Unravelling the past of cervid populations on the Pearl Island Archipelago (Panama) through a two dimensional geometric morphometric analysis of the lower third molar

Abstract

This study investigates the evolutionary and morphological divergence of Neotropical cervids across mainland and island populations, integrating size, shape, and ecological data. Three extant cervid species were analyzed: Mazama temama, Odocoileus virginianus, and Passalites nemorivagus, San José Island cervids, alongside extinct archaeological samples from Playa don Bernardo (PdB) on Pedro Gonzalez Island from Pearl Island Archipelago (Central Pacific, Panama). Morphometric analyses of lower third molars (m3) revealed distinct evolutionary trajectories shaped by geographic and ecological isolation. Centroid size analyses reveal significant interspecies differences, with O. virginianus being generally larger than other groups, while PdB cervids exhibit reduced sizes potentially linked to insular dwarfism. Shape analyses, including PCA and Procrustes ANOVA, demonstrate distinct morphological patterns among species, with P. nemorivagus showing unique traits, while PdB cervids cluster closely with O. virginianus and San José Island cervids. Canonical variate analysis (CVA) and phenotypic trees corroborate these relationships, highlighting evolutionary divergence influenced by ecological pressures. Statistical tests reveal significant species-level effects on size and shape, with minimal contributions from sex or species-sex interactions. Procrustes distance comparisons emphasize substantial morphological divergence between P. nemorivagus and other groups, while PdB cervids share closer morphological affinities with San José Island cervids and O. virginianus. These findings suggest a complex evolutionary history shaped by environmental constraints and isolation, underscoring the role of insular environments in driving morphological diversity among Neotropical cervids.