DOI: 10.5061/dryad.51c59zwgj
title: Data from: Evidence for reductions in physical and chemical plant defense traits in island flora

description: Reduced defense against large herbivores has been suggested to be part of
 the “island syndrome” in plants. However, empirical evidence for this
 pattern is mixed. In this paper, we present two studies that compare
 putative physical and chemical defense traits from plants on the
 California Channel Islands and nearby mainland based on sampling of both
 field and common garden plants. In the first study, we focus on five pairs
 of woody shrubs from three island and three mainland locations and find
 evidence for increased leaf area, decreased marginal leaf spines, and
 decreased concentrations of cyanogenic glycosides in island plants. We
 observed similar increases in leaf area and decreases in defense traits
 when comparing island and mainland genotypes grown together in botanic
 gardens, suggesting that trait differences are not solely driven by
 abiotic differences between island and mainland sites. In the second
 study, we conducted a common garden experiment with a perennial
 herb—Stachys bullata (Lamiaceae)—collected from two island and four
 mainland locations. Compared to their mainland relatives, island genotypes
 show highly reduced glandular trichomes and a nearly 100-fold reduction in
 mono- and sesquiterpene compounds from leaf surfaces. Island genotypes
 also had significantly higher specific leaf area, somewhat lower rates of
 gas exchange, and greater aboveground biomass than mainland genotypes
 across two years of study, potentially reflecting a broader shift in
 growth habit. Together, our results provide evidence for reduced
 expression of putative defense traits in island plants, though these
 results may reflect adaptation to both biotic (i.e., the historical
 absence of large herbivores) and climatic conditions on islands.
description: <strong>Study 1: Chaparral Shrub
 Sampling</strong> We selected five pairs of taxa
 characteristic of the chaparral plant community that occur on both the
 California Channel Islands and the nearby southern California mainland.
 Pairs were chosen because they are common representatives of the chaparral
 flora and also to match the taxa sampled in Bowen and Van Vuren (1997).
 Sampling consisted of either congeners or conspecifics from three plant
 families: Rosaceae (<em>Cercocarpus</em>,
 <em>Prunus</em>, <em>Heteromeles</em>),
 Papaveraceae (<em>Dendromecon</em>), and Rhamnaceae
 (<em>Ceanothus</em>). We collected leaf tissue in February and
 March of 2016 for use in morphological and chemical analysis. In total, we
 sampled 291 individual plants from five taxonomic pairs across six sites
 (three island, three mainland), for an average of approximately 10 plants
 per site. We collected leaf tissue for morphological
 analysis from focal plants by clipping branches containing variable
 numbers of leaves. When possible, we collected a branch from both the
 lower (&lt; 1 m in height) and the upper (&gt; 2 m in height)
 portion of the plant canopy to capture morphological differences
 associated with accessibility to mammalian herbivores. For analysis of
 cyanogenic glycosides, we collected individual leaves from the lower
 portion of the plant canopy for three species
 (<em>Heteromeles</em>, <em>Prunus</em>,
 <em>Cercocarpus</em>) and, when possible, included both fully
 mature/expanded leaf tissue as well as young/actively expanding leaf
 tissue. Leaf chemistry samples were immediately frozen on dry ice and were
 later transferred to a −80 °C freezer until processing. For each sampled
 plant, we recorded its GPS coordinates, elevation, and slope aspect (when
 relevant) using a handheld Garmin GPS device, and we also recorded the
 approximate stem diameter at 0.25 m above the ground using a digital
 caliper. For each sampled branch, leaves were removed
 and imaged using a flatbed scanner (CanoScan LiDE 120, 2400 × 4800
 dpi<sup>2</sup>) with a scalebar. We recorded the following
 measurements from each leaf: leaf area (without petiole), marginal leaf
 spinescence, and percent of leaf tissue missing due to herbivory. All
 measurements were taken using ImageJ v. 1.51. For a visual depiction of
 our measurement protocol, see Figure S2. Non-fully expanded leaves (n =
 809) were measured but were excluded from subsequent analyses. We also
 measured specific leaf area (SLA) at the level of branches by taking the
 cumulative area of all fully expanded leaves (in
 cm<sup>2</sup>) and dividing this by their cumulative mass (in
 g). To measure cyanogenic glycoside (CNglc) content, we
 followed a modified version of the evolved hydrogen cyanide (HCN) protocol
