Abstract Anthropogenic activities have increased exposure to heavy metal pollution in previously uncontaminated ecosystems, threatening plant communities. Considering that phenotypic variation underlies rapid adjustment to challenging environmental conditions in natural populations, the study of variation in traits related to plant response to heavy metal stress provides valuable insight into the likelihood of a population’s survival. This paper investigates patterns of intraspecific phenotypic variation for heavy metal accumulation and tolerance in bryophytes, one of the most resilient and relatively understudied plant taxa. We examined two moss species with contrasting affinities for heavy metals: the heavy metal specialist Scopelophila cataractae, and the facultative metallophyte Ceratodon purpureus. We sampled four populations of S. cataractae in close microhabitats with different contamination levels of Cd and Cu, one population of C. purpureus in an urban area, and separate lab-maintained male and female isolates from one population of C. purpureus growing in axenic conditions. After clonally propagating all populations under control, Cd and Cu treatments, we measured plant fitness, oxidative damage, and Cd and Cu accumulation. Scopelophila cataractae isolates from microhabitats with higher levels of metals in the field (Sc2, Sc3) were more tolerant than those collected in less contaminated microhabitats (Sc1, Sc4). Sc2 and Sc3 accumulated significantly less Cu in the leaves compared to the stem which could limit damage to their main photosynthetic organs and contribute to the observed differences in Cu tolerance. In contrast C. purpureus showed intraspecific differences in tolerance to Cd and Cu, but not in accumulation. These differences arose among isolates that had never been exposed to heavy metals before. We also report the first evidence for sexual dimorphism for Cd tolerance in this species, with females being more tolerant than males. Altogether, our results provide novel insights into the mechanisms used by bryophytes to deal with heavy metal stress, as well as the first evidence for metal-dependent, sex-specific differences in heavy metal tolerance in bryophytes.

中文翻译：

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两种不同生境特化的陆生苔藓物种重金属积累和耐受的模式和机制

摘要 人为活动增加了以前未受污染的生态系统中重金属污染的暴露，威胁着植物群落。考虑到表型变异是对自然种群中具有挑战性的环境条件进行快速调整的基础，因此对与植物对重金属胁迫反应相关的性状变异的研究为了解种群生存的可能性提供了宝贵的见解。本文研究了苔藓植物中重金属积累和耐受性的种内表型变异模式，苔藓植物是最具弹性和研究相对较少的植物类群之一。我们检查了两种对重金属具有不同亲和力的苔藓物种：重金属专家 Scopelophila cataractae 和兼性金属植物 Ceratodon purpureus。我们对四个 S 种群进行了采样。在具有不同 Cd 和 Cu 污染水平的封闭微生境中的白内障，城市地区的一个 C. purpureus 种群，以及从在无菌条件下生长的 C. purpureus 的一个种群中分离出实验室维护的雄性和雌性分离株。在对所有受控制的 Cd 和 Cu 处理的种群进行克隆繁殖后，我们测量了植物健康、氧化损伤以及 Cd 和 Cu 的积累。从野外金属含量较高的微生境（Sc2、Sc3）中分离出的白内障白内障比在污染较少的微生境中收集的那些（Sc1、Sc4）更具耐受性。与茎相比，Sc2 和 Sc3 在叶子中积累的 Cu 显着减少，这可以限制对其主要光合器官的损害，并有助于观察到的 Cu 耐受性差异。相比之下 C. purpureus 在对 Cd 和 Cu 的耐受性方面表现出种内差异，但在积累方面没有差异。这些差异出现在以前从未接触过重金属的分离株中。我们还报告了该物种对 Cd 耐受性的性别二态性的第一个证据，雌性比雄性更耐受。总而言之，我们的研究结果为苔藓植物处理重金属胁迫的机制提供了新的见解，以及苔藓植物对重金属耐受性的金属依赖性、性别特异性差异的第一个证据。