Polyandry in Black and Yellow Fire Salamanders Leads to Success

It turns out that polyandry may just provide an evolutionary advantage--at least where salamanders are concerned. Scientists have discovered that female fire salamanders mate with several males under natural conditions. This, in turn, grants them fitness-relevant benefits by increasing their number of offspring.

For a long time, scientists assumed that females in the animal world were monogamous. Males, in contrast, were thought to increase their reproductive success by mating with several females. Now, though, it turns out that polyandry is more of the rule in the animal world while monogamy is more of the exception.

In order to learn a little bit more about the mating behaviors of these species and why polyandry might provide an evolutionary advantage, the researchers examined the influence of mating behavior on the number of offspring in the black and yellow fire salamander.

Over the course of the spring season, a female salamander can deposit up to 50 living larvae in small streams and ponds. For this particular study, the scientists captured female salamanders on their way to deposit their larvae in a forest. Every day, the scientists collected the newborn larvae, took a small tissue sample and then returned the females to the forests. They then subjected the samples to genetic paternity analysis to find out just how many males the females had mated with.

In the end, the researchers found that some females had mated with as many as four males. The mixing of the sperm from many males in the spermatheca of the female also seemed to have positive effects; more eggs were fertilized and more larvae were finally deposited. In addition, it seems as if polyandry and sperm competition were important mechanisms to increase reproductive success and fitness of a female.

The findings are published in the journal Molecular Ecology.