Genetic Variation and Species Distribution of Subterranean Termites in the Southeastern U.S. Focusing on Family Structure and the Invasive Formosan Subterranean Termite

This work applies molecular genetic tools to distinguish the identity and understand the biology of termites, particularly Reticulitermes Holmgren and Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in the southeastern U.S. Termites are important economic pests costing billions of dollars annually to Americans but also are important wood decomposers in natural settings. Molecular tools are essential for species identification because of the morphological ambiguities among species. The cryptic nest structure of subterranean termites which prevents adequate sampling makes molecular genetic tools essential to examine an entire colony. A molecular diagnostic technique was created to differentiate Coptotermes formosanus, an invasive species in the U.S., from native subterranean termites. Using a multiplex PCR protocol, this method can distinguish C. formosanus even from a single specimen or sample lacking the diagnostic castes. In southern Mississippi, a new termite species was observed and confirmed genetically. Using both morphological and molecular phylogenetic evidence, Reticulitermes mississippiensis Janowiecki, Szalanski, and Austin sp. nov. is described here as a new species. The breeding structure of a termite colony refers to the number of male and female termites reproducing in the colony that contribute to the genetic diversity of the colony. While this is near impossible to determine from a field census, microsatellite DNA analysis has been previously applied to investigate this biological aspect in the North Carolina, South Carolina, Massachusetts, and Tennessee. Here, we apply these techniques to three species of Reticulitermes from three sites in northwest Arkansas. Generally, our results were similar to those previously observed with 22% of the colonies being simple families (one male and one female), 72% extended families (the offspring of one male and one female reproducing) and 6% being mixed families (where multiple unrelated reproductives are reproducing in the colony). This study observed the first mixed family colonies of Reticulitermes hageni Banks. While these results show interesting trends of family structure for each species, more sampling is required to verify these observations

Colony Breeding Structure of Reticulitermes (Isoptera: Rhinotermitidae) in Northwest Arkansas

Termites, as social insects, have a complicated life cycle in which the colony breeding structure, that is the number of and origin of reproductives in a colony, can vary in relation to age and environmental factors. In this study, we used genetic methods to characterize the breeding structure of three species of Reticulitermes from three sites in northwest Arkansas and compared two habitats: undeveloped, forested sites and developed, agricultural sites. We found 57.1% of R. flavipes (Kollar) in northwest Arkansas (n = 28) were simple families, 39.3% were extended families and 3.6% were mixed families. Similarly, for R. hageni Banks (n = 23), we found 58.3% simple families, 33.3% extended families, and 8.3% mixed families. All of the R. virginicus (Banks) samples (n = 5) were simple families. For R. flavipes and R. hageni, the percentage of extended families is intermediate to southeastern and northern USA populations, corresponding to the intermediate seasonality and climate in Arkansas. The level of inbreeding in Arkansas, estimated via FIT, was relatively high and similar to northern populations of Reticulitermes. There were significantly more extended family colonies at the developed site compared to the two undeveloped sites which contained more simple family colonies. This difference may occur as a strategy to cope with sparse resources in urban environments or as a consequence of different abiotic factors

Physiological and Behavioral Factors that Influence Colony Spatial Dynamics in Reticulitermes Termites

The termite genus Reticulitermes contains species that are important wood decomposers and major economic pests. In the U.S., there are eight species of Reticulitermes, many of which broadly overlap geographically. These species have similar resource requirements, presenting a research gap explaining how they partition resources. This dissertation focuses on understanding the distribution of Reticulitermes termite colonies in a natural forest environment and the influence of climate, physiological tolerances, tunneling behavior, and alarm communication on their distributions. To improve species identification, a genetic tool using inter-simple sequence repeats was developed to distinguish between the six species of Reticulitermes encountered in the eastern U.S. This tool was used to identify termite species in a study on the impact of climatic factors on termite activity. By establishing grids of wooden monitors sampled monthly in a natural forest site, species-specific foraging patterns were found in response to soil temperature and moisture. These differences may allow Reticulitermes species to co-exist by feeding on resources under varying climatic conditions. These foraging patterns cannot be explained by differences in physiological limits, as all species had approximately the same upper lethal limit (ULL), submersion, and desiccation tolerances. However, there was variation in ULL in R. flavipes across its range, which correlated to head width. Dry weight of R. flavipes also varied across its range and was correlated with precipitation levels during dry portions of the year. Tunneling behavior was compared between species, finding that R. flavipes tunneled faster and constructed more branches than the other two species. Additionally, soldier presence increased tunnel branching in R. flavipes, while soldier presence or even the chemical presence of a soldier increased tunneling speed in R. flavipes and decreased tunnel initiation time in R. hageni. Finally, the difference in vibroacoustic alarm behavior between R. flavipes, R. virginicus, and the invasive Formosan subterranean termite, Coptotermes formosanus, was assessed and the role of soldier caste on this response was determined. Soldier presence changed the alarm response level in R. virginicus to different stimuli but had little impact in R. flavipes and C. formosanus. Overall, the variable responses to climatic factors and behavioral differences among termite species found here further our understanding of resource partitioning in Reticulitermes