Host-parasite dynamics are often moderated by environments in which they occur and may be influenced by water quality changes resulting from anthropogenic activities. While we often think of the negative impacts of humans, land management on exurban lands could offset these impacts. Exurban lands are large-lot residential property outside of suburbia and are the fastest growing land use type in the US, yet their importance to local biodiversity is largely unknown. In agriculturally-dominated landscapes, exurban areas provide valuable habitat patches as landowners make different land management decisions from mowing to forest regeneration to creation of ponds for aesthetic or recreational purposes. We investigated the importance of regional and local factors as determinants of host and parasite responses in pond communities across an exurban landscape by evaluating aquatic snails and their associated parasites. We hypothesized that snail presence and abundance and trematode presence and prevalence could be predicted based on local pond characteristics more than surrounding landscape-level factors. We surveyed protected, exurban, and agriculture/golf courses ponds across southwestern Ohio for ramshorn snails (Helisoma trivolvis) and their trematode parasites. For each pond, we evaluated local factors, including water quality, and aquatic species richness, and regional landscape attributes, including land use.
Results/Conclusions
We observed ramshorn snails at 25 of 41 sampled ponds and trematodes at 80% of those sites with snails present, suggesting that these parasites are common in this region. Total dissolved nitrogen was significantly higher in agriculture and golf course ponds and likely drove increases in algal food resources promoting an increased snail abundance within these ponds. We also found that species richness of aquatic invertebrates and plants was positively correlated with snail presence, and these local factors had a greater influence on snail presence than the surrounding landscape, supporting our hypothesis. Parasite presence was positively associated with the richness of amphibians, which serve as second intermediate hosts for these parasites. Parasite prevalence was influenced by regional water attributes like wetland area near each focal pond, suggesting the water availability across the landscape may alter the spread of these parasites. Overall, exurban pond communities resembled protected ponds more closely than agricultural or golf course ponds, suggesting that exurban ponds may serve as a valuable habitat for conservation, depending on their management by residential landowners. This study highlights the importance of both local and regional factors on influencing host-parasite dynamics across the landscape.