The evolution of tail‐length in widowbirds (Ploceidae): tests of alternatives to sexual selection

Abstract

The long tails of male widowbirds (Euplectes, Ploceidae) have been used to test sexual selection theory, but alternatives to sexual selection have not been investigated. This study tests three alternative hypotheses for the evolution of tail‐length in widowbirds: apose‐matism, the unprofitable prey hypothesis and species recognition. Using museum specimens, geographic patterns of tail‐length were examined for evidence of character convergence (as predicted by the aposematism and unprofitable prey hypotheses) or character divergence (as predicted by the species recognition hypothesis) in areas where two pairs of species were sympatric. There was no consistent trend: one species showed evidence of character convergence and the other some evidence of divergence. Experimental manipulation of tail‐length in the Yellow‐shouldered Widowbird Euplectes macrourus also failed to support the species recognition hypothesis: there was no preference for males with species‐typical tail‐lengths but only a slight and non‐significant trend to favour short‐tailed males. There was also no evidence that mistaken identity led to territory loss following these experimental manipulations. Tail‐length of six Euplectes species did not correlate with unpalatability scores, as predicted by the aposematism hypothesis. These hypotheses do not appear to explain the evolution of long tails in widowbirds, suggesting that sexual selection is the sole factor favouring long tails. Interspecific variation in tail‐length remains unexplained.