Study Species and Site Selection
Yarrow (Achillea millefolium L.) is a perennial herbaceous plant widely distributed across temperate regions of the Northern Hemisphere and naturalized in North America. The species is notable for its morphological and ecological diversity, thriving in environments ranging from coastal lowlands to alpine zones. This dataset includes measurements from ten populations originally surveyed by Clausen et al. (1948) in California, USA. These sites span a climatic gradient, from 1 m to 3,200 m above sea level, encompassing diverse temperature and precipitation regimes.
Field Data Collection
In 2020, we revisited the historical survey sites to evaluate population persistence and collect plant growth data. At each site, the presence of yarrow was recorded, and plant height (measured from the base to the top of the inflorescence) was documented for ten randomly selected individuals in their reproductive phase. Seeds were also collected for subsequent experiments. Efforts were made to assess historical and current land-use contexts to rule out major non-climatic factors influencing plant growth.
Climatic and Growth Data Analysis
Original plant height data from the 1920s were combined with resurveyed measurements from 2020 to investigate temporal changes in growth. Climate data for the same periods, including mean annual temperature and precipitation, were sourced from publicly available databases. A linear regression model was applied to explore the effects of temperature, precipitation, and their interactions on plant height across time. Additionally, a stochastic ecological model was used to estimate long-term plant height changes, incorporating site-specific growth rates and climatic sensitivity metrics derived from principal component analysis (PCA). Random variability in mortality was also factored into the model.
Metabolomic Analysis
To examine metabolic diversity, seeds from selected populations were germinated in a controlled greenhouse environment. After 60 days, plants were transplanted and grown for an additional 60 days before secondary metabolite analysis. Volatile organic compounds (VOCs) were extracted using headspace solid-phase microextraction (HS-SPME) and analyzed via gas chromatography-mass spectrometry (GC-MS). Metabolomic data were processed and normalized for statistical analysis, including Partial Least-Squares Discriminant Analysis (PLS-DA) and Random Forest classification, to identify compounds distinguishing populations along the climatic gradient.
Scope and Limitations
This dataset provides a comprehensive resource for studying long-term phenotypic and metabolic responses to climate change in A. millefolium. While it emphasizes temperature and precipitation as key drivers, other biotic and abiotic factors are not explicitly controlled. These data serve as a foundation for exploring local adaptation, population persistence, and the ecological implications of climate change.
