Multiple mating - or polyandry - is beneficial for females, according to researchers at The University of Western Australia in a world-first experimental evolutionary study.
In an article published this week in the prestigious journal Ecology Letters Dr Renee Firman and her colleagues provide the first trans-generational, empirical demonstration that multiple mating drives increased embryo viability in a vertebrate.
Dr Firman said after observing 14 generations of both polygamously mated and monogamously mated lines of house mice, it appeared that the benefits of multiple mating outweighed the risks associated with reproduction.
"Risks associated with mating include increased likelihood of predation and disease, therefore females would need to benefit in some way from soliciting multiple partners," Dr Firman said.
Earlier work by Dr Firman and UWA's Winthrop Professor Leigh Simmons showed that males from polygamous lines had greater fertilisation success when competing against males from monogamous lines, and that increased ejaculate quality translated to improved sperm competitiveness in house mice. An evolutionary history of multiple mating in the polygamous lines may have allowed for the selection of good genes, such that those males that were successful in sperm competition had an intrinsic quality that resulted in offspring of greater fitness.
The new study shows that polyandry has the additional reproductive benefit to females of healthier and more numerous embryos. Males evolved from polyandrous lines were more likely to father offspring with greater viability - supporting the so-called ‘good sperm' hypothesis. And while it did not matter whether the females were from polyandrous or monogamous lines, all benefitted from matings with polyandrous males as they were more likely to produce healthy young.
Dr Firman has also worked on sperm competition in the Sandy Island mouse, a native to the Pilbara.