Phenotypic plasticity in the emission of terpenes by a threatened pine species (Pinus caribaea var. bahamensis): Effects of scale infestation and environment

Abstract

The Caicos pine is in decline in the Turks and Caicos Islands due to an invasive scale insect, Toumeyella parvicornis and climate change is likely to exacerbate this decline. We hypothesized that the rate of emission of volatiles may differ between trees at different locations and over time. Entrained volatiles were analysed by gas chromatography-mass spectrometry and six compounds were identified and included in multivariate analyses (CCA and NMDS) to distinguish between year, health condition and locations. The emissions collected from the same trees in May 2014 and May 2015 were not different. A two-way ANOVA of 2015 data alone showed that health and location interacted for individual compounds and total emissions, and it was only when data were compared separately (i.e. health condition only or location only) that trees could be resolved into distinct groups using CCA. Healthy trees from Pine Cay and Middle Caicos could be separated using emissions of β-phellandrene. In contrast unhealthy trees from Pine Cay were characterized by higher total emissions and of all compounds except the pinene isomers, while emissions from trees from Middle and North Caicos were identical. These differences may be a reflection of genetic or environmental differences between the populations. Terpenes could be useful to monitor health where there might not be visible indicators. Refinement of these findings would depend on more samples being collected over many years.