Vigor and competitiveness of native and invasive hoary cress populations with regard to the evolution of increased competitive ability
Mark Schwarzlaender, firstname.lastname@example.org, Jessica L. McKenney1, Michael G. Cripps, email@example.com, Kenneth P. Puliafico, firstname.lastname@example.org, and Hariet L. Hinz, email@example.com. (1) Univ. of Idaho, Dept. of Plant, Soil, and Entomological Sciences, P.O. Box 442339, Moscow, ID, (2) CABI Bioscience Switzerland Centre, Rue des Grillons 1, Delémont, Switzerland
Hoary cress, Lepidium draba (L.) is an invasive perennial mustard that is aggressively invading rangelands and riparian lands in the United States and Canada. We study hoary cress as a model system to 1) better understand factors facilitating invasiveness of this mustard, 2) predict the potential for biological control of L. draba, and 3) pre-release assess the potential efficacy of selected biological control agents. Previous studies, descriptively comparing the growth and herbivory pressure at field sites in the native and non-indigenous range, showed that L. draba grows more vigorously in the invaded range and that generalist insect herbivory is greater and specialist insect herbivory is less in the non-indigenous range. These results are in concordance with current invasion hypotheses, i.e., the evolution of increased competitive ability (EICA), the enemy release hypothesis (ERH), and the biotic resistance hypothesis (BRH). While the EICA hypothesis assumes a shift in resource allocation away from defense towards growth and/or reproduction due to evolutionary change in the absence of specialist natural enemies, the latter two hypotheses assume a release from biotic constraints (natural enemies and/or competition) or more favorable abiotic conditions in the non-indigenous range of the invasive plant. We compared the growth and competitiveness of ten Eurasian and ten North American L. draba populations in greenhouse experiments to specifically provide additional support for the EICA hypothesis. We also studied hoary cress responses to specialist and generalist insect herbivores in greenhouse experiments to verify earlier results on herbivory pressure in the native and non-indigenous range in regard to the ERH.
Species 1: Coleoptera Curculionidae Ceutorhynchusamericanus Keywords: biological control, invasion hypotheses