Higher thermal plasticity in flowering phenology increases flowering output

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..., Study species and populations
Hypericum maculatum (Crantz), H. montanum (L.) and H. perforatum (L.) are perennial herbs native to Europe. The study species share many characteristics, such as yellow flowers and leaf arrangement. The native ranges of H. maculatum and H. perforatum extend from southern to Northern Europe and they are commonly found in grassland habitats (GBIF Secretariat, 2022; GBIF Secretariat, 2022). Compared to H. maculatum and H. perforatum, H. montanum 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, H. montanum 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 distribut..., , # 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 ...