Otaki Joji M
Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Zoolog Sci. 2007 Aug;24(8):811-9. doi: 10.2108/zsj.24.811.
It has been proposed that phenotypic plasticity and genetic assimilation through natural selection partly determine the direction of divergent selection that eventually results in speciation. To elucidate a process of butterfly color-pattern evolution and speciation in the light of this hypothesis, morphological and physiological differences between a pair of sister species, the Painted Lady butterfly Vanessa cardui and the Australian Painted Lady butterfly Vanessa kershawi, were investigated. Ten different traits of wing color-pattern were indicated, most of which concerned the darker coloration of V. kershawi, with the notable exception of the blue foci at the center of the black focal elements only in V. kershawi. Differences in behavior and life history between the two species appeared to be minimal, but importantly, V. kershawi tends to prefer a "stressful" arid environment. The experimental treatment of pupae of V. cardui either by low temperature or by injection of thapsigargin, a stress-inducing chemical, readily produced individuals with the darker coloration and the blue foci as a result of a general stress response. These stress-induced color-pattern modifications were considered to be the revelation of phenotypic plasticity in V. cardui. Taken together, I propose that the ancestral species of V. kershawi had similar phenotypic plasticity. Natural selection exploited this plasticity and shaped the present V. kershawi as an independent species, whose specific color-pattern traits are by-products of this adaptation process.
有人提出，表型可塑性和通过自然选择的遗传同化在一定程度上决定了最终导致物种形成的分歧选择方向。为了根据这一假设阐明蝴蝶颜色模式进化和物种形成的过程，对一对姐妹物种——彩粉蝶 Vanessa cardui 和澳洲彩粉蝶 Vanessa kershawi 的形态和生理差异进行了研究。研究指出了翅色模式的10种不同特征，其中大多数与澳洲彩粉蝶颜色较深有关，唯一显著的例外是仅在澳洲彩粉蝶黑色焦点元素中心的蓝色斑点。这两个物种在行为和生活史方面的差异似乎很小，但重要的是，澳洲彩粉蝶倾向于偏好“恶劣的”干旱环境。通过低温或注射毒胡萝卜素（一种诱导应激的化学物质）对彩粉蝶蛹进行实验处理，由于一般的应激反应，很容易产生颜色较深且带有蓝色斑点的个体。这些由应激诱导的颜色模式变化被认为是彩粉蝶表型可塑性的体现。综上所述，我认为澳洲彩粉蝶的祖先物种具有相似的表型可塑性。自然选择利用了这种可塑性，将现在的澳洲彩粉蝶塑造为一个独立的物种，其特定的颜色模式特征是这一适应过程的副产品。
