Washington [US]: Inspired by the tsetse fly, scientists have developed the first mathematical model to explain how an individual's age and experience affect investment in their offspring. This increase-decrease pattern of allocation to offspring is seen in many mammals, birds and insects. Scientists at Bristol, with colleagues at Exeter and Oxford, found this pattern in an important disease-carrying insect, the tsetse fly. Tsetse flies give birth to live young that are nearly as big as their mother.
With colleagues at the Liverpool School of Tropical Medicine, the team studied tsetse mothers in the laboratory for their whole lives. Now, the team has made a mathematical model, published in the journal Proceedings of the Royal Society B, which to show how the pattern can be explained by changes the mothers experience as they get older.
Tsetse live on blood, a rich food supply that is hard to get. The insects have to fly a long way to find an animal and avoid its defences, such as a swatting tail. Tsetse probably get better at acquiring food through experience, but the energy they need to fly increases as their wings become worn. Tsetse mothers have evolved to respond to these effects when passing on fat to their offspring.
"We expect that parents have evolved optimal patterns of resources allocation to maximise their reproductive success," said lead author Dr Antoine Barreaux, research associate at the University of Bristol and now lecturer in Intertryp at Cirad in France. "Our work takes into account age-dependence in many factors, such as feeding ability, energetic costs, and mortality."