Center for Ecological Research, Kyoto University, Hirano 2-509-3, Otsu 520-2113, Japan.
School of Science, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.
Proc Biol Sci. 2021 Jan 27;288(1943):20202848. doi: 10.1098/rspb.2020.2848. Epub 2021 Jan 20.
Some flowering plants signal the abundance of their rewards by changing their flower colour, scent or other floral traits as rewards are depleted. These floral trait changes can be regarded as honest signals of reward states for pollinators. Previous studies have hypothesized that these signals are used to maintain plant-level attractiveness to pollinators, but the evolutionary conditions leading to the development of honest signals have not been well investigated from a theoretical basis. We examined conditions leading to the evolution of honest reward signals in flowers by applying a theoretical model that included pollinator response and signal accuracy. We assumed that pollinators learn floral traits and plant locations in association with reward states and use this information to decide which flowers to visit. While manipulating the level of associative learning, we investigated optimal flower longevity, the proportion of reward and rewardless flowers, and honest- and dishonest-signalling strategies. We found that honest signals are evolutionarily stable only when flowers are visited by pollinators with both high and low learning abilities. These findings imply that behavioural variation in learning within a pollinator community can lead to the evolution of an honest signal even when there is no contribution of rewardless flowers to pollinator attractiveness.
一些开花植物通过改变花的颜色、气味或其他花卉特征来指示其报酬的丰富程度，因为报酬会被消耗殆尽。这些花卉特征的变化可以被视为对传粉者的报酬状态的诚实信号。先前的研究假设，这些信号被用来维持植物层面对传粉者的吸引力，但从理论基础上，尚未很好地研究导致诚实信号发展的进化条件。我们通过应用一个包括传粉者反应和信号准确性的理论模型，研究了花朵中诚实奖励信号进化的条件。我们假设传粉者通过与报酬状态相关联的方式学习花卉特征和植物位置，并利用这些信息来决定访问哪些花朵。在操纵联想学习的水平的同时，我们调查了最佳的花朵寿命、有报酬和无报酬花朵的比例，以及诚实和不诚实的信号策略。我们发现，只有当花朵被具有高和低学习能力的传粉者访问时，诚实信号才是进化稳定的。这些发现意味着，即使无报酬花朵对传粉者吸引力没有贡献，传粉者群体中学习行为的变化也可以导致诚实信号的进化。
