Neuroanatomical differentiation in dimorphic male C. pallida and A. dawsoni bees (volumes)

Alternative reproductive tactics (ARTs) occur when there is categorical
variation in the reproductive strategies of a sex within a population.
These different behavioral phenotypes can expose animals to distinct
cognitive challenges, which may be addressed through neuroanatomical
differentiation. The dramatic phenotypic plasticity underlying ARTs
provides a powerful opportunity to study how intraspecific nervous system
variation can support distinct cognitive abilities. We hypothesized that
conspecific animals pursuing ARTs would exhibit dissimilar brain
architecture. Dimorphic males of the bee species Centris
pallida and Amegilla dawsoni use alternative mate
location strategies that rely primarily on either olfaction (large-morph)
or vision (small-morph) to find females. This variation in behavior led us
to predict increased volumes of the brain regions supporting their
primarily chemosensory or visual mate location strategies. Large-morph
males relying mainly on olfaction had relatively larger antennal lobes and
relatively smaller optic lobes than small-morph males relying primarily on
visual cues. In both species, as relative volumes of the optic lobe
increased, the relative volume of the antennal lobe decreased. In
addition, A. dawsoni large males had relatively larger mushroom body lips,
which process olfactory inputs. Our results suggest that the divergent
behavioral strategies in ART systems can be associated with
neuroanatomical differentiation.

替代性繁殖策略（Alternative reproductive tactics，ARTs）指种群内某一性别在繁殖策略上存在明确差异的现象。这些不同的行为表型（behavioral phenotypes）会使动物面临独特的认知挑战（cognitive challenges），而这些挑战可能通过神经解剖学分化（neuroanatomical differentiation）来应对。ARTs背后显著的表型可塑性（phenotypic plasticity）为研究种内神经系统变异（intraspecific nervous system variation）如何支持不同认知能力（cognitive abilities）提供了绝佳契机。我们假设，采用ARTs的同种动物会表现出不同的脑结构（brain architecture）。蜜蜂物种Centris pallida和Amegilla dawsoni的二态雄性（dimorphic males）采用替代性的配偶定位策略（mate location strategies），主要依赖嗅觉（olfaction）（大形态）或视觉（vision）（小形态）来寻找雌性。主要依赖嗅觉的大形态雄性比主要依赖视觉线索的小形态雄性拥有相对更大的触角叶（antennal lobes）和相对更小的视叶（optic lobes）。在这两个物种中，视叶的相对体积增加时，触角叶的相对体积会减少。此外，A. dawsoni的大形态雄性拥有相对更大的蘑菇体唇（mushroom body lips），该结构负责处理嗅觉输入（olfactory inputs）。我们的研究结果表明，ART系统中不同的行为策略可能与神经解剖学分化相关。