Krissa Skogen, Ph.D.

Conservation Scientist
Email: 
Phone: 
(847) 835-6919
Curriculum Vitae: 
Teaching and Research Affiliations: 

Adjunct Professor, Biological Sciences, Northwestern University

Selected Professional Associations: 
  • Board Member, American Institute of Biological Sciences
  • Science Advisory Board Member, Linda Loring Nature Foundation
  • HB4 Team Member, Homeward Bound Project for Women in STEMM 
  • Member, Botanical Society of America
  • Member, Ecological Society of America
  • Member, American Association of Plant Taxonomists
Research Interests: 
  • Reproductive and pollination biology
  • Plant-insect interactions 
  • Floral trait evolution
  • Population genetics
  • Anthropogenic threats to biodiversity
  • Understanding the causes and consequences of plant population and species decline
  • Onagraceae, Sphingidae, microlepidopterans
Understanding the diversity of life starts with uncovering the evolutionary histories and relationships between interacting organisms and landscapes. As a botanist, I am fascinated by the rich diversity of flowering plants (angiosperms) and the insects that interact with them - both pollinators and antagonists (herbivores, seed predators, etc.) - and how these interactions may help explain the great diversity we see today. Much of my work focuses on differences between hawkmoth- and bee-pollinated plant species and the implications for floral phenotypes (shape, color, size, scent), population connectivity, and species boundaries. I'm also intersted in the role that antagonists may play, especially those that are attracted to the same floral cues that attract pollinators (including color and scent) given the opposing, negative impacts of floral antagonists on plant fitness. Much of this work uses the Geographic Mosaic Theory of Coevolution as a model to explain the evolutionary relationships between members of the evening primrose family, Onagraceae, their hawkmoth and bee pollinators, and antagonist microlepidoptera in the genus Mompha (more info here).
 
I am also committed to plant conservation efforts, including investigating the impacts of anthropogenic factors on plants and pollinators. My previous work has investigated the impact of land use change on an endemic, hawkmoth-pollinated evening primrose, Oenothera harringtonii and the role that atmospheric nitrogen deposition may have played in the decline of the nitrogen-fixing legume, Desmodium cuspidatum.
 
Scent-mediated diversification of flowers and moths across western North America

We commonly think of floral scent for its role in attracting pollinators, but it can also be a cue for floral and seed predators. This project integrates chemical ecology and comparative genomics to explore the impact of past selective pressures on current patterns of diversity in non-model organisms: evening primroses, hawkmoths, bees, and micromoths. In particular, we are investigating how chemically-mediated interactions between flowering plants, pollinators, and enemies affect diversification at the population, species, and higher taxonomic levels. Onagraceae (evening primrose family) is one of the most species-rich families of night-blooming plants in North America. Many Onagraceae, particularly species in tribe Onagreae, produce floral scent that likely dictates the primary biotic drivers impacting plant fitness, including legitimate pollinators (hawkmoths, bees) and floral and seed predators (Mompha moths). The same floral characteristics (color, shape, scent) that attract pollinators are also suspected to attract floral antagonists to host plants. Mompha is one such moth genus that specializes on Onagraceae. A thorough survey of these micromoths associated with Onagreae in western North America will result in a more accurate assessment of diversity in this group. Three dimensions of biodiversity will be integrated through studies of (1) floral trait variation, (2) its genetic basis, and (3) their roles in driving patterns of diversity in Onagreae and Mompha. The identification of “hot” and “cold” spots of selection will provide a test of the role of scent in the creation and maintenance of biodiversity across landscapes and time.

This is a collaborative National Science Foundation-funded research project between myself, Jeremie Fant (Chicago Botanic Garden), Norm Wickett (Chicago Botanic Garden), Robert Raguso (Cornell University), Rachel Levin (Amherst College), Sylvia Kelso (Colorado College), Terry Harrison (University of Illinois at Urbana-Champaign), Jean-Francois Landry (Agriculture & Agri-Food Canada, Eastern Cereal and Oilseed Research Centre), Kathleen Kay (University of California, Santa Cruz), Mike Moore (Oberlin College), and Warren Wagner (Smithsonian Institution).

Long-Distance Pollinator Movement – Oenothera harringtonii
This project investigates pollination, reproduction, and gene flow in the Colorado Springs evening primrose (Oenothera harringtonii, Onagraceae), a species endemic to southeastern Colorado. The flowers of Oenothera harringtonii open soon after sunset and are pollinated primarily by hawkmoths. Hawkmoths can travel up to 20 miles in just one night, and may therefore contribute significantly to long-distance gene flow among populations. These moths feed on the nectar of Oenothera flowers, which they locate by the strong fragrance produced by the flowers. This species is found in an increasingly fragmented landscape; however, little is known of the impacts that fragmentation and light pollution may have on the community of pollinators upon which it relies for reproduction and long-term population persistence. Studying populations in both fragmented/developed and unfragmented areas will allow me to determine the extent to which habitat fragmentation and light pollution may be negatively impacting both hawkmoth populations as well as populations of Oenothera harringtonii. A combination of field, greenhouse, and molecular tools are being used to understand which pollinators visit flowers, to what they are attracted (floral scent, size, nectar sugar concentration, etc.), and whether plants are successfully reproducing (demographic data, hand pollinations), and to examine patterns of gene flow (microsatellite markers).

