(a) Relative fitness 1.50 1.25- 1.00- 0.75- BO NO 0.50- 31 32 generations generations, Net fitness 1996 Nature Publishing Group. Assay 8 Selected males Unselected males Remating Defense (b) Average number of dead females per vial (out of 32 total) 20- 10- 0- EA EB Selected CA CB Unselected Male line Figure 13.36 Antagonis- tic sexual selection in fruit flies (a) Sons per father, remat- ing rate, and defense in males selected for mating competitive- ness versus unselected males. Assayed after 31 and 32 gen- erations in two populations per treatment. (b) After 41 genera- tions, females mated to selected males (EA and EB) had higher mortality rates than those mated to unselected males (CA and CB) (p = 0.0194). After Rice (1996). Reprinted by permissions of Macmillan Publishers Ltd. W. R. Rice, 1996. "Sexually antagonistic male adaptation triggered by experimental arrest of female evolution." Nature 381: 232-234. Copyright © 1996
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Please consider the figure, which contains data that were collected by Rice
In the experiments that were performed by Rice
i. males competed intensely for females, which resulted in selection for traits like 'high likelihood to remate with the same female' and 'high proportion among fertilised eggs fathered.'
ii. only males experienced intense competition; females were obtained from a control population, in which no competition for mates was occurring, effectively fixing female responses.
iii. males that were selected for success in mating competition were characterised by greater fitness.
iv. when females were prevented from evolving compensatory life history traits, they incurred at least one cost for the benefits gained by males in increased reproductive success: greater female mortality (attributed to toxicity in male seminal fluid).
v. once established, enhanced male traits were irreversible.
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