Emma Goldberg, a Los Alamos National Laboratory and New Mexico Consortium scientist, has recently published her work “Heterogeneity in the rate of molecular sequence evolution substantially impacts the accuracy of detecting shifts in diversification rates” in the science journal Evolution.
Lineage-splitting and extinctions in the tree of life have taken place often throughout the history of life. It is not a rare event. Scientists have long been interested in identifying which factors affect the rates that lineages evolve to become distinct species (speciate) or go extinct.
Biologists have spent many years developing methods where they look at species and their common ancestors. Their goal is to identify where there are shifts in diversification rates, or the rates at which new species form and living species go extinct. They then look at whether these shifts are associated with certain traits. By using these methods, theoretical biologists have predicted that speciation and extinction rates vary across the tree of life.
In this publication, Goldberg and colleagues show that “asymmetric rates of sequence evolution lead to systematic biases in the inferred phylogeny, which in turn lead to erroneous inferences regarding lineage diversification patterns. Their results demonstrate that as the asymmetry in sequence evolution rates increases, so does the tendency to select more complicated models that include the possibility of diversification rate shifts.”
The results from this study suggest that any conclusion previously reached concerning shifts in diversification pattern should be treated with great caution, at least until any biases in the molecular substitution rate have been ruled out.
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