Genetic profiling of fire ants intercepted in Hawai'i

Hawaii is the most isolated island archipelago in the world separated by 4,000 km from the nearest continent.  Only half the insect orders are found in Hawaii.  No ants are native to Hawaii, all 60 species of ants there have been introduced, including five of the most damaging invasive ants, such as Solenopsis geminata, the tropical fire ant.  Invasive ants negatively impact native insects and other invertebrate groups such as snails and crustaceans.  In 2018 and 2019, Hawaii Department of Agriculture intercepted ants identified as Solenopsis sp.  Since, the highly destructive Solenopsis invicta, is not established in Hawaii, quarantine officials are very sensitive when an intercepted ant is identified as Solenopsis.  Thus, collected ants were submitted to the USDA-CMAVE, Imported Fire Ant and Household Insects Research Unit for further assessment.  Samples were subjected of DNA extraction followed by PCR amplification of the mitochondrial COX1 gene.  The new sequences were compared with previous published sequences from several species of Solenopsis species including: S. geminata, and S. invicta.  One sequence was closely related to the S. xyloni and/or S. amblychila, which are native ants from the source of origin of this intercepted ant (San Diego, California).  On the other hand, ants intercepted from a cargo from Lithuania, were closely related to sequences found in S. geminata from world-wide in tropical/sub-tropical areas.  This is an example of the use of molecular tools to confirm identification of invasive ants, where morphological species identification is difficult.