1 Dec 2022
Research led by a University of Cambridge scholar upsets established norms on impact of climate.
Paul Imrie
Job Title
The Burmese treeshrew. Image: Vassil / Wikimedia Commons
New evidence shows some mammals get bigger in warmer settings, upsetting established norms and suggesting climate change may impact on animal body size.
In a study published in Scientific Reports, recent changes noted in treeshrew body size supersede two of the most studied ecogeographical rules on body size variation in species.
A rule named after 19th century German biologist Carl Bergmann, called Bergmann’s rule, described individuals in colder climates – and typically at higher latitudes – had larger body sizes. The second – Foster’s rule, which followed a 1964 study by mammalogist J Bristol Foster – predicts island populations of small-bodied species are larger in size than mainland counterparts.
New research led by Maya Juman, a Gates Cambridge scholar and PhD student at the University of Cambridge, tested the rules in the northern treeshrew, a small mammal native to south and south-east Asia, against a dataset of museum specimens across a spatial and temporal range and climate data.
The researchers – from Cambridge, Yale University, University of Alaska Fairbanks and McGill University – found both rules had been inverted rapidly over time, with body size variation in specimens in the 19th century following Bergmann and Foster’s rules, but the pattern reversing in the 20th century.
According to the study results, northern treeshrews on the mainland have increased in size in warmer settings, but rainfall also plays a role. Bergmann’s rule upholds in island populations, but not mainland ones, while Foster’s island rule is upheld at higher latitudes, but not closer to the equator.
Researchers are now calling for experts to re-examine ecogeographical rules in light of global warming.
Ms Juman said: “Our study is the first to demonstrate a rule reversal over time in any species. We need to revisit some of our assumptions about size variation as our climate continues to rapidly change.”
“Recent and rapid ecogeographical rule reversals in northern treeshrews” is online.
