SGER: Exploratory Comparison of Eight Nuclear and mtDNA Sequences Among Selected Taxa of Deltocephaline Leafhoppers (Homoptera: Cicadellidae)

由于缺乏系统发育信息和属分离所需的明确特征，类似于Deltocephalus的叶蝉属给工作者带来了一个难题。为了更清楚地了解这一组的系统发育，研究人员希望对24个新北界属的子集进行分支和分子分析，其中药隔和新北界的融合似乎代表了该子集的突触特征。目前分子系统学领域的一个问题是，对于哪些DNA序列可以用于昆虫属水平的分类研究，还没有达成一致意见。到目前为止，几乎所有的分子系统学研究都在较高的分类水平上比较了物种。在这些水平上研究的大多数序列在较低的分类水平上是单态的。在另一个极端，有一些序列表现出广泛的种内变异，但可能在更高的分类水平上没有可识别的同源性。申请为期一年的资金，以检查在四个分类级别上选定的叶蝉的八种不同的DNA序列。已经确定了五个候选核区和三个mtDNA区。核DNA区域包括：1，2)rDNA顺反子中的两个内部间隔区(ITS1和ITS2)，3)rDNA顺反子28S的高变区，4)组蛋白H_2A基因内含子，5)核糖体S14蛋白基因及其内含子。线粒体基因是：1)12S rDNA的一个区域，2)16S rDNA和3)细胞色素氧化酶III基因的一个区域。所有的区域都将用聚合酶链式反应进行扩增和测序。这些区域将在Deltocephalinae亚科三个部落的三个物种之间进行初步比较，如果序列在这个水平上显示变异，将在三个部落中的两个部落内对另外两个物种进行比较。如果在部落内检测到属间变异，则将检查一个属内的两个物种。如果在这个水平上检测到变异，则将从同一物种的不同地理种群中收集种内变异的检查。利用该协议，可以确定可以使用这些序列中的每一个的分类水平。其目标是确定2-3个DNA序列，可用于对24个类Deltocephalus类叶蝉属的密集调查。

The Deltocephalus-like genera of leafhoppers have posed a difficult problem for workers because of an absence of phylogenetic information and definitive characters necessary for generic separation. Towards obtaining a clearer picture of phylogenies in this group, the investigators hope to perform cladistic and molecular analyses of a subset of 24 nearctic genera in which fusion of the connective and aedeagus appears to represent a synapomorphic character of the subset. A current problem in the field of molecular systematics is that there is no agreement as to which DNA sequences can be used in insect taxonomic studies at the generic level. Almost all molecular systematic studies to date have compared species at higher taxonomic levels. Most of the sequences which have been examined at these levels are monomorphic at lower taxonomic levels. At the other extreme there are sequences which demonstrate extensive intraspecific variation but which may present no recognizable homology at higher taxonomic levels. Funding is requested for one year to examine eight different DNA sequences in leafhoppers selected at four taxonomic levels. Five candidate nuclear regions and three mtDNA regions have been identified. The nuclear DNA regions include: 1,2) two internal spacers (ITS1 and ITS2) in the rDNA cistron, 3) a hypervariable region of the 28s from the rDNA cistron, 4) an intron in the invariant histone H2A gene and 5) the ribosomal S14 protein gene and its intron. The mitochondrial genes are: 1) a region of the 12s rDNA 2) the 16s rDNA and 3) a region of the cytochrome oxidase III gene. All regions will be amplified with PCR and sequenced. These regions will be initially compared among three species in three tribes in the leafhopper subfamily Deltocephalinae, if the sequences show variation at this level, two additional species will be compared within two of the three tribes. If intergeneric variation is detected within tribes then two species within one genus will be examined. If variation is detected at this level then an examination of intraspecific variation will take collection from different geographic populations of one species. With this protocol the taxonomic level at which each of these sequences can be used can be determined. The goal is to identify 2-3 DNA sequences which can be used in an intensive survey of 24 genera of the Deltocephalus-like genera of leafhoppers.