IMAGING, MORPHOLOGICAL KNOWLEDGE OF SPECIES, AND PHYLOGENY RECONSTRUCTION: A CASE STUDY IN PLIOMERID TRILOBITES
Simulations have shown that phylogenetic accuracy and resolution are reduced by inability to code characters for all taxa, not just the percentage of missing entries in any incomplete taxa. This is borne out in our analyses. Our primary dataset includes 29 species coded for 69 characters, from our photographs of specimens we collected at the type localities. Most characters are coded for all taxa. A second dataset consists of the 20 species now known to be represented in the literature (even if unrecognized at the time) coded only from the original illustrations. Dataset 2 is incomplete due to species that were known from few exoskeletal elements, or because the original illustrations did not show all relevant morphology. 25 uncodable or autapomorphic characters were removed from it. It contains no characters coded for all taxa. We analyzed both datasets using parsimony.
Analysis of Dataset 1 resulted in six well resolved, well supported trees (CI 0.64, RI 0.89, average GC bootstrap support of 74.6). Analysis of Dataset 2 resulted in nearly 1500 poorly resolved, poorly supported trees (CI 0.77, RI 0.88, average GC support of 35.2). The strict consenses reflect similar broad relationships between genera, but the low resolution of the second analysis obscures relationships within genera. These preliminary data suggest that much greater species-level phylogenetic precision is possible with wider application of modern imaging techniques.