ANT DIVERSITY IN MAINE LOWBUSH BLUEBERRY AND THE ECOLOGY OF A DOMINANT ANT SPECIES, FORMICA EXSECTOIDES

ANT DIVERSITY IN MAINE LOWBUSH BLUEBERRY AND THE ECOLOGY OF A DOMINANT ANT SPECIES, FORMICA EXSECTOIDES

By Beth A. Choate

Thesis Advisor: Dr. Frank Drummond

An Abstract of the Thesis Presented

in Partial Fulfillment of the Requirements for the

Degree of Doctor of Philosophy

(in Biological Sciences)

December, 2010

The ecology of the Allegheny mound ant, Formica exsectoides, was assessed in lowbush blueberry during a four-year study.  Formica exsectoides is a native species that builds large mounds throughout the landscape.  When searching for food, workers collected a variety of species with bees, wasps, other ant groups (Hymenoptera) and caterpillars (Lepidoptera) being the most common groups.  During these searches, ants traveled several meters (7-18 m) in a wide range of temperatures (14-35ºC) and had little impact on other important insect species. Laboratory studies demonstrated that ant colonies feed readily on young blueberry flea beetle and spanworm, two major blueberry pests.  Ant colonies fed continuously on flea beetles as densities increased.  Overall, these results indicate F. exsectoides is an efficient predator throughout lowbush blueberry that has little impact on other beneficial insects, thus efforts to conserve colonies should be made.  In order to learn more about this species, physical characteristics of mound-nests were evaluated.  Nest temperatures as they relate to air and soil temperatures, and the role of colonies in increasing soil nutrients were examined.

            A six-year survey of lowbush blueberry fields was conducted to identify ant species diversity and richness. In addition, F. exsectoides abundance was evaluated during a one-year study, and laboratory investigations into the impacts of common insecticides on this species were conducted.  Results indicated that fields with no chemical pesticide applications had a significantly greater number of species and greater abundance of F. exsectoides.  The edges and wooded areas surrounding fields had significantly greater species numbers with F. exsectoides being most common on field edges. High densities of weedy vegetation were significantly correlated with increased densities of F. exsectoides, indicating a need for vegetation that supports honeydew-producing insects such as aphids, leafhoppers and treehoppers. In laboratory studies, workers were sensitive to phosmet, a highly toxic insecticide commonly sprayed throughout blueberry fields.  Low toxicity insecticides such as acetamiprid and imidacloprid had little impact on worker survival in laboratory studies. Conservation of species diversity and F. exsectoides colonies may be accomplished through the reduction and judicious selection of insecticides, as well as allowing weedy vegetation growth throughout fields.