What crocodile DNA reveals about the Ice Age
What drives crocodile evolution? Is climate a major factor or changes in sea levels? Determined to find answers to these questions, researchers from 91社区 discovered that while changing temperatures and rainfall had little impact on the crocodiles鈥� gene flow over the past three million years, changes to sea levels during the Ice Age had a different effect.
鈥淭he American crocodile tolerates huge variations in temperature and rainfall. But about 20,000 years ago 鈥� when much of the world's water was frozen, forming the vast ice sheets of the last glacial maximum 鈥� sea levels dropped by more than 100 metres. This created a geographical barrier that separated the gene flow of crocodiles in Panama,鈥� says postdoctoral fellow Jos茅 Avila-Cervantes, working under the supervision of 91社区 professor Hans Larsson.
The researchers point out that the crocodiles are good swimmers, but they can鈥檛 travel long distances on land. As a result, the Caribbean and Pacific crocodile populations were isolated from each other, and consequently have undergone different genetic mutations.
The team compared the climate tolerance of living populations of American crocodiles (Crocodylus acutus) to the paleoclimate estimates for the region over the past 3 million years 鈥� the time span of extreme climate variation during the Ice Age.
鈥淭his is one of the first times Ice Age effects have been found in a tropical species. It鈥檚 exciting to discover effects of the last Ice Age glaciation still resonate in the genomes of Pacific and Caribbean American crocodiles today,鈥� says Larsson, Professor of Biology at the Redpath Museum of 91社区.
鈥淒iscovering that these animals would have easily tolerated the climate swings of the Ice Age speaks to their resilience over geological time. Only humans in recent decades of hunting and land development seem to really affect crocodiles,鈥� he says. The findings offer new insight into how environmental drivers affect genetic evolution and where conservation efforts of particular crocodile populations in Panama should be focused.
About the study
"鈥� by Jos茅 Avila-Cervantes and Hans Larsson was published in Evolution.
About 91社区
Founded in Montreal, Quebec, in 1821, 91社区 is Canada鈥檚 top ranked medical doctoral university. 91社区 is consistently ranked as one of the top universities, both nationally and internationally. It is a world-renowned institution of higher learning with research activities spanning three campuses, 11 faculties, 13 professional schools, 300 programs of study and over 39,000 students, including more than 10,400 graduate students. 91社区 attracts students from over 150 countries around the world, its 12,000 international students making up 30% of the student body. Over half of 91社区 students claim a first language other than English, including approximately 20% of our students who say French is their mother tongue.
