Susan Kalisz


Evolutionary Ecology

Susan Kalisz
Office: (412) 624-4281
Lab: (412) 624-4276
202 Clapp Hall
4249 Fifth Avenue
Pittsburgh, PA 15260

Dr. Kalisz received her Ph.D. in 1985 with Douglas W. Schemske at the University of Chicago, was an Associate Professor at Michigan State University Kellogg Biological Station, and joined the Department in 1995.

My lab has two main research foci: 


What are the causes and consequences of self-fertilization?  Where and why is selfing favored in nature?

Most plant species on Earth are hermaphrodites, with both male and female sexual functions within a single flower.  While hermaphrodites are capable of seed production through self-fertilization, plant species collectively express a dazzling range of mating systems from complete selfing to mixed mating to complete outcrossing. One overarching theme in the Kalisz lab is to determine how the plant mating systems and floral phenotypes are shaped by natural selection, drive diversification of new species, and mold the structure of plant genomes. Our recent findings revealed a dynamic system of repeated mating system transitions between outcrossing and selfing in the genus Collinsia and its sister genus Tonella (FIg 1) Using the emerging Collinsia/Tonella model system, we have an unprecedented opportunity to assess the extent to which common phenotypic and mating system transitions are mirrored by common genomic changes.  Targeting selfing/outcrossing sister pairs (Fig 1 boxes), we use population genomic and transcriptome analyses to illuminate the genetic architecture of mating system shifts including the fertilization proteins and other genes expressed in flowers, as well as changes in genome-wide polymorphism.  We also investigate the selective forces that favor selfing. Abiotic conditions such as short growing seasons and biotic conditions such as the availability of mates, plant population size, pollinator availability, and heterospecific pollen transfer have been widely implicated as important drivers of this mating system transitions.  Yet specifically how and why mating system transitions occur remain unanswered questions. To understand the adaptive significance of selfing, we focus on the ecological contexts that favor this ubiquitous transition in flowering plants. We explore these key issues in tandem through a combination of genome/ transcriptome analyses, greenhouse, field and array experiments, and biogeographic and GIS analyses applied to the powerful Collinsia system. The global loss of bees and other pollinators combined with the decline in their services for crops and wild populations increase the urgency for understanding mating system shifts to selfing.

Fig.1  Phylogeny of Collinsia and Tonella shows repeated small flower, selfing/large flower, outcrossing sister pairs.Fig.1 Phylogeny of Collinsia and Tonella shows repeated small flower, selfing/large flower, outcrossing sister pairs.



Can the context of species interaction within a plant community predict native and invasive species persistence or decline?

Fig 2.  Trillium erectum in flower at Trillium Trail.Fig 2. Trillium erectum in flower at Trillium Trail.A unifying research theme in the Kalisz lab is to determine how changes in the local context of species interactions can drive declines in community biodiversity and alter the population dynamics of native species to favor exotic invaders.  Our aim is to discover biotic and abiotic mechanisms that underlie successful invasion or conversely, community resistance to invasion, and are generally applicable. We explore the complex roles of herbivores and an allelopathic plant invader on the growth, physiology, AMF mutualism, and demographic performance of native forest understory herbaceous species. We have more that a decade of data from a long-term replicated experiment in a forest understory community of long-lived native perennial herbs (e.g. Fig 2). These data are collected from paired plots where deer either have access, or are excluded by fences. We investigate how native species interactions with this herbivore and the noxious invader (garlic mustard) shape the population-level performance and life history traits of individual species and the understory community as a whole (Fig. 3).

Fig 3. The forest understory at our long term study site is invaded with Alliaria petiolata (garlic mustard) and experiences high deer browse levels.Fig 3. The forest understory at our long term study site is invaded with Alliaria petiolata (garlic mustard) and experiences high deer browse levels.Critical questions we are exploring include:

  • To what extent does disruption of AMF-native plants mutualisms by the allelopathic invader alter native plant physiology and explain native species' population declines? 
  • Which life history traits buffer native species from the effects of enemies, like herbivores and invaders? 
  • How does the context of local species interactions with enemies and mutualists alter community level traits, community biodiversity and individual species dynamics?  

 We have discovered important physiological and life history trait responses that alter native plant performance through additional manipulative field and greenhouse experiments designed to complement the patterns emerging from our long-term field study. We employ state-of-the-art matrix projection models and integral projection models (IPM) to assess general responses on native and invasive species' population demography.  We will continue to use our results to inform conservation strategies and management plans at the local, state and national levels for ecosystems facing perturbations by invaders, habitat fragmentation and overabundant herbivores.

Recent Publications
  • Kalisz, S., R.B. Spigler and C.C. Horvitz. (2014) Overabundant herbivores depress natives, facilitate exotics: conclusive multi-year experimental results. PNAS: doi/10.1073/pnas.1310121111

  • Salcedo, A., S. Kalisz, and S.I. Wright. (2014)  Does mixed mating limited genomic consequences of increased selfing rates? Evidence from a recently derived sister species pair, Collinsia concolor and C. parryi. Journal of Evolutionary Biology. doi:10.1111.jeb12384

  • Hazzouri, K.M., J.S. Escobar, R.W. Ness, K.L. Newman, A.M. Randle, S. Kalisz and S.I. Wright. (2013) Comparative population genomics in Collinsia sister species reveals evidence for reduced effective population size, relaxed selection and evolution of biased gene conversion with an ongoing mating system shift. Evolution 67: 1263–1278 (doi:10.1111/evo.12027)

  • Wright S.I., S. Kalisz, T. Slotte (2013)  Evolutionary consequences of self-fertilization in plants.  Proc Royal Society B. Vol 280: (doi:10.1098/rspb.2013.0133).

