Trait plasticity and trade‐offs shape intra‐specific variation in competitive response in a foundation tree species

Abstract

Summary The ability to tolerate neighboring plants (i.e. degree of competitive response) is a key determinant of plant success in high‐competition environments. Plant genotypes adjust their functional trait expression under high levels of competition, which may help explain intra‐specific variation in competitive response. However, the relationships between traits and competitive response are not well understood, especially in trees. In this study, we investigated among‐genotype associations between tree trait plasticity and competitive response. We manipulated competition intensity in experimental stands of trembling aspen (Populus tremuloides) to address the covariance between competition‐induced changes in functional trait expression and aspects of competitive ability at the genotype level. Genotypic variation in the direction and magnitude of functional trait responses, especially those of crown foliar mass, phytochemistry, and leaf physiology, was associated with genotypic variation in competitive response. Traits exhibited distinct plastic responses to competition, with varying degrees of genotypic variation and covariance with other trait responses. The combination of genotypic diversity and covariance among functional traits led to tree responses to competition that were coordinated among traits yet variable among genotypes. Such relationships between tree traits and competitive success have the potential to shape stand‐level trait distributions over space and time.

Native plant species show evolutionary responses to invasion by Parthenium hysterophorus in an African savanna

“…2e). Studies on Arabidopsis thaliana (Baron et al ., 2015) and Populus tremuloides (Cope et al ., 2021) have demonstrated intraspecific genetic variability in competitive response and in plasticity of fitness‐related traits in response to competition. Phenotypic plasticity is genetically controlled and its extent and magnitude among populations can evolve through natural selection (Callaway et al ., 2003; Ghalambor et al ., 2007).…”

Chemical phenotype as important and dynamic niche dimension of plants

“…Additionally, biotic stresses such as competition with other plants may result in phytochemical changes, for example, in condensed tannins (Fig. 1b; Cope et al ., 2021). Both the definition of niche conformance and response traits do not involve any effects on other organisms or feedback with the environment; these effects are mediated by ‘effect traits’ involved in niche construction.…”

“…Both the definition of niche conformance and response traits do not involve any effects on other organisms or feedback with the environment; these effects are mediated by ‘effect traits’ involved in niche construction. For instance, phytochemicals that are produced in response to competition may turn into effect traits, if the phytochemical‐producing plant gains a competitive advantage (Cope et al ., 2021) and thus modifies the environment in a way that it is rewarded with a fitness gain. Another classical example of niche construction by phytochemicals as effect traits are herbivore‐induced plant volatiles that influence the structure of plant–insect interaction networks by serving as direct defense against herbivores and/or as attractants for the herbivores' enemies (Fig.…”

Compensatory phenolic induction dynamics in aspen after aphid infestation

“…In naturally varying stands of trees, correlative relationships between defence compounds and antagonists are often incomplete 29 – 31 , and although phenolic chemistry and genotype may explain resistance traits for particular biological associations, community associations with phenolic profiles are often weak 15 . Random events may partly explain the imperfect relationships, but inducibility also makes plant chemical profiles moving targets 32 , prompting the question of whether constitutive defence levels correlate with induced defence responses, or if either of the two better explain resistance properties.…”