大蚜亚科系统发育及其与寄主植物之间的演化关系

Lachninae is an important subfamily in Aphididae, Hemiptera, because many species are pests of forestry and they have some special characteristics both in morphology and life circle. It is an indispensable part of model on rebuilding phylogeny of aphid, even of the whole biological world. But the relationship of its tribes is still a puzzle. Its host rang is quite wide, including pine, cypress, broadleaf trees and grass. Whether the species feeding on gymnosperm or angiosperm are relatively developed ones? This question is still discussed since 1950s. This proposal is to settle these problems in Lachniniae based on macroscopical and microcosmic data. All the tribes and most of the genera in the subfamily will be selected as the samples here. There are 9 genes from 3 genomes used as molecular markers, EF-1α, LWO, CD, 18s rDNA from nuclear genome, COI, COII, Cytb from mitochondrial genome and 16s rDNA, gnd from genome of intracellular bacterial symbiont of aphid. The analysis of combined molecular, morphological and biological databases will suggest the phylogenetic relationships among the tribes in Lachninae. After mapping the macroscopical information on the phylogenetic trees, such as host plants, life circle, fossils, Paleoclimate, Paleogeology, etc., the relationship between Lachaninae and its host plants will be revealed in the tree. The results of this proposal will also be valuable in aphid speciation and mechanism research of pests.

大蚜亚科是半翅目蚜科中重要的类群，该亚科内部的系统发育关系至今没有令人信服的诠释。大蚜亚科同时取食裸子植物和被子植物，在明确大蚜亚科系统发育关系的基础上，开展该亚科蚜虫与寄主植物之间的演化关系研究，将对蚜虫物种分化及蚜类害虫形成机制研究具有重要理论意义和经济价值。本项目将基于前期研究积累，针对大蚜亚科已知的3个族和所有属进行大规模取样，选取来自3个基因组的9个基因，开展分子系统学和比较形态学研究；联合分析分子数据、形态学特征和生物学证据，重建客观清晰的大蚜亚科系统发育框架，阐明该亚科主要类群间的系统发育关系；进而基于客观详尽的系统发育框架，探讨该亚科与其寄主植物之间的演化关系。该研究不仅为解决昆虫高级阶元系统发育重建中的普遍性问题提供例证和经验，而且将丰富生物适应进化理论。

本研究选取来自亚洲和北美洲的大蚜亚科14属78种，基于线粒体基因COI、COII、Cytb以及核基因EF-1α和LWO的部分序列，使用最大简约法，贝叶斯法和最大似然法等方法开展大蚜亚科系统发育研究。研究结果支持大蚜亚科Lachninae的单系性。通过系统发育关系的解析，将大蚜亚科分类系统重新划分为5个族，大蚜族Lachnini、长喙大蚜族Stomaphidini、长跗大蚜族Tramini、瘤大蚜族Tuberolachnini和长足大蚜族Eulachnini，并建议将钝喙大蚜属Schizolachnus订正为长足大蚜属钝喙大蚜亚属Cinara (Schizolachnus) stat. nov.。. 基于大蚜亚科系统发育关系树，估算不同类群的分歧时间，重建大蚜亚科与寄主植物及取食部位的祖先状态，结合寄主植物的演化时间，探讨大蚜亚科与寄主之间的演化历史。研究结果表明大蚜亚科共同祖先在白垩纪取食古老被子植物，之后又辐射演化到裸子植物；分歧时间的估算结果显示，大蚜亚科与寄主植物具有多种演化关系；通过取食部位的祖先状态重建，暗示原始的大蚜祖先在古老的被子植物粗树枝取食，而叶片取食是一个相对衍生的性状。. 选取世界生物多样性热点地区之一的中国西南山地为研究区域，开展长足大蚜属Cinara物种多样性研究。基于304号3040个个体的形态特征和DNA条形码数据，以聚类法、ABGD法和GMYC法进行物种界定的结果显示，长足大蚜属物种具有很高的α物种多样性，候选物种达94个，其中86.2%物种为首次纪录；西南山地有长足大蚜属物种多样性分布中心3个，与松柏科寄主植物的多样性分布中心相对应；长足大蚜属物种及该属西南山地特有物种都在2500-3000米的中海拔地区呈现最高的丰富度。气候、生态和寄主植物生境变化可能是中国西南山地高海拔地区长足大蚜属物种多样性高的最重要因素。