( o as a subject are limited. There...)Biologists call for better choice of model organisms in 'evo-devo'

"There are upwards of 35 phyla of animals, and four of our six best models come from just one phylum.

"However, that doesn’t mean that simply choosing new models to plug holes in the phylogenetic tree is the best option for further progress in evo-devo."

Dr Jenner added: "The popular advice of choosing new model organisms to maximise phylogenetic spread is nice to show diversity, but it doesn’t necessarily lead to new general insights about evolution.

"Choosing new models in this way leaves it entirely a matter of chance whether a new model will illuminate a particular evo-devo theme.

"Instead, we urge workers to select new models specifically to illuminate hitherto neglected general themes within evo-devo.".

In other cases, new model organisms are chosen on the basis of how well they are thought to represent a particular ancestral organism. In connection to this practice, the researchers point to ‘basal bias?as another way that scientists may get it wrong when choosing new model organisms.

This occurs when scientists choose an organism because it was the first to branch off from its ancestor, rather than because it has known genetic or developmental similarities to it.

"We caution against this widely used rule of thumb, and advise the use of additional criteria, such as molecular branch lengths, to choose species as best representatives of ancestral body plans," said Dr Jenner.

"Just because an organism has sprung from the base of the evolutionary tree does not make it more primitive and representative.

"Equally, those that became separate species further down the evolutionary line are not necessarily increasingly different from that common ancestor.

"Among living species that descended from a particular common ancestor, those designated as ‘basal?are those that are separated from this ancestor by the smallest number of speci
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Source:University of Bath