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Advisor(s)
Abstract(s)
We evaluated population differences and drought-induced phenotypic selection on four
seedling traits of the Australian forest tree Eucalyptus pauciflora using a glasshouse drydown
experiment. We compared dry and mesic populations and tested for directional
selection on lamina length (reflecting leaf size), leaf shape, the node of ontogenetic
transition to the petiolate leaf (reflecting the loss of vegetative juvenility), and lignotuber
size (reflecting a recovery trait). On average, the dry population had smaller and broader
leaves, greater retention of the juvenile leaf state and larger lignotubers than the mesic
population, but the populations did not differ in seedling survival. While there was
statistical support for directional selection acting on the focal traits in one or other
population, and for differences between populations in selection gradient estimates
for two traits, only one trait—lamina length—exhibited a pattern of directional selection
consistent with the observed population differences being a result of past adaptation to
reduce seedling susceptibility to acute drought. The observed directional selection for
lamina length in the mesic population suggests that future increases in drought risk in the
wild will shift the mean of the mesic population toward that of the dry population. Further,
we provide evidence suggesting an early age trade-off between drought damage and
recovery traits, with phenotypes which develop larger lignotubers early being more
susceptible to drought death. Such trade-offs could have contributed to the absence of
population mean differences in survival, despite marked differentiation in seedling traits
Description
Original Research
Keywords
adaptation to drought trade-off leaf length and shape vegetative juvenility lignotuber size selection gradient generalized linear mixed model Eucalyptus pauciflora
Pedagogical Context
Citation
Costa e Silva J, Jordan R, Potts BM, Pinkard E and Prober SM (2021) Directional Selection on Tree Seedling Traits Driven by Experimental Drought Differs Between Mesic and Dry Populations. Front. Ecol. Evol. 9:722964
Publisher
Frontiers