Populations of the Graceful Twig Ant, Pseudomyrmex gracilis, Now Bridge the Distribution Gap between Their Native Range in Texas and Non-Native Range in Florida, USA

ABSTRACT Pseudomyrmex gracilis is an arboreal ant with an enormous native range stretching from Uruguay and Argentina in the south to southeastern Texas in the north. Non-native P. gracilis populations were first found in south Florida in 1960, and soon spread to other parts of the state. Subsequently, P. gracilis populations were found in Louisiana (starting in 1995), South Carolina (starting in 2008), Mississippi (starting in 2009), Georgia (starting in 2010), and Alabama (starting in 2011). Here, we document in more detail this expansion of P. gracilis populations in the southeastern US. Populations of P. gracilis now extend along the entire Gulf coast from Texas to Florida and to the Atlantic coast of South Carolina. Recent changes in habitat and/or climate appear to have allowed the expansion of both native populations north and east out of Texas and non-native populations north and west out of peninsular Florida. Peninsular Florida has long been viewed as a tropical “habitat island,” isolated from other tropical continental areas by freezing winter temperatures in north Florida. Now, many tropical species in south Texas appear to have a newly opened habitat corridor along the Gulf coast that could allow them to spread overland to peninsular Florida.