Intraspecific trait variation influences physiological performance and fitness in the South Africa shrub genus Protea (Proteaceae)

• Published in: Annals of botany Vol. 127; no. 4; pp. 519 - 531
• Main Authors: Nolting, Kristen M, Prunier, Rachel, Midgley, Guy F, Holsinger, Kent E
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 24.03.2021
• Subjects: Biological Evolution; Original; Phenotype; Plant Leaves; Proteaceae - genetics; South Africa; South Africa; trait–fitness relationship; Cape Floristic Region; functional traits; Proteaceae; South Africa; intraspecific trait variation; trait combinations; Protea; ecophysiology
• ISSN: 0305-7364; 1095-8290; 1095-8290
• DOI: 10.1093/aob/mcaa060

Global plant trait datasets commonly identify trait relationships that are interpreted to reflect fundamental trade-offs associated with plant strategies, but often these trait relationships are not identified when evaluating them at smaller taxonomic and spatial scales. In this study we evaluate trait relationships measured on individual plants for five widespread Protea species in South Africa to determine whether broad-scale patterns of structural trait (e.g. leaf area) and physiological trait (e.g. photosynthetic rates) relationships can be detected within natural populations, and if these traits are themselves related to plant fitness. We evaluated the variance structure (i.e. the proportional intraspecific trait variation relative to among-species variation) for nine structural traits and six physiological traits measured in wild populations. We used a multivariate path model to evaluate the relationships between structural traits and physiological traits, and the relationship between these traits and plant size and reproductive effort. While intraspecific trait variation is relatively low for structural traits, it accounts for between 50 and 100 % of the variation in physiological traits. Furthermore, we identified few trait associations between any one structural trait and physiological trait, but multivariate regressions revealed clear associations between combinations of structural traits and physiological performance (R2 = 0.37-0.64), and almost all traits had detectable associations with plant fitness. Intraspecific variation in structural traits leads to predictable differences in individual-level physiological performance in a multivariate framework, even though the relationship of any particular structural trait to physiological performance may be weak or undetectable. Furthermore, intraspecific variation in both structural and physiological traits leads to differences in plant size and fitness. These results demonstrate the importance of considering measurements of multivariate phenotypes on individual plants when evaluating trait relationships and how trait variation influences predictions of ecological and evolutionary outcomes.