Evolutionary patterns of mandible shape diversification of caviomorph rodents

ALVAREZ, A.; ERCOLI, MD; OLIVARES, AI; DE SANTI, NA; VERZI, DH

JOURNAL OF MAMMALIAN EVOLUTION

SPRINGER

Lugar: Berlin; Año: 2020 vol. 28 p. 47 - 58

1064-7554

Caviomorphs are a mainly South American rodent clade, whose high taxonomic andecomorphological diversity was reached through several major events duringCenozoic. In this study, we combine functional variables, geometric morphometrics, reconstruction of ancestral shapes, and macroevolutionary dynamics analyses to quantify the magnitude, direction, and rates of shape diversification of the mandible of caviomorphs, and to explore the morpho-functional implications and potential ecological catalysts (considering size, life habits, and preferred habitat) of the observed shape changes. Our analysis suggests that the mandible shape of caviomorphs is significantly related to habits and size, and has a better fit with an evolutionary model inwhich different pathways were taken by main clades. The morphological evolution of octodontoids stands out by pulses of rate acceleration, but without reaching particularly disparate morphotypes. Such pulses are mainly linked to the acquisition of fossorialadaptations, including short and robust mandibles, and the optimization of forces at incisors. Conversely, derived cavioids show slower but continuous shape changes that allowed them to reach the most divergent morphotypes, becoming progressively more specialized to an abrasive diet, in which slender mandibles, more marked anteroposterior movements, and a grinding action were favored. Interestingly, the major morphological changes described occurred mainly during the early Oligocene and lower late Miocene, a period of time that involved major global climatic events and strong changes in the vegetational structure of South America. The evolution of octodontoid and cavioid mandibles, seems to be related to the occupation of subterranean and epigean niches, respectively, of the progressively expanded open landscape during the Cenozoic of southern South America.