How does joint evolution of consumer traits affect resource specialization?

Consumers regularly experience trade-offs in their ability to find, handle and digest different resources. Evolutionary ecologists recognized the significance of this observation for the evolution and maintenance of biological diversity long ago and continue to elaborate on the conditions under which to expect one or several specialists, generalists or combinations thereof. Existing theory based on a single evolving trait predicts that specialization requires strong trade-offs such that generalists perform relatively poorly, while weak trade-offs favor a single generalist. Here, we show that this simple dichotomy does not hold true under joint evolution of two or more foraging traits. In this case, the boundary between trade-offs resulting in resource specialists and resource generalists is shifted toward weaker trade-off curvatures. In particular, weak trade-offs can result in evolutionary branching leading to the evolution of two coexisting resource specialists while the evolution of ...消费者在搜寻、处理与消化不同资源的能力方面，时常面临权衡（trade-offs）。进化生态学家早在很久以前便认识到这一观测结果对生物多样性演化与维持的重要意义，并持续深入阐释能够催生单一或多种特化类群（specialists）、泛化类群（generalists），或二者组合的环境条件。现有基于单一演化性状的理论预测，特化需要较强的权衡，使得泛化类群的表现相对逊色；而较弱的权衡则更利于单一泛化类群的演化。本研究表明，当两个或多个觅食性状（foraging traits）共同演化时，这一简单的二分法并不成立。在此情形下，导致资源特化类群与资源泛化类群出现的权衡边界，会向更弱的权衡曲率方向偏移。具体而言，较弱的权衡可引发进化分支（evolutionary branching），进而演化出两种共存的资源特化类群，而其演化过程……