永澤蛇眼蝶(Minois nagasawae)眼紋大小及數目的地理模式

Abstract

鱗翅目的眼紋形成與演化受到許多基因調控、環境因子及選汰作用的影響，長久以來受許多不同生物學研究領域關切。永澤蛇眼蝶(Minois nagasawae)為一年一世代眼蝶，分布在台灣3000m 以上高海拔，成蝶主要發生於秋季，其眼紋數目及大小呈現多型性。一世代性眼蝶眼紋多型性顯非源自季節適應現象。本研究於2003-2010 年間採集477 隻永澤蛇眼蝶，分別來自中央山脈、雪山山脈及玉山山脈共15 個地點，以線性迴歸分析眼紋大小、眼紋數目及鳥啄痕數目與緯度、性別及環境因子(十年均溫、十年平均雨量及十年每月平均日照時數)之關係。結果顯示眼紋大小顯著具有緯度效應，緯度愈高眼紋愈大；眼紋數目與鳥啄痕的分析中，緯度與性別因子顯著具有交互作用，高緯度地區雌蝶的眼紋數和鳥啄痕數目較雄蝶多；十年均溫、十年平均雨量及十年每月平均日照時數顯著影響眼紋大小與數目的變異。永澤蛇眼蝶平均有42%個體具有鳥啄痕，野外觀察發現6 種鳥類天敵，包括高海拔數量優勢的台灣噪眉(Garrulax morrisoniana)，顯示永澤蛇眼蝶面臨相當程度的鳥類捕食壓力。本研究認為環境因子與鳥類天敵捕食壓力是造成眼紋大小與眼紋數目地理分布模式的因素。

Eyespot formation and evolution involve gene expressions, environmental factors and selection forces. It has been the subject of extensive investigations by many different biological disciplines. Minois nagasawae, an univoltine satyrid butterfly inhabiting alpine zones above 3000m in Taiwan, is on the wing from July through October. The peak of occurrence is in the autumn. Phenotypic plasticity in terms of number and size are found on eyespots in M. nagasawae, and this variation is apparently not caused by seasonal factors for this univoltine species. In the present study, 477 individuals of M. nagasawae were collected from 15 locations belonging to Central Mountain Ridge, Hsuehshan Mountain Ridge and Yushan Mountain Ridge from 2003 to 2010. The regression among response variables (eyespot size, number, beak marks) and predictor variables (latitude, sex, environmental factors) were calculated respectively. The results show that a latitudinal gradient of eyespot size exits. Eyespot size increases with latitudes. For eyespot number and beak marks, the interaction between latitude and sex is significant. Females in higher latitudes have more eyespot number and beak marks than those in males. Environmental factors are also significant predictor variables for eyespot size and number. There were 42% of M. nagasawae with beak marks, and six avian predators were recognized in the field, with Formosan Laughing Thrush Garrulax morrisoniana as one of the dominant species at high elevations. We concluded that environmental factors and avian predation are both contributed to geographical variation of eyespot in size and number of M. nagasawae.