Is UV Ornamentation an Amplifier in Swordtails?

Do distinct male morphs use the same ornaments in different ways? Female preference for UV ornamentation and male activity was examined in two different male size classes of the swordtail Xiphophorus nigrensis: intermediate and large. UV ornamentation is preferred by females for both size classes, while high male activity is not. Large males have significantly greater intensity and saturation of UV reflectance for several body regions. Despite this difference in signal strength, intermediate sized males garnered a greater gain in female attention for UV ornamentation relative to large males. The differential payoff may be a result of different interactions between ornamentation and activity between the size classes. Females show significant preference for UV-ornamented intermediate males only when they are more active than their rival and not when the UV-ornamented male is less active, indicating that behavior might serve as an amplifier of UV ornamentation in this class. Meanwhile, large males gain from their UV-ornamentation only when they are less active than their rival, failing to support behavior as an amplifier for UV ornamentation in this size class. This interaction between size class and activity is significant, and suggests that UV and/or behavior play different roles for alternative male morphs competing for female attention.