Invasion Biology
Rapid Evolution of Exotic Plants
St. John's Wort - Hypericum perforatum
In collaboration with Dr. Montserrat Vilį, we asked whether St. John's Wort from introduced populations show evidence of rapid evolutionary change in response to an altered abiotic or biotic environment in North America. To accomplish this, we collected St. John's Wort seeds across Europe and North American and compared phenotypes of plants from native and introduced populations in common gardens in Washington, California, Spain and Sweden.
Brocortrol beetles, chrysolina quadrigemina, feeding on Hypericum.
Comparing traits of plants in common environments enabled us to examine the extent to which introduced genotypes possessed genetically-based differences in traits compared to plants from native populations. We also used AFLP neutral markers to determine the genetic relationships and phylogeographic patterns among these plants. Our results suggested that introduced populations of St. John's Wort have rapidly evolved latitudinal clines in size and fecundity across their introduced range, and that plants have also lost resistance to herbivores and pathogens. This material is based upon work supported by the National Science Foundation under Grants DEB-0296175 and DEB-318719.
Publications
- Colautti, R.I., J.L. Maron and S.C.H. Barrett. 2009. Common garden comparisons of native and introduced plant populations: latitudinal clines can obscure evolutionary inference. Evolutionary Applications 2: 187-199.
- Seifert, E.K., J.D. Bever and J.L. Maron. 2009. Evidence for the evolution of reduced mycorrhizal dependence during plant invasion. Ecology 90: 1055-1062.
- Maron, J.L., S. Elmendorf and M. Vilà. 2007. Contrasting plant physiological adaptation to climate in the native and introduced range. Evolution 61: 1912-1924.
- Maron, J.L. 2007. The relative importance of latitude matching and propagule pressure in the colonization success of an invasive forb. Ecography 29:819-286.
- Maron, J.L. and M. Vilà. 2008. Exotic plants in an altered enemy landscape: effects on enemy resistance. Pages 280-295 In: Specialization, Speciation and Radiation: the Evolutionary Biology of Herbivorous Insects (Kelley J. Tilmon, Ed.). University of California Press, Berkeley.
- Vilą, M., J.L. Maron and L. Marco. 2005. Evidence for the Enemy Release Hypothesis in Hypericum perforatum L. Oecologia 142: 474-479.
- Hierro, J., J.L. Maron and R.M. Callaway. 2005. A biogeographical approach to plant invasion biology: The importance of studying exotics in their introduced and native range. Journal of Ecology 93:5-15.
- Maron, J.L., M. Vilą, R. Bommarco, S. Elmendorf and P. Beardsley. 2004. Rapid evolution of an invasive plant. Ecological Monographs 74: 261-280.
- Maron, J.L., M Vilą and J. Arnason. 2004. Loss of natural enemy resistance among introduced populations of St. John's Wort, Hypericum perforatum. Ecology 85: 3243-3253.
- Vilą, M., A. Gómez and J.L. Maron. 2003. Are alien plants more competitive than their native conspecifics? A test using St. John's Wort (Hypericum perforatum). Oecologia 137: 211-215.
- Maron, J.L. and M. Vilą. 2001. Do herbivores affect plant invasion? Evidence for the natural enemies and biotic resistance hypotheses. Oikos 95: 363-373.
Diversity, Resource Availability, Invasion and Invader Impact
Experimental diversity plots.
We have created synthetic plant assemblages that vary in native plant species richness, functional richness and species identity. Across this nested series of assemblages we are altering water availability (by watering half of all assemblages), a critically limiting resource in dry grasslands of the intermountain west. These assemblages have been established for over 3 years now; in fall 2004 we invaded spatially separate subplots within these assemblages with spotted knapweed (Centaurea maculosa), dalmation toadflax (Linaria dalmatica), and sulfur cinquefoil (Potentilla recta), three of the most widespread and damaging invasive forbs in the intermountain west. A fourth subplot in each assemblage will remain uninvaded.
Experimental diversity plots.
By manipulating resource availability in the context of a diversity-invasibility study, and by maintaining plots that vary in diversity but are not invaded, we can explore how diversity and resource availability jointly influence invasibility and invader impact, something that few studies have attempted. By using different species of exotics that differ in their functional attributes, we can test whether functional overlap between natives and exotics provides invasion resistance or limits invader impact, and how this is affected by increasing resource availability. This material is based upon work supported by the National Science Foundation under Grant No. 0318719
Publications
- Maron, J.L., M. Marler, J. Klironomos, and C. Cleveland. 2011. Soil pathogens contribute to the positive plant diversity-productivity relationship. Ecology Letters 14: 36-41.
- Maron, J.L. and M. Marler. 2008. Field based competitive impacts of invaders on natives at varying resource supply. Journal of Ecology.
- Maron, J.L. and M. Marler. 2008. Effects of native species diversity and resource additions on invader impact. American Naturalist 172: S18-S33.
- Kittelson, P.M., J.L. Maron and M. Marler. 2008. Native diversity and invader impact: an exotic alters the leaf traits of two natives. Ecology 89: 1344-1345.
- Maron, J.L. and M. Marler. 2007. Native plant diversity resists invasion at both low and high resource levels. Ecology 88: 2651-2661.
- Callaway, R.M. and J.L. Maron. 2006. What have exotic invasions taught us over the past twenty years? Trends in Ecology and Evolution 21: 369-374.
