Competition and the distribution of spring peeper larvae

Area of Science:

• Ecology
• Amphibian Biology
• Population Dynamics

Background:

• Spring peeper (Pseudacris crucifer) and green frog (Rana clamitans) tadpole distributions often do not overlap, despite shared habitat preferences.
• Spring peepers are considered weaker competitors, leading to the hypothesis that green frogs competitively exclude them.

Purpose of the Study:

• To test the hypothesis that competition from green frog larvae limits spring peeper tadpole distribution.
• To investigate the effects of intraspecific and interspecific competition on tadpole performance.

Main Methods:

• A field enclosure experiment was conducted using a target-neighbor design.
• Constant density of spring peeper tadpoles was stocked with varying densities of green frog tadpoles.
• Effects on spring peeper survivorship, larval period, growth rates, and metamorphic size were measured.

Main Results:

• Increased green frog density had minimal impact on spring peeper survivorship, larval period, growth, or metamorphic size.
• Intraspecific competition among green frogs significantly reduced their growth rate (50%) and metamorphic size (11%).
• No evidence of interspecific competition limiting spring peeper distribution was found.

Conclusions:

• Interspecific competition from green frogs does not appear to limit spring peeper tadpole distributions.
• Species segregation in resource use or differing abilities to cope with resource scarcity may explain non-overlapping distributions.
• Other factors like predation or adult breeding site selection are likely more important in determining tadpole distribution.