Population structure and genetic diversity of the Critically Endangered bowmouth guitarfish (Rhina ancylostomus) in the Northwest Indian Ocean
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Abstract
The bowmouth guitarfish ( Rhina ancylostomus ) is a unique and understudied species of wedgefish with a distribution spanning the Indo-Pacific Oceans. Due to targeted and bycatch fisheries, this species is experiencing serious declines across its range. It is now considered among the most threatened species of elasmobranch. Despite this, species-specific management is limited, particularly around primary fishing hotspots. This is in part due to knowing very little about fundamental population processes. Here, we combine mitochondrial and single nucleotide polymorphism (SNP) data to carry out the first genetic assessment of R. ancylostomus across the Northwest Indian Ocean. We detect genetic differentiation across the northwest range, shaped by both oceanographic barriers and intrinsic dispersal constraints, and uncover a cline in genetic variation from east to west. These findings emphasise the importance of maintaining habitat connectivity while also identifying regions that may require heightened protection. In doing so, our study provides a critical baseline for conservation planning of R. ancylostomus and highlights the value of genomic data in elasmobranch conservation.
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Chondrichthyan fishes (sharks, rays, and chimaeras) are among the most endangered taxa on Earth. Most species exhibit life-history traits that make them particularly sensitive to both direct and indirect human impacts, especially fisheries (Jabado et al. 2024). In this context, genomic data can provide crucial insights into population structure and historical and current connectivity among populations, thereby informing conservation strategies. Increasing genomic research would also enhance our understanding of shark, ray, and chimaera diversity, including the identification of cryptic species and or subspecies.
In this study, Kipperman et al. (2025) investigate the population structure of the bowmouth guitarfish (Rhina ancylostomus), an endangered species in the understudied family Rhinobatidae. This represents the first analysis of …
Chondrichthyan fishes (sharks, rays, and chimaeras) are among the most endangered taxa on Earth. Most species exhibit life-history traits that make them particularly sensitive to both direct and indirect human impacts, especially fisheries (Jabado et al. 2024). In this context, genomic data can provide crucial insights into population structure and historical and current connectivity among populations, thereby informing conservation strategies. Increasing genomic research would also enhance our understanding of shark, ray, and chimaera diversity, including the identification of cryptic species and or subspecies.
In this study, Kipperman et al. (2025) investigate the population structure of the bowmouth guitarfish (Rhina ancylostomus), an endangered species in the understudied family Rhinobatidae. This represents the first analysis of population structure in this species. The authors combine over 3,000 nuclear SNPs, obtained using a restriction enzyme reduction-based DNA sequencing strategy, with mitochondrial data from 70 samples across six populations in the Northwest Indian Ocean. Their results reveal significant population structure driven by isolation-by-distance between eastern and western populations across most of the species' range, from Saudi Arabia to Taiwan. These findings highlight limited connectivity among populations and demonstrate the species' low dispersal capacity.
Further analyses of genetic diversity show that populations in eastern Saudi Arabia and Oman have significantly lower genetic diversity than those in the eastern part of the species’ range. The authors hypothesize that this pattern results from a westward colonization of the species from the Indo-Malayan archipelago.
The study has a few minor limitations, including unbalanced and incomplete sampling across the species’ range and a lack of detailed description of the SNP sequencing and bioinformatics pipeline, which is based on proprietary protocols. The absence of a reference genome is also a drawback. However, all these limitations are transparently acknowledged and discussed in the manuscript. Moreover, they do not undermine the robust analyses in the manuscript.
Kipperman and collaborators’ study provides important insights into the genetic structure of a critically endangered guitarfish species. Well-designed analyses such as this are essential for improving our knowledge of chondrichthyan population structures.
References
Jabado, R.W., Morata, A.Z.A., Bennett, R.H., Finucci, B., Ellis, J.R., Fowler, S.L., Grant, M.I., Barbosa Martins, A.P., & Sinclair, S.L. (eds.) (2024). The global status of sharks, rays, and chimaeras. Gland, Switzerland: IUCN https://doi.org/10.59216/ssg.gsrsrc.2024
Marja J. Kipperman, Rima W. Jabado, Alifa Bintha Haque, Daniel Fernando, P A D L Anjani, Julia LY Spaet, Emily Humble (2025) Population structure and genetic diversity of the Critically Endangered bowmouth guitarfish (Rhina ancylostomus) in the Northwest Indian Ocean. bioRxiv, ver.2 peer-reviewed and recommended by PCI Evolutionary Biology https://doi.org/10.1101/2024.03.15.585225
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