DOI: 10.5061/dryad.f4qrfj73k
title: Data from: Higher thermal plasticity in flowering phenology increases flowering output

description: Ongoing climate change poses an increasing threat to biodiversity. To
 avoid decline or extinction, species need to either adjust or adapt to new
 environmental conditions or track their climatic niches across space. In
 sessile organisms such as plants, phenotypic plasticity can help maintain
 fitness in variable and even novel environmental conditions and is
 therefore likely to play an important role in allowing them to survive
 climate change, particularly in the short term. Understanding a species’
 response to rising temperature is crucial for planning well-targeted and
 cost-effective conservation measures. We sampled seeds of
 three Hypericum species (H. maculatum, H. montanum, and H.
 perforatum), from a total of 23 populations originating from different
 parts of their native distribution areas in Europe. We grew them under
 four different temperature regimes in a greenhouse to simulate current and
 predicted future climatic conditions in the distribution areas. We
 measured flowering start, flower count, and subsequent seed weight,
 allowing us to study variations in the thermal plasticity of flowering
 phenology and its relation to fitness. Our results show that
 individuals flowered earlier with increasing temperature, while the degree
 of phenological plasticity varied among species. More specifically, the
 plasticity of H. maculatum varied depending on population origin, with
 individuals from the leading range edge being less plastic. Importantly,
 we show a positive relationship between higher plasticity and increased
 flower production, indicating adaptive phenological
 plasticity. The observed connection between plasticity and
 fitness supports the idea that plasticity itself may be adaptive. This
 study underlines the need for information on plasticity for predicting
 species' potential to thrive under global change and the need for
 studies on whether higher phenotypic plasticity is currently being
 selected for as natural populations experience a rapidly changing climate.
description: <em>Study species and populations</em>
 <em>Hypericum maculatum</em> (Crantz), <em>H.
 montanum</em> (L.) and <em>H. perforatum </em>(L.) are
 perennial herbs native to Europe. The study species share many
 characteristics, such as yellow flowers and leaf arrangement. The native
 ranges of <em>H. maculatum</em> and <em>H.
 perforatum</em> extend from southern to Northern Europe and they are
 commonly found in grassland habitats (GBIF Secretariat, 2022; GBIF
 Secretariat, 2022). Compared to <em>H. maculatum </em>and
 <em>H. perforatum</em>, <em>H. montanum</em> has a
 more limited range, especially at higher latitudes, and is a habitat
 specialist occurring more scarcely and mainly in woodlands (GBIF
 Secretariat, 2022). Out of the three species, <em>H.
 montanum</em> occurs within the narrowest range (range = 2.65ᵒC,
 mean = 0.89ᵒC) while having the highest average of annual temperatures
 (based on average calculated over the years 1970-2000).
 We obtained seeds, subject to availability, from across the study
 species´ European distribution areas to represent the trailing (southern
 distributional edge), core, and leading (northern distributional edge)
 parts of the species distributions. We chose seed accessions,
 <em>i.e</em>., seeds collected from the same location at the
 same time, among the accessions available in managed seed banks (e.g.,
 Millennium Seed Bank, The European Native Seed Conservation Network
 ENSCONET partners (Eastwood & Rivière, 2009)) and augmented them
 with populations collected afresh. In total, we included 23 populations in
 the experiment: six <em>H. maculatum</em>, six
 <em>H.</em> <em>montanum</em>, and 11 <em>H.
 perforatum</em> populations. 
 <em>Temperature treatments and greenhouse
 cultivation</em> We grew the plants under common
 garden conditions in greenhouses of the Viikki Plant Growth Facilities,
 University of Helsinki, from December 2021 to May 2022. In May, we
 transferred the plants outside for seed maturation. We collected seeds
 from the experimental individuals during summer and weighed them from
 August to October 2022. In the greenhouses, we grew the
 plants under four different temperature treatments with two replicates for
 each, totaling eight greenhouse compartments, and each species on a
 separate table within each compartment. The daytime (16h) temperatures
 were set to 16°C (“Cold”), 20°C (“Medium”), 24°C (“Warm”), and 28°C
 (“Hot”). The choice of temperature treatments was loosely based on data on
 average summer temperatures at the trailing-, core-, and leading
 distributional areas of the study species from the climatic information
 service WorldClim (https://www.worldclim.org). The night-time temperatures
 (8h) were set at 8°C and 10°C below the daytime temperature at the
 germination and vegetative stages, respectively. Photoperiod in all
 treatments was 16/8h light/dark. In addition to the automated temperature
 settings, we monitored realized temperature conditions at the plant level
 using temperature loggers (Lascar EL-USB-2-LCD+). The realized
 temperatures were somewhat higher than the set temperatures, particularly
 as solar radiation increased with the advancing spring, but the
 differences between treatments remained approximately equal.
 On the 1st of December 2021, we sowed 25 seeds per population and
 replicate into trays filled with the sowing mixture (Kekkilä kylvöseos W
 HS R8017; KEK31116) with seeds of two populations sown on each tray
 separated by a border of cardboard and sand. We then placed the trays on a
 water retaining rug on greenhouse growing tables and its soil topped with
 coarse sand after sowing the seeds. In the beginning of February 2022, we
 randomly chose up to ten (depending on availability) of the germinated
 plants per population, treatment, and replicate to be included in the
 experiment and transferred them from trays to individual 1L pots filled
 with soil (Kekkilä Professional Karkea Ruukutusseos; KEK33933) and we then
 placed the pots on a water retaining rug on greenhouse growing tables. At
 the same time, we propped up the plants on a support stick if the plant
 was large enough. We marked all plant individuals with QR-coded ID tags.
