Tim O'Connor, PhD

University of California, Berkeley
Department of Integrative Biology

Office: 4095 Valley Life Sciences Building
tko2 [at] berkeley [dot] edu

Education

University of California, Berkeley. Ph.D. in Integrative Biology (2016-2019)
University of Arizona. M.S. in Ecology and Evolutionary Biology (2012-2015)
University of Illinois. B.S. in Integrative Biology (2005-2009)

Employment

University of Oregon. Green Lab, Research Assistant (2010-2012)
Field Museum of Natural History. Moreau Lab, Research Assistant (2010)

Research Interests

How do species interactions affect biodiversity?
Explaining the tremendous diversity of herbivorous insects is an enduring challenge in evolutionary biology. Using creosote bush (Larrea tridentata, Zygophyllaceae) and its herbivores as a model system, I address how plant-insect interactions affect the generation, maintenance, and distribution of insect diversity. Creosote bush is a dominant shrub across the warm deserts of North America that has diversified through whole-genome duplication (polyploidy). Plants of different ploidy level (cytotype) are parapatric, show partial reproductive isolation (consistent with incipient speciation), and can differ phenotypically. The herbivorous insect community on creosote bush is rich with highly-specialized species that have adapted to creosote bush despite its considerable chemical defenses. My dissertation focuses on different members of this community to explore how interactions with host plants influence different dimensions of herbivore diversity (species, phenotypes, and genotypes). Much of my work is done in collaboration with Dr. Robert Laport (Rhodes College) and my advisor Dr. Noah Whiteman.
Host plant polyploidy and herbivore biogeography.
It is common for related plant cytotypes geographically isolate. More recently, some herbivores have been found to strongly discriminate between host plant cytotypes. Can the biogeography of polyploid plants thus shape the biogeography of their herbivores? We recently found that species interactions with gall midges (Diptera: Cecidomyiidae, Asphondylia spp.) differ among creosote bush cytotypes. As a result, contact zones between cytotypes are dispersal barriers for some gall midge species, shaping individual species ranges and patterns of gall midge diversity across North American deserts (O'Connor et al., In Press. Journal of Biogeography). 
Picture
Diploid (blue square) and tetraploid (yellow circle) creosote bush host distinct communities of Asphondylia gall midges in sympatry.
Picture
Some Asphondylia species specialize on a subset of creosote bush cytotypes (host plant indicated by plotting character). The effect of creosote bush cytotype on plant-herbivore interactions thus shapes the geographic distribution of herbivore species.
Co-divergence of creosote bush and its herbivore community.
Coordinated speciation of hosts and parasites (co-speciation) is common among many groups of specialized parasites. By contrast, there is little phylogenetic evidence of co-speciation between herbivores and their host plants. This may reflect the true rarity of co-speciation or challenges in detecting its signal from phylogenetic data. With Rob Laport and Noah Whiteman, I am using population-level genetic information (from ddRAD and RADcap sequencing) to test for co-divergence between creosote bush cytotypes and their insect herbivores.  Preliminary evidence suggests that the population genetic structure of some herbivores (including Bootettix argentatus​, pictured at left) reflects their host plant cytotype and is not solely the product of isolation by distance. I am now expanding my analysis to include eight taxonomically diverse members of the creosote bush herbivore community.
Picture
Bootettix argentatus (creosote bush grasshopper) near Tucson, AZ. © Tim O'Connor
Ecological drivers and evolutionary genetics of crypsis polymorphism.
The desert clicker (Ligurotettix coquilletti) displays remarkable variation in color across its range. Crypsis in this species can be decomposed into two major phenotypes: 1) base color and 2) pattern. Base color varies quantitatively among populations, while within populations, individuals have one of two discrete pattern morphs (uniform, or with a high-contrast pattern on the thorax and femur). Along with base color, pattern morph frequencies vary widely across the range of L. coquilletti. What can explain the geographic variation in adaptive traits? I am testing the hypothesis that each component of crypsis in L. coquiletti (base color and pattern) is under selection to match distinct elements of the environment. To do so I am quantifying the color and pattern of populations across the range of L. coquilletti and comparing these to two potential cryptic backgrounds (plant stems and bare ground). I have also identified loci associated with the apparently Mendelian pattern phenotype and designed sequence capture probes to target these and putatively neutral loci for sequencing. I am now genotyping and phenotyping hundreds of L. coquilletti to elucidate the evolutionary history of this species as well as its crypsis phenotype.
Picture
Crypsis variation in desert clickers. Base color differs across sites, and the frequencies of uniform (left photo in each pair) and patterned morphs (right photo in each pair) also varies widely across the species' range. © Tim O'Connor

