Fungus makes frog communities undergo “McDonaldization”By ANI
Wednesday, September 23, 2009
WASHINGTON - In a new research, scientists have said that the frog communities are undergoing the process of “McDonaldization”, thanks to a fungus hammering the biodiversity of their communities and making them resemble each other.
Everyone knows that frogs are in trouble and that some species have disappeared, but a recent analysis of Central American frog surveys shows the situation is worse than had been thought.
Under pressure from a fungal disease, the frogs in this biodiversity hot spot are undergoing “a vast homogenization” that is leaving behind impoverished communities that increasingly resemble one another.
“We’re witnessing the McDonaldization of the frog communities,” said Kevin G. Smith, Ph.D., associate director of the Tyson Research Center at Washington University in St. Louis.
In the new analysis, Smith determined that Batrachochytrium dendrobatidis, or Bd, a microscopic fungus that lives in water and moist soil, sickens or kills frogs.
Bd is called a chytrid fungus from the Greek chytridium, meaning “little pot” because small blisters filled with sperm-like, flagellated zoospores form in the skin of infected frogs.
Smith thought that the pathogen might be altering the frog communities, causing them to lose both alpha and beta diversity.
People had compared the susceptibility of different species to the fungus, but no one had looked for changes in the less appreciated beta diversity.
The baseline assumption of the analysis was that the pathogen was causing no change in beta diversity, the result that would be expected if it hit all species equally as it swept across the region.
Hoping to find a data set appropriate for the kind of analysis he had in mind, Smith got in touch with Karen R. Lips, a scientist who has monitored amphibian declines in Central America for many years.
Lips had species lists from six sites both before and after Bd appeared, and she was able to obtain data from two more sites, for a total of eight.
The beta diversity dropped even more precipitously than the alpha diversity because the fungus preferentially attacked endemic species found only at one or a few sites.
In homogenizing the frog communities, the fungus erased chapters in evolutionary history. Two rare families of frogs, the Aromobatidae and the Hemiphractidae, disappeared from the region.
Homogenization also knocked out ecological diversity.
Before the invasion there was a good mix of species in the region. Some species lived in streams, others on land, in trees and underground.
But the primarily aquatic fungus killed most of the water-loving species.
“Now the frog communities are typified by terrestrial species, which has changed the whole way the system works ecologically,” said Smith. (ANI)