Intraspecific trait variation across multiple scales: the leaf economics spectrum in coffee

Abstract

Summary Understanding species differences in plant functional traits has been critical in developing a mechanistic understanding of terrestrial ecological processes. Greater attention is now being placed on understanding the extent, causes and consequences of intraspecific trait variation (ITV). ITV is especially important in governing ecological processes in cropping systems, where only a small number of species or genotypes exist in high abundances. However, it remains unclear if key principles of trait‐based ecology – namely the leaf economics spectrum (LES) – also describe intraspecific variation in crop functional biology. There also remains a need to understand whether ITV within crops is random, or structured across environmental, management‐related or biological levels of organization in agroecosystems. We employed a nested design field survey to evaluate ITV in leaf traits in coffee (Coffea arabica), one of the world's most widespread tropical crops. We evaluated ITV in eight physiological, morphological and chemical leaf traits, across five nested categorical levels (sites, management systems, spatial location, plant identity, branch identity). We compared patterns of LES trait covariation in coffee, to interspecific patterns observed across over 700 wild plant species. Patterns of bivariate and multivariate ITV in coffee were broadly consistent with, but considerably weaker than, interspecific patterns associated with the LES, indicating that crops may systematically diverge from global patterns of trait trade‐offs observed in wild plants. Physiological traits varied most widely (coefficient of variation (cv) 42–107%), followed by morphological traits (cv = 15–38%) and chemical traits (cv = 3–11%). Physiological ITV was best explained by the site in which a coffee plant was growing (17–55% explained), while ITV for chemical traits was best explained by management treatments within sites (25–36%); morphological ITV was higher even at the individual tree level or branch level and remained largely unexplained. Our results support the hypothesis that artificial selection and high‐resource agricultural environments lead crops to systematically deviate from patterns of leaf trait covariation observed across wild plants species. Coupled with an understanding of how different traits vary systematically across multiple levels of biological organization, these findings help integrate ITV into future analyses of agroecosystem structure and function. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12790/suppinfo is available for this article.

Shifts in plant functional strategies over the course of wheat domestication

“…The comparison between intra‐ vs. interspecific LES remains scarce in the literature (e.g. Blonder, Violle, & Enquist, ; Donovan, Mason, Bowsher, Goolsby, & Ishibashi, ; Martin et al., ; Niinemets, ; Prieto et al., ; Vasseur, Violle, Enquist, Granier, & Vile, ). Two reasons may explain the lack of significant relationships in wheat.…”

A continental‐scale assessment of variability in leaf traits: Within species, across sites and between seasons

“…Refuting our hypothesis, we found that ITV outweighed interspecific variation for R dark , V cmax and P area ; this was true whether metabolic rates were normalized to the prevailing temperature or to a common reference temperature. For the metabolic traits, levels of variation within individual plants (18% for V cmax Prevailing and 20% for R dark Prevailing ) were lower than reported in a recent study in coffee crops which found that variation among leaves within an individual branch accounted for approximately 25% of total variation in light‐saturated photosynthesis (Martin et al., ). Overall, our results indicate that ITV can be an important, even dominant, component of leaf trait variation, especially for metabolic processes.…”

Plant evolutionary history mainly explains the variance in biomass responses to climate warming at a global scale

“…Theoretically, crops and species with larger geographic distributions may exhibit larger intraspecific variation because of more diverse selection pressures (Martin et al ., ) and stronger local adaptation (Münzbergová et al ., ). However, these expectations could not be tested in our datasets, because most of the global warming experiments were not designed to capture the intraspecific variation but rather to examine the average response of a species.…”