SUBTLE SEXUAL DIMORPHISM IN THE BAY-CAPPED WRENSPINETAIL (SPARTONOICA MALUROIDES; FURNARIIDAE) UNCOVERED THROUGH MOLECULAR SEX DETERMINATION

CARDONI DA ; MALDONADO JE; ISACCH JP; GREENBERG R

ORNITOLOGIA NEOTROPICAL

NEOTROPICAL ORNITHOLOGICAL SOC

Año: 2009 vol. 20 p. 347 - 355

1075-4377

The family Furnariidae comprises putatively sexually monomorphic species, such as the Bay-capped Wren-Spinetail (Spartonoica maluroides). The goal of this study was to test for possible dimorphism in this species. We sexed 65 individual Bay-capped Wren-spinetails using molecular techniques. We performed subsequently a stepwise discriminant function analysis (DFA) on ten morphological measurements to select the best subset of variables capable of differentiating the sexes. We found that males had a longer rufous cap and wings than females. Furthermore, the bill length-depth ratio values were higher in females than males, indicating that males had more robust bills than females. In an posteriori analysis, the discriminant function correctly determined the sex of 80% of the overall samples, (71 and 89% of males and females, respectively). We suggest that, in the light of these results indicating sexual dimorphism in a species previously thought to have none, other furnariid species be better examined to determine whether sexual dimorphism is actually common, albeit subtle, in this family. The functional significance of these differences needs further exploration.