Evidence of fine-scale genetic structure for reef manta rays Mobula alfredi in New Caledonia

March 2022

Hugo Lassauce, Christine L. Dudgeon, Amelia J. Armstrong, Laurent Wantiez & Emma L. Carroll

Keywords: Genetic diversity • Population structure • Management • Conservation • Genome-wide single nucleotide polymorphisms • SNPs

Summary: Limited knowledge exists regarding the genetic connectivity and drivers of genetic structure in manta ray populations. This study examined the genetic diversity and structure of reef manta rays (Mobula alfredi) at local and regional scales using genome-wide single nucleotide polymorphisms (SNPs). Fine-scale genetic differentiation was observed among three cleaning station aggregation sites in New Caledonia, as well as population structure between New Caledonia and East Australia. The findings emphasise the importance of considering genetic structure when establishing conservation management units for reef manta rays.

Abstract

“Our understanding of the genetic connectivity of manta ray populations and the drivers that shape genetic structure is still limited. This information is crucial to identify the spatial boundaries of discrete populations and guide decisions on units to conserve. In this study, we use genome-wide single nucleotide polymorphisms (SNPs) to assess the genetic structure and diversity of reef manta rays Mobula alfredi at a local scale within New Caledonia and regionally in the western Pacific Ocean. We provide the first evidence of fine scale genetic differentiation in M. alfredi, found between the 3 cleaning station aggregation sites in New Caledonia (n = 65) (N = 2676 SNPs, FST = 0.01, p < 0.0001). Furthermore, population structure was evident at the regional scale between individuals from New Caledonia (NC, n = 73) and East Australia (EA, n = 19) on the basis of genetic differentiation statistics (3619 SNPs, FST = 0.096, p < 0.0001) and clustering algorithms, with unidirectional gene flow detected from east (NC) to west (EA). These results reveal that reef manta rays can form genetically distinct groups within a relatively small geographic range and highlights the need to consider genetic structure when designating management units for conservation action and planning.”

Author Affiliations

  • UMR ENTROPIE-IRD-UR-UNC-CNRS-IFREMER, University of New Caledonia

  • The Manta Trust

  • School of Biomedical Sciences, The University of Queensland

  • School of Biological Sciences, University of Auckland

Funded by

  • Aquarium des Lagons

  • Southern Province of New Caledonia Scholarship

  • Rutherford Discovery Fellowship from the Royal Society of New Zealand Te Apārangi

  • Keidanren Nature Conservation Fund (KNCF) through the SATO YAMA UMI Project and Conservation International

  • Australian Research Council