Environmental factors influencing wood frog (lythobates sylvaticus) tadpole size

Abstract

Body size variation among individuals and populations within a species is important to study due to the ecological implications, specifically life history population dynamics. Variation in growth among individuals has been attributed to both inherent biological and environmental factors affecting an organism. Several models have been proposed to describe life history variation and tradeoffs. Understanding the controlling influence of body size variation in amphibians requires consideration of all factors. We evaluated which environmental factors have an impact on Lythobates sylvaticus tadpole body size. Our study site consisted of 57 wetlands (41 ephemeral and 16 permanent) in Chippewa County, Wisconsin. Tadpole body sizes, measured as snout vent lengths (SVLs), were surveyed in each wetland using minnow traps collected after 24 hours of being submerged. Environmental factors, including dissolved oxygen, canopy cover, pH, temperature, hydroperiod, and chlorophyll-a were quantified. We also considered possible size variations occurring in permanent versus ephemeral wetlands. Tadpoles in permanent ponds were significantly larger (F1,18 = 7.34, p-value = 0.014) than those in ephemeral ponds. Out of the environmental factors, pH resulted in a positive correlation with tadpole size (Adjusted R2 = 0.38, F2,17, p-value = 0.006). The results of our research provide evidence for a relationship between amphibian body size and environmental characteristics. The pH of wetlands may serve as a proxy for the relationship between peat accumulation, or immediate upland landscapes, most often acidifying Pinaceae family and the SVL of L. sylvaticus.