Meeting Abstract
Reliably quantifying the strength of visual sexual signals, such as iridescence, has been challenging across the field of evolutionary biology. The Iridescence Detection and Isolation Algorithm (IDIA) was designed to isolate the iridescent signal from photographs for quantification of ornamentation. The Gulf pipefish, S. scovelli, served as a model system due to their sex-role-reversed polyandrous mating system and sexual dimorphism, with females possessing sexually selected iridescent bands on their abdomens. Using the IDIA, female iridescence was reported in two ways, including a manual measurement of each individual band and an automated measurement taken by drawing a polygon around all bands on the torso, to remove user bias. Our results indicated that the iridescence calculated from the two approaches were strongly correlated. We were also able to detect geographical variation in female ornamentation and stronger iridescent bands in lab-reared females compared to their parental population. Females from the Florida coast had greater iridescence compared to females collected from the Texas coast. However, lab-reared fish from a Texas parental population showed the greatest iridescence overall, indicating environmental conditions, such as turbidity, could affect the strength of female visual signals. Lastly, we utilized the IDIA for an environmental application by detecting the development of iridescence in male pipefish exposed to synthetic estrogen. Exposed males began expressing banding patterns with iridescence levels within the range of females. The results from this study confirm the feasibility of using the IDIA for measuring sexually selected traits and investigating estrogen exposure in natural populations by detecting morphological changes in exposed males.
