The role of bite force in the evolution of head shape and head shape dimorphism in Anolis lizards

1. Patterns of convergent evolution in head shape, combined with performance measures, provide ideal opportunities to understand the processes driving its evolution. Anole lizards represent an excellent subject to test this, as recurrent habitat specialists or ecomorphs evolved independently across different islands. 2. We show that phenotypic similarity corresponds to both phylogenetic similarity and similarity in habitat, indicating that there is convergent evolution in head shape among ecomorphs. Moreover, we show that the evolution of tall, wide heads correlates with the evolution of higher bite forces, driving head shape variation among and within ecomorphs. 3. In addition, the processes affecting head shape variation can differ between sexes, leading to sexual head shape dimorphism. These processes might, however, still depend on the habitat. Consequently, there could also be convergent evolution in head shape dimorphism among ecomorphs. 4. We found no evidence for convergent evolution in sexual head shape dimorphism. Moreover, the sexual head shape dimorphism correlates poorly with bite force, suggesting that intersexual head shape differences are related to other functions. Different processes are thus driving the evolution of head shape and head shape dimorphism.

1. 头部形状的趋同演化模式结合性能指标，为解析驱动其演化的过程提供了绝佳契机。安乐蜥（Anole lizards）是检验该假说的理想研究类群，因为在不同岛屿上均独立演化出了多批重复出现的生境特化类群（即生态形态型，ecomorphs）。2. 本研究证实，表型相似性既与系统发育相似性相关，也与生境相似性存在关联，表明不同生态形态型间的头部形状存在趋同演化现象。此外，研究发现高宽型头部的演化与更高咬合力的演化显著相关，这推动了生态形态型内部及类群间的头部形状变异。3. 此外，调控头部形状变异的演化过程可能存在性别差异，进而催生头部形状的性二态性（sexual head shape dimorphism），但这类过程仍可能受生境条件的影响。因此，不同生态形态型之间也可能存在头部形状性二态性的趋同演化。4. 本研究未发现头部形状性二态性存在趋同演化的相关证据。同时，头部形状的性二态性与咬合力的相关性较弱，提示雌雄个体间的头部形状差异与其他功能相关。综上，驱动头部形状演化与驱动头部形状性二态性演化的是两套不同的过程。