蓬萊草蜥的體色變化與性擇

Abstract

顏色可作為許多動物傳遞訊息的溝通訊號。若一物種中的同一族群出現多種不同顏色型態，則稱之為體色多型性（color polymorphism）。許多研究指出體色多型性與選擇伴侶有關，因此在性擇中扮演重要的角色。蓬萊草蜥（Takydromus stejnegeri）廣泛分布在台灣西部平原與淺山地帶，無論公母，牠們的體色均可分為棕色型或綠色型，同時可能帶有白線或沒有白線，但我們仍不清楚蓬萊草蜥的體色變異程度、原因及功能。因此我們透過捉放法(capture-mark-recapture)進行長期的野外調查，並藉由擇偶實驗來釐清蓬萊草蜥的體色、身體品質擇偶偏好之間的關係。長期標放的研究自2017年持續至今，共捕獲了2796隻次的草蜥。結果顯示蓬萊草蜥進入繁殖季節時，雌蜥的體側會變成綠色，而雄蜥的體側或背部則會顯現出白線。我們也發現體色與身體品質有關，綠色雌蜥的尺度化質量指數（scaled mass index, SMI）高於棕色的雌蜥；而有白線雄蜥的尺度化質量指數則高於無白線的雄蜥。擇偶實驗的結果顯示綠色的雌蜥偏好綠色的雄蜥，棕色的雌蜥則無偏好，因此，體色不僅作為性成熟的訊號，同時也可能是吸引異性的訊號。Color polymorphism plays a crucial role in sexual selection. Stejneger's grass lizard (Takydromus stejnegeri) has many types of body coloration from a combination of green or brown, and striped or non-striped in both sexes. In order to the clarify relationships among the variation of body coloration, body condition, and mate preference, we conducted a capture-mark-recapture survey in the wild and mate choice experiments in the laboratory. Based on data from a total of 2796 marked individuals, we found that adult females tend to show green patches, while adult males tend to show white stripe during the breeding season. These colorations were associated with the body condition; lizards with higher scaled mass indexes (SMI) represented a stronger performance of these traits. In the mate choice experiments, we found that the green females preferred green males, while the brown females had no color preference. These results hinted that the green coloration is not just a sexual signal, but also associates with the preference of its owner. Our results suggest that the polymorphic colors on T. stejnegeri are determined by life stage, sex maturity, and perhaps link to inter-sexual selection.