Associations among soil salinity, plant communities, and predaceous arthropods that can influence ixodid distribution on the South Texas Coastal Plain.

Abstract

The subtropical coastal plain of Deep South Texas provides a wildlife corridor for hosts of disease-transmitting ixodid species, including the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini). Wind tides and storm surges push hypersaline Lower Laguna Madre water inland on occasion, creating substantial areas of saline soil dominated by sea ox-eye daisy, Borrichia frutescens (L.) DC, and inhabited by numerous mud flat fiddler crabs, Uca rapax (Smith). Ixodid populations, especially larvae, in the saline areas are mostly negligible because of saltwater toxicity to eggs, desiccation, and predators. Soil salinity, U. rapax populations, and ant foraging activity were determined for areas dominated by B. frutescens, areas with intermediate stands, and areas without the plant. Borrichia frutescens density and U. rapax populations were moderately correlated with soil salinity, but predatory ant foraging was not correlated with soil salinity, B. frutescens density, and U. rapax abundance. Borrichia frutescens stand density, however, was strongly correlated with numbers of U. rapax holes, hence, the plant is an indicator of negligible ixodid activity. GIS mapping of high-Borrichia habitats might be useful for refining surveillance of ixodid populations, particularly one-host ixodids, such as R. (B.) microplus.