Understanding Causes and Consequences of Species Decline – Desmodium cuspidatum
My previous research on the perennial legume, Desmodium cuspidatum (large-bracted tick-trefoil, Fabaceae), explored whether nitrogen deposition (acid rain) may contribute to the decline of a nitrogen-fixing plant species. This species has experienced a dramatic decline in the northeastern portion of its range in the last 30 years, from approximately 28 populations in the mid-1970s to just nine populations as of 2007. However, populations elsewhere in the species range have not declined. Interestingly, the pattern of decline in Desmodium cuspidatum is consistent with the pattern of nitrogen deposition in the United States: the highest, for the longest period of time, in the northeast. Studies of demography and reproductive biology revealed that extremely low reproductive success and recruitment (birth) rates might be limiting population growth. Furthermore, patterns of genetic diversity suggest that current populations harbor high levels of genetic diversity but might be threatened in the future if gene flow is restricted among existing populations.

Selected Publications: 

Wenzell*, K., A. McDonnell, J. Fant and K. Skogen. In Review. Floral color variation reveals contrasting patterns of genomic and phenotypic divergence within and among species of Castilleja. American Journal of Botany.

Patsis*, A., R. Overson, K. Skogen, N. Wickett, M. Johnson, W. Wagner, R. Raguso, J. Fant, and R. Levin. In Review. Elucidating the evolutionary history of Oenothera Sect. Pachylophus (Onagraceae): A phylogenetic approach. Systematic Botany.

Ksiazek-Mikenas*, K., Chaudhary, B. Larkin, D., and K. Skogen. In Review. A habitat analog approach establishes native plant communities on green roofs. Ecosphere.

Skogen, K., R. Overson, E. Hilpman*, and J. Fant. 2019. Hawkmoth pollination facilitates long distance pollen dispersal and reduces isolation across a gradient of land-use change. Annals of the Missouri Botanical Garden. 104(3): 495-511. https://doi.org/10.3417/2019475 Open Access.

Mikenas*, K., J. Fant, and K. Skogen. 2019. Pollinator-mediated gene flow connects green roof populations across the urban matrix: a paternity analysis of the self-compatible forb Penstemon hirsutus. Frontiers in Ecology and Evolution. 7: 299. DOI: 10.3389/fevo.2019.00299 Open Access.

Bruzzese*, D. J., D. L. Wagner, T. Harrison, T. Jogesh, R. P. Overson, N. J. Wickett, R. A. Raguso, and K. A. Skogen. 2019. Diversification in the microlepidopteran genus Mompha (Lepidoptera: Gelechioidea: Momphidae) is explained more by tissue specificity than host plant family. PLoS ONE. 14(6) e0207833. https://doi.org/10.1371/journal.pone.0207833  Open Access.

Rhodes, M. K.*, J. B. Fant, and K. A. Skogen. 2017. Pollinator identity and spatial isolation influence multiple paternity in an annual plant. Molecular Ecology. doi:10.1111/mec.14115

Jogesh, T., R. P. Overson, R. Raguso, and K. A. Skogen. 2017. Herbivory as an important selective force in the evolution of floral traits and pollinator shifts in a clade of evening primroses, Oenothera sect. Calylophus (Onagraceae). AoB Plants. 9(1) doi:10.1093/aobpla/plw088  Open Access.

Skogen, K. A., T. Jogesh, E. T. Hilpman*, S. L. Todd*, M. K. Rhodes*, S. Still, and J. B. Fant. 2016. Land-use change has no detectable effect on reproduction in a disturbance-adapted plant pollinated by long-distance dispersing hawkmoths. American Journal of Botany. 103(11):1950-1963. doi:10.3732/ajb.1600302  Open Access.

Lewis, E. M.*, J. B. Fant, M. J. Moore, A. P. Hastings, E. L. Larson, A. Agrawal, and K. Skogen. 2016. Microsatellites for Oenothera gayleana and O. hartwegii subsp. filifolia (Onagraceae) and their utility in section Calylophus. Applications in Plant Sciences. 4(2)  http://www.bioone.org/doi/pdf/10.3732/apps.1500107

Barak, R.*, J. Fant, A. Kramer, and K. Skogen. 2015. Assessing the value of potential "native winners" for restoration of cheatgrass-invaded habitat. Western North American Naturalist. 75:58-69.

