Genetic diversity of an undescribed cryptic maskray (Neotrygon sp.) species from Fiji

Abstract

Context The extinction risk of sharks and rays exceeds that of most other vertebrates. Genetic analyses can help identify conservation risks. Aims Identification of Fiji’s maskray and testing the null hypothesis of no genetic differentiation within the species over time. Methods Mitochondrial DNA cytochrome oxidase subunit 1 (COI) barcoding was used for species identification, and DArT-seq technology to monitor the genetic diversity. Cohort samples were collected in 2015 and 2022. A subset from each cohort was barcoded. The genetic survey was complemented by a size comparison between the two cohorts. Key results Barcoding of the COI gene showed a maximum similarity of 97.84% to Kuhl’s maskray (Neotrygon kuhlii) and 96.83% to the Coral Sea maskray (Neotrygon trigonoides), but no higher-level distinct species match to reference sequences in the Barcode of Life Datasystem. Genotyping of 56 individuals in two cohorts yielded 21,293 single nucleotide polymorphisms (SNPs), and 3871 SNPs per individual were retained. The neutral genetic diversity remained stable over time. The 2015 cohort showed positive inbreeding, with one full-sibling pair identified in each cohort. Body size comparisons indicated a significant reduction in disc length and width in the 2022 cohort. Conclusions The smaller body size of the 2022 cohort may hint at increased fishing pressure, but genetic diversity has not been affected. Thus, the null hypothesis is accepted. Implications These findings provide insights into the genetic diversity of Fiji’s maskray and enable a genetic comparison with current Neotrygon species known in the region. Taxonomy confirmation is needed, but the presence of a cryptic or potentially new maskray in Fiji seems plausible.