Evolutionary patterns in cranial growth in sigmodontines (Rodentia, Cricetidae)

FLORES D.; SEGURA V.; JAYAT J. PABLO

Zurich

Congreso; 96th Annual Meeting of the German Society for Mammalian Biology; 2023

German Society for Mammalian Biology

Evolutionary patterns in cranial growth in sigmodontines (Rodentia, Cricetidae)Flores, D.1,2 Segura, V.1, Jayat, P.1 1Unidad Ejecutora Lillo, (CONICET-FML). 2Instituto de Vertebrados, Fundación Miguel Lillo daflores@lillo.org.arSigmodontines comprise one of the most diverse radiations in neotropical mammals. Although cranial ontogeny has been studied in various mammals, it remains poorly studied in this group. In this report, we quantified the ontogenetic pattern for 22 sigmodontine species (Abrotrichini, Akodontini, Andinomyini, Oryzomyini, and Phyllotini tribes) and 8 outgroups (Cricetinae, Murinae, Gerbillinae, Spalacinae, Glirinae, and Thryonomyidae), generating partial reconstructions of ancestral allometric growth patterns, and evaluating the role of evolutionary history in the cranial ontogeny of the group. Sigmodontines are conservative in growth patterns, without a single pattern defining tribes. The allometric growth of the skull has mostly a negative trend, with Akodontini being the most isometric tribe and Phyllotini the most allometric one. The allometry of the variables associated with the neurocranium was mostly negative, while those linked to trophic functions showed some positive allometry or isometry. A general cranial elongation was detected, with variables associated with skull width or height showing lower rates, while elongation was a generalized pattern and likely a plesiomorphic condition. The growth and development of the skull were associated with changes in the musculature functionally involved in biting and chewing. Most of the changes occurred in early postnatal stages, achieving an early morphological optimum. Few changes in the growth rate were detected in the internal nodes, and stasis throughout the evolution was recurrent. The few synapomorphies that define the ancestry of Sigmodontinae conform a pattern with little laterally expanded zygomatic arches and globose braincases. The conserved pattern can be attributed to the biomechanically optimal morphology for processing omnivorous diets, suggesting that the generalized morphology allows the exploitation of multiple food types with little morphological adjustments.