Lydia Morley, University of Utah
In evolutionary/systematic biology, phylogenetic reconstruction relies on hypotheses gleaned from historical (usually fossil/ paleontological), morphological, or molecular data—compounded and analyzed by various statistical or logical methods that are intended to yield the most accurate evolutionary tree based on the data entered. Phylogenetic discordance usually occurs when different genetic data generate competing evolutionary hypotheses; or it is uncertain which, of all espoused, is the true phylogeny. Discordance is philosophically interesting because it can, in certain cases, pull apart justificatory sources concerning alternative analytical methods—especially in cases where the same data and evolutionary parameters are assumed, but discordant phylogenies nonetheless result. In other cases, discordance can allow us to understand genetic and lineage persistence, divergence, and manifestation over time—especially in cases where isolated molecular data (e.g. mitochondrial DNA versus nuclear DNA) generate discordant phylogenies for the same groups of organisms. Discordance can often be the foundation for discussion about the ontological status of species, about what should count as phylogenetic data, about what kinds of assumptions we should make regarding the nature of evolution, and so on. Understanding discordance provides a framework for understanding the nature of the scientific method and knowledge production therein; and specifically, in this case the precarious nature of phylogenetic reconstruction. Discordance shows us that even today, systematics is a dynamic and malleable process, in which the only thing really set in stone might be the paleontological data. In partnership with the GSLC, we began with a simple case: Divergent histories of the Polar Bear/Brown Bear complex, analyzed using both mitochondrial and nuclear DNA. Though both are ‘molecular data’, each convey a slightly different genetic history. Nonetheless, it turns out, contributing valuable evidence about the truly unique and intertwined histories of the two bear lineages. For our research we attended the Evolution Meetings, hosted annually by ASN, SSB, and SSE (this year in Portland, Oregon). We sought out similar cases of contemporary discordance presented by current evolutionary biologists from around the world. We have been working with the GSLC to provide these concrete cases in hopes of creating a module that would simply and clearly demonstrate modern attempts by real biologists to grapple with discordance. Our poster displays some of the most tractable cases, which illuminate Discordance engendered both by conflicting data, and by conflicting analytical methods. We have also outlined our current research project into the justificatory purchase of Parsimony, stemming from this endeavor.