Studies on two social forms, monogyne and polygyne, of the red imported fire ant (Solenopsis invicta) in Taiwan
Date Issued
2006
Date
2006
Author(s)
Lin, Yi-kai
DOI
en-US
Abstract
Solenopsis invicta Buren, the red imported fire ant (RIFA), was first found in Taiwan in October 2003. It has two social forms, monogyne in which a colony has a single queen, and polygyne in which a colony has multiple egg-laying queens. There are significant differences in ecology, physiology, genetics, and social behaviors between monogynous and polygynous colonies. The first part of this study is to focus on the distribution of the two social forms for realizing the dispersal and occupied niche in Taiwan, and the second part is to compare cuticular chemicals of the two social forms in the fire ant. The investigated areas were seriously infested counties, including Taipei, Taoyuan, and Chiayi Counties; the sampled colonies were 130, 66, and 37, respectively, that amounted to 233 colonies in total. Initially, the social forms of 22 colonies were determined by the number of egg-laying queens, and then confirmed by a molecular marker using specific primers of a gene Gp-9. The accuracy of molecular marker examined by using these two methods was reliable in Taiwanese colonies, and thus the other collected colonies were determined by this Gp-9 marker. Our result showed that the two social forms distributed sympatrically, nevertheless they are not evenly distributed. In most areas, polygynous colonies were more than monogynous, particularly in Taoyuan and Chiayi Counties, for instance only four out of 37 colonies were monogynous in Chiayi County; but in a few areas, monogynous colonies outnumbered polygynous, for example, Linkou Township of Taipei County had 77 monogynous colonies out of 86. Meanwhile, the cuticular chemicals of fire ant from both monogyne and polygyne were analyzed by gas chromatography and gas chromatography-mass spectrometry, and both castes of queens and workers were compared. Some hydrocarbons (i.e., mostly alkanes) and non-hydrocarbons (i.e., alkaloids) were significantly different in quantities between the two social forms, moreover an alkaloid-like substance was only found in monogynous workers. The two social forms did not cluster separately by principal component analysis nor by discriminant analysis of the chemicals with significantly different quantities; nevertheless both of those analyses displayed the monogynous queens were closer to each other than polygynous. For these cuticular chemicals in the fire ant have genetic basis, we suggest that lower genetic variation in monogynous queens was probably caused by strong selection pressure of monogynous workers to the conspecific but different colonies. Besides, it is consistent with the asymmetrical gene flow from monogynous to polygynous populations through males in monogyne. .Therefore, the cuticular chemicals can not be cluster well between monogynous and polygynous ants, and the variance of chemicals of the latter is higher than those of the former. However, the chemicals involved in discrimination behaviors need to be further confirmed in future.
Subjects
入侵紅火蟻
red imported fire ant
Solenopsis invicta
Type
thesis
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