Field data do not support a textbook example of convergent character displacement

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Speciation

Background:

• Convergent character displacement, where similar traits evolve in different species due to competition, has limited experimental support.
• Previous evidence relied on laboratory experiments, which may not accurately reflect natural conditions.

Purpose of the Study:

• To re-examine the evolution of melanic nuptial coloration in male three-spined sticklebacks (Gasterosteus aculeatus) in the Chehalis River drainage.
• To test the hypothesis that melanic coloration evolved due to competition with Olympic mudminnows (Norzumbra hubbsi).

Main Methods:

• Conducted cage experiments and naturalistic observations of stickleback-mudminnow interactions.
• Assessed competitive success for nesting territories between melanic and red sticklebacks against mudminnows.
• Examined the timing of melanic coloration development in relation to parental care.

Main Results:

• Melanic male sticklebacks showed no advantage over red counterparts when competing for territories with mudminnows.
• Competitive interactions between sticklebacks and mudminnows were infrequent in both experimental and natural settings.
• Melanic coloration developed after the hypothesized territory establishment period, during parental care.

Conclusions:

• The study refutes the sole experimental support for convergent character displacement in this system.
• Findings highlight the necessity of conducting behavioral studies under natural conditions to avoid experimental artifacts.