| Catantopidae is the biggest family in Acridoidea (Orthptera: Caelifera). It includes 16 subfamilies 93 genera in China, mostly distributed in Oriental realm, others in Paleoarctic realm. In this family there are some important pests in agriculture, such as Oxya chinensis, Patanga japonica, Chondracris rosea rosea, Calliptamus abbreviatus. The systematics study of them has not only theoretical but also practical value in grasshopper control, and plant protection. Currently, however, the molecular systematic research on Catantopidae insects is still very limited. In this study, we adopted ND2 and adjacent tRNAs gene sequence as molecular marker and reconstructed the phylogenetic relationships of 19 Catantopidae insects which belong to 8 subfamilies and 12 genera, hence providing molecular evidence for the systematic study of them.Mitochondrial ND2 gene has a relatively fast evolution rate, and recently has been widely used in the molecular systematic research of avian, fish and amphibian. It shows characteristic of a good molecular marker. In insect molecular systematics, however, only partial sequence was used in several studies. In this study we sequenced complete sequence of ND2 gene and 4 adjacent tRNAs (tRNA-Met, tRNA-Trp, tRNA-Cys & tRNA-Tyr) genes of 19 Catantopidiae insects and 2 outgroup taxa, totally 1251bp, by PCR product cloning and sequencing. Sequence alignment was firstly conducted by Clustal X, and then moderated by hand according to tRNA secondary structure. TψC loops and non-coding sequence were deleted due to ambiguous alignment, and the sequence was divided into two partition data sets, ND2 data set and tRNAs data set. MEGA 2.1 was used for sequence composition statistics, and PAUP*4.0bl0 (PPC) was used for phylogenetic signal tests, Partition Homogeneity test and phylogenetic reconstruction through MP, NJ and ML method. Moreover, MrBayes V3.0 was used to reconstruct the phylogenetic relationships by Bayesian inference method. Finally, several kinds of tests were performed to test the credibility of tree topology, or compare different tree topologies. Conclusions were showed below:1. ND2 length is 1023bp in all species studied except for Choroedocus violaceiepes, which is 1026bp. There are two interval bases (AC) between ND2 and tRNA-Trp in thetwo outgroup sequences, and in ingroup sequences, there is a two-base overlap (AA). tRNA loops have a high frequency of indels, and the alignment length is 193bp. There is an 8-base overlap between tRNA-Trp and tRNA-Cys complement sequence, and a non-coding interval sequence ranging from 4bp to 27bp between tRNA-Cys complement sequence and tRNA-Tyr complement sequence.2. Instead of ATG in the other species, the start codon in genera Ecphymacris and Apalacris is GTG. The terminal codon in Catantopidae is TAA, and TAG in the two outgroup taxa.3. High A+T% is observed (73.1% in ND2 and 80.5% in tRNAs) in this study. And ND2 gene has a high mutation rate, with 57.9% of variable sites, and fast evolution rate.4. The results of base substitution saturation analysis show that transition in the 1st and 3rd codon positions, together with that in the tRNA loop region has reached saturation. Random tree length distribution test and PTP test show that all of the 3 data sets contain strong phylogenetic signal, which indicates that they are not stochastic data. And partition homogeneity test of combined data set show that the heterogeneity is insignificant (<0.95%), therefore the partitioned data set can be combined for analysis.5. MP, NJ, ML and BI method were separately used to reconstruct the phylogenetic relationships of the 19 Catantopidae insects, and SH test based on likelihood method was used to compare the tree topologies produced by different methods. Among the three data sets, both of combined data set and ND2 data set can give good resolution for the phylogenetic relationships of taxa, and the result of SH test indicates that all trees based on combined data set and ND2 data set have no significant difference in topology, and each of them can be reasonable in the explanation of phylogenetic relationships among taxa. Also it indicates that ND2 gene complete sequence can be used as a good molecular marker to reconstruct the phylogenetic relationships of Catantopidae insects in the level of subfamily, genus and species. tRNA genes, however, have very limited resolution ability. The topologies of phylogenetic trees based on it have significant difference with those based on combined data set or ND2 data set. Therefore, when the sequence length is short, tRNA genes are not suitable to be used as molecular marker.6. This study doesn't give full resolution in the phylogenetic relationships among subfamilies, and there is still a little difference among different tree topologies. The probable reasons are the imperfection of taxa sampling and the outgroup selection problems.
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