Desiccation tolerance was a key trait that allowed plants to colonize land. However, little is known about the transition from desiccation tolerant non-vascular plants to desiccation sensitive vascular ones. Filmy ferns (Hymenophyllaceae) represent a useful system to investigate how water-stress strategies differ between non-vascular and vascular stages within a single organism because they have vascularized sporophytes and nonvascular gametophytes that are each capable of varying degrees of desiccation tolerance. To explore this, we surveyed sporophytes and gametophytes of 19 species (22 taxa including varieties) of filmy ferns on Moorea (French Polynesia) and used chlorophyll fluorescence to measure desiccation tolerance and light responses. We conducted phylogenetically informed analyses to identify differences in physiology between life stages and growth habits. Gametophytes had similar or less desiccation tolerance (ability to recover from 2 days desiccation at − 86 MPa) and lower photosynthetic optima (maximum electron transport rate of photosystem II and light level at 95% of that rate) than sporophytes. Epiphytes were more tolerant of desiccation than terrestrial species in both life stages. Despite their lack of greater physiological tolerances, gametophytes of several species occurred over a wider elevational range than conspecific sporophytes. Our results demonstrate that filmy fern gametophytes and sporophytes differ in their physiology and niche requirements, and point to the importance of microhabitat in shaping the evolution of water-use strategies in vascular plants.

耐旱性是允许植物在土地上定居的一个关键特性。然而，关于从干燥耐受的非维管植物到干燥敏感的维管植物的转变知之甚少。薄膜蕨类植物（Hymenophyllaceae）代表了一个有用的系统，用于研究单个生物体内非维管和维管阶段之间的水分胁迫策略如何不同，因为它们具有带血管的孢子体和非维管配子体，它们各自具有不同程度的干燥耐受性。为了探索这一点，我们调查了莫雷阿岛（法属波利尼西亚）上 19 种（包括品种在内的 22 个分类群）薄膜蕨类植物的孢子体和配子体，并使用叶绿素荧光来测量干燥耐受性和光响应。我们进行了系统发育知情分析，以确定生命阶段和生长习惯之间的生理差异。与孢子体相比，配子体具有相似或更低的干燥耐受性（在 - 86 MPa 下从 2 天干燥中恢复的能力）和较低的光合最佳状态（光系统 II 的最大电子传输速率和该速率的 95% 的光照水平）。在两个生命阶段，附生植物都比陆生植物更能耐受干燥。尽管它们缺乏更大的生理耐受性，但与同种孢子体相比，几种物种的配子体发生在更宽的海拔范围内。我们的研究结果表明，薄膜蕨类配子体和孢子体在生理学和生态位要求方面存在差异，并指出微生境在塑造维管植物用水策略演变方面的重要性。