Patterns of skull development in anurans: Size and shape relationship during postmetamorphic cranial ontogeny in five species of the Leptodactylus fuscus Group (Anura: Leptodactylidae)

Abstract

The effect of allometric ontogenetic changes on morphology has been examined primarily in larval stages of anurans. To our knowledge, such studies after metamorphosis are non-existent, and this information is important because the skull acquires its adult configuration in that period. Using geometric morphometrics, we studied postmetamorphic shape changes in the skull of five species of the Leptodactylus fuscus Group (Leptodactylus bufonius, Leptodactylus elenae, Leptodactylus fuscus, Leptodactylus latinasus, and Leptodactylus mystaceus), a group of smallto medium-sized frogs. Size change is an important factor in explaining shape change during postmetamorphic growth in four of these species; ontogenetic trajectories have in general parallel directions and similar rates of shape change. L. latinasus skulls tend to differ in size and shape from the others, and the allometric model, although significant, explains low percentages of shape change. The diverging slope of its ontogenetic trajectory indicates nonheterochronic, allometric repatterning change regarding the ontogenies of L. bufonius, L. elenae, and L. fuscus. Conversely, ontogenetic scaling appears as the main mechanism modeling shape change as regard to L. mystaceus; hence, we suggest that a process of progenesis determines the small, juvenile-like cranium of L. latinasus. The disparity analysis shows a broader morphological divergence in metamorph morphospace than in adults, suggesting that postmetamorphic stages can contribute with informative characters to phylogenetic analysis. Differences in shapes between metamorphs and adults indicate that many changes occur after metamorphosis, but whether these changes result from internal or ecological requirements at different stages remains unknown.