蓬萊草蜥(Takydromus stejnegeri)色型間的被捕食風險與存活率差異

Abstract

動物色彩是一個迷人的研究領域，隱含了多種選擇壓力之間的平衡。理解這些力量如何塑造動物顏色信號在演化和生態學中至關重要。在這項研究中，我們研究了蓬萊草蜥（Takydromus stejnegeri）體色訊號的被捕食成本和配偶偏好之間的權衡。該蜥蜴展示了季節和個體間的色型變異，在非繁殖季，大多數個體是純棕色的，而在繁殖季，許多個體會展現出綠色的側腹和背部的白色條紋。我們將其劃分為四種主要的色型：綠色白線型、綠色無白線型、棕色白線型和棕色無白線型。先前的配偶選擇實驗指出雌性蜥蜴偏好同色的雄性，而綠色的雄性則對棕色的雌性有偏好。我們所提出的假說是：蓬萊草蜥的色型變異由複雜的交配系統維持，而體色和白線特徵的季節性盛行率則是由捕食壓力驅動的。我們使用光譜儀和數位影像分析來評估各色型在季節性背景下的辨識度和可偵測性，並使用Cormack-Jolly-Seber模型和四年的捕捉-標記-再捕捉數據來估算各色型的存活率。結果顯示，在非繁殖季，相較於綠色型，棕色型在背景中的辨識度和可偵測性較低，而繁殖季時的情況則相反。存活率估計結果與之相應，顯示在繁殖季時，棕色無白線型存活率最低，而綠色白線型的存活率最高。此結果指出儘管兩種側面顏色都受益於交配系統，但棕色型因為承受相對較高的捕食風險，而綠色形態因其隱蔽性具有額外的存活優勢，使得綠色型成為繁殖季的主要色型。此外，我們發現背部的白色條紋在蜥蜴的身體上形成高強度邊緣的圖案，且有白線的色型比無白線的色型具有更高的存活率，這些白線可能具有破壞性或迷惑性著色的功能。整體而言，我們的研究強調了性選擇和自然選擇作用力在不同生態季節中的動態互動，並展示了這些演化過程如何塑造動物色彩。Animal coloration is a fascinating field that reveals the balance among multiple selection forces. Understanding how these forces shape animal color signals is crucial in evolutionary biology and ecology. In this study, we examined the trade-off between predation cost and mate preference in visual signal of a color polymorphic lizard, Takydromus stejnegeri, which exhibits both seasonal and individual color variations. During the non-breeding season, most individuals are plain brown, while in the breeding season, many develop green flanks and white stripes. We identified four main morphs: green flanks with or without white stripes, and brown flanks with or without white stripes. Previous mating experiments reveal that females prefer males with the same flank coloration, and green males show a preference for brown females. We hypothesize that the complex mating system maintains these color variants, while predation pressure drives the seasonal prevalence of flank colorations and white stripes. Using spectrometry and digital image analysis, we assess morph discrimination and detectability against seasonal backgrounds and employed Cormack-Jolly-Seber model with 4-year capture-mark-recapture data to estimated survival rates. Our findings showed that brown morphs are less discriminable and detectable than green morphs during the non-breeding season, while the pattern reversing in the breeding season. Estimation of survival rates confirmed that the brown-without-stripes morph has the lowest survival rates, and the green-with-stripes morph has the highest during the breeding season. This suggests that although both flank colorations benefit from the mating system, brown morphs incur relatively higher predation risk, while green morphs have an additional survival advantage due to their concealment, resulting in the dominance of green morphs during the breeding season. Additionally, dorsal white stripes create a high-intensity edge pattern on lizard’s body, and show higher survival rates for striped morphs than non-striped morphs. This indicated that the white stripes may serve as disruptive or distractive coloration. Overall, our study highlights the dynamic interactions between sexual and natural selection forces across ecological seasons, illustrating how these evolutionary processes shape animal color design.