1. Departamento de Ecología Evolutiva, Instituto de Ecología, UNAM, AP 70-275, CP 04510 México DF, México

Correspondence to: Constantino Macías Garcia¹ Correspondence and requests for materials should be addressed to C.M.G. (Email: maciasg@servidor.unam.mx).

Abstract

Conventional models^{1, 2, 3, 4} explaining extreme sexual ornaments propose that these reflect male genetic quality^{2, 3, 4} or are arbitrary results of genetic linkage between female preference and the ornament¹. The chase-away model⁵ emphasizes sexual conflict: male signals attract females because they exploit receiver biases^{6, 7, 8, 9}. As males gain control of mating decisions, females may experience fitness costs through suboptimal mating rates or post-copulatory exploitation. Elaboration of male signals is expected if females increase their response threshold to resist such exploitation. If ornaments target otherwise adaptive biases such as feeding responses^{8, 9, 10}, selection on females might eventually separate sexual and non-sexual responses to the signal. Here we show that the terminal yellow band (TYB) of several Goodeinae species evokes both feeding and sexual responses; sexual responsiveness phylogenetically pre-dates the expression of the TYB in males and is comparable across taxa, yet feeding responsiveness decreases in species with more elaborated TYBs. Displaying a TYB is costly, and thus provides an example where a trait arose as a sensory trap but has evolved into an honest signal.

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