A Multifunction Trade-Off has Contrasting Effects on the Evolution of Form and Function.

Area of Science:

• Evolutionary biology
• Biomechanics
• Comparative anatomy

Background:

• Trade-offs in anatomical apparatus use for multiple functions are considered evolutionary constraints.
• Recent studies suggest traits linked to trade-offs may evolve more rapidly, challenging the idea that multifunctionality always suppresses diversification.

Purpose of the Study:

• To investigate the evolutionary dynamics of feeding mechanics and morphology in fish.
• To contrast species using suction feeding exclusively with those using multifunctional feeding (suction and biting).
• To test the hypothesis that multifunctionality stifles functional diversification.

Main Methods:

• Comparative analysis of feeding kinematics and head shape evolution.
• Utilized geometric morphometrics and macroevolutionary models (Ornstein-Uhlenbeck) in RevBayes.
• Contrasted evolutionary rates between obligate suction feeders and multifunctional biters.

Main Results:

• Feeding kinematic traits diversified over 13.5 times faster in suction feeders compared to biters.
• This difference is attributed to mechanical trade-offs between biting and suction performance in multifunctional species.
• Morphological evolution, specifically head shape, evolved significantly faster in biting fish, contrasting with kinematic evolution.

Conclusions:

• Multifunctionality appears to stifle functional diversification in feeding biomechanics, supporting a long-held evolutionary prediction.
• The study highlights a potentially weak or complex relationship between form and function in evolutionary processes.
• Feeding apparatus multifunctionality presents a unique case study in evolutionary constraints and diversification rates.