Expression of Constitutive and Inducible Chemical Defenses in Native and Invasive Populations of Alliaria petiolata

Abstract

The Evolution of Increased Competitive Ability (EICA) hypothesis posits that invasive plants in introduced habitats with reduced herbivore pressure will evolve reduced levels of costly resistance traits. In light of this hypothesis, we examined the constitutive and inducible expression of five chemical defense traits in Alliaria petiolata from four invasive North American and seven native European populations. When grown under common conditions, significant variation among populations within continents was found for trypsin inhibitors and peroxidase activity, and glucosinolates and trypsin inhibitors were significantly jasmonate-inducible across populations. Across populations, constitutive levels of glucosinolates and trypsin inhibitors were negatively correlated with their degree of induction, with three North American populations tending to have lower constitutive levels and higher inducibility of glucosinolates than the seven European populations. Alliarinoside and isovitexin 6"-O-beta-glucopyranoside levels were both higher in North American plants than in European plants, but levels of these compounds were generally increased by jasmonate in European plants and decreased by the same treatment in North American plants. Aside from the tendency for invasive populations to have reduced constitutive glucosinolate levels coupled with increased inducibility, little support for the predictions of EICA was evident in the chemical defenses that we studied.

Additive genetic variation in resistance traits of an exotic pine species: little evidence for constraints on evolution of resistance against native herbivores

“…As pointed out by Orians and Ward (2010) and Inderjit (2012), constraints on the evolution of defence/resistance traits do not appear to be more common in exotic species, but few experiments have tested this hypothesis (Oduor et al, 2011). Moreover, there is an important gap in knowledge regarding genetic variation for induced defences in exotic plant species (Cipollini et al, 2005;Eigenbrode et al, 2008;Wang et al, 2012). As there is increasing evidence that plants respond to herbivory damage with highly specific responses (Bingham and Agrawal, 2010;Karban, 2011), it is reasonable to argue that inducibility of defences in exotic species may vary inside versus outside of their native range based on differences in the identity and number of herbivore species consuming the plant in each area.…”

Immigration of susceptible hosts triggers the evolution of alternative parasite defence strategies

“…Migration may also affect the type of host defence that is favoured by selection [6,7]. One reason for this is that host migration may affect the temporal variation in exposure to parasites, as well as the mean force of infection (the frequency at which infections take place), both of which are predicted to influence the relative benefits of defences that are associated with fixed versus parasite-dependent (induced) fitness costs [8][9][10].…”

Exotic Plant Invasion in the Context of Plant Defense against Herbivores

“…A complete change in the allocation of resources from defense to growth and/or reproduction was therefore not observed. Cipollini et al (2005) found similar trends in the expression of constitutive and inducible defense in four North American invasive and seven native European populations of A. petiolata. They found that invasive populations of A. petiolata have lower constitutive levels and higher inducible levels of glucosinolates compared to native populations.…”

“…There is mixed support for EICA (see also Willis et al, 1999;Cipollini et al, 2005;Cañ o et al, 2009), which is not surprising considering the conditionality and complexities of almost all ecological interactions. Maron et al (2004) measured levels of the defense chemicals hypericin and pseudohypericin in exotic North American and native European genotypes of Hypericum perforatum.…”