 We separated the individuals of each population into replicates A and B,
 each with up to ten plants. To avoid microclimatic biases, we periodically
 rotated both the germination trays and later the plant pots. We regularly
 fertilized the plants, approximately every 3 weeks with fertilizer
 solution.    Watering was implemented by an automated
 watering system with treatment-specific schedules to keep all experimental
 plants equally moist. The watering system of <em>H. perforatum
 </em>in the “Hot”-treatment, replicate A, broke at the end of March
 leaving the plants dry for some days, which we take into account in the
 interpretation of the results. <em>Data
 collection</em> Starting two months after
 sowing, we collected flowering phenology data by monitoring the plants two
 times per week and recording the date of the first observation of an open
 flower for each plant individual. During a four-week
 data collection phase at peak flowering (April-May), we counted flowers at
 different stages (<em>i.e</em>., bud, flowering, flowered,
 seed capsule), except for <em>H. maculatum</em> and
 <em>H. montanum</em> populations which could not be counted in
 the “Medium” and “Cold” treatments due to limited time. For each study
 individual, up to five seed capsules or withered flowers were marked to
 ensure a matching collection of seeds after ripening. After the flowering
 counts, we transferred the plants to outdoor conditions at the Kumpula
 Botanic Garden to allow the seeds to ripen over the summer, whereafter we
 collected them. We dried the collected seeds for a minimum of five days in
 RH 15% and cleaned them using sieves (800µm and 250µm), after which we
 counted and weighed them. We used average seed mass (total seed mass /
 total seed number) as a measure of reproductive output, as some of the
 seeds could have dispersed before the capsules were collected, rendering
 the total seed number an unreliable proxy measure of fitness.
 <em>References</em> Eastwood,
 R., & Rivière, S. (2009). The ENSCONET Virtual Seed Bank.
 ENSCONEWS, 5.  
description: # Higher thermal plasticity in flowering phenology increases flowering
 output ## Description of the data and file structure
 "Flowering_time.csv" "Flower_count.csv"
 "Seed_mass.csv" "ThermalPlasticity.R"
 "Watering_schedule.docx" "greenhouse_conditions.docx"
 Data was used in the publication: Kotilainen, A., Mattila, A. L. K.,
 Møller, C., Koivusaari, S., Hyvärinen, M., & Hällfors, M. 2023. Higher
 thermal plasticity in flowering phenology increases flowering output.
 Submitted to *Ecology and Evolution*. Non-available data is indicated by
 "NA" throughout all datasets. ### Flowering\_time.csv | Value |
 Description | | :---------------- |
 :------------------------------------------------------------------------------------------------------------------------- | | Format | comma-separated value | | Number of rows | 1431 | | Number of columns | 6 | | Species | Scientific name of species (abbreviated). Hpe = Hypericum perforatum, Hma = Hypericum maculatum, Hmo = Hypericum montanum. | | Treatment | Cold (16°C), Medium (20°C), Warm (24°C), or Hot (28°C)  | | Replicate | Replicate distinguishing treatment and species | | Accession | Accession ID based on species and distribution range | | UniqueID | Unique ID for each individual | | DateFlow | Date of flowering (YYYYMMDD) | ### "Flower\_count.csv" | Value | Description | | :---------------- | :------------------------------------------------------------------------ | | Format | comma-separated value | | Number of rows | 744 | | Number of columns | 15 | | Species | Scientific name of species (abbreviated). Hpe = Hypericum perforatum. | | Treatment | Cold (16°C), Medium (20°C), Warm (24°C), or Hot (28°C)  | | Replicate | Replicate distinguishing treatment and species | | Accession | Accession ID based on species and distribution range | | UniqueID | Unique ID for each individual | | DateMeasured | Date of the measurement in YYYYMMDD format | | Alive | Alive = 1, Dead = 0 | | Buds\_number | Number of buds per individual at the date of the measurement | | Flowers\_number | Number of flowers per individual at the data of the measurement | | Whithered\_number | Number of whithered flowers per individual at the data of the measurement | | SeedCaps\_number | Number of seed capsules per individual at the date of the measurement | ### Seed\_mass.csv | Value | Description | | :---------------- | :-------------------------------------------------------------------------- | | Format | comma-separated value | | Number of rows | 744 | | Number of columns | 10 | | Species | Scientific name of species (abbreviated). Hpe = Hypericum perforatum. | | Treatment | Cold (16°C), Medium (20°C), Warm (24°C), or Hot (28°C)  | | Replicate | Replicate distinguishing treatment and species | | Accession | Accession ID based on species and distribution range | | DateMeasured | Date of the measurement in YYYYMMDD format | | NumbSeedCapsules | Number of seed capsules collected | | TotalSeedMass\_g | Total seed mass for five sampled seed capsules per individuals in grams (g) | | XOSeeds\_Y.N | Seeds, yes (Y) or no (N) | | NumberOfSeeds | Number of seeds counted from the number of seed capsules collected | ## R Code A combined R script for is provided ("ThermalPlasticity.R") for the data analyses used in the publication. ## Word documents Detailed information for the experimental watering schedule ("Watering_schedule.docx"), as well as the temperature settings and realized temperature for the greenhouse chambers conditions ("greenhouse_conditions.docx") are provided.