Banca de QUALIFICAÇÃO: MARSILIO SECUNDO PEREIRA DA ROCHA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : MARSILIO SECUNDO PEREIRA DA ROCHA
DATE: 24/03/2022
TIME: 09:00
LOCAL: Google meet: https://meet.google.com/vya-ygsp-jef
TITLE:

SEQUENTIAL PROCESSES OF CYTOGENOMIC DIVERGENCE IN DAMSELFISHES OF THE GENUS Stegastes Jenyns, 1840 (POMACENTRIDAE) FROM THE ATLANTIC: INTER AND INTRASPECIFIC VARIATION AND HYBRID ZONE ANALYSIS

KEY WORDS:

Fish cytogenetics, karyotype evolution, cytotaxonomy, pericentric inversion, rDNA.

PAGES: 58
BIG AREA: Ciências Biológicas
AREA: Genética
SUBÁREA: Genética Animal
SUMMARY:

The Pomacentridae (damselfishes) family is an extremely diverse and abundant group of fish in rocky areas and coral reefs in tropical and subtropical oceanic areas. In the Western South Atlantic there are four genera of which Stegastes is the most representative. Variations in coloration and overlapping meristic characters make the taxonomy of the species of the genus, in certain cases, uncertain. In this sense, the insular forms S. rocasensis, S. sanctipauli and S. fuscus trindadensis, have deserved attention regarding their taxonomic status and relationships with the coastal species S. fuscus and S. variabilis. Preliminary cytogenetic aspects of these species may range from cryptic to conspicuous. Population comparisons, definition of microstructural aspects of chromosomes, and inferences of post-zygotic blocks can help in the taxonomic definition and phylogenetic relationships of these species. Here, cytogenomic information is presented, through fluorescent in situ hybridization of rDNA sequences from most species of the genus Stegastes from the Atlantic coast of South America, including those from the São Pedro and São Paulo Archipelago, Fernando de Noronha and Trindade Island. Additionally, karyotypic patterns were investigated in a probable hybridization zone of S. fuscus and S. variabilis along the coast of Rio Grande do Norte, Northeast region of Brazil. The species presented 2n=48, with high NF values (88-90). Heterochromatin has a similar distribution, with conspicuous blocks in the centromeric and pericentromeric regions. The Ag-NORs loci are unique, except for S. variabilis, which presented multiple sites. The samples of S. rocasensis from the Fernando de Noronha and São Pedro and São Paulo Archipelagos (previously S. sanctipauli) have similar karyotypes and structural specificities such as a pair of chromosomes carrying colocalized 18S and 5S rDNA sites, corroborating the absence of cytogenetic divergence between them. S. fuscus from Trindade Island (S. fuscus trindadensis) showed a syntenic arrangement of adjacent 18S and 5S rDNA sites, in contrast to the population of S. fuscus from the coast, only non-syntenic sites, indicating a conspicuous variation that gives it an Evolutionarily Significant Unit (ESU) status. Cytogenetic patterns of samples of S. variabilis and S. fuscus in a possible hybrid zone, did not reveal intermediate karyotypes, suggesting a rare sporadic event and not maintained contemporaneously. The cytogenetic patterns of the species allow clear cytotaxonomic distinction at species levels and intraspecific categories (S. fuscus) and confirm a chromosomal evolution, numerically conserved, but predominantly modeled by multiple pericentric inversions throughout the evolutionary history of this genus.

BANKING MEMBERS:
Externo à Instituição - GIDEÃO WAGNER WERNECK FELIX DA COSTA
Externa à Instituição - KARLLA DANIELLE JORGE AMORIM
Presidente - 1199139 - WAGNER FRANCO MOLINA