Rhebergen Flor T, Stewart Kathryn A, Smallegange Isabel M
Institute for Biodiversity and Ecosystem Dynamics University of Amsterdam Amsterdam The Netherlands.
Institute of Environmental Sciences Leiden University Leiden The Netherlands.
Ecol Evol. 2022 Aug 1;12(8):e9145. doi: 10.1002/ece3.9145. eCollection 2022 Aug.
Male secondary sexual traits often scale allometrically with body size. These allometries can be variable within species and may shift depending on environmental conditions, such as food quality. Such allometric plasticity has been hypothesized to initiate local adaptation and evolutionary diversification of scaling relationships, but is under-recorded, and its eco-evolutionary effects are not well understood. Here, we tested for allometric plasticity in the bulb mite (), in which large males tend to develop as armed adult fighters with thickened third legs, while small males become adult scramblers without thickened legs. We first examined the ontogenetic timing for size- and growth-dependent male morph determination, using experimentally amplified fluctuations in growth rate throughout juvenile development. Having established that somatic growth and body size determine male morph expression immediately before metamorphosis, we examined whether the relationship between adult male morph and size at metamorphosis shifts with food quality. We found that the threshold body size for male morph expression shifts toward lower values with deteriorating food quality, confirming food-dependent allometric plasticity. Such allometric plasticity may allow populations to track prevailing nutritional conditions, potentially facilitating rapid evolution of allometric scaling relationships.
雄性第二性征通常与体型呈异速生长关系。这些异速生长在物种内部可能存在差异，并且可能会根据环境条件（如食物质量）而发生变化。这种异速生长可塑性被认为会引发局部适应以及异速生长关系的进化多样化，但目前记录不足，其生态进化效应也尚未得到充分理解。在此，我们对球螨进行了异速生长可塑性测试，在球螨中，体型大的雄性往往发育为有武装的成年战斗者，其第三条腿变粗，而体型小的雄性则成为没有变粗腿部的成年攀爬者。我们首先利用整个幼体发育过程中实验性放大的生长速率波动，研究了与体型和生长相关的雄性形态决定的个体发育时间。在确定了体细胞生长和体型在变态前立即决定雄性形态表达后，我们研究了成年雄性形态与变态时体型之间的关系是否会随食物质量而变化。我们发现，随着食物质量变差，雄性形态表达的阈值体型向更低的值移动，证实了食物依赖的异速生长可塑性。这种异速生长可塑性可能使种群能够追踪当前的营养状况，潜在地促进异速生长关系的快速进化。