Rhodes, M.*, J. Fant, and K. Skogen. 2014. Local topography shapes fine-scale spatial genetic structure in the Arkansas Valley evening primrose, Oenothera harringtonii (Onagraceae). Journal of Heredity.105:900-909.

Ksiazek*, K., J. Fant, and K. Skogen. 2014. Native forbs produce high quality seeds on Chicago green roofs. Journal of Living Architecture. http://greenroofs.org/resources/JOLAsubmission%5B6%5Dfinal.pdf

Ksiazek*, K., J. Fant and K. Skogen. 2012. An assessment of pollen limitation on Chicago green roofs. Landscape and Urban Planning. 107(4):401-408.

Skogen, K., K. H. Holsinger, and Z. G. Cardon. 2011. Nitrogen deposition and the decline of a regionally threatened legume, Desmodium cuspidatum. Oecologia. 165(1):261-269.

Skogen, K., L. Senack*, and K. Holsinger. 2010. Dormancy, small seed size and low germination rates contribute to low recruitment in Desmodium cuspidatum (Fabaceae). Journal of the Torrey Botanical Society. 137(4):355-365.

Tienes, M.*, K. Skogen, P. Vitt and K. Havens. 2010. Optimal monitoring of rare plant populations - Report for the USDA Forest Service.

(* indicates student author)

Graduate Students: 
Susan Deans (Northwestern University, Ms. expected 2023)
Katie Wenzel (Northwestern University, Ph.D. expected 2021), Co-advisor.
Katherine Andrews (Northwestern University, M.S. 2019) Precipitation frequency negatively impacts plant survivorship, growth, phenology and herbivory in Oenothera harringtonii.
Kelly Ksiazek (Northwestern University, Ph.D. 2017) The Potential of Green Roofs to Provide Habitat for Native Plant Conservation.
Dan Bruzesse (Northwestern University, M.S. 2016) Host use and diversification of the genus Mompha (Lepidoptera: Gelechioidea: Momphidae).
Ben Cooper (Northwestern University, M.S. 2016) Revealing patterns of evolution in a recently radiated plant group, the Sundrops (Oenothera Section Calylophus: Onagraceae) using target enrichment.
Emily Lewis (Northwestern University, M.S. 2015) Differences in population genetic structure of hawkmoth- and bee-pollinated species of Oenothera (Onagraceae) are more pronounced at a landscape scale.
Matthew Rhodes (Northwestern University, M.S. 2013) Spatial genetic structure and nonrandom pollination success in Oenothera harringtonii (Onagraceae).
Ricardo Rivera (Northwestern University, M.S. 2013) Quantitative genetics in a fragmented landscape, a study of heritable floral traits in Oenothera harringtonii (Onagraceae).
Rebecca Barak (Northwestern University, M.S. 2012) Species interactions between native forbs and invasive cheatgrass (Bromus tectorum L.) in the Colorado Plateau.
Emily Booth (Northwestern University, M.S. 2011) Potential effects of climate change on Penstemon palmeri at Zion National Park, Utah, U.S.A.
Melissa Gray (Northwestern University, M.S. 2011) The effects of floral density manipulation on the pollination and reproductive success of Penstemon pachyphyllus.
Postdocs: 
Tania Jogesh, Ph.D. - NSF Dimensions of Biodiversity - Landscapes of linalool: scent-mediated diversification of flowers and moths across western North America. DEB 1342873
Rick Overson, Ph.D. - - NSF Dimensions of Biodiversity - Landscapes of linalool: scent-mediated diversification of flowers and moths across western North America. DEB 1342873
Websites: 

Skogen Lab 

Research in the Skogen Lab combines a variety of different scientific approaches to answer broad-scale conservation and biodiversity questions to ultimately guide policy and management decisions. In particular, the research that my students and I conduct integrates data on pollination biology, reproductive biology, population genetics, and threats imposed by anthropogenic activities, including nitrogen deposition, habitat fragmentation, and climate change. This website provides information on research conducted by myself and my students, as well as news, photos, and videos of current and previous research.

NSF Dimensions of Biodiversity: Landscapes of Linalool - Scent-mediated diversification of flowers and moths across western North America 

This project integrates chemical ecology and comparative genomics to explore the impact of past selective pressures on current patterns of diversity in non-model organisms: evening primroses, hawkmoths, bees, and micro moths. Onagraceae (evening primrose family) is one of the most species-rich families of night-blooming plants in North America. Many Onagraceae, particularly species in tribe Onagreae, produce floral scent that likely attracts pollinators (hawkmoths, bees). The same floral characteristics (color, shape, scent) that attract pollinators are also suspected to attract floral antagonists to host plants. Mompha is one such moth genus that specializes on Onagraceae. Three dimensions of biodiversity will be integrated through studies of (1) functional diversity, (2) genetic diversity, and (3) taxonomic diversity.