Environment rather than character displacement explains call evolution in glassfrogs

Area of Science:

• Bioacoustics
• Evolutionary Biology
• Ecology

Background:

• The acoustic adaptation hypothesis (AAH) suggests signals evolve for environmental compatibility, predicting call homogenization.
• Ecological character displacement (ECD) proposes signals diverge to avoid interference, predicting call differentiation in sympatry.
• These hypotheses offer contrasting predictions for signal evolution in diverse communities.

Purpose of the Study:

• To test the relative importance of AAH and ECD in shaping advertisement call evolution in glassfrogs.
• To investigate how environmental factors and species interactions influence anuran communication signals.

Main Methods:

• Employed comparative phylogenetic analyses to examine call evolution in a diverse family of neotropical anurans (glassfrogs).
• Assessed correlations between call parameters (temporal and spectral) and environmental variables (vegetation density, temperature).
• Investigated patterns of call convergence and divergence among co-occurring species and populations.

Main Results:

• Acoustic adaptation to the environment appears to be a stronger selective force than species interactions.
• Temporal call parameters correlated with vegetation density, supporting AAH predictions.
• Spectral call parameters showed unexpected inverse correlations with vegetation density and correlations with temperature.
• Call convergence was frequently observed among co-occurring species and across different glassfrog communities.
• Evidence for character displacement was rare, suggesting signal similarity costs are not always a primary driver of divergence.

Conclusions:

• Habitat filtering, driven by acoustic adaptation, is a major factor promoting call convergence in glassfrogs.
• Ecological character displacement plays a less significant role in driving divergent selection on glassfrog calls.
• Signal similarity may not always incur significant costs, challenging the universal applicability of ECD in anuran communication systems.