Study Organisms

Publications

IN PREPARATION
  • O'Connor, TK, J Wang, and NK Whiteman. Host-plant specialization and phylogeography of  desert clicker grasshopper.
  • O'Connor, TK, M Sandoval, J Wang, and NK Whiteman. Balancing selection and local adaptation jointly determine crypsis variation in desert clicker grasshopper.
  • O'Connor, TK, KM Yule, and NK Whiteman. Host plant and geography shape contrasting patterns of divergence in two herbivores of creosote bush (Larrea tridentata).

​SUBMITTED
  • Gloss, A., AC Nelson Dittrich, RT Lapoint, B Goldman-Huertas, KI Verster, JL Pelaez, ADL Nelson, J Aguilar, E Armstrong, JLM Charboneau, SC Groen, DH Hembry, CJ Ochoa, TK O’Connor, S Prost, H Suzuki, S Zaaijer, PD Nabity, and NK Whiteman. Evolution of herbivory remodels a Drosophila genome.

PUBLISHED                 Press: Popular Science                 Press: Science, NPR, Smithsonian, Scientific American, Science Daily
                Selected for PeerJ Picks 2014

Grants and Awards

  • 2019 - Department of Integrative Biology Summer Grant
  • 2018 - American Society of Naturalists Student Research Award
  • 2018 - Philomathia Graduate Fellowship in Environmental Sciences
  • 2018 - Department of Integrative Biology Summer Research Grant
  • 2017 - Philomathia Graduate Fellowship in Environmental Sciences
  • 2017 - Department of Integrative Biology Summer Research Grant
  • 2017 - Essig Museum of Entomology Walker Grant
  • 2016 - Southwestern Association of Naturalists Howard McCarley Research Grant
  • 2016 - Orthopterists' Society Theodore J. Cohn Research Grant
  • 2016 - American Museum of Natural History Theodore Roosevelt Memorial Grant
  • 2015 - University of Arizona Graduate and Professional Student Council Travel Grant
  • 2015 - University of Arizona Graduate and Professional Student Council Research Grant
  • 2014 - Society for Integrative and Comparative Biology Grant-in-Aid of Research
  • 2014 - Society for the Study of Evolution Rosemary Grant Award
  • 2014 - Mycological Society of America Clark T. Rogerson Student Research Award
  • 2014 - University of Arizona College of Science Galileo Circle Scholarship
  • 2012 - NSF Graduate Research Fellowship
  • 2012 - NSF IGERT Fellowship in Comparative Genomics​

Invited Talks

  • UC Berkeley Essig Brunch. April 2019.
  • Entomological Society of America Organized Meeting, "Orthopteroids: Small Orders, Big Ideas." November 2018.
  • UC Berkeley Essig Brunch. April 2017.
  • Arizona Native Plant Society, Tucson Chapter. March 2015.

Teaching

  • Population and Evolutionary Genetics. UC Berkeley, Spring 2017
  • Ecology, Evolution, and Organismal Biology. UC Berkeley, Fall 2016 / Spring 2018 / Spring 2019
The Whiteman Lab | Integrative Biology | University of California | Berkeley, CA 94720

Photographs are copyright protected by Noah Whiteman, Whiteman lab members, or were obtained through Creative Commons licenses.