 described in Experiment 2 of Gleadow et al. (2011). We only collected
 tissue for species in the Rosaceae (<em>Cercocarpus</em>,
 <em>Heteromeles</em>, <em>Prunus</em>), which are
 known to produce CNglcs, and included paired samples of mature (“old”) and
 expanding (“young”) leaf tissue from each plant, where possible. For a
 full description of methods used to quantify CNglc content, see
 Supplemental Materials. In total, we generated 194 measurements of CNglc
 content from 108 individual plants. We also sampled
 leaf tissue from two botanical gardens (Santa Barbara Botanic Garden and
 Rancho Santa Ana Botanic Garden) on the mainland that featured island and
 mainland genotypes of the species of interest, grown from either seed or
 cuttings. All leaf tissue collection, morphological analysis, and chemical
 analysis were conducted in the same way as described above, although SLA
 was not measured for botanical garden plants. In total, we sampled an
 additional 40 plants (18 island and 22 mainland genotypes) from these
 common environments. We also took advantage of a series
 of herbivore exclosures on Santa Catalina Island—which still has
 introduced deer and bison present—to test for the potential effects of
 herbivore-mediated plasticity in plant traits. Because of the relatively
 small number of intact exclosures available, our sampling across species
 was somewhat uneven, though we were able to sample a total of 24 plants
 inside of exclosures and 35 plants outside of exclosures (Table S1). Note
 that plants in the herbivore exclosures experience gene flow from
 genotypes outside the exclosure through pollen and seed.
 <strong>Study 1: Abiotic Variation between
 Sites</strong> Island and mainland sites have
 generally similar climates, although island locations may have more
 frequent nocturnal fog that reduces summertime evaporative water loss. To
 formally measure climatic differences between island and mainland
 locations, we used recorded coordinates from each plant to extract
 bioclimatic variables from the WorldClim2 database at 1 km resolution. We
 used principal component analysis (PCA) to explore variation in climate
 data and found that the first PC axis explained more than 83% of overall
 variation and was dominated by a single bioclimatic variable, temperature
 seasonality (BIO4). This axis separated island sites from the two more
 inland mainland sites (Stunt Ranch, Santa Monica Mtns.), which have higher
 temperature seasonality, while the third mainland site (Gaviota) had lower
 temperature seasonality and was more akin to island sites. The second PC
 axis explained 13% of the overall variation and included loadings for
 precipitation-related variables; this axis separated the drier Santa
 Catalina Island from all remaining sites. Island and mainland sites may
 also differ in soil properties; however, we did not attempt to quantify
 this potential variation. <strong>Study 1:
 Statistical Analyses</strong> We analyzed our
 data using multilevel linear mixed models implemented in the lme4 package
 in R version 4.1.3 to account for the hierarchical nature of our data.
 Response variables of interest were leaf area, SLA, marginal leaf
 spinescence, and leaf CNglc content. Leaf area and CNglc content were
 log-transformed to ensure that model-estimated confidence intervals were
 above 0; SLA and marginal leaf spinescence were untransformed. For
 marginal leaf spinescence, we only included
 <em>Heteromeles</em> and <em>Prunus</em> since
 these were the only species with stiff, rigid spines. Likewise, because
 CNglc levels in <em>Cercocarpus</em> were ~100x lower than in
 <em>Prunus</em> and <em>Heteromeles</em> (and
 often below our detection limit), CNglc analysis was restricted to the
 latter two species. Covariates that were included in each model included
 the site of collection, canopy position (upper versus lower), north/south
 slope aspect, and east/west slope aspect. We considered including
 elevation and stem diameter (as a proxy for plant age) as covariates,
 though because of limited within-site and within-species variation in
 these measures, we ultimately omitted them from analyses. Furthermore, we
 attempted to include bioclimatic variables as covariates in these models,
 but because of the relatively limited spatial scale of sampling across
 sites and within sites and the 1 km<sup>2</sup> resolution of
 the bioclim dataset, we captured relatively little overall climatic
 variability for most bioclimatic variables. For each
 response variable, we fit an overall model that included all samples
 collected in situ across all species (n = 4,096 leaves from 291 plants).
