Geometric morphometrics reveal a potential hybridization zone in endemic species of Hypancistrus (Siluriformes: Loricariidae) from the lower and middle rio Xingu

Abstract

The Volta Grande do Xingu, one of the most important refuges of freshwater fish diversity in the Amazon, hosts a complex ecosystem where endemic species of Hypancistrus, such as H. zebra, H. seideli, and H. yudja, coexist sharing the same habitat. The drastic environmental changes caused by the construction of the Belo Monte Hydroelectric Plant and the severe droughts experienced in recent years, exacerbated by climate change, have fragmented their habitats and might be increasing contact between these three species. Using geometric morphometrics, this study reveals a concerning morphological overlap between H. seideli and H. yudja which indicates hybridization in impacted areas and threatens to dilute the unique genetic characteristics of these parental species. In contrast, H. zebra remained morphologically distinct, reinforcing its status as a highly vulnerable species. Hybridization poses a threat to the genetic integrity of the parent species and may accelerate the decline of already endangered species in this rapidly degrading environment. These findings are crucial for guiding conservation strategies and understanding the complex diversification processes in the rio Xingu.