Thompson John N
Departments of Botany and Zoology, Washington State University, Pullman, Washington, 99164.
Evolution. 1993 Oct;47(5):1585-1594. doi: 10.1111/j.1558-5646.1993.tb02177.x.
Four allopatric populations of the widely distributed western anise swallowtail butterfly, Papilio zelicaon, use different plant genera as hosts, but simultaneous choice experiments showed that these populations have diverged only slightly in oviposition preference. Of the four populations-two from southeastern Washington State, one from coastal southwestern Washington State, and one from central California-three use hosts that are not available to any of the others. Although variation for the degree of preference for particular plant species occurred within and among populations, all four populations ranked hosts in the same overall order. Monophagy on a local, low-ranking host outside the range of high-ranking hosts did not necessarily lead to the loss of preference for those high-ranking hosts, thereby indicating that the high-ranking hosts would still be accepted, and in some cases even preferred, if a population encountered them again. Hence, the overall preference hierarchy among P. zelicaon populations appears to be evolutionarily conservative. Analyses of differences among families within the California population indicated that increased preference for some hosts is inversely correlated, whereas preference for other hosts may be uncorrelated. Positive correlations may also occur but were not observed among the plant species tested. Overall, the results indicate local monophagy on different plant species in P. zelicaon has not involved major reorganizations in the preference hierarchy of ovipositing females, even in populations that may have fed on a low-ranking host for many generations. Instead, small increases in preference for local hosts have occurred within an evolutionarily conservative preference hierarchy.
广泛分布的西部茴芹凤蝶（Papilio zelicaon）的四个异域种群以不同的植物属作为寄主，但同时选择实验表明，这些种群在产卵偏好上仅略有分化。在这四个种群中，两个来自华盛顿州东南部，一个来自华盛顿州西南部沿海地区，一个来自加利福尼亚州中部，其中三个种群所使用的寄主是其他种群无法利用的。尽管在种群内部和种群之间存在对特定植物物种偏好程度的差异，但所有四个种群对寄主的总体排序相同。在高等级寄主范围之外，对当地低等级寄主的单食性并不一定会导致对那些高等级寄主偏好的丧失，这表明如果一个种群再次遇到高等级寄主，它们仍然会被接受，在某些情况下甚至更受青睐。因此，泽氏凤蝶种群之间的总体偏好等级似乎在进化上是保守的。对加利福尼亚种群内不同家族之间差异的分析表明，对某些寄主偏好的增加呈负相关，而对其他寄主的偏好可能不相关。在所测试的植物物种之间也可能存在正相关，但未观察到。总体而言，结果表明，即使在可能以低等级寄主为食许多代的种群中，泽氏凤蝶对不同植物物种的局部单食性也并未涉及产卵雌蝶偏好等级的重大重组。相反，在进化上保守的偏好等级内，对当地寄主的偏好有小幅增加。