 These models were of the form (in lme4 syntax): 
 
 <strong><em>Response
 </em></strong><strong><em>variable ~
 IM*</em></strong><strong><em>Species + Covariates
 + (1|Site/Plant.ID/Branch.ID)</em></strong>
   
 where IM corresponds to whether
 samples came from an island or mainland site. Plant species interacts with
 island vs. mainland status to allow for variation in the magnitude of
 island vs. mainland contrasts across species. The collection site was
 included as a random intercept, with plant ID nested within the site and
 branch ID nested within the plant ID. Since specific leaf area was
 calculated by pooling leaves from within branches, the SLA model does not
 include a branch ID term. To assess within-species differences in trait
 expression between islands and mainland locations, we used the emmeans
 package. For two of the response variables (marginal
 spinescence, CNglc content), we included additional parameters based on a
 priori hypotheses. In the model considering marginal spinescence, we
 included an interaction between island/mainland status and canopy position
 to allow for the degree of spinescence heteroblasty to vary across
 locations. In the model considering CNglc content, we included a term for
 leaf age (old vs. young) based on our sampling scheme and predictions from
 optimal plant defense theory that younger leaf tissue should be more
 heavily defended against herbivores . To test for
 genetically based differences in trait values, we analyzed samples
 collected from botanic garden plants in a separate set of linear mixed
 models. These models were similar to those described above and were of the
 form: 
 <strong><em>Response variable ~ Source_IM*Species +
 Covariates + (1|Plant.ID/Branch.ID)</em></strong>
 (1) 
 where Source_IM refers to whether
 each plants’ original provenance was an island or mainland location. As
 above, we also estimated within-species differences between island and
 mainland locations using the emmeans package. Because
 we sampled the same species as Bowen and Van Vuren (1997), we can compare
 insularity effects across studies (our field sampling, our botanic garden
 sampling, and the field sampling from Bowen and Van Vuren). To do so, we
 calculated standardized effect sizes (Cohen’s d<sub>s</sub>)
 for each measured trait. Since Bowen and Van Vuren only report t
 statistics and sample sizes, we used the following formula for Cohen’s
 d<sub>s</sub>: where t corresponds to the mean of their
 reported t statistics, and n<sub>1</sub> and
 n<sub>2</sub> correspond to sample sizes from island and
 mainland locations. To generate effect size estimates and corresponding
 confidence intervals from our in situ and botanic garden sampling, we used
 the effect size package. Finally, to test for the
 effects of introduced herbivores on plant traits on Santa Catalina Island,
 we separately analyzed all trait data from Santa Catalina and included a
 term to account for whether samples came from inside versus outside of an
 herbivore exclosure. <strong>Study
 2: <em>Stachys
 bullata</em>–Background</strong>
 <em>Stachys bullata</em> (Lamiaceae) is a perennial
 herbaceous plant that occurs in coastal California from approximately
 Orange County to the San Francisco Bay Area, with populations present on
 Santa Cruz, Santa Rosa, and Anacapa Islands. It reproduces both clonally
 via rhizomes and sexually and is described as being glandular, with
 aromatic foliage that is characteristic of many plants in the Lamiaceae.
