Aday D Derek, Philipp David P, Wahl David H
Program in Ecology and Evolutionary Biology, University of Illinois, Champaign, IL 61820, USA.
Oecologia. 2006 Feb;147(1):31-8. doi: 10.1007/s00442-005-0242-x. Epub 2005 Sep 15.
The ultimate body size that an individual fish achieves can be a function both of direct effects of growth or indirect effects associated with the timing of sexual maturation (and associated energetic tradeoffs). These alternatives are often invoked to explain variation in body size within and among fish populations, but have rarely been considered simultaneously. We assessed how resource availability and timing of maturation interact to influence individual body size of bluegill (Lepomis macrochirus). Resource availability (high and low food) and the social structure of the population (presence or absence of large, mature males) were varied in experimental ponds. Food ration affected growth (larger fish in the high food treatments) and the social structure of the population affected timing of maturation (early maturation of males in the absence of large males). Treatment effects, however, were sex-specific; males responded to the social structure of the population and females were more responsive to resource availability. We also found individuals that became sexually mature were smaller than those that remained immature, although results were sex-specific and resource dependent. For males, individuals that matured were smaller when resources were limited; mature and immature females showed no difference in body size regardless of food ration. We show that both resource availability and the processes that control timing of maturation interact in sex-specific ways to influence body size of bluegill. These results suggest that a more robust explanation for variable body size requires consideration of sex-specific interactions between ecological (food and growth) and evolutionary (timing of maturation) mechanisms.
一条鱼最终能达到的体型大小，既可能是生长直接作用的结果，也可能是与性成熟时间相关的间接作用（以及相关的能量权衡）的结果。人们常常援引这些因素来解释鱼类种群内部和种群之间体型大小的差异，但很少同时考虑这两个因素。我们评估了资源可利用性和成熟时间如何相互作用，以影响蓝鳃太阳鱼（Lepomis macrochirus）的个体体型大小。在实验池塘中，改变资源可利用性（高食物量和低食物量）以及种群的社会结构（大型成熟雄性的存在与否）。食物配给影响生长（高食物量处理组中的鱼体型更大），种群的社会结构影响成熟时间（没有大型雄性时雄性早熟）。然而，处理效果具有性别特异性；雄性对种群的社会结构有反应，而雌性对资源可利用性更敏感。我们还发现，性成熟的个体比未成熟的个体体型小，尽管结果具有性别特异性且依赖于资源。对于雄性来说，在资源有限时成熟的个体体型较小；无论食物配给如何，成熟和未成熟的雌性在体型大小上没有差异。我们表明，资源可利用性和控制性成熟时间的过程以性别特异性的方式相互作用，从而影响蓝鳃太阳鱼的体型大小。这些结果表明，对于体型大小变化更有力的解释需要考虑生态（食物和生长）和进化（成熟时间）机制之间的性别特异性相互作用。
