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Molecular Phylogeny of the Sawfly Family Based on Partial Sequences of 16S rRNA and 12S rRNA Gene

Author: WangDeMing
Tutor: WeiMeiCai
School: Central South University of Forestry Science and Technology
Course: Forest Protection
Keywords: Tenthredinidae mtDNA 16S rRNA 12S rRNA Molecular Phylogeny
CLC: S769
Type: Master's thesis
Year: 2010
Downloads: 53
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Abstract

Tenthredinidae belonging to Hymenoptera Tenthredinoidea, is the largest family of Tenthredinoidea. At present, the research of molecular systematics of the Tenthredinidae insect is far behind other biological groups. Partial gene sequence were obtained from 46 samples by the methord adopted 16S rRNA and 12S rRNA as molecular markers and based on molecular biology angle, which includes 29 species Tenthredinidae insects belonging to 7 subfamilies 19 genera,1 species Argidae insect belonging to 1 subfamily 1 genus and 16 species sawflies which are downloaded from GeneBank. The result shows that the length of the two gene sequences were 372bp and 374bp. A preliminary study of the phylogenetic relationships of the partial species of Tenthredinidae insects by two kinds of common methods:Bayesain and NJ phylogenetic tree reconstruction is done. The conclusions are as follows:1. The average content of T, C, A, G of 16S rRNA gene sequence is 42.5%,6.9%, 37.1% and 13.5%. The content of A+T of 16S rRNA gene sequence is 79.6%, while the content of G+C of 16S rRNA gene sequence is 20.4%. The average content of T, C, A, G of 12SrRNA gene sequence is 40.2%,8.7%,38.1% and 13.0%. The content of A+T of 12SrRNA gene sequence is 78.3%, while the content of G+C of 12SrRNA gene sequence is 21.7%. The results also show the content of A+T is apparently more higher than the content of G+C, which is much more higher the average level (64%) in insect’s gene sequences. In addition, it shows that the two genes in base composition are biased, which are concordant with the characteristic that the high content of A+T in insect’s mitochondrial DNA sequences.2. The replacement of nucleotide in the mass shows that the transversions is more common than conversions in the 16S rRNA and 12S rRNA gene sequences (including the outgroup) which is obtained from this study. The rate of conversion in 16S rRNA gene sequences is 4.27%, while the rate of transversion is 12.52%. The ratio (R) of the rate of conversion and transversion is 0.3. The rate of conversion in 16S rRNA gene sequences is 9.33%, while the rate of transversion is 19.25%. The ratio (R) of the rate of conversion and transversion is 0.5.3. The results of phylogenetic relationships about some species of Tenthredinidae in this study are as follows:Tenthredinidae insects belonging to 7 subfamily,19 genera,29 species in this study constitute a monophyletic group. The relationships among Tenthredo, Metallopeus and Rhogogaster are more closer than others, which agrees with the above view that they constitute a monophyletic group. This study supports that Macrophya is monophyletic and Tenthredopsi and Aglaostigma constitute a monophyly. The relationships between Dolerus and Selandria are more closer, which agrees with the conclusion of the recent research (Schulmeister,2003). The insects of Nematinae constitute a monophyly. The species of Tenthredinidae insects which is in the same group or the same genus clustered together, and the genera of the same subfamily in Tenthredinidae mostly get together for priority. These results show that morphological classification is valid and credible. Moreover, the objects of this study also include the group which is more closer with the Tenthredinidae insects, such as Argidae, Blasticotomidae, Megalodontesidae, Xyelidae, Pamphiliidae, Cephidae, Macroxyelidae insects. The phylogenetic relationships in rank of family is in general accord with the conclusion of Schulmeister’s research (Schulmeister,2003) and the diference between them is that Athalia insects are a separate branch which is far away from the location of Tenthredinidae in the phylogenetic relationship tree, according to the research of Schulmeister (Schulmeister,2003). While Athalia insects are not far away from the location of Tenthredinidae insects in this study. It’s a independent branch in Tethredinidae insects and the relationship among Athalia and other subfamilies is a parallel relationship.4. The study of phylogenetic relationships of some kind Tenthredinidae insects are done by using 16S rRNA and 12S rRNA gene sequence in this paper. The results show that the 16S rRNA gene is more appropriate in the research of phylogenetic relationships among the genera and the 12S rRNA gene is better for the research of phylogenetic relationships among subfamilies or genera. But they are not very good if it’s used among species under genera. Because this study adopts 16S rRNA and 12S rRNA as molecular markers, so partial gene sequence can only be obtained. The information which these gene fragments contain is limited. Furthermore, the species of Tenthredinidae involved in this paper which is the largest group of Tenthredinoidea and is devided into 18 subfamilies in classification system in 1900 is few. Therefore, the study of molecular systematics should increase more species and molecular markers in order to do more precise analysis in the future.

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