Reassessing Genetic Diversity of the Endangered <scp> <i>Brycon insignis</i> </scp> (Characiformes): A Landscape Perspective After a Decade of Environmental Disturbances

ABSTRACT Landscape genetics has emerged as a useful approach for inferring how environmental changes impact genetic variation and population structure within species. Brycon insignis , commonly known as piabanha or Tiete tetra, is a fish species endemic to the Paraíba do Sul basin in southeastern Brazil. Unfortunately, its population has declined over recent decades, and it is currently listed as Endangered in red books maintained by Brazil and the IUCN. We assessed the current genetic diversity of the four remaining populations of B. insignis in the region using microsatellite DNA loci and compared this to results of an assessment conducted over a decade ago. Our goal was to evaluate the current genetic status of these wild populations and assess how environmental changes relate to changes in genetic diversity over time. The respective populations remain notably distinct genetically ( D EST = 0.34, F ST = 0.07), and comparison of results from 2009 and the present shows significant loss of genetic diversity within populations. The genetic structuring observed in the B. insignis populations may be attributable to environmental changes and demographic isolation. Additionally, decreased genetic variation may jeopardize the long‐term viability of the isolated populations, in turn threatening the viability of the species. Our findings examined the effects of ongoing habitat degradation within the context of existing riverscape fragmentation and highlighted the loss of genetic diversity as a key response variable in landscape genetic models.