Leaf litter input to ponds can dramatically alter amphibian morphological phenotypes

Area of Science:

• Ecology
• Evolutionary Biology
• Amphibian Biology

Background:

• Phenotypic plasticity is well-studied in growth and development, but less so in morphology.
• Morphological plasticity, specifically in leg length, is crucial for anuran mobility, influencing predator avoidance, prey capture, and seasonal movements.
• Relative hind leg length differences greater than 5% in anurans significantly impact jumping abilities, driven by resource availability and predation pressures.

Purpose of the Study:

• To investigate the variability of relative leg length in anuran metamorphs.
• To determine the influence of environmental factors, including leaf litter, on relative leg length.
• To assess the implications of altered leg length for anuran fitness in response to environmental changes.

Main Methods:

• Measured relative leg length (leg length/snout-to-vent length × 100%) in four anuran species: Hyla versicolor, Lithobates sylvaticus, L. sphenocephalus, and Anaxyrus americanus.
• Conducted aquatic mesocosm studies to examine the effects of plant litter type and quality on metamorph development.
• Analyzed the influence of environmental variables such as water quality, predation, resource levels, and temperature on relative leg length.

Main Results:

• Relative leg length exhibited significant variability, ranging from 44% to 120% of SVL across species, with highest within-species variation in L. sylvaticus.
• Leaf litter input was identified as a significant predictor of relative leg length in ranid frogs (L. sylvaticus and L. sphenocephalus).
• Ranid frogs reared in mesocosms with grass litter had longer legs than those with no litter; deciduous leaves resulted in intermediate leg lengths.

Conclusions:

• Leaf litter composition directly influences anuran metamorph relative leg length, suggesting a mechanism for morphological plasticity.
• Habitat alterations due to land use, invasive species, and climate change may impact anuran mobility and fitness through changes in leg length.
• Understanding leg length plasticity is critical for predicting anuran population dynamics and conservation needs in response to environmental shifts.