Chemical ecology of Eschscholzia californica: comparing alkaloid content between native and invaded ranges

Abstract

Invasive plants can generate significant impacts on biodiversity. The understanding what determine their invasiveness is a central issue in Ecology. When one exotic plant arrives to a new range, they are chemically defended against native predators. If they cannot be recognized by native predators, chemical defenses are no longer adaptive. Then, they can allocate energy to other functions. These responses can vary among different parts of plants as herbivores can be selective. We have worked in the chemical ecology of Eschscholzia californica and invasive plant of Central Chile. We examined total alkaloid content of different plant parts (leaves, shoot and root), comparing native (California) and invasive populations (Central Chile). We found non-significant alkaloid differences between native and invasive populations. However, we found significant differences among populations of Central Chile. Herbivory was almost absent in leaves but some damage can be observed in the flowers. Roots had the highest alkaloid content both in the native and in the invaded range. The absence of regional differences (native vs invaded) suggest that alkaloid concentration is a constitutive defense. Thus, alkaloid content is a conserved trait that does not change irrespective of herbivory pressure.