Functional ecology of congeneric variation in the leaf economics spectrum

Abstract

Summary Variation in resource availability can lead to phenotypic plasticity in the traits comprising the world‐wide leaf economics spectrum (LES), potentially impairing plant function and complicating the use of tabulated values for LES traits in ecological studies. We compared 14 Carex (Cyperaceae) species in a factorial experiment (unshaded/shaded × sufficient/insufficient P) to analyze how changes in the network of allometric scaling relationships among LES traits influenced growth under favorable and resource‐limited conditions. Changes in leaf mass per area (LMA) shifted the scaling relationships among LES traits expressed per unit area vs mass in ways that helped to sustain growth under resource limitation. Increases in area‐normalized photosynthetic capacity and foliar nitrogen (N) were correlated with increased growth, offsetting losses associated with mass‐normalized dark respiration and foliar N. These shifts increased the contributions to growth associated with photosynthetic N‐use efficiency and the N : P ratio. Plasticity in LMA is at the hub of the functional role of the LES as an integrated and resilient complex system that balances the relationships among area‐ and mass‐based aspects of gas exchange and foliar nutrient traits to sustain at least some degree of plant growth under differing availabilities of above‐ and below‐ground resources.

Correlational selection and genetic architecture promote the leaf economics spectrum in a perennial grass

“…For the LES to evolve, leaf economics traits must exhibit genetic variation. But leaf economics traits and correlations between traits can also be driven by environmental factors, like fertilization and drought (Sherrard and Maherali 2006, Fajardo and Siefert 2018, Ji et al 2020.…”

Quantitative trait locus mapping reveals an independent genetic basis for joint divergence in leaf function, life-history, and floral traits between scarlet monkeyflower (Mimulus cardinalis) populations

“…Unrelated plant taxa often converge on suites of correlated traits, such as the floral selfing syndrome (Sicard and Lenhard, 2011) or points along the leaf economics spectrum (Wright et al, 2004). Similar spectra sometimes exist within genera and species, with parallel variation in physiological, morphological, and life-history traits across environmental gradients (Mason and Donovan, 2015;Muir et al, 2016;Fajardo and Siefert, 2018;Anderegg et al, 2018;Sartori et al, 2019;Ji et al, 2019). Consistent trait correlations across taxa may arise from fundamental genetic constraints mediated by developmental and physiological tradeoffs.…”

“…On the other hand, intra-specific variation in leaf functional traits often opposes or blurs LES patterns evident at larger taxonomic scales (Derroire et al, 2018;Anderegg et al, 2018), suggesting that different processes may structure intra-specific vs. inter-specific co-variation among leaf traits. Particularly in herbaceous taxa, cross-species and cross-population variation only partially recapitulate the LES, suggesting that leaf level tradeoffs do not underpin community-level associations (Mason and Donovan, 2015;Muir et al, 2016;Ji et al, 2019;Agrawal, 2020). Furthermore, even when intra-generic associations between climate, life history and leaf ecophysiology are strong, they are ambiguous about mechanism, as population structure and correlated selection can generate association without a necessary functional relationship (Agrawal, 2020).…”

Quantitative trait locus mapping reveals an independent genetic basis for joint divergence in leaf function, life‐history, and floral traits between scarlet monkeyflower (Mimulus cardinalis) populations

“…Quantitative trait locus mapping reveals an independent genetic basis for joint divergence in leaf function, lifehistory, and floral traits between scarlet monkeyflower (Mimulus cardinalis) populations Unrelated plant taxa often converge on suites of correlated traits, such as the floral selfing syndrome (Sicard and Lenhard, 2011) or points along the leaf economics spectrum (Wright et al, 2004). Similar spectra sometimes exist within genera and species, with parallel variation in physiological, morphological, and life-history traits across environmental gradients (Mason and Donovan, 2015;Anderegg et al, 2018;Fajardo and Siefert, 2018;Sartori et al, 2019;Ji et al, 2020). Consistent trait correlations across taxa may arise from fundamental genetic constraints mediated by developmental and physiological tradeoffs.…”

“…Indeed, assays of phenotypic selection and genetic correlations in desert annuals suggest a lack of plants with the (favored) trait combinations that could break LES correlations (Kimball et al, 2013; Angert et al, 2014). However, intra‐specific variation in leaf functional traits often does not fully recapitulate the LES (Anderegg et al, 2018; Derroire et al, 2018), particularly in herbaceous taxa (Mason and Donovan, 2015; Muir et al, 2017; Agrawal, 2020; Ji et al, 2020). Thus, it is often not clear what ecological and evolutionary processes (e.g., constraint, natural selection, and/or plasticity) generate large‐scale patterns of trait correlation among leaf traits, preventing prediction of evolutionary responses to novel conditions.…”