Experimental evolution of competing bean beetle species reveals long-term reversals of short-term evolution, but no consistent character displacement

Interspecific competition for shared resources should select for evolutionary divergence in resource use between competing species, termed character displacement. Many purported examples of character displacement exist, but few completely rule out alternative explanations. We reared genetically-diverse populations of two species of bean beetles, Callosobruchus maculatus and C. chinensis, in allopatry and sympatry on a mixture of adzuki beans and lentils, and assayed oviposition preference and other phenotypic traits after four, eight, and twelve generations of (co)evolution. C. maculatus specializes on adzuki beans; the generalist C. chinensis uses both beans. C. chinensis growing in allopatry emerged equally from both bean species. In sympatry, the two species competing strongly and coexisted via strong realized resource partitioning, with C. chinensis emerging almost exclusively from lentils and C. maculatus emerging almost exclusively from adzuki beans. However, oviposition preferenc...针对共享资源的种间竞争，通常会驱使竞争物种在资源利用策略上产生演化分化，该过程被称为性状替换（character displacement）。尽管已有诸多被认为属于性状替换的实例，但其中极少能够完全排除其他解释的可能性。本研究将两种豆象——四纹豆象（Callosobruchus maculatus）与绿豆象（Callosobruchus chinensis）的遗传多样种群，分别置于异域分布（allopatry）与同域分布（sympatry）的实验条件下，以红小豆与小扁豆的混合基质进行饲养，并在经过4代、8代及12代的（共）演化后，检测其产卵偏好（oviposition preference）与其他表型性状（phenotypic traits）。其中四纹豆象专性寄居于红小豆，而广食性的绿豆象可利用两种豆科作物。在异域分布条件下饲养的绿豆象，从两种豆科作物中羽化的个体数量基本相当；而在同域分布条件下，两个物种种间竞争激烈，并通过显著的实际资源划分实现共存：绿豆象几乎仅从小扁豆中羽化，四纹豆象则几乎仅从红小豆中羽化。然而，其产卵偏好……