Dental ecomorphology, phylogeny and biogeography of Tapiridae (MAMMALIA, PERISSODACTYLA)

Abstract

Family Tapiridae (Mammalia, Perissodactyla) has been widely studied in the literature in the past decades. However, the taxonomy of the family showed numerous synonymies and several species were described based on dental and/or fragmented cranial remains. Previous works have shown how problematic it is, as teeth carry low phylogenetic information for Tapirus. This thesis aims to propose the usage for dental characters in ecomorphology inferences of seed dispersal for tapirs. This thesis also aimed to reassess the phylogeny, divergence times and morphological evolution of Tapiridae with changes to previous discrete morphological matrices, especially regarding a lesser usage of dental characters. In chapter 1, ordination and statistical results suggest that tooth shape is conservated between Tapirus species and that size is the main factor affecting variation. This evidence suggests that tooth shape alone is not reliable for distinguishing or describing tapir species. The occlusal surface area (OSA) of tapir cheek teeth as a predictor of seed dispersal potential pointed to South American tapirs being good seed dispersers. North American tapirs present variable OSAs, Asian tapirs have a low capacity for dispersion and all European tapirs were probably efficient seed dispersers. In chapter 2, we performed phylogenetic analyses including both discrete and quantitative 2D morphometric matrices. We used a larger number of cranial characters over teeth characters in the discrete matrix, and no dental characters were used in the quantitative matrix. The inclusion of 2D morphometric data in discrete morphological matrix seems not have significant impact on topologies. Genus Tapirus was recovered as monophyletic in our three phylogenetic hypotheses. North American tapirs are polyphyletic. South American tapirs form a clade. Tapiridae diverged at some point from the Middle Eocene to the Late Oligocene, in North America. Tapirus also originated in North America with divergence times ranging from the latest Oligocene/Early Miocene to the Late Miocene. DEC and DIVA biogeographic models available in the BioGeoBEARS package of R programming environment were applied to the three topologies. Tapirids dispersed at least two times from North America to Eurasia, as shown by biogeographic analysis. Tapirus dispersed from North America to Eurasia multiple times and to South America in a single event. Most of our biogeographic inferences are consistent with the presence of transient or permanent land bridges. This thesis represents the first phylogenetic hypothesis for tapirids including European Tapirus, along with the first formal biogeographic analysis for the family.