Frog and Toad are Friends: A Biodiversity Story


photo by PlanMyGreen

A study out of Colorado University finds that biodiversity is good for toad legs. Two species of amphibians, the American toad and the gray tree frog, seem to have a symbiotic relationship. When there are no gray tree frogs in an ecosystem, American toads are more likely to have malformed legs.
Biodiversity in Action
The toads and the frogs have a parasite in common, the trematode parasite. This little guy causes deformities in the legs of the American toads, but the gray frogs and especially their tadpoles, seem to"act as sponges" and are able to ease the toad's plight. Furthermore, the tadpoles' immune systems seem to be tough enough to regulate the number of trematode parasites in an environment.

The Study of Biodiversity
The study's leader, Pieter Johnson displayed that American toads raised in tanks without gray tree frogs were more likely to have the leg deformity, but when gray tree frogs were added to the tank, there was a reduction in malformations.


"In the absence of parasites, the toads and frogs are pure competitors, but when the parasites are in the ecosystem, the adage 'the enemy of my enemy is my friend' comes into play for the toads," Johnson said. "This is one of the first experimental studies to definitively show that an increase in diversity of host species actually can reduce parasite transmission and disease,"

Pollution Boosts the Parasites
Agricultural waste gets into ponds and lakes. This will often raise the nitrogen and phosphorus levels. These chemicals help the trematode population, making the toads all the more susceptible to their attacks. One-legged toads don't last very long in the wild. If the gray tree frog population lowers, the American toad population will surely fall as well.

Biodiversity Protects Creatures from Illness
According to Johnson, the decline of biodiversity is bad for all creatures. Humans are more likely to contract Lyme disease in places where other large mammals are scarce. Prairie dogs are apparently susceptible to the bubonic plague spread by fleas.

The Fate of Frog and Toad

One-third of amphibians are threatened and forty-percent of amphibians are in decline. Frog and toad, whether competitors or friends, will have to overcome these and other challenges together.

More on Amphibians
The Frogs Still Need Your Help!
Making 2008 the Year of the Frog
Been Frog Watchin' Lately?

Tags: Animals | Biodiversity

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