Life history stability under climate change: a wildflower at the northern edge of its range

Stabilities of life history traits for a widespread native perennial wildflower, Rudbeckia laciniata L., are described for five populations near the northern edge of its range in North America. Theory proposes that such populations experience variable levels of stress as suitable abiotic conditions shift north or south from year to year, which destabilizes their life histories. With climate change, however, rising temperature may increase stability, by reducing the frequency or intensity of exposure to sub‐optimal low temperatures. To investigate these ideas, stability was quantified as year‐to‐year variability in height, number of flower/seed heads, seasonal development, and density for flowering stems from 1999 to 2023. Proportional variability (PV) provided the most consistent estimates among three stability metrics that were tested. In all populations, three of four traits were remarkably stable (low PV), stem density less so. Monthly mean daily temperatures near the populations revealed climate change over 25 years: declining in April by 4.1°C, rising in June by 3.5°C. This local climate change, particularly rising June temperatures, caused declines in stem height and density. Contrary to expectations from life history theory, growth and development traits of R. laciniata were stable in the five northern populations, and climate change destabilized two traits: flowering stem height declined by 16% and stem density by 90% over two decades, threatening the future reproductive success of four wild populations.