A PHYLOGENETIC COMPARATIVE ANALYSIS OF TAPINOMA SESSILE (SAY) IN EASTERN TENNESSEE WITH A DESCRIPTION OF A NEW SPECIES OF TAPINOMA

The odorous house ant (Tapinoma sessile [Say], Hymenoptera: Formicidae: Dolichoderinae) is a commonly encountered nuisance pest ant in eastern Tennessee and much of the nation. Endemic to the U.S., northern Mexico, and southern Canada, this morphologically nondescript ant’s broad geographical distribution within many ecosystems raises questions about (1) its adaptive capacity to morphological groups, climate and elevation, and (2) whether possible cryptic species exist. Adaptive convergence occurs when selection causes different populations to share phenotypic expressions. I employed a phylogenetic comparative method to examine adaptive convergence to extrinsic elevational and climatic traits and intrinsic morphological variation in eastern Tennessee populations of T. sessile. I generated an inferred phylogeny using a mitochondrial cytochrome oxidase gene COI, standard myrmecological morphological measurements, and three software programs, OUwie, SURFACE, and extendedSurface, to explore adaptive convergence in populations. COI sequences from T. sessile reported from outside my collecting areas were obtained from GenBank to explore a larger continental inferred phylogeny and population relationships with elevation and climate. I determined that T. sessile has adaptive convergence to elevation and climate and that haplotypes in eastern Tennessee and North America are more varied than previously reported. My comparison of 14 worker, 22 male, and 22 female characters, revealed significant morphological variation within eastern Tennessee populations of T. sessile. In addition, a sympatric novel species of Tapinoma, superficially like T. sessile, was discovered. This new species, designated Tapinoma heleni sp. nov., has a significantly lower number of mandibular teeth and denticles and displays a distinctly different colony structure than T. sessile. This study suggests that Tapinoma sessile has the potential to be a significant temperate invasive due to its adaptive capacity to various elevational and climatic regimes and is most likely capable of adapting to predicted changes in climate. The discovery of the sympatric T. heleni sp. nov. suggests that Tapinoma described as T. sessile may be separate species warranting a more thorough review of curated specimens and greater attention to taxonomic assignment. Tapinoma heleni sp. nov. was only detected in natural areas; thus, its pest status is not known at this time.