Defining vertical bars in relation to female preference in the swordtail fish Xiphophorus cortezi (Cyprinodontiformes, Poeciliidae)

Mr. Morris et al., Defining vertical bars in relation to female preference in the swordtail fish Xiphophorus cortezi (Cyprinodontiformes, Poeciliidae), ETHOLOGY, 107(9), 2001, pp. 827-837
Citations number
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ISSN journal
0179-1613 → ACNP
Year of publication
827 - 837
SICI code
Defining a male trait in relation to female preference is an important step towards determining the role that female preference has played in the evol ution of a male trait. The pigment pattern 'vertical bars' is a complex mal e trait that functions as a sexual signal in swordtail fishes. A previous s tudy suggested that X. cortezi females had a preference for males with more vertical bars. In that study, however, bar number had been reduced on the stimulus males by removing the most posterior bars, which changed the dista nce over which the bars spanned, in addition to changing bar number. To det ermine whether X. cortezi females have a preference for greater bar span an d/or number of bars, we tested for female preference in two experiments. Fi rst, we gave females a choice between males with a greater bar span or a sm aller bar span, holding bar number and total pigmented area constant. Femal es spent significantly more time with the males with the smaller bar span. This result, together with results from the previous study, suggest that fe males do not assess bar span alone, but possibly a composite component of t he bars, such as bar frequency (number of bars/bar span). Secondly, we gave females a choice between six thinner bars or one wider bar of equal pigmen ted area. The six-bar treatment had a greater bar span in addition to more bars. We detected no preference for either treatment. These results suggest that the previously detected preference for more bars may actually reflect a preference for greater pigmented area. Finally, we present data on natur al variation in the bars for X. cortezi and use principal components analys is to provide a composite definition of this trait.