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Background and Aims Species delimitation can be challenging when analysing recently diverged species, especially those taxonomically synonymized owing to morphological similarities. We aimed to untangle the relationships between two grassland species, Petunia guarapuavensis and Petunia scheideana , exploring the dynamics of fast divergence and addressing their species delimitation. Methods We used a low-coverage genome sequencing and population genomic approach to distinguish species and populations between P. guarapuavensis and P. scheideana. Our analysis focused on detecting structuration, hybridization/introgression and phylogenetic patterns. We used demographic models to support species delimitation while exploring potential phylogeographical barriers influencing gene flow. Key Results Our findings indicated differentiation between the two species and revealed another lineage, which was phylogenetically distinct from the others and had no evidence of gene flow with them. The presence of a river acted as a phylogeographical barrier, limiting gene flow and allowing for structuration between closely related lineages. The optimal species delimitation scenario involved secondary contact between well-established lineages. Conclusions The rapid divergence observed in these Petunia species explains the lack of significant morphological differences, because floral diagnostic traits in species sharing pollinators tend to evolve more slowly. This study highlights the complexity of species delimitation in recently diverged groups and emphasizes the importance of genomic approaches in understanding evolutionary relationships and speciation dynamics. [ABSTRACT FROM AUTHOR]

Closely related and young species often show high morphological similarity, challenging their identification and correct assignment. Molecular markers and integrative approaches have contributed to solving many taxonomic uncertainties. In this study, we evaluated the genetic variability and ecological features of Petunia guarapuavensis and Petunia scheideana , over which there is a taxonomic debate. Both species are endemic and rare, distributed in the subtropical highland grasslands in southern South America. We based our analyses on nuclear microsatellite and plastid sequences, aiming to disentangle the taxonomic ambiguities that made some consider these entities synonymous despite occupying different clades in the genus phylogenetic tree. Our findings support that there is genetic differentiation between these species, suggesting that they are independent taxonomic entities despite sharing floral traits and a few molecular polymorphisms. The low genetic sharing between the species is likely due to a common ancestor and recent divergence time. In contrast, their morphological similarity can be attributed to the absence of selective pressure, as both grow under similar ecological conditions. This study emphasizes that adding more than one sequence per species, combining data with dissimilar inheritance patterns, and exploring data through different methodologies help to disentangle taxonomic incongruences and reveal diversity that might otherwise remain hidden. [ABSTRACT FROM AUTHOR]

Several technological approaches have been used to develop vaccines against COVID-19, including those based on inactivated viruses, viral vectors, and mRNA. This study aimed to monitor the maintenance of anti-SARS-CoV-2 antibodies in individuals from Brazil according to the primary vaccination regimen, as follows: BNT162b2 (group 1; 22) and ChAdOx1 (group 2; 18). Everyone received BNT162b2 in the first booster while in the second booster CoronaVac, Ad26.COV2.S, or BNT162b2. Blood samples were collected from 2021 to 2023 to analyze specific RBD (ELISA) and neutralizing antibodies (PRNT50). We observed a progressive increase in anti-RBD and neutralizing antibodies in each subsequent dose, remaining at high titers until the end of follow-up. Group 1 had higher anti-RBD antibody titers than group 2 after beginning the primary regimen, with significant differences after the 2nd and 3rd doses. Group 2 showed a more expressive increase after the first booster with BNT162B2 (heterologous booster). Group 2 also presented high levels of neutralizing antibodies against the Gamma and Delta variants until five months after the second booster. In conclusion, the circulating levels of anti-RBD and neutralizing antibodies against the two variants of SARS-CoV-2 were durable even five months after the 4th dose, suggesting that periodic booster vaccinations (homologous or heterologous) induced long-lasting immunity. [ABSTRACT FROM AUTHOR]

The species A rotaviruses (RVA) are important gastroenteric pathogens that infect humans and animals. RVA genotype G3P[9] has been described in human-animal reassortment events, and the complexity of its hosts motivates the genetic investigation of this strain. Therefore, the aim of this study is to analyse a G3P[9] sample that was detected in a child with acute gastroenteritis. The 1A3739 sample featured the constellation G3P[9]-I18-R3-C3-Mx-A19-N3-T3-E3-H6. The sequence for VP3 gene was not obtained. The phylogeny showed a closer relationship among genes VP7, VP1, NSP3, NSP4, and NSP5 with genes of animal origin, such as chiropter, alpaca, equine, and simian. In addition, the genes VP6 and NSP1 belong to the new genotypes I18 and A19, respectively. The emergence of strains such as these can interfere with the effectiveness of the RVA vaccine, and continuous monitoring is therefore important. Additional studies are needed to determine the evolutionary source and to identify a possible reservoir of RVA in nature. [ABSTRACT FROM AUTHOR]