 However, island populations have been noted to have non-aromatic foliage
 as well as larger leaves and flowers than their mainland relatives [34],
 and densities of glandular trichomes appear to be much lower on island
 plants (Figure 2C). <strong>Study 2:<em>
 Stachys bullata</em> Common Garden
 Experiment</strong> To determine whether observed
 trait variation between island and mainland <em>S. bullata
 </em>populations is environmentally or genetically determined, we
 set up a multi-year common garden experiment in which we grew island and
 mainland <em>S. bullata</em> genotypes together at the Santa
 Barbara Botanic Garden (SBBG). Plants were collected in the field in late
 2015 from two island (Santa Cruz, Santa Rosa) and four mainland locations
 as rhizomes, which were transported to UC Davis and shallowly planted in
 potting mix. Plants were grown in 1-gallon pots for approximately three
 months and were then split into clonal replicates that were grown in their
 own 1-gallon pots. In total, we collected 44
 <em>S.</em><em> bullata</em> genotypes that were
 separated into 112 individual plants. In February 2016,
 we set up a common garden plot at the SBBG located on an east-facing slope
 that received partial or full sun throughout the year. Plants were spaced
 at a distance of 1 m apart from each other in a gridded pattern. The plot
 was surrounded by a 2 m fence to prevent browsing by deer, and each plant
 was enclosed in a cage made from hardware cloth to limit root herbivory by
 pocket gophers (<em>Thomomys bottae</em>), which were common
 at the site. We installed a drip irrigation system to assist with initial
 plant establishment. Plants were outplanted randomly with respect to
 island/mainland status in late February and early March of 2016 and
 received approximately 2L of water from a drip irrigation system at 1-week
 intervals between March and August 2016. In late August 2016, we ceased
 supplemental watering, and plants subsequently only received water from
 ambient precipitation. Plants became dormant in October 2016 and then
 subsequently began to regrow naturally in early February 2017. In
 addition, we set up a smaller common garden at the Santa Cruz Island
 Reserve, although due to concerns over the introduction of non-native
 genotypes, this common garden consisted of only genotypes from Santa Cruz
 Island. We generated four categories of data from
 common garden <em>S. bullata</em> plants. Three measures
 (biomass, SLA, gas exchange) were related to plant growth, while one
 measure (leaf surface chemistry) was related to plant defense. For biomass
 measurements, we collected all above-ground biomass at the end of each
 growing season (in 2016 and 2017) and recorded its dry mass. For SLA, we
 collected leaf tissue from each plant in April 2017 and measured leaf area
 and dry mass from fully expanded <em>S. bullata</em> leaves.
 In April 2017, we used a Li-6800 portable photosynthesis system (LI-COR
 Biosciences Inc., Lincoln, NE) to measure gas exchange rates on the most
 recent mature leaves that were sun exposed. For details on gas exchange
 measurements, see Supplemental Materials. For leaf
 chemistry, we focused on volatile organic compounds (VOCs) present on leaf
 surfaces and in glandular trichomes. Plants in the Lamiaceae are known for
 their exceptional diversity of terpenoid compounds, which are a diverse
 group of plant secondary metabolites thought to be involved in defense
 against herbivores and pathogens, plant communication, and modulating
 thermal and oxidative stress. We used a modified version of the protocol
 described in Pratt et al. (2014) for measuring terpenes in
 <em>Artemisia californica</em> (Asteraceae). Briefly, in April
 of 2017, after &gt; 1 year of growth in the common garden, we used a
 hole punch to collect six leaf discs, each from a different leaf, from
 approximately 75 <em>Stachys</em> plants across all genotypes.
 Leaf surface chemistry was quantified using gas chromatography-mass
 spectrometry (GCMS) for a subset of 47 of these plants. For a full
 description of chemical methods, see Supplementary Materials.
 <strong>Study 2: <em>Stachys</em> Data
 Analysis</strong> We analyzed aboveground biomass
 using a linear mixed effects model of the form: 
 
 <strong><em>Aboveground biomass ~ IM + Year +
 (1|Source.Pop/Genotype) + (1|Column) +
 (1|Row)</em></strong> 
 (3) 
 where IM refers to whether a given plant
 originated from an island or mainland site, and column and row refer to
 the location of plants within the common garden grid. To analyze gas
 exchange measurements, because of our smaller sample, we used a simple
 linear model with net carbon assimilation (A<sub>net</sub>) as
 the response and provenance (island vs. mainland) as the
 predictor. To analyze plant chemistry, we divided each
 integrated peak area by its corresponding internal standard peak area to
 standardize all values. We added all peaks together to achieve a
 cumulative compound abundance measure and also separated compounds based
 on their biochemical pathway (e.g., monoterpenes, sesquiterpenes, aromatic
 compounds). We used non-metric multidimensional scaling to visualize
 compositional differences between sites.
