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Examining differences among recently diverged populations can provide insight into the traits and evolutionary mechanisms that drive or maintain divergence. The genus Sturnella includes 2 recently diverged species, Sturnella magna (Eastern Meadowlark) and S. neglecta (Western Meadowlark), the former of which has a complex of subspecies distributed across the Americas. Of the S. magna subspecies that occur in the United States, S. m. lilianae is the only one with a disjunct range, occurring in the southwestern United States and central Mexico. It also has markedly different song patterns than all other S. magna subspecies. In order to assess population differentiation, we performed whole-genome sequencing of 35 birds and analyzed song characteristics from 85 birds. Songs from each species and S. m. lilianae were diagnosable using linear discriminant function analysis and support divergence in song between all taxa. Phylogenetic analysis and admixture proportions support 3 distinct clades within North American meadowlarks, and tests of introgression failed to detect a significant signal. Overall, our results indicate that S. m. lilianae exhibits high levels of genetic and vocal differentiation from both S. magna and S. neglecta, with no evidence of introgression between any group, and forms a distinct evolutionary lineage. We thus recommend the elevation of S. m. lilianae to species status. [ABSTRACT FROM AUTHOR]

Since its discovery by the physician Alexander Ogston in 1880, Staphylococcus aureus is considered a pathogen with high potential to cause multiple infections in humans and animals. S. aureus is the type species of the group, considered the most virulent, responsible for a wide spectrum of diseases, ranging from infections of the skin and soft tissues to severe life threatening infections. The impact of S. aureus strains on health is the resistance to multiple antibiotics that may occur, especially to methicillin. Through the years, the rate of morbidity and mortality has increased despite the large number of antibiotics available in the world. S. aureus is part of the normal human flora, between 25 and 50% of the healthy population is colonized by the bacteria, being a risk for dissemination. This can be acquired through contact with other people or by environmental exposure. In recent years, infections with this microorganism has increased significantly, particularly by S. aureus strains resistant to methicillin. The Center for Infectious Diseases estimated that in the U.S. in 2005, there were 94,360 invasive infections caused by methicillin-resistant S. aureus. However, in recent years there has been a steady increase in infections caused by strains of methicillin-resistant S. aureus, with a different sensitivity to antibiotics affecting the healthy population without having prior contact with hospitals or health clinics. These infections, caused by methicillin resistant S. aureus acquired in the community, can develop various diseases, being the most common skin and soft tissues infections. Molecular epidemiology studies are very important because they have enabled us to understand the evolutionary relationships among strains, as well as know the origin of the clones during outbreaks. [ABSTRACT FROM AUTHOR]