Spellman Lab Research

Research Interests

My research interests lie in the fascinating and often complex processes that govern the evolution of birds. The projects in my lab use molecular genetic and genomic approaches to study avian systematics, population biology, biogeography, molecular ecology, evolution in hybrid zones, and host-parasite co-evolution. Also, I consider myself a natural historian and as such, proudly engage in specimen-based research. Like Joseph Grinnell, I believe that scientific specimens provide an ongoing documentation of regional biodiversity as well as the raw material required to quantify and understand this diversity. It is the observational natural history data that I (and others before me) collect that drives and has developed my research interests. Every time I venture into the field, I develop new questions that will inevitably become the focus of future research projects.

My current principal research projects include (detail follows):
-Multilocus comparative phylogeography North American birds
-Evolution in North American avian hybrid zones
-Evolution of avian malarial parasites in geographically structured host species
-Molecular systematics of various avian taxa (Bombycillidae, Fluvicoline flycatchers, Aegithalidae)

Featured Research Projects:

Multilocus comparative phylogeography of North American birds

Collaborators: Dr. John Klicka, Barrick Museum of Natural History, UNLV; Dr. Scott V. Edwards Museum of comparative Zoology, Harvard University.
Funding: National Science Foundation, DEB

 
Project Summary: Since the Modern Synthesis, evolutionary biologists have postulated that the climatic oscillations of the Quaternary promoted speciation in temperate zone organisms. Models of climate-driven allopatric speciation were developed for many groups of temperate organisms, but in no group was an explicit speciation model developed with more detail than in North American birds. During this period, the prevailing paradigm for speciation in North American birds led researchers to suggest that the advancing glaciers of the Quaternary fragmented widespread ancestral species, forming sister species pairs represented today by eastern and western forms. Over the last decade, this paradigm has become the topic of a focused debate. A majority of contemporary studies have used mitochondrial DNA sequences and molecular dating techniques to discern whether divergence times for putative sister taxa are correlated with the timing of Pleistocene glacial advances. Although, these students contributed considerable to our understanding of North American avian diversity and they continue to incite debate, a comprehensive overview of how temperate zone birds were impacted by Pleistocene events remains elusive. It is now well understood that the single locus (mtDNA) approach used in these earlier works is not sufficient to accurately determine species divergence times, or to describe in detail the demographic events accompanying speciation. A synthesis of both the temporal and spatial aspects of diversification is required in order to fully understand the effect of environmental changes on the birds of North America. We are examining both the temporal and spatial aspects of North American avian diversification in relation to Quaternary environmental change through a multilocus comparative phylogeographic study of co-distributed pine and oak woodland birds.

Evolution in North American avian hybrid zones

Project Summary: The genomic analysis of avian hybrid zones can provide an understanding of the roles of intrinsic and extrinsic selection on the evolution of reproductive isolation and maintenance of species boundaries. I use genomic variation to examine the genetic landscape (admixture modeling and cline analysis) of hybrid zones between species pairs that come into contact in the North American Great Plains. What is unique about these zones is that they were sampled and studied extensively 40-50 years in the past and ancient DNA techniques allow us to compare the genetic landscape of these zones as they existed then to as they are now. This comparison will allow hypotheses to be tested that can usually only be addressed by the long-term monitoring of hybridizing species.