description: # Evidence for Reductions in Physical and Chemical Plant Defense Traits in
 Island Flora
 [https://doi.org/10.5061/dryad.51c59zwgj](https://doi.org/10.5061/dryad.51c59zwgj) This dataset consists of three primary data sources: (1) Morphological and chemical measurements of leaf traits, collected from five taxonomic pairs of chaparral shrubs (*Ceanothus megacarpus*, *Cercocarpus betuloides*, *Dendromecon rigida/harfordii*, *Heteromeles arbutifolia*, *Prunus ilicifolia*) at three sites on the California Channel Islands (Santa Rosa, Santa Cruz, Santa Catalina) and three sites on the California mainland. (2) Morphological and chemical measurements of the same leaf traits from the same species, but this time measured from plants growing at botanic gardens (3) Morphological, chemical, and biomass data from a common garden experiment with *Stachys bullata*, with genotypes from two islands (Santa Rosa, Santa Cruz) and four mainland locations In addition, our analysis also includes bioclimatic data and local precipitation data accessed from publicly available sources. ## Description of the data and file structure This dataset is organized into two folders: **data_files** and **scripts** --- ***DATA_FILES*** Within the **data_files** folder, there are folders for "**Shrubs**" (corresponding to 1 and 2 above) and "**Stachys**" (corresponding to 3 above). **SHRUBS** The **Shrubs** folder contains one file (**Bowen and Van Vuren Effect Sizes.xlsx**), which summarizes the results from Bowen and Van Vuren (1997 ([https://www.jstor.org/stable/2387407](https://www.jstor.org/stable/2387407), directly as reported in their Tables 2, 3, 4, and 5 in the main text. Variables in this datafile include: 1. Trait - the plant trait that was measured in their study 2. Genus - the taxonomic unit being measured 3. t - the value of the t-statistic from a paired t-test of island vs. mainland samples for a given genus 4. n island - sample size for island plants 5. n mainland - sample size for mainland plants 6. Cohen's D - derived value that expresses insularity effect size for a given measure The **Shrubs** folder also contains four subfolders: **Cyanide**, **Images**, **Mapping**, and **Morphology** The **Cyanide** folder contains two files: 1. **cyanide_calibration.csv** - file containing measurements used to define calibration curve for quantifying evolved HCN from leaf tissue. 1. conc = concentration of potassium cyanide (KCN) standard used in calibration (mg/L) 2. abs = absorbance value returned by VWR V-1200 spectrometer, measured at 510 nm 2. **cyanide_measurements.csv** - file containing measurements of evolved HCN from field and botanic garden leaf tissue. PlantID values are the same as those reported for all other morphological measurements. "NA" values in this dataset correspond to samples whose absorbance values were outside the range of our calibration curve or that were otherwise not suitable to include in analysis. 1. Age = whether leaf tissue was newly expanded ("young") or mature ("old") 2. Tissue_Mass = amount of frozen tissue used in assay (mg) 3. Dilution 1 = amount of water (mL) into which evolved HCN (in NaOH) was added prior to titration with citric acid. This value is 30 mL for all samples. 4. Dilution 2 = dilution factor. Here, a value of 1 means that 5 mL of citrate buffer was mixed with 5 mL water (1:1 ratio) and used in the subsequent reaction. A value of 10 means that 1 mL of citrate buffer was mixed with 10 mL water (1:10 ratio). 5. Sample Concentration = concentration of HCN in sample (mg/L), calculated using the calibration curve above. Samples with absorbance values above 0.500 were omitted and re-measured at reduced concentration, as this was beyond the concentration limit recommended by the manufacturer instructions. 