Wcislo William T, Tierney Simon M
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panamá.
Biol Rev Camb Philos Soc. 2009 Feb;84(1):19-37. doi: 10.1111/j.1469-185X.2008.00059.x. Epub 2008 Nov 22.
Most bees forage for floral resources during the day, but temporal patterns of foraging activity vary extensively, and foraging in dim-light environments has evolved repeatedly. Facultative dim-light foraging behaviour is known in five of nine families of bees, while obligate behaviour is known in four families and evolved independently at least 19 times. The light intensity under which bees forage varies by a factor of 10(8), and therefore the evolution of dim-light foraging represents the invasion of a new, extreme niche. The repeated evolution of dim-light foraging behaviour in bees allows tests of the hypothesis that behaviour acts as an evolutionary pacemaker. With the exception of one species of Apis, facultative dim-light foragers show no external structural traits that are thought to enable visually mediated flight behaviour in low-light environments. By contrast, most obligate dim-light foragers show a suite of convergent optical traits such as enlarged ocelli and compound eyes. In one intensively studied species (Megalopta genalis) these optical changes are associated with neurobiological changes to enhance photon capture. The available ecological evidence suggests that an escape from competition for pollen and nectar resources and avoidance of natural enemies are driving factors in the evolution of obligate dim-light foraging.
大多数蜜蜂在白天采集花卉资源，但觅食活动的时间模式差异很大，在弱光环境中觅食已经多次进化。在九个蜜蜂科中有五个科已知存在兼性弱光觅食行为，而四个科已知存在专性弱光觅食行为，并且至少独立进化了19次。蜜蜂觅食时的光照强度相差10的8次方倍，因此弱光觅食的进化代表了对一个新的极端生态位的入侵。蜜蜂中弱光觅食行为的反复进化使得对行为作为进化起搏器这一假设的检验成为可能。除了一种蜜蜂外，兼性弱光觅食者没有被认为能在低光环境中实现视觉介导飞行行为的外部结构特征。相比之下，大多数专性弱光觅食者表现出一系列趋同的视觉特征，如增大的单眼和复眼。在一个经过深入研究的物种（金腹隧蜂）中，这些视觉变化与神经生物学变化相关，以增强光子捕获。现有的生态学证据表明，摆脱对花粉和花蜜资源的竞争以及躲避天敌是专性弱光觅食进化的驱动因素。
