Abstract
Declining rainfall is projected to have negative impacts on the demographic performance of plant species. Little is known about the adaptive capacity of species to respond to drying climates, and whether adaptation can keep pace with climate change. In fire-prone ecosystems, episodic recruitment of perennial plant species in the first year post-fire imposes a specific selection environment, offering a unique opportunity to quantify the scope for adaptive response to climate change. We examined the growth of seedlings of four fire-killed species under control and drought conditions for seeds from populations established in years following fire receiving average-to-above-average winter rainfall, or well-below-average winter rainfall. We show that offspring of plants that had established under drought had more efficient water uptake, and/or stored more water per unit biomass, or developed denser leaves, and all maintained higher survival in simulated drought than did offspring of plants established in average annual rainfall years. Adaptive phenotypic responses were not consistent across all traits and species, while plants that had established under severe drought or established in years with average-to-above-average rainfall had an overall different physiological response when growing either with or without water constraints. Seedlings descended from plants established under severe drought also had elevated gene expression in key pathways relating to stress response. Our results demonstrate the capacity for rapid adaptation to climate change through phenotypic variation and regulation of gene expression. However, effective and rapid adaptation to climate change may vary among species depending on their capacity to maintain robust populations under multiple stresses.
Highlights
Bioclimatic modelling of species distributions suggests that extinction rates may increase dramatically in response to future climate change, with potentially large losses in biodiversity [1,2,3,4,5]
Multivariate analysis through canonical discriminant function suggested significant overall difference in physiological response for six measured growth and drought-related traits between seedlings derived from populations established in years with average-to-above-average winter rainfall (HiR) and those derived from populations established in years with at least 20% below-average winter rainfall (LoR) in B. hookeriana and H. costata, when growing in conditions with full water supply
Seedlings of B. hookeriana from LoR sites had higher water content per unit root length and higher water content per leaf area than seedlings from HiR sites, indicating higher efficiency in water uptake and water use in those seedlings whose parents were established in drought years compared with those whose parents were established in average-to-wet years
Summary
Bioclimatic modelling of species distributions suggests that extinction rates may increase dramatically in response to future climate change, with potentially large losses in biodiversity [1,2,3,4,5]. These projections raise great concerns about the deleterious consequences globally for biodiverse floras [6]. Increases in drought are of particular concern because drought has the capacity to cause sudden and extreme vegetation change, especially when combined with fire in such Mediterranean-type shrublands which already have low baseline water levels [15,17]
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