Flexibility and variations in morphological and physiological traits are the key for insect herbivores to adapt to environments. The cotton–melon aphid Aphis gossypii Glover is a polyphagous insect which populations exhibit host specialization. Feeding experience on specific host plants converted host specialization in this aphid. However, adaptive changes of this aphids during the host conversion are still unclear. Here, we examined variations in body length, leg segments, and host preference of the cotton-specialized and cucurbit-specialized aphids, A. gossypii, induced by novel host plants. We found that on the original host plants, body, femur, tibia, and tarsus of the cucurbit-specialized aphids were significantly longer than these of the cotton-specialized aphids. However, feeding on zucchini or cowpea resulted in the short body and leg segments in the cucurbit-specialized aphids, whereas led to the long body and leg segments or no changes in the cotton-specialized aphids, and consequently, the tarsus lengths became equal between the cotton- and cucurbit-specialized aphids. Interestingly, the change trends of the relative lengths of leg segments to body length with the increase of reared generation on zucchini were almost different between the cucurbit-specialized and cotton-specialized aphids, especially the relative length of tarsus, but on cowpea, the trends were similar. Meanwhile, feeding on zucchini altered host preference of the cotton-specialized aphids, but not of the cucurbit-specialized aphids. Novel host plants induce adaptive changes in leg segments and host preference of aphids, suggesting the conversion of host specialization.

中文翻译：

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新寄主植物诱导的形态和偏好的适应性变化介导了棉蜜蚜的寄主专业化

形态和生理特性的灵活性和变化是昆虫食草动物适应环境的关键。棉蚜蚜Aphis gossypii Glover是一种多食性昆虫，其种群表现出寄主特化。在特定寄主植物上的取食经验使该蚜虫的寄主专业化。然而，尚不清楚在宿主转化过程中该蚜虫的适应性变化。在这里，我们研究了棉蚜和葫芦蚜A. gossypii的体长，腿节和寄主偏好的变化。，由新型寄主植物诱导。我们发现，在原始寄主植物上，葫芦丝特化蚜虫的身体，股骨，胫骨和架明显长于棉花特化蚜虫。然而，以西葫芦或cow豆为食会导致葫芦丝专用蚜虫的身体和腿部较短，而导致葫芦丝专用蚜虫的身体和腿部较长，甚至没有变化，因此，between节的长度在棉花和葫芦特有的蚜虫。有趣的是，葫芦类和棉花类蚜虫的腿段相对长度随体长的变化趋势随西葫芦生长量的增加而变化，特别是节的相对长度几乎不同，但是cow豆的趋势相似。与此同时，以西葫芦为食，改变了棉花特化蚜虫的寄主偏好，但葫芦特化蚜虫却没有改变寄主的偏好。新型寄主植物诱导了腿节的适应性变化和蚜虫的寄主偏好，暗示了寄主特化的转化。