Is UV ornamentation an amplifier in swordtails?

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Sexual Selection

Background:

• Sexual selection drives the evolution of elaborate male ornaments.
• Male morphs can arise from different developmental pathways, potentially leading to varied signal expression and usage.
• The interplay between ornamentation and behavior in mate choice is complex and can vary with male phenotype.

Purpose of the Study:

• To investigate female preference for UV ornamentation in two male size classes (intermediate and large) of the swordtail Xiphophorus nigrensis.
• To determine how male activity interacts with UV ornamentation in influencing female attention.
• To explore whether UV ornamentation and male behavior play distinct roles for alternative male morphs competing for mates.

Main Methods:

• Comparative analysis of female preference for UV ornamentation and male activity across intermediate and large male swordtails.
• Quantification of UV reflectance intensity and saturation in different body regions for each size class.
• Statistical examination of the interaction between male size class, UV ornamentation, and male activity in attracting female attention.

Main Results:

• Females preferred UV ornamentation in both intermediate and large males, but not high male activity.
• Large males exhibited greater UV reflectance intensity and saturation than intermediate males.
• Intermediate males gained more female attention per unit of UV ornamentation when more active, acting as an amplifier, while large males gained from UV ornamentation only when less active.

Conclusions:

• UV ornamentation and male activity play size-dependent roles in mate competition for Xiphophorus nigrensis.
• Behavior can amplify UV ornamentation in intermediate males, but not in large males.
• Alternative male morphs may utilize ornaments and behaviors differently to attract female attention, highlighting the complexity of sexual selection.