re: Adding Taxa

A new phylogenetic study by Wiens and Tiu (2012) concluded: “We show that adding taxa that are highly incomplete can improve phylogenetic accuracy in cases where analyses are misled by limited taxon sampling. These surprising empirical results confirm those from simulations, and show that the benefits of adding taxa may be obtained with unexpectedly small amounts of data. These findings have important implications for the debate on sampling taxa versus characters, and for studies attempting to resolve difficult phylogenetic problems.”

Nice to hear. I agree.
All three of my trees (reptiles, pterosaurs and basal therapsids) include incomplete taxa. Some with skulls. Some without. Some just bits and pieces. Most, however, are complete. It’s important to include odd and incomplete taxa, just to know where they belong. Problems come when skull only taxa nest with skull-less taxa. Even so, that can be overcome with complete sisters.

Interestingly:
The Wiens and Tiu (2012) study found turtles closer to archosaurs than lizards with mammals the outgroup. Not sure why turtle DNA is closer to archosaurs when their morphology says otherwise. And I wonder why mammal DNA doesn’t nest closer to archosaurs when their morphology says otherwise. Bottom line: the morphology has to support the DNA and vice versa. Since prehistoric taxa will never give us DNA, we’re stuck with morphology, so long as a sufficient number of taxa are included. The more the better. 500+ taxa is not a bad start.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Wiens JJ, Tiu J 2012. Highly Incomplete Taxa Can Rescue Phylogenetic Analyses from the Negative Impacts of Limited Taxon Sampling. PLoS ONE 7(8): e42925. doi:10.1371/journal.pone.0042925

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