Changes in phenological events in response to a global warming scenario reveal greater adaptability of winter annual compared to summer annual Arabidopsis ecotypes

BACKGROUND AND AIMS The impact of global warming on life cycle timing is uncertain. We investigated changes in life cycle timing in a global warming scenario. We compared Arabidopsis thaliana ecotypes adapted to the warm/dry Cape Verdi Islands (Cvi), Macaronesia, and the cool/wet climate of the Burren (Bur), Ireland, Northern Europe. These are obligate winter and summer annuals respectively. METHODS Using a global warming scenario predicting a 4°C temperature rise from 2011 to circa 2080 we produced F1 seeds at each end of a thermogradient tunnel. Each F1 cohort (cool and warm) then produced F2 seeds at both ends of the thermal gradient in winter and summer annual life cycles. F2 seeds from the winter life cycle were buried at three positions along the gradient to determine the impact of temperature on seedling emergence in a simulated winter life cycle. KEY RESULTS In a winter life cycle, increasing temperatures advanced flowering time by 10.1 days °C-1 in the winter annual and 4.9 days °C-1 in the summer annual. Plant size and seed yield responded positively to global warming in both ecotypes. In a winter life cycle, the impact of increasing temperature on seedling emergence timing was positive in the winter annual, but negative in the summer annual. Global warming reduced summer annual plant size and seed yield in a summer life cycle. CONCLUSIONS Seedling emergence timing observed in the north European summer annual ecotype may exacerbate the negative impact of predicted increased spring and summer temperatures on their establishment and reproductive performance. In contrast, seedling establishment of the Macaronesian winter annual may benefit from higher soil temperatures that will delay emergence until autumn, but which also facilitates earlier spring flowering and consequent avoidance of high summer temperatures. Such plasticity gives winter annual Arabidopsis ecotypes a distinct advantage over summer annuals in expected global warming scenarios. This highlights the importance of variation in the timing of seedling establishment in understanding plant species responses to Anthropogenic Climate Change.