6. Tissue Concentration = value relating dilution factor and sample mass to sample concentration. Expressed in milligrams of HCN per gram of leaf tissue. The **Images** folder contains all scanned leaf images (n = 626). File names correspond to plant species, plant ID, sampling site, and canopy position (see chaparral_leaf_morphology.csv below for a full description). So, for example, CMEG44_SMM_Upper refers to Ceanothus megacarpus, Plant ID = 44, sampled from the Santa Monica Mountains (SMM), upper canopy. Note also that each leaf within each image is individually numbered. The **Mapping** folder contains two files: 1. **shrubs_coordinates.csv** - contains coordinates and elevation for all field-sampled plants, recorded using a handheld Garmin GPS unit 2. **site_coordinates.csv** - contains broad site-level coordinates used for making map in Figure 1 The **Morphology** folder contains two files: 1. **chaparral_leaf_morphology.csv** - the primary datafile for this study, with each row (n = 5665) corresponding to a single leaf. For a visual depiction of the measurement protocol, see Supplemental Figures. Leaf measurements reported as NA generally correspond to leaves that were severely damaged, from which measurements could be reliably taken. 1. Index = sorting variable 2. IM = refers to whether a given plant was growing at an island or mainland site 3. Source = the original provenance of a given plant. For all field-sampled plants, the value here is the same as the value for "Site" 4. Site = the location where plants were sampled. Includes all field sampling locations as well as the two botanic gardens 5. Exclosure = yes/no variable, only relevant to Catalina Island, describing whether sampled plant was inside of a deer exclosure 6. Species = taxon being measured 7. Plant = Plant ID, a unique value for each individual plant. Note that botanic garden samples have their own non-integer codes, and for Rancho Santa Ana Botanic Garden, these codes can be cross-referenced against the garden's living collections 8. Position = refers to whether a sampled branch came from the upper (&gt;2m) or lower portion of the plant's canopy 9. Aspect = recorded from the Garmin GPS, refers to predominant downward slope direction. Not recorded for botanic garden plants (marked as NA) or for plants from completely flat ground. 10. Elevation = elevation in meters of sampled plants 11. Diameter1 = diameter (cm) of the primary plant trunk at 0.25m (NA means that stem could not be reliably measured) 12. Diameter2 = diameter (cm) of any secondary plant trunk at 0.25m (only applicable for multi-stemmed plants; NA means that stem could not be reliably measured) 13. Stem_Area = derived measure of stem area (cm^2), based on trunk diameter, used as a rough proxy for plant age (NA means that stem could not be reliably measured) 14. 1st_year = refers to whether an individual leaf was newly emerged growth (1) or fully expanded and mature (0) 15. Leaf_ID = corresponds to the numbers in each leaf scan; identifies each individual leaf from a given branch 16. Leaf_Length = leaf length (cm) along its primary axis, excluding the petiole 17. Leaf_Area_petiole = leaf area (cm^2), including the petiole 18. Leaf_Area_no.petiole = leaf area (cm^2), excluding the petiole 19. Internal_area_correction = cumulative area of any "holes" missing within the leaf perimeter (cm^2) 20. True_area = Leaf_Area_no.petiole minus Internal_area_correction (cm^2) 21. Leaf_area_corrected = leaf area, after manually filling in gaps missing due to presumed herbivore damage (cm^2) 22. Leaf_area_corrected_final = Leaf_area_corrected minus Internal_area_correction (cm^2) 23. Area_no_spines = leaf area after connecting vertices created by leaf spines (cm^2), using to calculate spinescence (%) 2. **shrub_leaf_masses.csv** - cumulative mass (g) of fully expanded leaf tissue from each branch, summed across all individual leaves. Used for calculating specific leaf area (SLA). **STACHYS** The **Stachys** folder contains three subfolders: **Chemistry**, **Morphology**, and **Setup** The **Chemistry** folder contains two files and one sub-directory: 1. **stachys_chromatograms** contains raw GC-MS readout for six leaf chemistry samples. Within each of the corresponding subfolders, the tic_front.csv file was used to generate the chromatograms shown in Figure 6A. 2. **stachys_compound_list.csv** is the full list of compounds detected in our samples. RT refers to the retention time (in minutes) of each compound. Identifications are putative. 