CLUE TO WHY FEMALES LIVE LONGER THAN MALES
A study from the
University of Exeter has found that male flies die earlier than their female
counterparts when forced to evolve with the pressures of mate competition and
juvenile survival. The results could help researchers understand the mechanisms
involved in aging.
The research,
published in the journal Functional Ecology, used populations of
the fly Drosophila simulans that had evolved under different
selection regimes. The study shows that mate competition (sexual selection),
along with survival (natural selection), is tougher on male aging than it is on
females reducing their lifespan by about a third.
Some species, like the
flies in this study, age quickly over a number of days while others --
including some trees and whales -- age slowly across centuries.
Professor David Hosken
from Biosciences at the University of Exeter said: "We found dramatic
differences in the effects of sexual and natural selection on male and female
flies. These results could help explain the sex differences in lifespan seen in
many species, including humans, and the diverse patterns of aging we observe in
nature."
The flies were
subjected to elevated or relaxed sexual and natural selection and left to
evolve in these conditions. To elevate sexual selection groups of males were
housed with single females. A stressful temperature was used to elevate natural
selection.
Males court females by
singing, dancing and smelling good but their efforts come at considerable cost
and this cost is amplified when they also have to cope with stressful
temperatures.
The results of the
study showed that under relaxed sexual and natural selection, male and female
flies had very similar lifespans -- around 35 days. However males that evolved
under elevated sexual selection and elevated natural selection had a much
shorter lifespan -- just 24 days -- and died seven days earlier than females
under the same conditions.
Both sexual selection
and natural selection were found to affect lifespan but their effects were
greatest on males. The findings show that the sexes can respond differently to
the same selection regimes.
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