Dissertation Research: Phylogeny, Host Plant Shifts, and Geographical Origin of the genus Trirhabda (Coleoptera: Chysomelidae)

甲虫的多样性，隶属于鞘翅目，远远超过任何其他动植物物种的多样性。由于超过一半的已知甲虫是草食性的，研究与寄主植物利用有关的物种形成机制，以及甲虫和它们的寄主植物潜在的协调进化(共同进化)，应该为理解甲虫明显的进化成功提供洞察力。进化关系(进化史)假说为研究这种机制提供了基础。叶甲科(叶甲科)属于第四大甲虫家族，使它们成为地球上最成功的有机体之一。研究生Zuzana Swigonova在Karl Kjer博士的指导下，正在研究蝶类Trirhabda属，目的是确定该物种之间的进化关系，确定近缘种是否以密切相关的植物为食，揭示寄主植物偏好的历史和寄主植物在物种之间的转移，揭示物种亲缘关系和地理分布之间的任何模式，并确定该属最可能的生物地理起源地区。本论文主要研究三叶甲属叶甲(鞘翅目：叶甲科)，其中包括来自美洲墨西哥北部的26种(北方种)和来自墨西哥和中美洲的8种(南方种)。北方物种在许多生态学方面都得到了研究，对它们的寄主植物选择性和生活史也有了很好的了解。相比之下，没有关于南方物种的寄主植物协会或生态的信息。南方的八种甲虫中有六种是在墨西哥发现的。北方物种的甲虫以菊科和水飞科的少数植物为食。与叶甲科的其他物种不同，它们在卵期越冬。幼虫和成虫以寄主植物的叶子和花序为食。化蛹发生在寄主植物下方的土壤中。每个Trirhabda种的生活史都受到寄主植物生活史的强烈影响。该属的几个北方物种已被用作生物制剂，以控制正在经历二次演替的田野中的杂草。尽管Trirhabda种已经被用于许多生态学研究，尽管其中一些物种具有重要的经济意义，但还没有系统的研究表明该属之间的进化关系。系统发育关系将从三个独立的数据集中推断出来：一个形态数据集和两个分子数据集。形态数据将包括文献中描述的仔细检查和重新评估的字符。新的特征，包括口部的感受器，将用扫描电子显微镜进行检查。分子数据将包括线粒体小亚基核糖体RNA的DNA序列，线粒体细胞色素氧化酶的第一亚基，以及核糖体ITS(内部转录间隔物)序列。

0073200Kjer and Swigonova The diversity of beetles, grouped under the insect order Coleoptera, far exceeds the diversity of any other animal or plant group. Because more than half of all known beetles are herbivorous, studies of mechanisms of speciation in relation to host plant utilization, and potential coordinated evolution of beetles and their host plants (coevolution), should provide insights to understanding the evident evolutionary success of beetles. Hypotheses of evolutionary relations(phylogeny) provide a foundation for the study of such mechanisms. The leaf beetles (Chrysomelidae) belong to the fourth largest family of beetles, making them among the most successful organisms on the earth. Graduate student Zuzana Swigonova, advised by Dr. Karl Kjer, is studying the chrysomelid genus Trirhabda, in order to determine evolutionary relationships among the species, determine whether closely related species feed on closely related plants, revealthe history of host plant preference and host plant shifts among the species, disclose any pattern between species relatedness and geographic distribution, and identify the area that is the most probable biogeographical origin of the genus. The dissertation focuses on leaf beetles of the genus Trirhabda(Coleoptera: Chrysomelidae) which contains 26 species from America north of Mexico ("northern species") and 8 species from Mexico and Central America ("southern species"). The northern species have been studied in many ecological aspects and much is known about their host plant preference and life cycle. In contrast, there is no information about host plant association or ecology of the southern species. Six out of the eight southern species are found in Mexico.Beetles of the northern species feed on a narrow range of plants in the families Asteraceae and Hydrophyllaceae. Unlike other species from the family Chrysomelidae, they overwinter in the egg stage. Larvae and adults feed on leaves and inflorescence of the host plant. Pupation takes place in the soil below the host plant. The life history of each of the Trirhabda species is strongly influenced by the life history of their host plant. Several northern species of the genus have been used as biological agents in control of weeds in fields undergoing secondary succession. Despite the fact that Trirhabda species have been used in many ecological studies and despite the economic importance of some of the species, there has been no systematic study proposing evolutionaryrelationships within this genus. Phylogenetic relationships will be inferred from three independent data sets: one morphological and two molecular. Morphological data will include carefully examined and reevaluated characters described in the literature. New characters, including sensillae of the mouth parts, are to be examined using scanning electron microscopy. Molecular data will include DNA sequences of mitochondrial small subunit ribosomal RNA, the first subunit of mitochondrial cytochrome oxidase, and nuclear ribosomal ITS (internal transcribed spacer) sequences.