Knowledge Bank

Identification of conspecific individuals is necessary to prevent hybridization in areas where two closely-related species coexist. Greater and Lesser Prairie-Chickens (Tympanuchus cupido and T. pallidicinctus) are two closely-related species, whose ranges have expanded recently, and now overlap. There is behavioral evidence that the two species may be hybridizing. We sought to examine whether feather coloration could be used to differentiate between species, and to estimate the hybridization rate. Our hypothesis was that Greater Prairie-Chickens and Lesser Prairie-Chickens differed in feather coloration and patterning, and that birds of hybrid origin would show intermediate feather characteristics. Spectroscopy readings and feather measurements were taken from both Greater and Lesser Prairie-Chicken reference populations and compared to the birds in the area of overlap to determine species identity. We conducted two discriminant analyses. The first utilized number of bars, length of the feather, and length of the subterminal bar to differentiate between parental species. We ran a separate analysis with the same information as previously, but also including brightness and the dark bars and light bars, to determine if spectroscopy readings increase the accuracy of the model. Hybrids were defined as individuals that were not assigned to either parental species.
The discriminant analysis was able to differentiate between Greater and Lesser Prairie-Chickens with a high degree of certainty. We found a hybridization rate of between 4.1 and 7.3%. The analysis with color was able to determine species identity with higher confidence than the analysis without color. Our hypothesis that Greater Prairie-Chickens and Lesser Prairie-Chickens differ in feather coloration and patterning was supported. Hybrids had some intermediate traits such as subterminal bar length and brightness of the light band. Future work should identify the multiple factors that can influence hybridization rate in these taxa, such as relatedness, population size, aggressive behavior, and environmental disturbance that must be taken into account when trying to understand hybridization.