Contests for female attention turns males into better performers - in fruit flies

Giving females an opportunity to choose the male they

mate with leads to the evolution of better performing males, according to new

research into the behaviour of fruit flies performed by University of

Sheffield, University of St Andrews and the Leibniz Institute for Zoo and

Wildlife Research in Berlin, Germany.

In this study, Dr Allan Debelle from the University’s Department of

Animal and Plant Sciences recorded the love song of male fruit flies from the

species Drosophila pseudoobscura under different experimental

conditions. In this species, males court females with “love songs” by rapidly

beating their wings, at a rate of around 6,000 beats per minute.

In order to test how female choice can affect the evolution of male

characteristics, groups of flies were kept for 110 generations in either

male-biased populations (where every female could choose among several males)

or in populations where monogamy was enforced (where a female only had access

to one male).

At the end of this selection process – 8 years of mate choice

experiments in captivity – the researchers found that males from the two types

of populations differed in how fast they could beat their wings. In populations

where females could choose their mate, males displayed more power and endurance

when producing their love song than their counterparts that had evolved under

enforced monogamy.

Dr Allan Debelle, who conducted the study as part of his PhD under the

supervision of Dr Rhonda Snook at the University of Sheffield, said these

results suggest that mate choice can be an important driver of the evolution of

motor performance, "Our research shows that when, at each generation,

females are given a choice among several mates performing energetically costly

courtship, the motor performance of males in that population can respond to

this selection process and progressively improve."

Because singing in fruit

flies involves an important muscular effort, one possibility is that males

under female selection did not solely evolve better singing skills but an

overall better physical performance. Consistent with this, the researchers

found that such males not only sing at higher tempo than the others, but they

can also maintain a higher tempo for longer.

Dr Alexandre Courtiol, co-first author of this study, and a researcher

at the Leibniz Institute for Zoo and Wildlife Research, comments, "Our

findings suggest that males evolve to divest from the construction of powerful

bodies and the demonstration of spectacular feats when females do not use these

characteristics to discriminate (e.g. in our experiments, they were prevented

to do so)".

Publication:

Debelle

A,Courtiol A, Ritchie MG, Snook RR (2017): Mate choice intensifies

motor signaling in Drosophila. Animal Behaviour,  https://doi.org/10.1016/j.anbehav.2017.09.014.

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