Morphological v. MolecularThis year we learned about two kinds of phylogenetic trees. Originally scientists based the organization of this tree on morphological and developmental data. However, new molecular data such as DNA sequences have provided another source of information in order to determine common ancestry. What similarities or agreements exist between morphological and molecular trees? How are they different?

Coyne brings up the point that certain groups of organisms are considered to be separate species even though they look exactly alike. For example, the group of fruit flies, Drosophila, is recognized as nine separate species due to differences in where they live and who they bite. Conversely, there are groups like humans that look very different, yet still have the ability to successfully mate together and are considered the same species. This brings up the question on whether or not "designation of species is an arbitrary exercise" or not (171). Therefore, what advantages are there to organizing the species into phylogenetic trees even through there are obvious inconsistencies and debates within the system?
Morphological characters were initially chosen based on observations of collected materials and a general search of appropriate literature. Slides of whole leaves, leaf cross-sections, and stem cross-sections mounted in Hoyer's solution were prepared for each semaphoront. The same samples used in the molecular analyses were scored. Quantitative characters were measured a minimum of five times (from different leaves or cells), and an average of the measurements was used for the final character analysis. Quantitative characters (e.g. cell numbers, leaf dimensions) were plotted to scan for the presence of discrete breaks in the character states and/or to conduct analyses of variances. Characters that were (a) difficult to homologize across numerous taxa, (b) invariant among the taxa included or (c) impossible to discretize into character states (continuously variable quantitative characters) were eliminated.