Genomic diversity of the gastropod Littoria flava (King & Broderip, 1832) and study of gene flow patterns

Author(s)

Thainá Cortez Silva

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2020-07-24

Examining board members

Sonia Cristina da Silva Andrade; Gustavo Muniz Dias; Cristina Yumi Miyaki; Vera Nisaka Solferini

• Advisor: Sonia Cristina da Silva Andrade

Abstract

Seascape genetics has been dedicated to understanding how the movement of organisms affects populations connectivity. For species with planktonic larvae, this is not a trivial task, since trajectories and duration of larval stages are hardly predictable. Many of these groups often reveal little or no genetic differentiation among populations. However, recent studies have identified species presenting a strong genetic structure on both large and small spatial scales. This study aimed to understand the demographic processes and environmental factors shaping the population dynamics of a non-model organism. With this purpose, we used Genotyping-by-Sequencing (GBS) to obtain Single-Nucleotide-Polymorphisms (SNPs) markers and two mitochondrial genes (mtDNA) of Littoraria flava. The samples were collected from 11 locations distributed along the Brazilian coast, where in six horizontal transects were designed. The demographic history analysis using mtDNA suggested demographic expansion in the Sabiaguaba and Alagoas populations (Tajima\'s D = -1.665 and -1.174, respectively, p-value < 0.05). Based on 6,094 SNPs markers, three distinct clusters across the sampled populations (K = 3) were found. Additionally, a weak but significant genetic structure was detected for both sets of markers (mtDNA FST = 0.01353 and SNPs FST = 0.07675, p < 0.05). There were no signs of substructure among the sites within transects, diverging from previous results using allozymes. Most populations revealed heterozygote deficiency with high values of FIS. Despite the results that might reflect a gene flow according to a metapopulation model, other phenomena could produce the same patterns. The seascape genetic analyses indicated that predictors related to temperature and precipitation are potential preditors to cause local adaptation. Some loci containing candidate SNPs appear to be important functions on larval locomotion, sensory organs, sperm mobility and epithelial adhesion to the substrate. Despite the poor knowledge about these mechanisms in L. flava, considering their functional relevance, these traits could be under environmental selection and/or adaptation. (AU)

• FAPESP's process: 18/05118-3 - Genomic diversity of gastropod Littoraria flava (King & Broderip, 1832) and study of gene flow patterns
• Grantee: Thainá Cortez Silva
• Support Opportunities: Scholarships in Brazil - Master