Tsuboi Masahito, Takahashi Tetsumi
Department of Biology, Lund University, Lund, Sweden.
Institute of Natural and Environmental Sciences, University of Hyogo, Sanda, Japan.
J Evol Biol. 2024 Dec 2;37(12):1563-1575. doi: 10.1093/jeb/voae101.
The evolution of sexual dimorphism is widely acknowledged as a manifestation of sex-specific genetic architecture. Although empirical studies suggested that sexual dimorphism evolves as a joint consequence of constraints arising from genetic architecture and sexually divergent selection, it remains unclear whether and how these established microevolutionary processes scale up to the macroevolutionary patterns of sexual dimorphism among taxa. Here, we studied how sexual selection and parental care drive sexual dimorphism in cichlid fishes from Lake Tanganyika. We found that male-male competition, female choice, and maternal mouthbrooding are associated with sexual dimorphism in body length, body colour, and head length, respectively, despite strong allometric relationships between body length and head length. Within-species (static) allometry of head length on body length evolved as sex-specific responses to mouthbrooding, where females evolved higher intercepts while males evolved steeper slopes. Thus, selection to increase mouth size in mouthbrooders may have broken down and reorganized the pattern of allometric constraints that are inherently strong and concordant between sexes. Furthermore, sex-specific responses to mouthbrooding left a remarkably clear signature on the macroevolutionary pattern, resulting in a decoupling of co-evolution in parameters of static allometries between sexes observed exclusively within maternal mouthbrooders. Our study provides multiple lines of evidence that are consistent with the idea that macroevolutionary patterns of sexual dimorphism in Lake Tanganyika cichlids result from sexually divergent selection. Our approach illustrates that an examination of within-population phenotypic variance in the phylogenetic comparative framework may facilitate nuanced understandings of how macroevolutionary patterns are generated by underlying microevolutionary processes.
性二态性的进化被广泛认为是性别特异性遗传结构的一种表现。尽管实证研究表明，性二态性是遗传结构产生的限制和性别差异选择共同作用的结果，但这些已确立的微观进化过程是否以及如何扩展到不同分类群中性二态性的宏观进化模式仍不清楚。在这里，我们研究了性选择和亲代抚育如何驱动坦噶尼喀湖丽鱼科鱼类的性二态性。我们发现，雄性间竞争、雌性选择和母性口育分别与体长、体色和头长的性二态性相关，尽管体长和头长之间存在很强的异速生长关系。头长对体长的种内（静态）异速生长进化为对口育的性别特异性反应，其中雌性进化出更高的截距，而雄性进化出更陡的斜率。因此，对口育者增加口大小的选择可能打破并重新组织了两性之间原本很强且一致的异速生长限制模式。此外，对口育的性别特异性反应在宏观进化模式上留下了非常明显的特征，导致仅在母性口育者中观察到的两性之间静态异速生长参数的协同进化解耦。我们的研究提供了多条证据，支持坦噶尼喀湖丽鱼科鱼类性二态性的宏观进化模式是由性别差异选择导致的这一观点。我们的方法表明，在系统发育比较框架内检查种群内表型方差，可能有助于更细致地理解潜在的微观进化过程如何产生宏观进化模式。
