Department of Biology, University of Louisiana, Lafayette, LA, 70503, USA.
Am J Bot. 2023 Aug;110(8):e16207. doi: 10.1002/ajb2.16207. Epub 2023 Jul 17.
Annual plants often exhibit drought-escape and avoidance strategies to cope with limited water availability. Determining the extent of variation and factors underlying the evolution of divergent strategies is necessary for determining population responses to more frequent and severe droughts.
We leveraged five Mimulus guttatus populations collected across an aridity gradient within manipulative drought and quantitative genetics experiments to examine constitutive and terminal-drought induced responses in drought resistance traits.
Populations varied considerably in drought-escape- and drought-avoidance-associated traits. The most mesic population demonstrated a unique resource conservative strategy. Xeric populations exhibited extreme plasticity when exposed to terminal drought that included flowering earlier at shorter heights, increasing water-use efficiency, and shifting C:N ratios. However, plasticity responses also differed between populations, with two populations slowing growth rates and flowering at earlier nodes and another population increasing growth rate. While nearly all traits were heritable, phenotypic correlations differed substantially between treatments and often, populations.
Our results suggest drought resistance strategies of populations may be finely adapted to local patterns of water availability. Substantial plastic responses suggest that xeric populations can already acclimate to drought through plasticity, but populations not frequently exposed to drought may be more vulnerable.
一年生植物通常表现出逃避和避免干旱的策略，以应对有限的水分供应。确定不同策略演变的程度和基础因素，对于确定种群对更频繁和更严重干旱的反应是必要的。
我们利用五个横跨干旱梯度的金光菊种群，在操纵性干旱和定量遗传学实验中，研究了抗旱性特征中的组成性和终末干旱诱导反应。
种群在逃避和避免干旱相关特征方面有很大的差异。最湿润的种群表现出独特的资源保守策略。在经历终末干旱时，干旱种群表现出极端的可塑性，包括更早开花、更短的高度、增加水分利用效率和改变 C:N 比。然而，可塑性反应也在种群之间存在差异，两个种群生长速度减慢，开花节点更早，另一个种群生长速度增加。虽然几乎所有的特征都是可遗传的，但表型相关性在处理和种群之间有很大的不同。
我们的结果表明，种群的抗旱策略可能与当地的水分供应模式密切适应。大量的可塑性反应表明，干旱种群已经可以通过可塑性来适应干旱，但不经常暴露在干旱下的种群可能更脆弱。