3. **stachys_leaf_vocs.csv** is the full data matrix of leaf volatile compounds, with each sample as its own row and data columns each corresponding to a single compound. Values in this data matrix correspond to integrated peak areas, which are a proxy for the abundance of each compound. The **Morphology** folder contains two files: 1. **Anet-stbu.xlsx** contains gas exchange measurements for 26 plants measured in the common garden. The gas exchange column is net carbon assimilation, expressed as CO2 uptake per unit time per unit leaf area (µmol of CO2 m-2 s-1). 2. **sla_sbbg.csv** contains specific leaf area measurements for *Stachys* plants in the common garden. Note that plant #54 had died by the time of data collection, hence its values of NA across all columns. 1. ID = individual plant ID 2. SLA = cumulative area/ cumulative mass (cm^2/g) 3. leaves = refers to the number of leaves used for generating SLA measurement 4. area/leaf = cumulative area/ leaf number (cm^2/leaf) The **Setup** folder contains three files: 1. **321dailys.xls** is a file containing annual precipitation records (inches) for the Santa Barbara Botanic Garden, accessed from: [https://www.countyofsb.org/2328/Daily-Rainfall-Data-XLS](https://www.countyofsb.org/2328/Daily-Rainfall-Data-XLS) 2. **Field_Setup_SBBG.csv** is the primary file containing details on the primary garden experiment. Note that samples with masses recorded as NA were either dead at the time of sampling. Plants grown on Santa Cruz Island have values of NA for row and column, as this common garden was not arranged in a grid. 1. Index = individual plant ID 2. Population = provenance of plant 3. Garden = whether plants were grown at the Santa Barbara Botanic Garden (primary common garden site) or at the field station on Santa Cruz Island (secondary garden location with only Santa Cruz genotypes) 4. Genotype = identifier given to field-collected rhizomes, which were then propagated and split prior to planting out 5. Cumulative_Mass = mass (g) of paper bag and all of its contents, used for measuring end-of-season plant aboveground biomass 6. Bag_Mass = mass (g) of bag itself (without its contents) 7. Inside_Bag_Mass = mass (g) of smaller paper bags contained within larger bags, including all of their contents. Though not analyzed, these inside bags included all plant biomass collected from outside of the gopher cage that plants were growing in. 8. Inside_Bag_Only_Mass = as above, mass (g) of inner bag itself (without its contents) 9. Year = whether biomass was collected in 2016 or 2017 10. Row = grid location within common garden. Row 1 was at the bottom of the slope shown in Figure 2. 11. Column = grid location within common garden. 3. **stachys_coordinates.csv** contains coordinates for the six collecting sites, used to make the map in Figure 2. --- ***SCRIPTS*** All analyses for this project were conducted in the R programming language (version 4.1.3). Scripts used for analysis are arranged in two folders: **Shrubs** and **Stachys** The **Shrubs** folder contains the following scripts: 1. **coordinates_shrubs_stachys.R** - script used for generating all maps, including those in Figures 1 and 2 and the Google Earth maps in the supplementary figures 2. **cyanide_calibration.R** - script for plotting the calibration curve for relating evolved absorbance values to evolved HCN 3. **shrub_leaf_morphology_chemistry.R** - primary analysis script for manuscript, containing all major statistical analyses and plotting 4. **shrubs_BioClim.R** - script used for extracting bioclimatic data for field-sampled plants; containing code generating climate figures shown in supplementary materials The **Stachys** folder contains the following scripts: 1. **sbbg_precip_data.R** - very short script for summarizing water year totals for 2017 at the Santa Barbara Botanic Garden 2. **stachys_analysis.R** - primary script for generating all analyses and figures for *Stachys* common garden data 3. **stbu_gas_exchange.R** - script for analyzing gas exchange in common garden *Stachys* Note that for recreating some analyses and figures, users will need a Google Maps API key and will need to download data from the bioclim database. --- ## Sharing/Access information Data, code, and figures associated with this project are also available on GitHub at the following link: [https://github.com/micahfreedman/manuscripts/tree/master/Island_Mainland](https://github.com/micahfreedman/manuscripts/tree/master/Island_Mainland)