When Colonizers Compete: Evaluating Interactions between Larval Anurans Across a Leaf Litter Gradient

The competition-colonization trade-off hypothesis predicts that good colonizers are poor competitors, but good colonizers often coexist in new habitats. Blanchard's Cricket Frogs (Acris blanchardi) are a species of concern and effective colonizers of wetland habitats. Previous studies suggested that Green Frogs (Lithobates clamitans) can outcompete Cricket Frogs, which could contribute to their declines. We examined interactions between these anuran tadpoles across a leaf litter gradient. These species were reared in outdoor mesocosms with leaf litter (0.25 or 1.0 kg) in six community types including ponds that were tadpole-free, or that contained Cricket Frog tadpoles (25 or 50), Green Frog tadpoles (25 or 50), or tadpoles of both species (25 of each). Leaf litter quantity, rather than community composition, had the greatest impact on anuran development and the aquatic community, which may be attributable to increased abundance of periphyton and phytoplankton in high leaf litter treatments over time. High leaf litter treatments produced anurans with larger mass and quicker development on average than low leaf litter treatments. Cricket Frogs showed a trend of lower total survival in high-density communities regardless of competitor identity. Green Frog tadpoles, in contrast, had greater mass in high-density mixed communities than in high-density communities with only Green Frogs, suggesting that they were facilitated by Cricket Frog presence. Our study suggests that colonizing species may be less susceptible to competition with other colonizers and in some cases may enhance the success of each other, boosting the probability of successful colonization events.