Does a male nest builder have the same head shape as his mate? Sexual dimorphism in Leptodactylus fuscus (Anura: Leptodactylidae)

Males of Leptodactylus fuscus (Schneider, 1799) construct subterranean chambers with the snout. The chamber is used for oviposition in a foam nest. Due to this behaviour, it's inferred that there are different selective pressures according the sex. We aimed to evaluate the occurrence of sexual dimorphism in the head shape of L. fuscus through geometric morphometrics analysis of 97 specimens (51 males and 46 females). We determined 21 landmarks in the dorsal view and 14 landmarks in the lateral view of the head. We found that part of the shape variation in the dorsal view can be attributed to allometry, with larger individuals having wider heads. We performed a Principal Component Analysis for each view and found a broad overlap in the head shape between males and females. After removing the effect size, discriminant analysis revealed that the head shape differs significantly between the sexes. In general, males were found to have broader, less dorsoventrally-flattened heads with nostrils spaced further apart from one another and more caudally, and a longer and spatulate shaped snout. The differences in the head shape that we found are congruent with what is expected for males that used their head in burrowing behavior.