Population genetic structure of the shark Squalus albicaudus (Chondrichthyes: Squaliformes) in the Atlantic ocean, based on genetic molecular markers

Author(s)

Aisni Mayumi Corrêa de Lima Adachi

• Document type: Master's Dissertation
• Press: Botucatu. 2022-03-04.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
• Defense date: 2022-01-28
• Advisor: Fausto Foresti

Abstract

Overfishing causes changes in the life strategy of populations of organisms, especially in relation to sharks and rays, organisms that make up the group of elasmobranchs. Thus, understanding the structure of populations becomes an important tool for the conservation and management of fish stocks. The genus Squalus (family Squalidae) is currently composed of 35 species of sharks that are popularly called dogfish. This genus constitutes one of the most taxonomically problematic groups of sharks due to the great morphological similarity between their species. Besides the fact in the Atlantic Ocean there are about 11 species of the genus Squalus; however, these species of this group have never had their populations analyzed in the Brazilian coast. As a result of these factors and the scarcity of data on the species Squalus albicadus that occurs in the Northeast and Southeast regions of Brazil, they are currently classified as “data deficient” on the IUCN Red List (International Union for Conservation of Nature). In this context, the main objective of the present study is to track SNPs (Single Nucleotide Polymorphism) markers to assess the genetic diversity and population structure of the species S. albicaudus occurring in the Northeast and Southeast regions of Brazil. A ddRADSeq library was generated from 31 samples of S. albicaudus obtained from coastal locations in Pernambuco (n=14), Rio de Janeiro (n=4) and São Paulo (n=13). Marker screening was performed after sequencing, and 455 SNPs were obtained. The genetic diversity indices were low for both observed and expected heterozygosity and the inbreeding coefficient (FIS) was negative in all analyzed locations, indicating an excess of heterozygotes; the pairwise FST ranged from 0.0365 (Rio de Janeiro x São Paulo) to 0.0157 (Pernambuco x São Paulo), demonstrating the absence of population structuring. The STRUCTURE and DAPC analyzes indicated that the individuals belong to a genetic grouping that are distributed in the same proportions among the localities and that they are related; and a high gene flow was detected between individuals, calculated by estimating the number of migrants. The effective population size (Ne) was low. In this first study to evaluate the genetic diversity and population structure of the species S. albicaudus, the results obtained show evidence of the occurrence of panmixia for the analyzed localities. Therefore, the information obtained is considered essential for the knowledge of the stock of this species, in addition to emphasizing the need for studies for proper management and conservation. (AU)

• FAPESP's process: 19/15148-0 - Biogeographic analysis of the shark Squalus cubensis (Chondrichthyes: Squaliformes) in the Atlantic Ocean, based on genetic markers
• Grantee: Aisni Mayumi Corrêa de Lima Adachi
• Support Opportunities: Scholarships in Brazil - Master