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.Abstract
Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) on (A) mass at and days to metamorphosis for Blanchard's Cricket Frogs (CF) and (B) tadpole mass and Gosner stage at experimental day 61 for Green Frogs (GF). Values represent means ± 1 SE.
Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) on proportion of tadpoles active for Blanchard's Cricket Frogs (CF) and Green Frogs (GF) at three times during the experiment. Values represent means ± 1 SE.
(A) Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) on survival to metamorphosis (meta) and total survival (tot) for Blanchard's Cricket Frogs (CF) and Green Frogs (GF) and (B) effects of community composition (single species with 25 or 50 tadpoles/mesocosm, or both species with 25 tadpoles of each/mesocosm) on survival. ** indicates P < 0.05 and * indicates a P < 0.10. Values represent means ± 1 SE.
Effects of community composition on (A) mass at and days to metamorphosis for Blanchard's Cricket Frogs (CF) and (B) tadpole mass and Gosner stage at experimental day 61 for Green Frogs (GF). Treatments with different letters indicate statistical differences according to Scheffe's test. Values represent means ± 1 SE.
Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) on chlorophyll-a relative abundance as proxies for (A) periphyton and (B) phytoplankton over time. Values represent means ± 1 SE.
Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) and community composition (25 or 50 Blanchard's Cricket Frogs [CF] or Green Frogs [GF]) on nutrient responses, including (A) total nitrogen, (B) total phosphorus, (C) ammonium, (D) nitrate, and (E) phosphate. Values represent means ± 1 SE.
Effects of the amount of leaf litter (LL) input (0.25 or 1 kg) on (A) pH, (B) dissolved oxygen (DO), (C) conductivity, and (D) temperature over time. Values represent means ± 1 SE.
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