Biology Department, East Carolina University, Greenville, NC, United States.
Department of Biology and Biochemistry, University of Houston, Houston, TX, United States.
PeerJ. 2023 Jun 30;11:e15533. doi: 10.7717/peerj.15533. eCollection 2023.
Aposematism continues to be a phenomenon of central interest in evolutionary biology. The life history of the mimic poison frog, , relies heavily on aposematism. In order for aposematic signals to be effective, predators must be able to learn to avoid the associated phenotype. However, in , aposematism is associated with four different color phenotypes that mimic a complex of congeneric species occurring across the mimic frog's geographic range. Investigations of the underlying mechanics of color production in these frogs can provide insights into how and why these different morphs evolved. We used histological samples to examine divergence in the color production mechanisms used by to produce effective aposematic signals across its geographic range. We measured the coverage of melanophores and xanthophores (the area covered by chromatophores divided by total area of the skin section) in each color morph. We find that morphs that produce orange skin exhibit a higher coverage of xanthophores and lower coverage of melanophores than those that produce yellow skin. In turn, morphs that produce yellow skin exhibit a higher coverage of xanthophores and lower coverage of melanophores than those that produce green skin. Generally, across the morphs, a high ratio of xanthophores to melanophores is associated with colors of brighter spectral reflectance. Together, our results contribute to the understanding of color production in amphibians and document divergence in the histology of a species that is subject to divergent selection associated with aposematism.
警戒色在进化生物学中仍然是一个备受关注的现象。拟毒蛙的生活史在很大程度上依赖于警戒色。为了使警戒信号有效，捕食者必须能够学会避免与相关表型相关联。然而，在拟毒蛙中，警戒色与四种不同的颜色表型相关联，这些颜色表型模拟了在其地理分布范围内出现的同属物种的复杂组合。对这些青蛙中颜色产生的潜在机制的研究可以深入了解这些不同形态是如何以及为何进化而来的。我们使用组织学样本来研究 在其地理分布范围内产生有效警戒信号所使用的颜色产生机制的差异。我们测量了每种颜色表型中黑色素细胞和黄色素细胞（色素覆盖的区域除以皮肤切片的总面积）的覆盖率。我们发现，产生橙色皮肤的形态表现出比产生黄色皮肤的形态更高的黄色素细胞覆盖率和更低的黑色素细胞覆盖率。反过来，产生黄色皮肤的形态比产生绿色皮肤的形态表现出更高的黄色素细胞覆盖率和更低的黑色素细胞覆盖率。一般来说，在所有形态中，黄色素细胞与黑色素细胞的高比值与更明亮的光谱反射颜色相关。总的来说，我们的结果有助于理解两栖动物的颜色产生，并记录了一个受与警戒色相关的分歧选择影响的物种的组织学差异。
