"It's always better for offspring if parents can mate with preferred partners, but it's becoming clear that when parents can't have that preferred partner, they have ways of making up for it," said Patricia Adair Gowaty, a Distinguished Research Professor of Ecology and Genetics at the University of Georgia and lead author of the study.
"When female 'choosers' were in enforced pairs with males they did not prefer, they laid more eggs. Similarly, when males are paired with females they do not prefer, they ejaculate more sperm. This compensation seems to be a way of making the best of a bad job," Gowaty added.
The new study's strongest arguments for the Compensation Hypothesis is that it includes experimental results in Tanzanian cockroaches, fruit flies, pipefish, wild mallards and feral house mice. When each species faced experimental constraints on their will to choose their mate, individuals found ways around the issue that could improve the chances that offspring could survive and perhaps even flourish.
"Just how an individual finds its best mate isn't really known, though there's some evidence that he or she may be somehow sensing the advantage of the potential mate's immune system in relation to the chooser's own," said Gowaty.
She points out that many factors are probably at work, including behavioural cues and what potential resources a mate may bring.
While the strategies for dealing with non-preferred mates can help offspring, advantages for the mating pairs themselves are less clear. In experimental situations, for example, females mated to non-preferred males didn't live as long as females mated to their preferred choice.
One interesting aspect of the study is its implication that all individuals in a species have a flexible response to such problems as constraints on expression of their mating preferences. If that's true, it hints that compensation may evolve—which could add an unexpected wrinkle to the story of natural selection.
"How compensation evolves is crucial," Anderson said.
"The study also has implications for conservation because it suggests that the best way to keep species alive may be, if possible, to let individuals choose their own mates," said Gowaty