Jaw Morpho-Functional Diversity, Trophic Ecology, and Historical Biogeography of the Neotropical Suckermouth Armored Catfishes (Siluriformes, Loricariidae)

Abstract

Tropical South America is renowned for its unparalleled biodiversity. Among vertebrates, fish diversity exceeds that of any other group. Estimates of total Neotropical fish richness range between 5000 and 8000 species, of which approximately 3600 (45–72%) are currently described; and of described species, nearly 20% (>700 spp.) are catfishes in the Neotropical-endemic family Loricariidae. Loricariid catfishes, popularly known as plecos in the aquarium trade, are distinguished by their armor plating, ventral oral disk, and highly derived jaw structure and function. Loricariids have likely existed in South American rivers in close to their modern form since at least the Late Cretaceous, and they are part of a superfamilial lineage (Loricarioidea) that is sister to all other catfishes, and has likely inhabited South American rivers since well into the Early Cretaceous. Today, loricariids have radiated to consume a variety of basal food resources including algae, detritus, seeds, sponges, insects, and even wood, the surface layers of which are gouged into by specialized taxa having hypertrophied jaw muscles and teeth shaped like adzes. In this dissertation, I attempt to fill major gaps in the knowledge of loricariid taxonomy, jaw morphological and functional diversity, trophic ecological structure, and historical biogeography. My taxonomic research has resulted in the discovery and/or description of dozens of new loricariid species and at least three new genera. Published results of this work are summarized in Appendix I. In chapter two of this dissertation, I describe jaw morpho-functional diversity across a diverse assemblage of 25 species, 12 genera, five tribes, and two subfamilies of loricariids from the upper Amazon Basin in Northern Peru. In chapter three, I describe gross aspects of loricariid assemblage trophic structure as revealed by carbon and nitrogen isotope data from 19 loricariid assemblages ranging in species richness from two to 16 species, and geographically broadly distributed across northern South America. In chapter 4, I review the geological and hydrological history of the Guiana Shield, a highly biodiverse and geologically ancient region of northern South America which shelters a broad range of basal and derived loricariid lineages. From these studies, it is clear that tremendous loricariid diversity accumulated in the Neotropics gradually over tens of millions of years and across a broad geographic range, and that their novel oral morphology has likely been key to their diversification across a variety of basal resources consumed almost exclusively by invertebrate faunas at more temperate latitudes.