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>Adaptation to larval crowding in Drosophila ananassae and Drosophila nasuta nasuta : increased larval competitive ability without increased larval feeding rate
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Adaptation to larval crowding in Drosophila ananassae and Drosophila nasuta nasuta : increased larval competitive ability without increased larval feeding rate
The standard view of adaptation to larval crowding in fruitflies, built on results from 25 years of multiple experimental evo-lution studies onDrosophila melanogaster, was that enhanced competitive ability evolves primarily through increased larvalfeeding and foraging rate, and increased larval tolerance to nitrogenous wastes, at the cost of efficiency of food conversion tobiomass. These results were at odds from the predictions of classicalK-selection theory, notably the expectation that selec-tion at high density should result in the increase of efficiency of conversion of food to biomass, and were better interpretedthrough the lens of?±-selection. We show here that populations ofD. ananassaeandD. n. nasutasubjected to extreme larvalcrowding evolve greater competitive ability and pre-adult survivorship at high density, primarily through a combination ofreduced larval duration, faster attainment of minimum critical size for pupation, greater time efficiency of food conversion tobiomass and increased pupation height, with a relatively small role of increased urea/ammonia tolerance, if at all. This is avery different suite of traits than that seen to evolve under similar selection inD.melanogaster,andseemstobeclosertotheexpectations from the canonical theory ofK-selection. We also discuss possible reasons for these differences in results acrossthe three species. Overall, the results reinforce the view that our understanding of the evolution of competitive ability in fruit-flies needs to be more nuanced than before, with an appreciation that there may be multiple evolutionary routes through whichhigher competitive ability can be attained.
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