DOI: 10.5061/dryad.crjdfn39d
title: Data for: Adaptive plasticity to drought of Grime’s CSR strategies

description: Grime’s strategies (Competitor, Stress tolerator, Ruderal; CSR) represent
 viable trait combinations with which species deal with environmental
 conditions. CSR strategies are broadly used to understand plant adaptation
 to the environment, yet their plastic responses have received little
 attention. A globally-calibrated tool (StrateFy) estimates CSR strategies
 using specific leaf area (SLA), leaf dry matter content (LDMC) and leaf
 area (LA) data, but these three traits can hardly characterise whole-plant
 responses to the environment individually. CSR strategies reflect
 trade-offs among growth, survival and reproduction, at both leaf and
 whole-plant levels, thus integrating several functions. We hypothesised
 that CSR strategies and the three constituent traits would show
 independent plasticity patterns, and that CSR strategies would be more
 likely to show adaptive responses, i.e., to fit expected functional
 responses to environmental gradients. We compared phenotypic plasticity to
 drought in single traits (SLA, LDMC and LA) with the integrated plasticity
 of the resulting CSR strategy. The study species was the invasive plant
 Mesembryanthemum crystallinum, which is distributed in arid and semiarid
 Chile. We found that trait plasticity was rather idiosyncratic and
 contrary to what would be expected from a functional adjustment to
 drought: LDMC did not change (expected response: increase) and SLA
 increased (expected response: decrease). Conversely, plastic responses of
 CSR strategy and LA were consistent with functionally adaptive responses
 to drought in all populations: S-strategy increased, while C-strategy and
 LA decreased. We advocate the use of Grime’s CSR theory as an integrative
 approach to further our understanding of adaptive plasticity in plants.
description: <em>Mesembryanthemum crystallinum</em> is an annual
 succulent native to South Africa that has invaded (semi)arid regions
 worldwide (Adams et al. 1998). In Chile, <em>M.
 crystallinum</em> is distributed in coastal areas between 24°S and
 34°S, from the Atacama Desert to Mediterranean regions (Fuentes et al. 2013, Madrigal-González et al.
 2013). We assessed phenotypic plasticity to drought in
 <em>M. crystallinum</em> in a greenhouse experiment with two
 watering treatments (moist vs drought). Seeds were collected in ten
 coastal populations distributed between 29.10°S and 30.56°S (Supporting
 information). We sowed ca. 400 seeds from each population (20 seeds from
 20 mother plants) in 1-L pots filled with a mixture (2:1) of sand and
 field-collected soil. Soil was collected in a site close to the centre of
 the distribution range of <em>M. crystallinum</em> in Chile
 (El Romeral; see Supplementary material); specifically, we collected soil
 from microsites free from <em>M. crystallinum</em>, where soil
 salinity is not high enough to trigger responses to stress conditions
 (León et al. 2011, De La Cruz et al.
 2023). We thinned the seedling groups to ensure growth
 synchrony across populations, which showed similar germination percentages
 (χ<sup>2</sup><sub>(9,400)</sub> = 7.09, p = 0.628; arcsine-transformed data). Two paired seedlings from each mother plant were assigned to each water treatment 10-12 weeks later. Plants in moist and drought treatments were watered with 140 ml of tap water twice a week and 70 ml of tap water once a week, respectively. This watering schedule is equivalent to 29.2% (50 mm) and 25.4% (14 mm) of mean annual precipitation in the southernmost and second-to-northernmost populations, respectively, which corresponds to the precipitation reported for the last four years (Supporting information; www.ceazamet.cl). Initial N was 800 plants (10 populations × 2 treatments × 20 mother plants × 2 replicates) distributed across 16 blocks. A total of 61 plants died during the experiment. After three months growing in the watering treatments (i.e., plants totalling six months in the greenhouse), and when plants produced the first flower buds, we harvested three leaves per individual. We chose leaves that had recently transitioned to maturity and located in the mid of a side shoot. These leaves were scanned and weighed to obtain leaf area (LA, mm<sup>2</sup>) and fresh leaf weight (mg). Leaves were dried at 70 °C for 72 h and dry weight was recorded (mg). Subsequently we estimated specific leaf area (SLA, leaf area/leaf dry mass; mm<sup>2</sup> mg<sup>-1</sup>) and leaf dry matter content (LDMC, 100*leaf dry weight/leaf fresh weight; %), following Pérez-Harguindeguy et al. (2013). We estimated the relative contribution (%) of competitiveness (C), stress tolerance (S) and ruderality (R) for all individuals using StrateFy (Pierce et al. 2017).