Moore Jordan M, DeVoogd Timothy J
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
Department of Psychology, Cornell University, Ithaca, NY 14853, USA.
Proc Biol Sci. 2017 May 17;284(1854). doi: 10.1098/rspb.2017.0469.
Vertebrate brains differ in overall size, composition and functional capacities, but the evolutionary processes linking these traits are unclear. Two leading models offer opposing views: the concerted model ascribes major dimensions of covariation in brain structures to developmental events, whereas the mosaic model relates divergent structures to functional capabilities. The models are often cast as incompatible, but they must be unified to explain how adaptive changes in brain structure arise from pre-existing architectures and developmental mechanisms. Here we show that variation in the sizes of discrete neural systems in songbirds, a species-rich group exhibiting diverse behavioural and ecological specializations, supports major elements of both models. In accordance with the concerted model, most variation in nucleus volumes is shared across functional domains and allometry is related to developmental sequence. Per the mosaic model, residual variation in nucleus volumes is correlated within functional systems and predicts specific behavioural capabilities. These comparisons indicate that oscine brains evolved primarily as a coordinated whole but also experienced significant, independent modifications to dedicated systems from specific selection pressures. Finally, patterns of covariation between species and brain areas hint at underlying developmental mechanisms.
脊椎动物的大脑在整体大小、组成和功能能力方面存在差异，但将这些特征联系起来的进化过程尚不清楚。两种主要模型提供了相反的观点：协同模型将大脑结构协变的主要维度归因于发育事件，而镶嵌模型则将不同的结构与功能能力联系起来。这两种模型通常被认为是不相容的，但必须将它们统一起来，以解释大脑结构的适应性变化是如何从先前存在的结构和发育机制中产生的。在这里，我们表明，鸣禽是一个物种丰富的群体，表现出多样的行为和生态特化，其离散神经系统大小的变化支持了这两种模型的主要元素。根据协同模型，核体积的大部分变化在功能域之间是共享的，异速生长与发育序列相关。根据镶嵌模型，核体积的残余变化在功能系统内是相关的，并预测特定的行为能力。这些比较表明，鸣禽的大脑主要作为一个协调的整体进化，但也经历了来自特定选择压力对专用系统的重大独立修改。最后，物种与脑区之间的协变模式暗示了潜在的发育机制。
