Leaf extracts from an exotic tree affect responses to chemical cues in the palmate newt, Lissotriton helveticus

Abstract

Chemical communication in aquatic species can affect many key life history traits, such as prey and predator detection and mate searching. However, changes in the environment can disrupt the effectiveness of signals and the ability of individuals to detect these signals. Many studies have examined the effect of secondary compounds from exotic plants on the ecology and physiology of a range of taxa, but whether the replacement of natural forests with exotic trees influences the behavioural responses of animals by disrupting chemical communication has rarely been investigated. We experimentally tested how eucalypt tree chemicals influenced three key aspects of chemical communication in adult male palmate newts. We tested for effects of both exposure to eucalypt water (i.e. extracts obtained by soaking leaves in mineral water) and the origin of newts (eucalypt plantations and natural oak forests). We examined whether exposure to eucalypt water altered the chemosensory ability of males to detect pools containing females or conspecific alarm cues and to find food. We found that eucalypt leachates had different effects on each behavioural trait. Fewer males detected female chemicals when exposed to the eucalypt than the oak water treatment, independent of the males' habitat of origin. Newts from oak forest were less able to detect conspecific alarm cues signalling predatory events when exposed to eucalypt water than when exposed to oak water, or than newts from eucalypt plantations for either water treatment. The ability of males to find food using chemical cues was similar in oak and eucalypt treatments. Our results suggest that chemical compounds not previously encountered during the evolutionary history of the species can influence the ability to respond to predators and locate mates. Future studies should explore the fitness costs associated with a reduced ability to respond to predators or detect mates.