Scientists find new clues as to why animals grow bigger in the cold

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Washington, Feb 25 (ANI): Scientists have across new clues that offers new insight to Bergmann's rule that animals grow larger at high, cold latitudes than their counterparts closer to the equator.

The scientists, who found the solution to this 163-year-old puzzle, were from the University of Houston, US.

While traditional explanations have been based on body temperature being the driving force of this phenomenon, this group of community ecologists hypothesize that better food makes high-latitude animals bigger.

Chuan-Kai Ho, a Ph.D. graduate from UH in ecology and evolution, his adviser and UH professor of biology and biochemistry Steven Pennings, and their collaborator Thomas Carefoot from the University of British Columbia opened up a new line of study into Bergmann's rule.

The research program in Pennings' lab over the last decade has offered the most extensive work done on the general problem of latitudinal variation in plant-herbivore interactions.

This latest finding from Pennings' groundbreaking research at UH on this subject came from one of Ho's doctoral dissertation chapters.

Studying three different plant-eating species - grasshoppers, planthoppers and sea snails - collected from along the Atlantic coast to Japan, respectively, the researchers fed these herbivores plants from both high and low latitudes and found that they all grew better when fed plants from the higher latitudes.

This indicates that Bergmann's rule could reflect that plants from high latitudes provide better food than those from low latitudes.

These latest findings, according to Ho, indicate that studies of Bergmann's rule should consider ecological interactions in addition to the more traditional theories of physiology based on responses to temperature.

Over the years, work in Pennings' lab has shown that, although low-latitude plants are less nutritious and better protected by chemical defenses, they experience heavy damage from herbivores, which are more abundant at low latitudes.

Future study, according to Pennings, should focus on why there are more herbivores at lower latitudes despite the lower-quality food sources.

A likely explanation is that herbivore populations are limited at high latitudes by a short growing season and high death rates during cold winters.

"While the explanations discovered in our current study only apply to herbivores, it may be that carnivores and omnivores also might grow larger as a consequence of eating larger herbivores," o said. (ANI)

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