First evidence of polyandry for amazonian stingray (Potamotrygon wallacei Carvalho, Rosa & Araújo 2016) based on genome-wide SNP data

The Amazonian freshwater stingray Potamotrygon wallacei, endemic to the Rio Negro basin, although heavily exploited in ornamental fish trade, is largely neglected in terms of basic biology, including its reproductive system. Polyandry is a widespread reproductive strategy in elasmobranchs, however, evidence from freshwater potamotrygonids is scarce. To address this knowledge gap, the present study developed highly polymorphic single nucleotide polymorphism (SNP) genomic markers for P. wallacei and applied them to investigate kinship patterns in wild-caught gravid females and their litters. This study used genomic polymorphic SNP markers in 18 individuals from five family groups to assess kinship patterns. The average gene diversity was low, however, He (0.435–0.476) and Ho (0.530–0.653) were higher, with Ho > He, suggesting small-sample bias or heterozygote excess from family-level sampling. Polyandry was detected in three families, while two families exhibited monogamy. This molecular approach allowed the discovery of polyandry in P. wallacei, providing novel insights into its reproductive biology and contributing to broader understanding of mating system evolution in Neotropical freshwater elasmobranchs.