Competitive asymmetry and local adaptation in Trinidadian guppies

1. The outcome of competition between individuals often depends on body-size. These competitive asymmetries can drive variation in demographic rates, influencing the ecology and evolution of life-histories. The magnitude and direction of such asymmetries differ among taxa, yet little is known empirically about how adaptation to resource limitation alters competitive asymmetries.
2. Here, we investigate the relationship between size-dependent competitive ability and adaptation to resource limitation.
3. We examined size-dependent competition in two ecotypes of Trinidadian guppy, adapted to high or low levels of resource competition. Using aquaria-based competition experiments, we describe how the size and ecotype of competitors influence somatic growth rate, whilst controlling for the confounding effect of niche differentiation. We replicated our study across two independent evolutionary origins of the 'competitive' ecotype.
4. The two 'competitive' ecotypes differed markedly in size-...