Parasites Defy Biodiversity Rules

For decades, scientists have observed that biodiversity is highest near the equator and decreases toward the poles, a pattern called the latitudinal diversity gradient, which occurs across ecosystems and all forms of life. A new FAU study reveals a surprising twist: certain trematode parasites – worm-like organisms that cycle through snails, crabs and fish – are actually more common in cooler, temperate waters than in the tropics. While most species and parasites peak near the equator, infections in crabs, small fish and adult fish increase with latitude, showing that these parasites can defy traditional biodiversity rules.

The researchers found that temperature, how far hosts move, and local conditions all affect parasite infections. In the tropics, hosts live closer to their heat limits, so parasites are more likely to kill them. In cooler temperate waters, hosts handle infections better, letting parasites survive and complete their lifecycles. These results help explain how parasites shape ecosystems and evolution – and could give scientists clues about how diseases might respond to changes in climate.

“This study reveals that parasite distributions can defy global biodiversity patterns,” said Christopher Moore, Ph.D., first author and a former post-doctoral researcher at FAU’s Harbor Branch Oceanographic Institute. “We found that trematode infections don’t just peak in snails, as previously documented, they also increase in crabs and fish farther from the equator. It’s a striking example of how ecological patterns we think we understand can have fascinating exceptions.”

Read the press release.