Postdoctoral Researcher
Pryer Lab, Duke University
james.beck[at]duke.edu
Links:
I’m trained as a plant systematist and population geneticist. My research interests reflect both fields, and often the level of evolutionary divergence where the two are indistinguishable.
As a population geneticist, I'm interested in evolutionary patterns just above and just below the species (lineage) level.
Patterns just above the lineage level are often complicated due to the relatively shallow time depth involved and the ease with which closely related lineages can fuse (hybridize) to form new lineages. These situations are frequently described as "species complexes." In these cases morphological characters are inconsistent indicators of lineage composition, and molecular characters often provide a more accurate picture. My postdoctoral work with Kathleen Pryer and Mike Windham involves an analysis of recently formed hybrid polyploid species in the fern genus Astrolepis.
Polyploid evolution in the star-scaled cloak ferns (Astrolepis). The genus Astrolepis comprises four known diploid species and an array of auto and allopolyploid hybrids. We are using both chloroplast and nuclear DNA sequence data to reconstruct the tree-like relationships between the diploids and the reticulate relationships between each polyploid hybrid and its parents. In addition, at least one of the named allopolyploids has arisen multiple times, and we are investigating both the number of these origins and the level of morphological and ecological divergence among unique lineages.
Patterns just below the lineage level are dominated by the matrix of gene flow across the lineage's geographic range. A variety of forces interact to promote or inhibit gene flow, including the dispersal capacity of the organism, landscape features, and human activity. My Ph.D. work evaluated these forces in the plant model organism Arabidopsis thaliana.
Population genetics of Arabidopsis thaliana. My dissertation research focused on evaluating historical and relatively recent process that have shaped the geographic array of genotypes within A. thaliana. Analysis of our 10-locus dataset provided strong evidence that range movements during the Pleistocene glacial cycles have had a lasting effect on the geographic structure of A. thaliana genomes. Our data also suggested that human-mediated dispersal has partially degraded the natural pattern of isolation by distance in European populations of A. thaliana.
As a systematist, I'm interested in reconstructing the evolutionary relationships between lineages, and using these phylogenies to understand biogeography and character evolution.
Genome evolution in tribe Eupatorieae (Asteraceae). I've recently joined an effort led by Mike Windham (Duke) to examine chromosome number in a large set of samples collected by the late Robert King. This set of new chromosome numbers will greatly add to existing counts for the group, and will be considered in the light of available phylogenies.
Evolution and biogeography of Leavenworthia and Selenia (Brassicaceae). I've used DNA sequence data to reconstruct the phylogenetic relationships within these sister genera. Our phylogeny of Leavenworthia indicated that the switch between self-incompatibility and self-compatibility has occurred multiple times within the genus.
Systematics and evolution of Solidago (Asteraceae). The goldenrods (Solidago) are a recently derived, species-rich, and taxonomically complicated genus. I and several collaborators have an ongoing interest in reconstructing the phylogeny of Solidago and understanding the origin and population biology of individual lineages.
