Connectivity of Neotropical River Basins in the Central Guiana Shield Based on Fish Distributions

Abstract

The Guiana Shield in northeastern South America contains some of the largest tracts of intact forests on the globe. Guyana alone has more than 80% forest cover. In south-central Guyana a unique biogeographic feature allows for a hydrological connection between the Guiana Shield with the Amazon basin via the Rupununi savannas and wetlands (Rupununi Portal). This corridor allows for connectivity between two of the most biodiverse, carbon rich, and intact forests in the world. The significance of this (and other) hydrological corridors for terrestrial and aquatic species is underappreciated in the scientific literature. We attempt to determine the importance of the surrounding mosaic of habitats that influence fish assemblages in the Rupununi Portal. We extensively sampled fishes in this corridor over six expeditions. Multivariate analyses revealed significant trends in fish assemblage structure and environmental conditions. We found high species richness and diversity within the Takutu (Amazon River drainage) and Rupununi rivers (Essequibo River drainage). Fish assemblages were found to be most similar within the specific river drainages with some similarity within forest and savanna sites. A second Rupununi portal was revealed in the South Rupununi, at the upper Rupununi and Takutu Rivers. Ordination analyses found water body type, vegetation and water chemistry to be significantly structuring the fish assemblages of the Rupununi. Our study reveals the interdependent nature of the various habitats in the Rupununi that facilitate high biodiversity and maintain the ecosystem. With the increase in human activity in this region, and the increased connectivity of the region with the rest of the world through better roads, this area is in danger of being modified and fragmented to a point where ecosystem services begin to fail. We recommend demarcating a protected area in the region that considers the diversity of associated habitats and the importance of the ecological portal joining two diverse river basins.

Biogeography of the neotropical freshwater stingrays (Myliobatiformes: Potamotrygoninae) reveals effects of continent‐scale paleogeographic change and drainage evolution

“…The close relationships between Branco, Essequibo, and Guiana Shield taxa recovered for the Pliocene and Pleistocene can be explained by intermittent river connections between the lower portions of these drainages (as discussed in Lima, 2017); alternatively, these patterns could be related to headwater capture events between the Branco and the proto‐Berbice (a large drainage system from the central Guiana Shield that drained most of the Guyana and parts of Brazil, Venezuela, and Surinam from the Cenozoic to the Pleistocene – see Sinha, 1968; Lujan & Armbruster, 2011; Schaefer & Vale Júnior, 1997). Pleistocene and younger interactions between the Branco and Essequibo basins can be attributed to the Rupununi Portal, a flooded savanna area that allows for seasonal faunal interchange between these basins (De Souza et al, 2012, 2020; Hubert & Renno, 2006; Lovejoy & Araújo, 2000).…”

Biogeographic reconstruction of the migratory Neotropical fish family Prochilodontidae (Teleostei: Characiformes)

“…the Prone‐8 hypothesis of Lujan & Armbruster, 2011). Alternatively, the lineage may have dispersed from Proto‐Berbice to the central Amazon basin and then to north‐eastern Brazil, using corridors resembling those connecting the modern Branco and Essequibo basins (Fontenelle et al, 2021; Lujan & Armbruster, 2011; de Souza et al, 2020).…”

Utilization of species checklist data in revealing the spatial distribution of fish diversity

“…Multivariate statistical analyses can reveal significant trends in fish assemblage structure and environmental conditions (de Souza et al ., 2020). Multivariate analysis, including hierarchical cluster and MDS, determined relationships among the six fish assemblages in the present study.…”