Ecomorphological changes of the mandibles of two living caiman species in the post-hatching ontogeny. 11° Symposium on Morphometrics and Evolution of Shape

FERNANDEZ BLANCO, MARÍA VICTORIA; GUILLERMO H. CASSINI; PAULA BONA

Montpellier

Simposio; 11° Symposium on Morphometrics and Evolution of Shape; 2021

Institute of Evolutionary Science of Montpellier

Ontogenetic morphological transformation of the mandible of living crocodiles has beenpoorly studied. We have explored the inter- and intraspecic variation of the mandible in twoextant caiman species, exploring the relationship between these morphological changes and diet,from a quantitative approach. We applied three-dimensional geometric morphometric methodson post-hatching ontogenetic mandibular series of Caiman latirostris and C. yacare. Weperformed interspecic Principal Component Analysis (PCA), and intraspecic Regression andPartial Least Squares (PLS) analyses using the Morpho package in R software. Only PC1 andPC2 were meaningful (explaining the 33.08% and 16.36% of the variance, respectively). Specieswere segregated along the PC1 with C. yacare located on the positive values (slender mandibles)and C. latirostris on the negative ones (robust mandibles). Both the PC2 and the regressionanalyses showed shape changes along the ontogeny (common and specic pattern, respectively)with juveniles of both species in the negative values and adults towards positive ones. Allometricscaling explains 19.01% of variation in C. yacare and 22.31% in C. latirostris. The adultmandible is longer, wider and taller than the juvenile (more conspicuous in C. yacare). The PLSanalysis of both species shows a signicant relationship between ontogenetic shape variation anddiet. Although proportions and feeding items are similar in the two caiman species (e.g., adultsof both species feed mainly on vertebrates), crustaceans are a very important component of thediet in the juveniles of C. latirostris whereas snails are for C. yacare. Summarizing, commonmorphological changes occurring during ontogeny seems to reect the same mechanical requirementsfor crushing and killing in both species, driven by ontogenetic changes in the diet frominvertebrates to vertebrates. Additionally, dierences in the mandible morphology (gracile androbust) could be related to dierent feeding mechanical requirements (stiness and toughness)and to dierent habitat preferences.