Could a fungal parasite have caused some of the many amphibian population declin
ID: 53483 • Letter: C
Question
Could a fungal parasite have caused some of the many amphibian population declines and extinctions in recent decades? One study found that the number of yellow-legged frogs (Rana muscosa) plummeted after the chytrid Batrachochytrium dendrobatidis reached the Sixty Lake Basin area of California. Yellow-legged frogs can be killed by B. dendrobatidis infection. In the years leading up to the chytrid's 2004 arrival, there were more than 2,300 frogs in these lakes. By 2009, only 38 frogs remained; all the survivors were in two lakes (yellow) where researchers had applied a fungicide to reduce the chytrid's impact. Part A Do the data indicate that the chytrid caused or is correlated to the drop in frog numbers? The timing of the declines and the survival of frogs treated with fungicides suggest that the chytrid caused the decline in frog populations. The data suggest that chytrid fungi are only correlated to frog population declines because in many lakes, the chytrid appeared only after frog populations had already declined. The data suggest that the chytrid caused the decline because populations in areas without the chytrid are thriving, whereas populations exposed to the chytrid have gone extinct. There is no evidence that chytrid fungi directly harm frogs, suggesting that the fungi are only correlated to frog population declines.Explanation / Answer
The timing of the declines and the survival of frogs treated with fungicides suggest that the chytrid caused decline in frog populations.
* The data did not provide any information on survival of yellow legged frogs without the chitrid population. The data clearly shows that only after the chitrid arrival, the fog population declined. There is no evidence in the data that chitrid fungi directly harmed the frogs. Hence, these 2nd, 3rd, and 4th options does not accord with the information provided.