduced populations have increased rates of change; and body size does not increase through time.
“Overall, findings from earlier published analyses have largely held-up in analyses of our new dataset that encompass a much larger breadth of species, traits and human disturbances,” Gotanda said.
The team believes the database will serve as a stepping stone for further analyses to understand patterns of contemporary evolution. For example, postdoctoral researcher Lucas Gorné in Gotanda’s research group and supported through a fellowship from the Faculty of Mathematics and Science is continuing to work with the database to answer more questions about rapid phenotypic change.
“I’m most interested in in whether disturbances are generating confounding or synergistic effects,” said Gotanda.
The research is cautious to infer evolution from phenotypic rates of change as more research is needed to discover whether the traits exhibited are truly heritable (coming from parental genes) or plastic (generated by phenotypic changes in the environment within a lifespan).
“A common garden experiment involving the comparison of genetically distinct strains, families or populations under identical environmental conditions would help to uncover the extent that the rates of change we observe can be attributed to contemporary evolution,” Gotanda said.
Brock Faculty of Mathematics and Science Dean Ejaz Ahmed said he is looking forward to the discoveries Gotanda’s research supports.
“They are now the caretakers of an invaluable list, allowing exploration and expansion for future scientists to build upon,” he said.