Associations of Leaf Spectra with Genetic and Phylogenetic Variation in Oaks: Prospects for Remote Detection of Biodiversity

Abstract

Species and phylogenetic lineages have evolved to differ in the way that they acquire and deploy resources, with consequences for their physiological, chemical and structural attributes, many of which can be detected using spectral reflectance from leaves. Recent technological advances for assessing optical properties of plants offer opportunities to detect functional traits of organisms and differentiate levels of biological organization across the tree of life. Here, we connect leaf-level full range spectral data (400-2400 nm) of leaves to the hierarchical organization of plant diversity within the oak genus (Quercus) using field and greenhouse experiments in which environmental factors and plant age are controlled. We show that spectral data significantly differentiate populations within a species and that spectral similarity is significantly associated with phylogenetic similarity among species. We further show that hyperspectral information allows more accurate classification of taxa than spectrally-derived traits, which by definition are of lower dimensionality. Finally, model accuracy increases at higher levels in the hierarchical organization of plant diversity, such that we are able to better distinguish clades than species or populations. This pattern supports an evolutionary explanation for the degree of optical differentiation among plants and demonstrates potential for remote detection of genetic and phylogenetic diversity.

Diversification, adaptation, and community assembly of the American oaks (Quercus), a model clade for integrating ecology and evolution

“…Evolutionary priority effects are another mechanism by which the deep past influences current ecosystem function. I return to my earlier hypothesis that particular ecosystem functions of oak‐dominated forests in North America may be understood as attributable to evolutionary legacies rather than to adaptations or acclimations to current climate and geology (see also Cavender‐Bares et al ., ). To summarize the logic, the sympatric parallel diversification of the oaks occurred because of ecological opportunity at a particular time in Earth's history, and the ability to adapt to a wide range of habitats in multiple lineages simultaneously.…”

“…However, other leaf traits, such as SLA and spectral regions closely associated with photochemistry and light-harvesting pigments, are not ( Fig. 7; Cavender- Bares et al, 2016b). Transitions between deciduousness and evergreenness across a densely sampled phylogeny of the American oaks reveal evolutionary conservatism but also represent important adaptive changes in response to climate.…”

“…The large canopy size of oak trees makes their detection by remote sensing possible. At the leaf level, oak species and lineages can be differentiated spectrally, including genetically based phenotypic differences among populations (Cavender-Bares et al, 2016b). Physiological functions of individual trees and ecosystem properties can both be detected in this manner (Gamon et al, 1990(Gamon et al, , 1995Gamon & Qiu, 1999;Moya et al, 2001;Flexas et al, 2002;Freedman et al, 2002;Asner et al, 2010;Asner & Martin, 2011;.…”

Mapping multi‐scale vascular plant richness in a forest landscape with integrated LiDAR and hyperspectral remote‐sensing

“…, Cavender‐Bares et al. ). Our results generally support this conclusion, though only at pixel resolutions coarse enough to adequately incorporate sub‐pixel heterogeneity and at ground scales large enough to subsume local diversity (Rocchini , Schmidtlein and Fassnacht ).…”

Community-wide consequences of variation in photoprotective physiology among prairie plants

“…Because these optical types correspond to functional roles, their existence can help explain the effectiveness of remote sensing in measuring biodiversity (Jetz et al 2016) and scaling up plant physiology to whole ecosystems Bazzaz 2004, Ollinger et al 2008). The potential for reflectance spectroscopy to provide an integrated picture of plant function means that it may be useful to treat diversity in spectral properties as a kind of biodiversity alongside functional, phylogenetic, and other betterrecognized dimensions of biodiversity (Cavender-Bares et al 2017).…”