Stoehr Andrew M, Glaenzer Katelyn, VanWanzeele Devin, Rumschlag Samantha
Department of Biological Sciences Butler University Indianapolis Indiana USA.
U.S. EPA Great Lakes Toxicology and Ecology Division Duluth Minnesota USA.
Ecol Evol. 2024 May 1;14(5):e11309. doi: 10.1002/ece3.11309. eCollection 2024 May.
Phenotypic plasticity is the ability of an organism to alter its phenotype in response to environmental cues. This can be adaptive if the cues are reliable predictors of impending conditions and the alterations enhance the organism's ability to capitalize on those conditions. However, since traits do not exist in isolation but as part of larger interdependent systems of traits (phenotypic integration), trade-offs between correlated plastic traits can make phenotypic plasticity non- or maladaptive. We examine this problem in the seasonally plastic wing melanism of a pierid (Order Lepidoptera, Family Pieridae) butterfly, L. Several wing pattern traits are more melanized in colder than in warmer seasons, resulting in effective thermoregulation through solar absorption. However, other wing pattern traits, the spots, are less melanized during colder seasons than in warmer seasons. Although spot plasticity may be adaptive, reduced melanism of these spots could also be explained by resource-based trade-offs. Theory predicts that traits involved in resource-based trade-offs will be positively correlated when variation among individuals in resource acquisition is greater than variation among individuals in resource allocation strategies, and negatively correlated when variation in allocation is greater than variation in acquisition. Using data from both field studies and laboratory studies that manipulate dietary tyrosine, a melanin precursor, we show that when allocation to thermoregulatory melanism (ventral hindwing, and basal dorsal fore- and hindwing "shading") varies substantially this trait is negatively correlated with spot melanism. However, when there is less variation in allocation to thermoregulatory melanism we find these traits to be positively correlated; these findings are consistent with the resource-based trade-off hypothesis, which may provide a non- or maladaptive hypothesis to explain spot plasticity. We also show that increased dietary tyrosine results in increased spot melanism under some conditions, supporting the more general idea that melanism may involve resource-based costs.
表型可塑性是生物体根据环境线索改变其表型的能力。如果这些线索是即将到来的环境条件的可靠预测指标，并且这种改变能增强生物体利用这些条件的能力，那么这可能具有适应性。然而，由于性状并非孤立存在，而是作为更大的相互依赖的性状系统（表型整合）的一部分，相关可塑性性状之间的权衡可能会使表型可塑性失去适应性或产生不良适应性。我们在一种粉蝶（鳞翅目，粉蝶科）——菜粉蝶的季节性可塑性翅黑色素沉着现象中研究了这个问题。几个翅图案性状在较冷季节比在较暖季节黑色素沉着更明显，通过阳光吸收实现有效的体温调节。然而，其他翅图案性状，即斑点，在较冷季节比在较暖季节黑色素沉着更少。虽然斑点可塑性可能具有适应性，但这些斑点黑色素沉着减少也可以用基于资源的权衡来解释。理论预测，当个体在资源获取方面的差异大于个体在资源分配策略方面的差异时，参与基于资源权衡的性状将呈正相关；当分配方面的差异大于获取方面的差异时，则呈负相关。利用来自野外研究和实验室研究的数据，这些研究操纵了黑色素前体——膳食酪氨酸，我们发现，当分配到体温调节黑色素沉着（后翅腹面以及前翅和后翅基部背面的“阴影”）的变化很大时，该性状与斑点黑色素沉着呈负相关。然而，当分配到体温调节黑色素沉着的变化较小时，我们发现这些性状呈正相关；这些发现与基于资源的权衡假说一致，该假说可能为解释斑点可塑性提供一个非适应性或不良适应性假说。我们还表明，在某些条件下，增加膳食酪氨酸会导致斑点黑色素沉着增加，支持了更普遍的观点，即黑色素沉着可能涉及基于资源的成本。
