A Hotspot Atop: Rivers of the Guyana Highlands Hold High Diversity of Endemic Pencil Catfish

The Pakaraima Mountains are an ancient mountain range along the borders of Guyana, Brazil and Venezuela. The high plateau is drained by multiple river systems in all directions. Although hypotheses have been presented for the biogeographical relationships of lowland rivers, the interconnectivity of rivers on the top of the plateau is unknown. With multiple complex rivers in a small, upland area, we predicted a high level of endemism for stream fishes and complex biogeographical relationships. We explored this with the incredibly diverse pencil catfish genus Trichomycterus. Using collections from recent expeditions to the Pakaraima Mountains of Guyana, we amplified three mitochondrial (16S, COI and Cytb) and one nuclear marker (rag2). We constructed individual gene trees and a concatenated tree to determine the placement of these taxa within the Trichomycterus of the trans-Andean/Amazonian clade. Herein, we identify six endemic lineages of Trichomycterus from the highlands of the Pakaraima Mountains. Of the identified lineages, we find two species occupying multiple basins, suggesting that Pakaraima streams either maintain connectivity or had some degree of recent connectivity.