Gillespie Joseph J, Kjer Karl M, Duckett Catherine N, Tallamy Douglas W
Department of Entomology and Applied Ecology, University of Delaware, Newark, DE 19717-1303, USA.
Mol Phylogenet Evol. 2003 Oct;29(1):161-75. doi: 10.1016/s1055-7903(03)00256-2.
Historically, chemical ecologists assumed that cucurbitacin feeding and sequestration in rootworm leaf beetles is a remnant of an ancient association between the Luperini (Coleoptera: Chrysomelidae; Galerucinae) and Cucurbitaceae (ancestral host hypothesis). Under this premise, rootworms that do not develop on cucurbits but undergo pharmacophagous forays for cucurbitacins are thought to do so to supplement novel host diets that lack these bitter compounds. The ancestral host hypothesis is supported from studies of pyrrolizidine alkaloid pharmacophagy in Lepidoptera but has not been subjected to phylogenetic analysis within the Luperini. New evidence that this feeding behavior is better correlated with an adult affinity for pollen than with larval host offers the possibility that Old and New World rootworm species with an affinity for cucurbitacins converged on this behavior through apomorphic taste receptor modifications (loose receptor hypothesis). Here we test the monophyly of cucurbitacin feeding within the Luperini by using nuclear and mitochondrial sequence data to infer phylogenetic relationships among 49 taxa representing tribes of the Galerucinae and subtribes of the Luperini. The resulting phylogenetic hypothesis is mostly concordant with existing tribal and subtribal delineations within the Subfamily Galerucinae sensu stricto (Galerucinae not including the flea beetles). The establishment of ancestry among the subtribes of the Luperini refutes the monophyly of cucurbitacin feeding and cucurbit specialization, with the New World Diabroticina being paraphyletic to the Old World Aulacophorina and cosmopolitan Luperina. These data unambiguously support the convergent evolution of cucurbitacin feeding in rootworms and are inconsistent with the ancestral host hypothesis.
从历史上看，化学生态学家认为，根叶甲摄取和储存葫芦素是卢氏叶甲族（鞘翅目：叶甲科；叶甲亚科）与葫芦科之间古老关联的遗留（祖先寄主假说）。在此前提下，不在葫芦科植物上发育但会对葫芦素进行药食性觅食的根叶甲，被认为这样做是为了补充缺乏这些苦味化合物的新寄主食物。祖先寄主假说在鳞翅目吡咯里西啶生物碱药食性研究中得到了支持，但尚未在卢氏叶甲族内部进行系统发育分析。有新证据表明，这种取食行为与成虫对花粉的喜好度的相关性，要强于与幼虫寄主的相关性，这表明对葫芦素有喜好的新旧世界根叶甲物种，可能是通过同源异形味觉受体修饰（松散受体假说）趋同于这种行为。在这里，我们通过使用核基因和线粒体序列数据，来推断代表叶甲亚科族和卢氏叶甲族亚族的49个分类单元之间的系统发育关系，从而检验卢氏叶甲族内摄取葫芦素行为的单系性。由此得出的系统发育假说，大多与狭义叶甲亚科（不包括跳甲的叶甲亚科）内现有的族和亚族划分一致。卢氏叶甲族亚族之间祖先关系的确立，驳斥了摄取葫芦素行为和葫芦科专一化的单系性，新大陆的黄瓜叶甲亚族相对于旧大陆的凹胫叶甲亚族和世界性的卢氏叶甲亚族而言是并系的。这些数据明确支持根叶甲摄取葫芦素行为的趋同进化，与祖先寄主假说不一致。
