Speciation, niche differentiation and reproductive isolation in European cereal leaf beetles (Genus Oulema, Coleoptera, Chrysomelidae)

植食性昆虫不仅代表了地球上的主要辐射之一，而且也构成了迄今为止共域物种形成的一些最强烈的例子。新物种形成的两个关键步骤，即新兴物种之间的生态位分化和生殖隔离，在这里特别容易界定和测试。本提案旨在利用谷类叶甲(Oulema spp.)作为一个模范系统。Oulema属包括欧洲的几种草本植物(禾本科)，根据外部和生殖器形态的变化，认为谷类害虫O.Blackopus包括第二个隐种，O.ruafyanea。通过结合繁殖、饲养和食物选择实验，我们计划确定这两种共生形式实际上是否构成了独立的物种，或者更确切地说，是组成了目前在食性和生殖特征上存在分歧的初生物种。推测的诊断性状的形态评分和利用AFLP(扩增片段长度多态)对两种形式之间的基因流进行基因分析将补充数据。为了追踪与寄主转移有关或不与寄主转移相关的物种形成事件的顺序，将进行基于mtDNA序列的系统发育分析。

Phytophagous insects represent not only one of the major radiations on earth but also comprise some of the strongest cases for sympatric speciation to date. Two crucial steps in the formation of new species, niche differentiation and reproductive isolation between emerging species, can especially easily be delimited and tested here. This proposal aims to trace both steps using cereal leaf beetles (Oulema spp.) as a model system. The genus Oulema comprises several grass (Graminaceae) feeding species in Europ e. Based on variation in external and genitalic morphology, it has been claimed that the cereal pest species, O. melanopus, includes a second cryptic species, O. rufocyanea. Through a combination of breeding, rearing and food choice experiments, we plan to establish whether these two sympatric forms actually constitute separate species or rather incipient species that are currently diverging in their feeding habits and reproductive characters. Morphological scoring of presumed diagnostic characters and gene tic analysis of gene flow between the two forms by AFLP (amplified fragment length polymorphisms) will complement the data. To trace the order of speciation events that were or were not associated with host shifts in the European Oulema species, a phylogenetic analysis based on mtDNA sequences will be undertaken.