Data from: 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, 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.