Matching habitat choice could be brightness-based instead of hue-based in green–brown polymorphic grasshoppers

Some prey species have evolved background matching, that is, they resemble their surrounding environment in terms of colour and/or brightness. When prey populations inhabit patchy environments, they may even have evolved specialised phenotypes: each phenotype matching a specific subset of patches. To benefit from the match between their phenotype and this subset of patches, individuals should preferentially select patches within that subset, a process known as matching habitat choice. Matching habitat choice is particularly beneficial to colour polymorphic prey populations, as it reduces individual and population-level predation risk. We tested for matching habitat choice in green-brown polymorphic grasshoppers using experimental arenas lined with green-brown checkerboards. Because previous work suggested that grasshoppers may distinguish green and brown solely achromatically, individuals were tested on green-brown checkerboards that were either achromatically-mismatched (different lumi..., Study models
Meadow grasshoppers (Pseudochorthippus parallelus) and slant-faced grasshoppers (Acrida ungarica) were collected from the field in the summer of 2024. We collected P. parallelus as adults in late June in east-central Germany, and A. ungarica as nymphs in mid-July in northern Italy. Both species are green-brown polymorphic, featuring uniform green and uniform brown individuals. A. ungarica can show longitudinal stripes that have been described as disruptive colourations (Pellissier et al., 2011), though almost none of our individuals feature such patterns. A. ungarica individuals can undergo slow ontogenetic colour changes, but note that brown-to-green transitions are noticeably more frequent than green-to-brown transitions – they represented 63% of all colour changes we observed in the present study (26 out of 41). In this study, brown-to-green transitions happened shortly before moulting, while green-to-brown transitions happened shortly after moulting.

Matching habitat c..., # Data from: Matching habitat choice could be brightness-based instead of hue-based in green–brown polymorphic grasshoppers

Summary:

Some prey evolved background matching to evade visually guided predators. In heterogeneous environments, background matching can be met by a specialist phenotype that resembles a specific subset of the environment. Specialist phenotypes need to engage in matching habitat choice by preferentially selecting patches against which they are best concealed to optimise their fitness. Theory predicts that matching habitat choice can help maintain adaptive genetic polymorphisms. Matching habitat choice could then contribute to the maintenance of the green–brown polymorphism in orthopterans, for which balanced maintenance has been argued, buthas yet to be mechanistically explained. We tested matching habitat choice by green–brown polymorphic grasshoppers in experimental arenas covered with green–brown checkerboards that are achromatically-matched or achromatically..., ,

部分猎物物种演化出了背景匹配（background matching）策略，即其体色与/或亮度与周遭环境高度相似。当猎物种群栖息于斑块化环境中时，它们甚至可能演化出特化表型（specialised phenotypes）：每一类表型对应匹配某一特定的环境斑块。为了从自身表型与对应斑块的匹配关系中获益，个体应优先选择该类斑块，这一过程被称为栖息地匹配选择（matching habitat choice）。栖息地匹配选择对体色多态（colour polymorphic）的猎物种群尤为有益，因为它能降低个体乃至种群整体的被捕食风险。我们以绿褐体色多态蝗虫为研究对象，使用铺设有绿褐棋盘格的实验场地（experimental arenas）开展栖息地匹配选择行为测试。过往研究表明，蝗虫或许仅通过消色差视觉区分绿色与褐色，因此本研究使用了消色差不匹配（亮度差异……，研究模型）的绿褐棋盘格开展个体测试。

草甸蝗（Pseudochorthippus parallelus）与斜纹蝗（Acrida ungarica）于2024年夏季野外采集。我们于6月末在德国中东部地区采集了草甸蝗的成虫，于7月中旬在意大利北部地区采集了斜纹蝗的若虫。两个物种均表现为绿褐体色多态，存在纯绿色与纯褐色两种个体类型。斜纹蝗个体可呈现纵向条纹，这类条纹被归类为干扰色（disruptive colourations，Pellissier等，2011），但本研究采集的个体几乎均无此类斑纹。斜纹蝗个体可发生缓慢的个体发育体色变化（ontogenetic colour changes），值得注意的是，褐色向绿色的转变频率显著高于绿色向褐色的转变：本研究中观察到的41次体色变化里，有26次为褐转绿，占比63%。本研究中，褐转绿的体色变化发生在蜕皮（moulting）前不久，而绿转褐的变化则发生在蜕皮后不久。

# 数据来源：《绿褐体色多态蝗虫的栖息地匹配选择或基于亮度而非色调》

摘要：
部分猎物演化出背景匹配策略，以躲避依靠视觉定位的捕食者。在异质环境中，背景匹配可通过特化表型实现，这类表型与环境中某一特定斑块子集高度相似。特化表型的个体需要通过栖息地匹配选择行为，优先选择最利于自身隐蔽的斑块，以此提升自身适合度。理论研究预测，栖息地匹配选择有助于维持适应性遗传多态性。因此，栖息地匹配选择或可解释直翅目（orthopterans）昆虫绿褐体色多态的维持机制——此前学界虽提出该多态性存在平衡维持现象，但尚未有机制层面的合理解释。我们以铺设有消色差匹配或消色差……的绿褐棋盘格的实验场地，测试了绿褐体色多态蝗虫的栖息地匹配选择行为。