Are urban and rural tardigrade (Tardigrada) communities distinct and determined by pH: A case study from Fresno County, California

Tardigrades were collected from 73 urban sites and 24 rural locations in Fresno County, California to determine if differences existed in community structure between the two environments. Only 22 percent of urban samples were positive for tardigrades, as compared to 74 percent of rural samples. Samples from urban sites contained significantly fewer species than rural sites, although the average density did not vary significantly between urban and rural sites. Twenty-six different species were identified, with seven exclusively in the urban samples, 16 found only from rural samples, and three species found in both environments. Similarity analysis indicated urban communities were more similar to one another compared to similarities among rural communities, indicating significant differences between urban and rural communities. Tardigrades appeared to prefer habitat with a lower pH in both urban and rural locations. While our findings do support the negative relationship between urban sites and tardigrade richness, it was not explained by the lower pH typically associated with urban habitats. Further, we identified two species of Isohypsibius not previously recorded in the Western Hemisphere. The genus Eremobiotus was found for the first time in the Americas, and a species of Ramazzottius for the first time in North America.