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Performance-based inference of selection on stomatal length and specific leaf area varies with climate-of-origin of the forest tree, Eucalyptus ovata
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Orientador(es)
Resumo(s)
Understanding how functional traits affect plant performance and fitness is a key step in unravelling the role of
natural selection in shaping the evolutionary trajectory of populations. We examined early-age selection acting
on leaf traits via their effects on growth performance and fitness, measured in Eucalyptus ovata trees planted in a
common-garden field trial embedded in a reforestation planting in Tasmania, Australia. We focused on two
important leaf traits - stomatal length and specific leaf area (SLA) - measured two years after planting, and
compared interplanted E. ovata groups originating from dry and wet home-site climates, with the trial site having
intermediate long-term mean annual rainfall. Two-year height growth was used as the performance attribute,
and the time-averaged tree survival over the subsequent six years as the fitness component. There was evidence
for performance-based selection on the leaf traits, with the strength and form of selection depending on the trait
and climate group being considered. In this sense, selection in the dry group operated mainly on stomatal length
where a combination of directional (favouring longer stomata) and stabilizing selection was detected, whereas
selection in the wet group acted only on SLA and was purely stabilizing. Estimates of performance-based
correlational selection were not statistically significant. For both climate groups, estimates of fitness-based selection
gradients provided evidence for significant directional (but not quadratic) selection on height performance,
favouring individuals with faster growth, but did not indicate statistical support for direct effects of the
leaf traits on tree survival, conditional on measured performance. These results validated qualitative inferences
of selection from the performance-based analysis, and suggested that selection on the leaf traits appeared to be
mediated by their effects on early-age height performance, which in turn directly influenced later-age survival.
We discuss the mechanisms by which the focal traits may have affected height performance, and likely factors
contributing to the different patterns of phenotypic selection observed in the two groups experiencing the same
environment. We also provide expressions of analytical derivatives that were developed for the estimation of
selection gradients based on a logistic regression model relating a binary fitness response to linear and nonlinear
covariate terms for the target regressor variables.
Descrição
Palavras-chave
Phenotypic selection Selection gradients Performance gradients Leaf functional traits Growth performance Tree survival
Contexto Educativo
Citação
Costa e Silva, J., Potts, B.M., Prober, S.M. Performance-based inference of selection on stomatal length and specific leaf area varies with climate-of-origin of the forest tree, Eucalyptus ovata, Perspectives in Plant Ecology. Evolution and Systematics. Volume 62, 2024, 125765.