Experimental manipulation reveals a trade-off between weapons and testes.

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Sexual Selection

Background:

• Sexual selection theory predicts a trade-off between pre-copulatory traits (weapons) and post-copulatory traits (testes).
• Resource availability can mask these trade-offs, as individuals may invest in both trait types.
• Mictis profana (Hemiptera: Coreidae) uses hind legs as sexually selected weapons for female access.

Purpose of the Study:

• To experimentally investigate the resource allocation trade-off between sexually selected weapons and testes in Mictis profana.
• To determine if resource allocation to weapons influences investment in post-copulatory traits.

Main Methods:

• Experimental hind leg autotomy in developing Mictis profana males to prevent weapon development.
• Comparison of trait expression (testes mass, other sexual and natural traits) between weaponless males and a control group (mid-leg autotomy).
• Analysis of wild adult male population for correlations between weapon and testes investment.

Main Results:

• Males experimentally prevented from developing hind leg weapons invested proportionally more in testes mass compared to controls.
• No significant differences were observed in other pre-copulatory, post-copulatory, or naturally selected traits between groups.
• A positive correlation between testes and weapon investment was found in wild adult males.

Conclusions:

• Experimental manipulation revealed a resource allocation trade-off between pre- (weapons) and post-copulatory (testes) sexual traits in Mictis profana.
• The study highlights the importance of experimental approaches to uncover resource allocation trade-offs that may be masked by natural variation.
• Findings contribute to understanding the complex interplay of resource allocation in shaping sexual trait evolution.