RESUMO
Although there is general consensus that sampling of multiple genetic loci is critical in accurate reconstruction of species trees, the exact numbers and the best types of molecular markers remain an open question. In particular, the phylogenetic utility of sex-linked loci is underexplored. Here, we sample all species and 70% of the named diversity of the New World wren genus Campylorhynchus using sequences from 23 loci, to evaluate the effects of linkage on efficiency in recovering a well-supported tree for the group. At a tree-wide level, we found that most loci supported fewer than half the possible clades and that sex-linked loci produced similar resolution to slower-coalescing autosomal markers, controlling for locus length. By contrast, we did find evidence that linkage affected the efficiency of recovery of individual relationships; as few as two sex-linked loci were necessary to resolve a selection of clades with long to medium subtending branches, whereas 4-6 autosomal loci were necessary to achieve comparable results. These results support an expanded role for sampling of the avian Z chromosome in phylogenetic studies, including target enrichment approaches. Our concatenated and species tree analyses represent significant improvements in our understanding of diversification in Campylorhynchus, and suggest a relatively complex scenario for its radiation across the Miocene/Pliocene boundary, with multiple invasions of South America.
Assuntos
Aves Canoras , Animais , Evolução Biológica , Cromossomos , DNA Mitocondrial , Filogenia , Análise de Sequência de DNARESUMO
Birds have a ZZ and ZW sex chromosome system (male and female, respectively). On the short arm of the Z chromosome of Gallus gallus domesticus there is a repetitive region called MHM region, which is absent on the W chromosome, that causes a natural copy number difference of the MHM region between the sexes, making possible the development of a quantitative PCR (qPCR) sexing assay, based on the Z chromosome double dose. Twenty-seven samples of tissues from eight adult Gallus gallus domesticus (four males and four females) were used to establish the parameters of the MHM copy-number sexing assay. We blinded sexed 20 chicks using 140 samples from different tissues (heart, brain, gonad, kidney, lung, muscle, and blood). The success rate of the assay was 100% (140/140). It required small amounts of DNA (0.39â¯ng), opening the perspective to the use of the assay in studies in which the amount of available DNA is limited.
Assuntos
Galinhas/genética , Análise para Determinação do Sexo/veterinária , Animais , Cromossomos/química , Variações do Número de Cópias de DNA , Feminino , Masculino , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Sequências Repetitivas de Ácido Nucleico , Caracteres Sexuais , Análise para Determinação do Sexo/métodosRESUMO
La ausencia de dimorfismo sexual en los estadios juveniles y durante la edad adulta de gran cantidad de especies de aves, dificulta o imposibilita la determinación del sexo basados en el fenotipo. El empleo de marcadores moleculares para determinar el sexo de las aves es una herramienta útil debido a la exactitud y rapidez de los resultados y a su vez se constituye en un método que minimiza el estrés durante la toma de muestra, comparado con otras técnicas invasivas que pudieran afectar la salud o estabilidad biológica del animal. La determinación temprana del sexo en aves resulta de especial relevancia cuando se consideran programas de conservación ex situ, producción, explotación y estudios de ecología de poblaciones. Esta revisión presenta las metodologías usadas para determinar el sexo, haciendo especial énfasis en herramientas moleculares, presentando sus ventajas y limitaciones.
The lack of sexual dimorphism in nestling, juvenile or adult birds of large number of avian species, makes it difficult or impossible sex determination based on phenotipic characteristics. To use molecular markers for bird sex determination is a rapid and safe procedure; moreover this methodology minimizes the stress during sampling, compared to other invasive techniques that could affect the health or biological stability of the animal. The early sex determination in birds is of particular importance when considering ex situ conservation programs, production, exploitation or population ecology studies. This review presents the methodologies used to sex determination, making emphasize on molecular tools, showing its advantages and limitations.