High chemical diversity of a plant species is accompanied by increased chemical defence in invasive populations

Abstract

Mechanisms contributing to the invasive success of plants are still only partly understood. A main assumption is that an escape from specialized enemies in introduced ranges allows a reduction of chemical defences resulting in an increase in growth and reproduction and thus increased competitive ability of introduced plants. Not only variation in concentration but also variation in composition of chemical compounds between individuals may be a key advantage for plants introduced to novel areas impeding adaptation of different plant antagonists. To investigate quantitative and qualitative variation of putative defence compounds and investment of resources in growth, we conducted a common garden experiment in the native range with seeds of 13 native and 9 introduced populations of Tanacetum vulgare, an aromatic plant forming different chemotypes. After 3.5 months, plants of introduced populations had similar biomass but more stems and higher concentrations of volatile secondary compounds (mainly terpenes) than plants of native populations. Both native and invasive T. vulgare populations exhibited high chemotypic variation with nine chemotypes occurring on both continents, whereas several were found exclusively either in plants originating from the native (n = 10) or invasive (n = 2) range. Due to the known negative effects of many mono-and sesquiterpenes on various organisms, we propose that high concentrations of these secondary compounds accompanied by high chemotypic diversity may facilitate the invasion success of a plant species.

Variation of pyrrolizidine alkaloids in Senecio vulgaris plants from native and invasive ranges

“…However, the results do not support our prediction and the prediction of the SDH that the invasive plants produce more diverse of PAs than the native ones. In fact, some previous studies supported that plants from invasive populations contain more composition of qualitative compounds than the native ones, such as the case of invasive Tanacetum vulgare plants (Wolf et al, 2011).…”

“…Indeed, results from many previous experiments support the predictions. They compared PA variation between native and invasive plants and reported that the PA levels significantly increased in the invaded area (Doorduin & Vrieling 2011;Wolf et al 2011). For example, invasive populations of S. inaequidens, S. pterophorus (Cano et al 2009), S. pterophorus (Castells et al 2014) and S. jacobaea (Joshi & Vrieling 2005;Stastny et al, 2005;Lin 2015) showed significantly higher total PA concentration than their native populations.…”

From plants to herbivores: novel insights into the ecological and evolutionary consequences of plant variation

“…Applying a metabolomic approach, a few steroidal glycoalkaloids could be revealed that show negative correlations with slug feeding. High chemotypic diversity can also be found in other plant taxa and may be maintained as it impedes the adaptation of herbivores (Wolf et al 2011). Similarly, the review by Coley et al (2018) highlights that if neighboring trees in the tropics differ in their defenses, they are unlikely to share herbivores and thus coexistence of different plant and herbivore communities is enhanced.…”

Exotic Plant Invasion in the Context of Plant Defense against Herbivores

“…These authors concluded that invasion success of Senecio species depends upon the potential of a particular genotype to survive and spread in the novel environment of the introduced range. In a common garden study, Wolf et al (2011) studied variations in defense chemicals (mainly VOCs) and allocation of resources to growth by growing seeds of 13 native and nine invasive populations of Tanacetum vulgare, a European native introduced to North America as a medicinal plant. It was found that North American invasive populations of T. vulgare had more than one additional stem and higher amounts of VOCs compared to native European populations.…”