Van Buskirk Josh, Cereghetti Eva, Hess Julia S
Evolutionary Biology & Environmental Studies University of Zürich Zürich Switzerland.
Ecol Evol. 2017 Apr 17;7(11):3745-3750. doi: 10.1002/ece3.2978. eCollection 2017 Jun.
Models suggest that the mechanism of competition can influence the growth advantage associated with being large (in absolute body size or relative to other individuals in the population). Large size is advantageous under interference, but disadvantageous under exploitative competition. We addressed this prediction in a laboratory experiment on tadpoles competing for limited food. There were 166 target individuals spanning a 10-fold range in body mass reared for 3 days with three other individuals that were either the same size, half as large, or twice as large as the target. Relative growth rate (proportion per day) declined with size, and absolute growth rate (mass per day) reached a peak at intermediate size and declined thereafter. Tadpoles grew slowly if they were large relative to their competitors, although relative body size was less important than absolute size. As a result, size variation declined in groups that were initially composed of individuals of variable size. Thus, bigger was not better under exploitative competition. Our results help connect individual-level behavior with individual growth and the size distribution of the population.
模型表明，竞争机制会影响与体型较大（绝对体型或相对于种群中其他个体的体型）相关的生长优势。在干扰竞争中，体型大是有利的，但在剥削性竞争中则是不利的。我们在一项关于蝌蚪争夺有限食物的实验室实验中验证了这一预测。有166个目标个体，其体重范围跨越10倍，与另外三个个体一起饲养3天，这三个个体的体型要么与目标个体相同、要么是目标个体的一半大、要么是目标个体的两倍大。相对生长率（每天的比例）随体型增大而下降，绝对生长率（每天的体重）在中等体型时达到峰值，此后下降。如果蝌蚪相对于其竞争者体型较大，它们生长缓慢，尽管相对体型不如绝对体型重要。结果，最初由不同体型个体组成的群体中体型差异减小。因此，在剥削性竞争中，体型越大并不越好。我们的研究结果有助于将个体水平的行为与个体生长以及种群的体型分布联系起来。
