Morphological data, phylogenomics and recalcitrant nodes

In this paper we examine the relative contribution of information to nodes in a phylogenomic analysis combined with morphological datasets. We examine the behaviour of branch support metrics using the partitioned Bremer support (PBS) and its likelihood counterpart partitioned likelihood support (PLS). These metrics measure the contribution of a data partition to a node in question, and can be easily computed for likelihood and parsimony. Specifically, we assess the ratios of support values for morphological data to molecular data at this recalcitrant node. We find that there is a strong linear correlation between this ratio with the weight of the weaker partition where a flip (the flip weight) in topology ensues. This linear relationship allows us to estimate the amount of morphological data it will take to flip a phylogenomic hypothesis. For the datasets we use in this study flip weights are surprisingly small.