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The genus Aeromonas Stanier 1943 (Martin-Carnahan and Joseph, 2005) is a Gammaproteobacteria (Proteobacteria, Bacteria) that comprises a group of Gram-negative, rod-shaped bacteria, which are autochthonous to aquatic environments worldwide and are usual microbiota (as well as primary or secondary pathogens) of fish, amphibians and other animals (Janda and Abbott, 2010). We used the divergence time of Escherichia coli and Salmonella enterica as the calibration point.
Molecular dating and macro evolutionary birth–death models were used to determine the temporal pattern of lineage diversification and significant changes in diversification rates were estimated using models with constant and variable diversification rates (Rabosky, 2006). Explosive evolutionary radiations: decreasing speciation or increasing extinction through time? doi: 10.1111/j.1558-5646.2008.00409.x Pub Med Abstract | Cross Ref Full Text | Google Scholar Retchless, A.
Following the publications of Zuckerkandl and Pauling (1965) and Kimura (1968), molecular dating has been based on the molecular clock hypothesis of a constant chronological rate of sequence change (Lemey and Posada, 2009).
More recently, several methods based on molecular sequence data have been developed to estimate speciation and extinction rates from phylogenies reconstructed from contemporary taxa.We also determined the constant of diversification (λ) values, which in all cases were very similar, about 0.01 species/Ma, a value clearly lower than those described for different eukaryotes. Prokaryotes are an essential and largely unnoticed component of the earth’s biota. The limited studies in this field have been mainly based on pathogenic bacteria, in which diversification rates seem not to be constant (Morlon et al., 2012). The main objective of this work is to determine the divergence time and the pattern of diversification of Aeromonas from phylogenetic data obtained applying Bayesian reconstructions. Controversially, the very few studies on free-living or symbiotic bacteria suggest a constant rate of diversification (Martin et al., 2004; Vinuesa et al., 2005). The phylogeny was constructed from the sequences of two housekeeping genes determined in 150 strains corresponding to the different species of this bacterial genus.
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Despite the importance of diversification rates in the study of prokaryote evolution, they have not been quantitatively assessed for the majority of microorganism taxa.