Meyer Abigail R, Valentin Maria, Liulevicius Laima, McDonald Tami R, Nelsen Matthew P, Pengra Jean, Smith Robert J, Stanton Daniel
Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota, 55108, USA.
Biology Department, Saint Catherine University, Saint Paul, Minnesota, 55105, USA.
Am J Bot. 2023 Feb;110(2):e16114. doi: 10.1002/ajb2.16114. Epub 2023 Feb 13.
The long-term potential for acclimation by lichens to changing climates is poorly known, despite their prominent roles in forested ecosystems. Although often considered "extremophiles," lichens may not readily acclimate to novel climates well beyond historical norms. In a previous study (Smith et al., 2018), Evernia mesomorpha transplants in a whole-ecosystem climate change experiment showed drastic mass loss after 1 yr of warming and drying; however, the causes of this mass loss were not addressed.
We examined the causes of this warming-induced mass loss by measuring physiological, functional, and reproductive attributes of lichen transplants.
Severe loss of mass and physiological function occurred above +2°C of experimental warming. Loss of algal symbionts ("bleaching") and turnover in algal community compositions increased with temperature and were the clearest impacts of experimental warming. Enhanced CO had no significant physiological or symbiont composition effects. The functional loss of algal photobionts led to significant loss of mass and specific thallus mass (STM), which in turn reduced water-holding capacity (WHC). Although algal genotypes remained detectable in thalli exposed to higher stress, within-thallus photobiont communities shifted in composition toward greater diversity.
The strong negative impacts of warming and/or lower humidity on Evernia mesomorpha were driven by a loss of photobiont activity. Analogous to the effects of climate change on corals, the balance of symbiont carbon metabolism in lichens is central to their resilience to changing conditions.
尽管地衣在森林生态系统中发挥着重要作用，但其适应气候变化的长期潜力却鲜为人知。尽管地衣常被视为“极端微生物”，但它们可能无法轻易适应远超历史规范的新气候。在先前的一项研究（史密斯等人，2018年）中，在一个全生态系统气候变化实验中移植的中型树花地衣在经历1年的变暖和干燥后出现了严重的质量损失；然而，这种质量损失的原因并未得到探讨。
我们通过测量地衣移植体的生理、功能和繁殖属性，研究了这种由变暖导致的质量损失的原因。
在实验性变暖超过2°C时，出现了严重的质量和生理功能损失。藻类共生体的丧失（“白化”）以及藻类群落组成的更替随着温度升高而增加，这是实验性变暖最明显的影响。二氧化碳浓度升高对生理或共生体组成没有显著影响。藻类光合生物的功能丧失导致了质量和特定菌体质量（STM）的显著损失，进而降低了持水能力（WHC）。尽管在受到更高压力的地衣体中仍可检测到藻类基因型，但地衣体内的光合生物群落组成向更高的多样性转变。
变暖和/或较低湿度对中型树花地衣的强烈负面影响是由光合生物活性丧失所致。类似于气候变化对珊瑚的影响，地衣中共生体碳代谢的平衡对于它们适应变化条件的恢复力至关重要。
