Department of Biology, University of California, Riverside, California 92521, USA.
Evolution. 2010 Jun;64(6):1583-93. doi: 10.1111/j.1558-5646.2009.00922.x. Epub 2009 Dec 10.
Early theories of life-history evolution predict that increased predation on young/small individuals selects for delayed maturation and decreased reproductive effort, but such theory only considers changes in mortality. Predators reduce prey abundance and increase food to survivors. Theory that incorporates such indirect effects yields different predictions. Trinidadian killifish, Rivulus hartii, inhabit communities with and without guppies. Guppies prey on young Rivulus and Rivulus densities decline and growth rates increase when guppies are present. Prior work showed that Rivulus phenotypes from communities with guppies matured earlier and had higher fecundity, consistent with theories that incorporate indirect effects. Here we examined the genetic basis of these differences by rearing 2nd generation, laboratory-born Rivulus from sites with and without guppies under two food levels that match natural differences in growth. Many locality x food interactions were significant, often reversing the relationship between communities. Such interactions imply that there are fitness trade-offs associated with adaptation to high or low resource environments. On high food, Rivulus from localities with guppies matured earlier, produced many small eggs, and exhibited increased reproductive investment; these differences reversed on low food. Our results suggest that indirect effects mold Rivulus evolution and thereby highlight connections between community processes and evolutionary change.
早期的生活史进化理论预测，对幼体/小型个体的捕食增加会选择延迟成熟和减少生殖努力，但这种理论只考虑了死亡率的变化。捕食者会减少猎物的数量，并增加幸存者的食物。将这种间接效应纳入考虑的理论会产生不同的预测。特立尼达的脂鲤，Rivulus hartii，栖息在有和没有孔雀鱼的群落中。孔雀鱼捕食幼体脂鲤，当孔雀鱼存在时，脂鲤的密度下降，生长速度增加。先前的研究表明，来自有孔雀鱼的群落的脂鲤表现型更早成熟，繁殖力更高，这与纳入间接效应的理论一致。在这里，我们通过在匹配自然生长差异的两种食物水平下，从有和没有孔雀鱼的地点饲养第二代、实验室出生的脂鲤，来研究这些差异的遗传基础。许多地点 x 食物的相互作用是显著的，经常反转了群落之间的关系。这种相互作用意味着与适应高或低资源环境有关的适应性权衡。在高食物水平下，来自有孔雀鱼的地点的脂鲤更早成熟，产生了许多小卵，并表现出增加的生殖投资；在低食物水平下，这些差异则相反。我们的研究结果表明，间接效应塑造了脂鲤的进化，从而突出了群落过程和进化变化之间的联系。
