RAPID: Ant community responses to a 1000-year flooding event

William Marsh Rice University, Houston TX

Investigators

Abstract

Extreme weather events, such as catastrophic fires or floods, are expected to become more likely under global environmental change. Scientists have a relatively poor understanding of how such extreme events influence the abundance of plants and animals, including species that affect human well-being such as pollinators or invasive pests. Improving this scientific understanding requires that we learn from natural disasters. This project examines how extreme flooding associated with Hurricane Harvey in August 2017 affected the abundance and community composition of ants in the Big Thicket region of east Texas. This region hosts dozens of native ant species that provide valuable ecosystem services, such as decomposition and pest control, as well as noxious invasive species (fire ants and tawny crazy ants). The researchers will use "before" and "after" samples to test the hypothesis that Hurricane Harvey disrupted east Texas ant communities, favoring an increase in abundance and extent of invasive ants. The research will be conducted in coordination with the National Park Service, who hope to learn more about the ecological effects of Hurricane Harvey. The scientists will communicate their results to the public in the Texas communities of Houston and Beaumont, which were affected by fire ants and strongly affected by Harvey's floodwaters. Ecological theory suggests that the relative abundance and even presence of species in communities may be driven as much by historical contingencies associated with rare events as by filtering from average environmental conditions. Forecasts for environmental change in the 21st century include an increase in frequency of extreme events, and ecologists are increasingly called upon to predict their consequences. The researchers will study how the 1,000-year flooding associated with Hurricane Harvey modified the taxonomic and functional trait composition of Big Thicket ant communities. The researchers will leverage three years of pre-event sampling to contrast the abundance, diversity, and species composition of ant communities before and after Harvey's floodwaters. Importantly, pre-event work demonstrated that exotic ant species had begun to penetrate the intact native communities. The researchers will evaluate whether Hurricane Harvey increased opportunities for invasion by exotic ants. They will conduct monthly pitfall sampling at 19 established sites to document changes in ant communities, and test whether changes in response to the hurricane are transient or represent new stable states. They will also assemble a functional trait database for these communities to test whether taxonomic shifts were driven by the filtering of species-specific traits that confer tolerance to flooding. Functional traits of interest include risk-spreading strategies such as polygyny (multiple queens per colony) and polydomy (multiple nesting locations). As the floodwaters have just now receded in the study area, there is an urgent window of opportunity to study the dynamics of ecological response and recovery.