Molecular Phylogeny Of Seven Genera Of The Subfamiliy Dolichoderinae (Hymenoptera:Formicidae)

Dolichoderinae belongs to Formicidae, Hymenoptera. The subfamily Dolichoderinae is a large group in the family Formicidae. According to Bolton there are approximately692described species,28genera all over the world, with the greatest diversity in the New and Old World tropics and Australia. Many unkown species are awaited to be described. Amomg them40species,8genera had been recorded in China. The genus-level classification of Dolichoderinae is controversial and there is no any molecular phylogenetic studies on it in China before.In this paper,16species of7genera of Dolichoderinae are studied with molecular systematics. The mitochondrial COI (about822bp), COII (about552bp) and Cytb(about426bp) gene fragments were amplified and sequenced, with Polyrhachis jianghuaensis and Diacamma rugosum as outgroup and combining gene fragments sequences of Leptomyrmex unicolor which downloaded from the GeneBank. The base frequences, base substitutions, codons frequence, amino acids composition and genetic distances of DNA sequences were analyzed by using Clustal X1.83, MEGA4.1, PAUP4.1, tRNAscanse1.21and MrBayesV3.1softwares. The phylogenetic relationships of these species at genus level were reconstructed by using Neighbor Joining (NJ), Bayesian Inference (BI) and Maximum Parsimony (MP) methods. Discuss on phylogeny of the taxa involved in the research. Summarizing these results, the conclusions are as follows:1. The component analysis based on COI, COII and Cytb gene sequences show that the final data matrix contained1801bp (918conserved sites,883variable sites,657parsimony-informative sites,226singleton sites). The variation sites take49percentage of total data and the parsimony-informative sites take36,5percentage of total data. The average content of T, C, A, G of COI+COII+Cytb gene sequences is40.0%,17.1%,33.0%,9.8%. The content of A+T of COI+COII+Cytb gene sequence is73.0%, while the content of G+C of COI+COII+Cytb gene sequence is26.9%. The results show that the content of A+T is distinctly higher than G+C, and is much higher than the average level in insect’s gene sequences. In addition, the genes in base composition are biased, which are concordant with the characteristic of the high content of A+T in mitochondrial DNA sequences. And there is a strong bias on amino acids.2. Through analysis of the transitions and transversions the results show that the COI+COII+Cytb gene sequence of the ratio (R) of conversion and transversion is0.90. Transition is a little higher than transversion. Transversion occurs between A and T and transition occurs between T and C. Analysis of the sequence substitution saturation shows that the substitution is not saturated. It is can be used in the analysis of the phylogeny.3. The analysis of the P-distance show that the genetic distance of COI+COII+Cytb gene ranges from0.038to0.329. The homology is very high.4. NJ,MP,and BI methods are used to reconstruct the phylogenetic relationships separately based on the datas of COⅠ+COⅡ+Cytb gene. The results from comparing three trees indicates that topologies of all the phylogenetic trees have a little difference, but molecular Phylogenetic trees derived from NJ, BI and MP mehods are similar in topology.5. Based on the topologies of the three trees, we draw the conclusion:(1) The taxonomic status of Leptomyrmex is uncertain in three phylogenetic trees. According to phylogenetic trees, Leptomyrmex belonging to Bothriomyrmecini and Iridomyrmex and Ochetellus of this tribe are not clustered together. But the result of phylogenetic trees show that the relationship of Leptomyrmex and Bothriomyrmex is near.(2) The species of Tapinoma and Liometopum are clustered together in three phylogenetic trees, indicating that they have rather near relationships in phylogeny, the result support the conclusion of nuclear gene, but different from that of morphology classification.(3) The result strongly support the relationship of (Technomyrmex+(Tapinoma, Liometopum)), which was consistent with the traditional morphology classification.(4) In phylogenetic trees, the species of Iridomyrmex and Ochetellus are clustered together, suggesting that the phylogenetic relationships are near, which was consistent with the traditional morphology classification result.(5) All the species of Dolichoderus are clustered together and constitute a monophyletic group individually, which was consistent with the morphology classification. The reliable phylogenetic relationship of8species of Dolichoderus is ((((((D. flatidorsus, D. taprobanae),(D. rugocapitus, D.feae)), D. thoracicus), D.incisus), D. sibiricus), D. pilosus).