Genetic analysis of the near infrared spectral phenome of Eucalyptus globulus

Foliar phytochemical variation in foundation tree species not only creates a complex selection mosaic to which herbivores and pathogens respond but can also structure dependent communities and even impact on ecosystem processes. Understanding the evolutionary and co-evolutionary consequences of this variation in chemistry requires knowledge of the genetic basis of this variation within foundation species. While it is important to identify individual foliar chemical compounds that influence biotic interactions, it may also be of great benefit to have a more holistic approach to quantifying phytochemical variation. This holistic approach is appropriate when an assessment of overall phytochemical diversity and similarity is desired and when there is a need to explore beyond the framework of readily assayed phytochemicals or those of proven bioactivity. Near infrared reflectance spectroscopy (NIRS) provides a means to rapidly characterise the holistic physicochemical profile of individual biological samples and we call this the spectral phenome. Using the Australian forest tree species, Eucalyptus globulus, as a model we investigate the scales (between species, between populations and families within species and within families at the genome level) at which genetic variation of the foliar spectral phenome occurs. We also show that variation in this foliar spectral phenome influences foliage arthropod communities and we identify co-locating quantitative trait loci (QTL) for key spectral regions and dominant foliar terpenes.