Application of genetic diversity for the molecular phylogeny of Strumigenys and inferring invasion origin of Solenopsis invicta
Date Issued
2006
Date
2006
Author(s)
Hung, Yu-Tang
DOI
en-US
Abstract
Intraspecific divergence and phylogenetic relationships of Strumigenys between different localities in Eastern Asia were respectively inferred from sequences of the internal transcribed spacer 2 (ITS2) of rDNA and cytochrome oxidase subunit I, II (COI, COII) of mtDNA. The ITS2 sequences of Strumigenys in different species vary in length from 659 to 943 bp, due to large repeated insert-deletion fragments. The length of amplified mtDNA COI and COII sequences are ca. of 782 and 576 bp. The average GC content of ITS2, COI, and COII are 60.8%, 28.9%, and 23.9%, respectively. Secondary structures from ITS2 sequences are similar and present several conserved structure motifs. Eleven species and three unidentified species of Strumigenys were analyzed using both the maximum parsimony (MP) and maximum likelihood (ML) methods by ITS2 sequences. Results revealed that two of the unidentified species from Matsu Island are closely related to S. formosensis and S. solifontis, respectively while the third unidentified species from Orchid Island seems to be closely related to S. lacunosa. However, ITS2 sequences cannot resolve the relationship of S. solifontis, S. chuchihensis, S. lewisi, and Matsu SJ. The situation was the same as mtDNA COI and COII sequences. Although the diversity in ITS2, COI, and COII sequence are high, these data can still be a potential marker for primary analysis of the molecular phylogeny of Strumigenys at the species level on islands around Taiwan. Sixty-seven populations belong to 12 species and 9 unidentified species were used in mtDNA COI and COII sequence analyses. The topologies obtained reveal similar condition with ITS2. The diversity of these two sequences is still too high to clear the relationships among species. These phenomena pointed out the species-level polyphyly or paraphyly patterns and these patterns may be due to the incomplete lineage sorting. The migrate route of four tropical group species (S. formosensis, S. orchidensis, S. stenorhina, and an unidentified species from Beigan Island (Matsu CB)), can be slightly clarified. The possibility of dispersal direction of S. formosensis can also be extrapolated from north to east and south. The S. hispida, S. solifontis, S. lewisi, and unidentified species Matsu SJ, have the prospect of Japan-Ryukyu-Taiwan pathway to disperse outward. In order to clarity the dispersal route and/or invasive origin of the red imported fire ant (Solenopsis invicta, RIFA), which was first reported from Taiwan in October 2003, the method of mtDNA COI and COII sequences analysis were also applied to RIFA. In total 66 populations were collected in Taiwan, with 35 populations from Taoyuan County, 16 populations from Chiayi County, 13 populations from Taipei County, and two scatter distributed populations in other counties. Sixteen populations from Australia provided by the Fire Ant Control Centre, and 15 populations from USA, including South Carolina, Louisiana, Mississippi, and Texas, were also used in this study. The analysis of their mtDNA COI and COII sequences by MP and ML both present same topologies. RIFA populations of Chiayi, Australia, and most United States were clustered together. Taoyuan-Taipei populations clustered with the rest populations of United States. Although this topologies can not clarify the actual invasion source and the detail routes of dispersal of RIFA, however, the most likely scenario is United States, and may be introduced singly from one place, or multiply from the same places. The occasionally invaded spots of Miaoli and Yilan would be dispersed by human activities from Taoyuan-Taipei areas.
Subjects
瘤顎家蟻
入侵紅火蟻
核糖體DNA
粒線體DNA
親緣關係
Strumigenys
Solenopsis invicta
rDNA
mtDNA
phylogeny
Type
thesis