Assessing ichthyofauna diversity and the potential response to climatic change in the Orinoco basin in Colombia.

This project aims to describe the diversity of freshwater fishes in the Orinoco River basin, specifically in its piedmont and llanos region, evaluating species endemism (including the description of new ones), phylogeographic patterns, and the ability of fish populations to adapt to arid conditions and hypoxic aquatic environments. There are 6,255 known freshwater Neotropical fishes, more than a thousand of these in the Orinoco basin. However, knowledge on regional patterns of diversity, particularly from this region, is scarce. Recent surveys in the Orinoco River basin have shown high species richness, culminating in the description of several new taxa. The Orinoco River Basin shows a heterogeneous spatial scenario flowing from the humid Andean foothills to the seasonally wet-dry Llanos. In terms of species distribution, it shows a south-north gradient with tributaries in the south (e.g., Guaviare basin) being distinct from the northern tributaries (e.g., Meta basin). This gradient affects species distribution and might potentially affect phenotypes and genetic diversity between populations. Fishes in this region are threatened by agriculture and cattle ranching development and highly susceptible to threats associated with climate change (e.g., warmer, and drier climates in the future), given their limited dispersal capabilities restricted to riverine connections. Because of it, here we also proposed to evaluate phenotypic and genetic responses to drier environments, to clarify if local adaptation to dryer climates is possible. For that, we will examine species in the Llanos that evolved morphological adaptions to hypoxia ¿ a condition commonly found in the region during the dry season. By combining high-resolution data on species diversity and how adaptive processes may contribute to the population¿s persistence, in this project, we will be able to understand how the ichthyofauna differ along the Orinoco tributaries, unveil unknown diversity and, show how freshwater species can potentially cope with future drier climates.