This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new study led by researchers in the Eco-Evo-Devo lab at the University of Ottawa finds that ants can decouple antenna size from both head and body size as they develop into different social castes, revealing how social signals and hormones help shape traits for specialized colony roles. Bigger animals usually have bigger body parts.
It's one of biology's most familiar patterns. Yet some ants appear to break that rule. The discovery offers a new view of how evolution can loosen biological constraints and produce new combinations of traits.
The study, titled "Breaking trait scaling via the evolution and regulation of dimorphic decoupling in ants," is published in Proceedings of the National Academy of Sciences. The researchers studied Pheidole, a highly diverse genus of ants whose colonies include small workers and much larger soldiers. Within each caste, antennae still grow in proportion to body size.
Surprisingly, across castes, the relationship changes: the ranges of worker and soldier antenna sizes completely overlap, despite the fact that soldiers have substantially larger heads and bodies. "It was total serendipity. We were sitting at the microscope and Erica (Erica Vong is a graduate researcher and student at uOttawa and lead author of this study) showed me the antennae of two individuals.
One was clearly smaller, yet it turned out to be from the soldier," says Rajendhran Rajakumar, associate professor in the Department of Biology at uOttawa's Faculty of Science; the research was conducted in his lab. "Much like when you are getting your favorite latte, both castes have small, medium and large sizes of overlapping antennae." It turns out that the big antennae were from the biggest worker and the small antenna was from the smallest soldier, which is still much bigger in both head and body size. "Biologists have long assumed that traits such as antennae generally scale predictably with body size," Rajakumar says.
"Our findings show that evolution can decouple a trait from body size in one context while preserving that relationship in another." The team combined laboratory experiments, field data, museum collections and comparative analyses. Measurements from 565 Pheidole species showed that this unusual antennal pattern is widespread across the genus. Comparisons with other ants suggest it may have originated near the common ancestor shared by Pheidole and the closely related Cephalotes turtle ants.
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