THE KOHN LAB IS LOOKING FOR Ph.D. STUDENTS! STUDENTS MAY WORK ON ANY OF THE RESEARCH AREAS OUTLINED ON THE RESEARCH PAGE, OR ANY RELATED PROJECT.
Kohn lab members:
Dr. Joshua Kohn grew up in Berkeley CA. He received a B.A. in Biology from Reed College, a Ph.D. in Biology from the University of Pennsylvania and was a post-doc at the U. of Toronto before coming to UCSD. He is currently Chair of the the Section of Ecology, Behavior, and Evolution.
Yoshiaki Kono is a BS/MS student using morphological and molecular tools to study Africanization in honey bees of in Southern California. Africanized bees arrived in San Diego County in the late 1990’s and are now very common perhaps adding to the astounding dominance of honey bee pollinators on common native plants throughout the county. He recently received a fellowship from the Agouron Foundation for summer research.
Tyler (Brock) Wooldridge is an undergraduate working on barcoding of San Diego Biodiversity. He is currently barcoding polychaetes from sandy beach habitats. He recently received a fellowship from the Agouron Foundation for summer research.
Lauren Kitayama is an undergraduate working on barcoding of crustacea collected from sandy beach habitats in San Diego County. She recently received a fellowship from the Agouron Foundation for summer research.
Former lab members:
Ph.D. Students (completion year)
Anne Elizabeth (Betty) Fetscher (1999): Betty’s experimental evaluation of hypotheses to explain the touch-sensitive stigma of Diplacus (Mimulus) aurantiacus broke new ground in our understanding of conflict between the male and female functions of hermaphroditic flowers and how floral features may evolve to mitigate these conflicts. Betty is now an Ecologist with SCCWRP (The Southern California Coastal Water Research Project) a public agency for environmental research.
Dr. Boris Igić (2005): Dr. Igić completed several major comparative studies on the history of the S-locus in the Solanaceae and the inferences that can be made from understanding this history. Specifically, he showed that RNase-based self-incompatibility found in the Solanaceae, Plantaginaceae and Rosaceae was likely homologous. If RNase based incompatibility was a feature of the common ancestor of these families then it is the ancestral trait for a large fraction of the dicots. In addition, RNase-based incompatibility in the Solanaceae was shown to be frequently and irreversibly lost. The continued presence of incompatibility despite frequent loss leads to the prediction that SI confers a macroevolutionary advantage by either increasing speciation or decreasing extinction. This prediction has now been tested and confirmed using modern comparative methods. Dr. Igic is an Associate Professor at the University of Illinois, Chicago.
Dr. Matthew Stresfeld (2005): Dr. Streisfeld studied the striking pattern of flower color variation in Diplacus (Mimulus) auriantiacus in San Diego County, and the selective and genetic processes that underlie it. Populations near the coast have red flowers while those inland have yellow flowers. Where the morphs meet, intermediate and pure forms segregate in hybrid swarms. Dr. Streisfeld found that the two major pollinators of this species (hummingbirds and hawkmoths) have strong preferences for alternative floral ecotypes but there is little genetic differentiation between yellow and red populations except at loci that control flower color. Dr. Streisfeld is an Assistant Professor at the University of Oregon where he continues work on the molecular basis and selective forces underlying flower color variation.
Dr. Timothy Paape (2009): Dr. Paape investigated S-locus variation in the poppy family (Papaveraceae). This family has gametophytic self-incompatibility whose molecular basis is not S-RNases. Papaveraceae therefore provide a great comparative system to observe the evolutionary dynamics of the gametophytic S-locus operating under entirely different molecular basis from all families previously studied. Before Dr. Paape’s work, only four Papaveraceae S-allele sequences were known. Dr. Paape sequenced and analyzed 87 putative S-alleles from two species of Papaver and one species from each of the genera Romneya, Argemone, and Platystemon. He found very high sequence diversity among Papaver self-incompatibility alleles, but much lower levels of both sequence diversity and shared ancestral polymorphism in the other genera. Dr. Paape is now a post-doc in at the University of Zurich’s Institute of Evolutionary Biology and Environmental Studies.
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BS/MS students:
Kai Yeung (2005): Kai published a study of mating system and ploidy variation in Lycium californicum (Solanaceae). According to the hypothesis of Miller and Venable, loss of incompatibility due to polyploidy often leads to the evolution of separate sexes to ensure outcrossing. Kai found that diploid populations or L. californicum were unisexual (hermaphroditic) and self-incompatible or polyploidy and functionally dioecious (separate males and females). The result supports the Miller and Venable hypothesis. Kai is now a Ph.D. student in the Pharmaceutical Outcomes Research and Policy program at the University of Washington.
Paul Bilinski (2010): Paul studied the site of self-pollen inhibition across the range of floral morphologies present in the Papaveraceae. Despite long use of self-incompatibility in Papaver as a model system in incompatibility research, there were no reports on the mechanics of pollen tube inhibition in the poppy family outside this genus. In Papaver, pollen tube growth is inhibited upon germination, just as contact with the stigma is made. But Papaver lacks a style so stigmatic inhibition might be stigmatic for lack of further female guidance tissue. Paul found that throughout the family which displays a wide array of floral morphologies, pollen tubes are inhibited as soon as they come into contact with living female tissue. Paul is now studying plant genomics as a UC Davis Ph.D. student in the Ross-Ibarra lab.
Post-docs (final year):
Dr. Adam Richman (1999) pioneered the sequencing and analysis of self-incompatibility (S-) alleles from natural populations of plants. His work opened up an entire field of using the S-locus to obtain historical information about populations and lineages in self-incompatible plants. Dr. Richman is an associate professor in the Plant Sciences and Plant Pathology department at Montana State University
Dr. Olivier Raspé (2001) completed the first studies of S-alleles in natural populations of Rosaceae. He is currently a researcher at the National Botanic Garden of Belgium
