Nemertopsis bivittata (Hoplonemertea), Lineus sanguineus (Heteronemertea) e Perinereis ponteni (Polychaeta): validity of species, gene flow and genetic diversity on Brazilian coast

Author(s)

Cecili Barrozo Mendes

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2022-03-30

Examining board members

Sonia Cristina da Silva Andrade; Federico David Brown Almeida; Karina Lucas da Silva Brandão; Paulo Cesar de Paiva

• Advisor: Sonia Cristina da Silva Andrade; Cinthya Simone Gomes Santos

Abstract

Understanding the main factors influencing connectivity among marine animal populations has been the subject of several studies for decades, with the mobility of individuals being recognized as one of the determining factors. Species with long larval development (e.g. planktotrophic) usually have better connected populations than species with direct or short larval development (e.g. lecithotrophic), due to their greater dispersal capacity. However, other bionomic features and the environment also have a major influence on connectivity. In addition, the perception of population connectivity can also be affected by the presence of cryptic species, since such species can have extreme morphological similarity. Thus, the present work evaluated how environmental heterogeneity influences the connectivity of species with different reproductive modes, through comparative landscape genomics techniques. For this purpose, we used the species Perinereis ponteni (Polychaeta, with sexual reproduction and lecithotrophic larvae), Lineus sanguineus (Heteronemertea, with asexual and sexual reproduction, and lecithotrophic larvae) and Nemertopsis bivittata (Hoplonemertea, with sexual reproduction, and presumably planktotrophic larvae). In order to guarantee the monophyly of all species, the populations studied were taxonomically assessed. In this sense, we sampled populations along the Brazilian coast. The collected animals were used in DNA extraction for SNPs prospection, using the Genotyping by Sequencing (GBS) technique. Furthermore, we followed the behavior and larval development of the hoplonemertean Emplectonema viride as a proxy for the development of N. bivittata, since both are from the Emplectonematidae family and live in extremely similar environments. However, the species N. bivittata is actually a complex of species, with three distinct evolutionary units on the Brazilian coast. These were described as, Nemertopsis berthalutzae, Nemertopsis pamelaroeae and Nemertopsis caete, the latter being present only on the coast of Alagoas. The observation of E. viride larval development indicated the presence of planktotrophic larvae, with long development, taking an average of 120 days for quite subtle metamorphosis (noticed mainly by changes in ciliation and behavior). The larvae feed primarily on barnacle nauplius and cyprids. Our palaeodistribution and demography analyzes indicate the presence of a refuge in the Southeast region during the Last Glacial Maximum, from where the populations expanded. As for landscape genomic analyses, we observed that species with shorter larval development tend to have more structured populations, but still with significant gene flow. However, similar environmental factors affect connectivity in all species, with temperature and precipitation being the most common. These factors are associated with the presence of SNPs candidates for natural selection in three of the four species studied. These findings reinforces how important local and global environmental conditions are for animal connectivity and, therefore, for the genetic diversity of species. (AU)

• FAPESP's process: 16/20005-5 - Nemertopsis bivittata (Nemertea) e Perinereis ponteni (Polychaeta:Annelida): validity of species, gene flow and genetic diversity on Brazilian coast
• Grantee: Cecili Barrozo Mendes
• Support Opportunities: Scholarships in Brazil - Doctorate