DOI: 10.5061/dryad.vdncjsz62
title: Native Australian seedlings exhibit novel strategies to acclimate to repeated heatwave events

description: Heatwaves are becoming more intense and frequent. Plant photosystem
 thermal thresholds can vary with species, but also shift in response to
 environmental triggers. Both upper and lower thresholds can acclimate to
 repeated heatwaves through ecological stress memory, where prior exposure
 primes them for subsequent events. The extent to which acclimation to
 repeated heat stress events varies among environmental origin and/or
 species is unknown. Different acclimation strategies might reflect biome
 of origin, or may be species-specific. For 12 species from two contrasting
 biomes – extreme desert and benign coastal temperate – we investigated
 responses to two simulated heatwaves, via shifts in upper and lower
 critical temperatures of photosystem II, and the difference between these
 thresholds, thermal tolerance breadth (TTB).  Biome of origin had
 no effect on thermal tolerance. Observed differences among species
 following heat events suggested two possible acclimatory strategies. In
 some cases, species increased thermal thresholds during the first
 heatwave, but at the cost of reduced thermal tolerance during the second
 heatwave, a sprinter strategy. Other species acclimated to the first
 heatwave and further increased thermal tolerance to a second heatwave,
 indicative of ecological stress memory, a marathoner strategy. 
 Synthesis: These among-species responses to heatwaves could suggest
 distinct vulnerabilities and resilience to repeat heat stress events, with
 some species having limited capacity to tolerate consecutive heatwaves,
 possibly as the cost of acclimation is too great, with other species
 having the advantage of increased tolerance via stress memory, helping
 them survive future stress, at least in the short-term.
description: ## Native Australian seedlings exhibit novel strategies to acclimate to
 repeated heatwave events Contains 15 files: (1) Analysis - R scripts
 required to replicate analysis and figures in the manuscript and
 supplementary material: DRYAD biome and species lmer models.R DRYAD Delta
 models.R DRYAD Figure 2.R DRYAD supp.R (2) Datasets (11 files total):
 dfcold.csv dfhot.csv dfTTB.csv For analysis of effect of treatment and
 time period on seedling tcrit_hot, tcrit_cold and thermal tolerance
 breadth Columns: * stage - the time period of when the measurement was
 taken; 1,2,3,4 * biome - desert (extreme), coastal temperate (benign) *
 species - Acacia longifolia, Acacia salicina, Acacia victoriae, Banksia
 integrifolia, Capparis mitchellii, Carex appressa, Casuarina pauper,
 Eucalyptus largiflorens, Flindersia maculosa, Lomandra longifolia,
 Melaleuca hypericifolia, Pittosporum undulatum * treatment - 0_HW,
 control; 1_HW, one heatwave; 2_HW, two heatwaves * block_rep - replicate;
 1, 2, 3, 4, 5 * ID - a unique identifier for each leaf * wkend - whether
 the plants experienced a two-day period of heat * delay - whether the
 plants experienced a delay in watering with potential water stress * tcrit
 - the inflection point between the fast and slow rise phases of the T- F0
 curve (Knight and Ackerly 2002) delta_slopes.csv For analysis comparing
 the slopes of the sprinters and marathoners' thermal tolerance
 breadth Columns: * species - Acacia longifolia, Acacia salicina, Acacia
 victoriae, Banksia integrifolia, Capparis mitchellii, Carex appressa,
 Casuarina pauper, Eucalyptus largiflorens, Flindersia maculosa, Lomandra
 longifolia, Melaleuca hypericifolia, Pittosporum undulatum * biome -
 desert (extreme), coastal temperate (benign) * block - replicate; 1, 2, 3,
 4, 5 * slope - the calculated slope between stage 1 and stage 3 * group -
 marathoner; sprinter mcoldHWsum.csv mcoldRECsum.csv mhotHWsum.csv
 mhotRECsum.csv TTBHWsum.csv TTBRECsum.csv For graphing the sprinters vs.
 marathoners groups Columns: * species- Acacia longifolia, Acacia salicina,
 Acacia victoriae, Banksia integrifolia, Capparis mitchellii, Carex
 appressa, Casuarina pauper, Eucalyptus largiflorens, Flindersia maculosa,
 Lomandra longifolia, Melaleuca hypericifolia, Pittosporum undulatum *
 biome - desert (extreme), coastal temperate (benign) * stage - the time
 period of when the measurement was taken; 1,2,3,4 * mTTB - mean thermal
 tolerance breadth * sdTTB - standard deviation of thermal tolerance
 breadth * nTTB - number of replicates * seTTB - standard error of thermal
 tolerance breadth DRYAD_supp.csv For calculating the mean of the control
 vs. the treatment at each stage, for each species * test - which
 measurement was taken; tcrit hot, tcrit cold, ttb * stage - the time
 period of when the measurement was taken; 1,2,3,4 * biome - desert
 (extreme), coastal temperate (benign) * species - Acacia longifolia,
 Acacia salicina, Acacia victoriae, Banksia integrifolia, Capparis
 mitchellii, Carex appressa, Casuarina pauper, Eucalyptus largiflorens,
 Flindersia maculosa, Lomandra longifolia, Melaleuca hypericifolia,
 Pittosporum undulatum * treatment - 0_HW, control; 1_HW, one heatwave;
 2_HW, two heatwaves * block_rep - replicate; 1, 2, 3, 4, 5 * ID - a unique
 identifier for each leaf * wkend - whether the plants experienced a
 two-day period of heat * delay - whether the plants experienced a delay in
 watering with potential water stress * tcrit - the inflection point
 between the fast and slow rise phases of the T- F0 curve (Knight and
 Ackerly 2002) * ttb - thermal tolerance breadth measurement