  • Spigler, R.B., and S. Kalisz (2013) Phenotypic plasticity in mating system traits in the annual Collinsia verna. Botany: 10.1139/cjb-2012-0227

  • Hale, A.N. and S. Kalisz. (2012) Perspectives on allelopathic disruption of plant mutualisms: An exploration of potential mechanisms and consequences. Plant Ecology 213: 1991-2006. (doi: 10.1007/s11258-012-0128-z).

  • Kalisz, S., A.M. Randle, D. Chaiffetz, M. Faigeles, A. Butera, C. Beight. (2012) Dichogamy correlates with outcrossing rate and defines the selfing syndrome in the mixed mating genus, Collinsia. (invited paper, special issue on Plant Mating) Annals of Botany doi:10.1093/aob/mcr237.

  • Winn, A. A., E. Elle, S. Kalisz, P.-O.Cheptou, C. G. Eckert, C. Goodwillie, M. O. Johnston, D. A. Moeller, R. H. Ree, R. D. Sargent, M. Vallejo-Marin. (2011) Insight into the causes of mixed mating in plants from the magnitude and timing of expression of inbreeding depression. Perspectives paper in Evolution 65: 3339–3644.

  • Hale, A.N., S.J. Tonsor, and S. Kalisz. (2011)  Testing the mutualism disruption hypothesis: a physiological mechanism for invasion of intact perennial plant communities. Ecosphere 2:Article 110

  • Cantor, A., A. Hale, J. Aaron, M.B. Traw, and S. Kalisz (2011) Low allelochemical concentrations detected in garlic mustard-invaded forest soils can inhibit fungal growth and AMF spore germination. Biol. Invasions : DOI 10.1007/s10530-011-9986-x

  • Baldwin, B.G., S. Kalisz, and W.S. Armbruster (2011) Phylogenetic perspectives on diversification, diversity, and phytogeography of Collinsia and Tonella (Plantaginaceae). American Journal of Botany 98:731-753.

  • Burke, D.J., M.N. Weintraub, C.R. Hewins, and S. Kalisz (2011) Relationship between soil enzyme activities, nutrient cycling and soil fungal communities in a northern hardwood forest. Soil Biology and Biochemistry 43:795-803.

  • Whitney, K.D., E.J. Baack, J.L. Hamrick, M.J. Godt, B.C. Barringer, M.D. Bennett, C.G. Eckert, C. Goodwillie, S. Kalisz, I.J. Leitch, and J. Ross-Ibarra (2010) A role for non-adaptive evolution in plant genome size evolution? Evolution 64: 2097-2109.

  • Heckel, C.D., N.A. Bourg, W.J. McShea, and S. Kalisz (2010) Nonconsumptive effects of a generalist ungulate herbivore drive decline of unpalatable forest herbs. Ecology 91:319-326.

  • Eckert, C.G., S. Kalisz, M.A. Geber, R. Sargent, E. Elle, P.O. Cheptou, C. Goodwillie, M.O. Johnston, J.K. Kelly, D.A. Moeller, E. Porcher, R.H. Ree, M. Vallejo-Marin, and A.A. Winn (2010) Plant mating systems in a changing world. Trends in Ecology and Evolution 25:35-43.

  • Goodwillie, C., R.D. Sargent, C.G. Eckert, E. Elle, M.A. Geber, M.O. Johnston, S. Kalisz, D.A. Moeller, R.H. Ree, M. Vallejo-Marin, and A.A. Winn (2009) Correlated evolution of mating system and floral display traits in flowering plants and its implications for the distribution of mating system variation. New Phytologist 185:311-321.

  • Randle, A.M., J.B. Slyder, and S. Kalisz (2009) Can differences in autonomous selfing ability explain differences in range size among sister-taxa pairs of Collinsia (Plantaginaceae)? An extension of Baker's Law. New Phytologist 183:618-629

  • Knight, T.M., L. Smith, J. Dunn, J. Davis, and S. Kalisz (2009) Deer facilitate invasive plant success in a Pennsylvania forest. Natural Areas Journal 29:110-116

  • Knight, T.M., H. Caswell, and S. Kalisz (2009) Population growth rate of a common understory herb decreases non-linearly across a gradient of deer herbivory. Forest Ecology and Management 257:1095-1103.

  • Johnson, M.O., E. Porcher, P.-O. Cheptou, C.G. Eckert, E. Elle, M.A. Geber, S. Kalisz, J.K. Kelly, D.A. Moeller, M. Vallejo-Marin, and A.A. Winn (2009) Correlations among fertility components can maintain mixed mating in plants. American Naturalist 173:1-11.

  • Porcher, E., J.K. Kelly, M.O. Johnston, P.-O. Cheptou, C.G. Eckert, and S. Kalisz. 2009. The genetic consequences of fluctuating inbreeding depression and the evolution of plant mating systems. Journal of Evolutionary Biology 22:708-717.

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