title: Contemporary evolution of an invasive grass in response to elevated atmospheric CO(2) at a Mojave Desert FACE site.
abstract: Elevated atmospheric CO2 has been shown to rapidly alter plant physiology and ecosystem productivity, but contemporary evolutionary responses to increased CO2 have yet to be demonstrated in the field. At a Mojave Desert FACE (free-air CO2 enrichment) facility, we tested whether an annual grass weed (Bromus madritensis ssp. rubens) has evolved in response to elevated atmospheric CO2 . Within 7 years, field populations exposed to elevated CO2 evolved lower rates of leaf stomatal conductance; a physiological adaptation known to conserve water in other desert or water-limited ecosystems. Evolution of lower conductance was accompanied by reduced plasticity in upregulating conductance when CO2 was more limiting; this reduction in conductance plasticity suggests that genetic assimilation may be ongoing. Reproductive fitness costs associated with this reduction in phenotypic plasticity were demonstrated under ambient levels of CO2 . Our findings suggest that contemporary evolution may facilitate this invasive species' spread in this desert ecosystem.
authors.affiliation: The Nature Conservancy, 555 Capitol Mall, Suite 1290, Sacramento, CA, 95814-4605, USA.
authors.forename: Judah D
authors.initials: JD
authors.lastname: Grossman
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Rice
mesh_terms: D005075:Biological Evolution; D031724:Bromus / Q000378:metabolism / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D003889:Desert Climate; D058865:Introduced Species; D018521:Plant Physiological Phenomena
chemical_list: D002245:Carbon Dioxide
keywords: Bromus rubens; contemporary evolution; desert ecosystem; elevated atmospheric CO2; genetic assimilation; invasive species; norms of reaction; phenotypic plasticity; stomatal conductance