Measurement of volatile terpene emissions in 70 dominant vascular plant species in Hawaii: aliens emit more than natives

Aim: Alien plant invasion is prominent in the Hawaiian islands. There are many factors involved in invader success. To date, there is a general lack of information about one of them, which we aimed to study here: the terpene emission capacity of both Hawaiian native and alien plants. Location: Oahu (Hawaii). Methods: We screened 35 alien and 35 native dominant plant species for monoterpene emissions in Oahu island. The emission rates were measured from field-grown plants under standardized conditions of temperature and quantum flux density in the lab. Results: The emission rates of total terpenes ranged from 0 microg g-1 h-1 to 55 microg g-1 h-1, and altogether 15 different terpenes were emitted in detectable amounts by the overall set of species . A phylogenetic signal was observed for total terpene emissions. Total terpene emission rates were higher in aliens than in native species (12.8 ± 2.0 versus 7.6 ± 1.9 microg g-1 h-1 respectively). Main conclusions The greater terpene emission capacity may confer protection against multiple stresses may partly account for the invasive success, and may make invasive species more competitive in response to new global change-driven combined stresses. These results are consistent with aliens coming from very diverse ecosystems with generally higher biotic and abiotic stress pressures, and having higher nutrient concentrations. On the contrary, these results are not consistent with the “excess carbon” hypotheses. These results indicate changes in vegetation terpene emissions brought about by alien plant invasions.