Data from: Leaf form and photosynthetic physiology of Dryopteris species distributed along light gradients in eastern North America

1.Despite the ubiquity of ferns and at least tacit recognition by botanists that their physiology is unique among land plants, most studies on fern physiology have focused on only a few, locally distributed, usually distantly related species. No previous study has attempted to examine physiological adaptations in a group of widespread taxa that are closely related and whose relationships are well understood. Here we report leaf form and physiological measures for such a group, the eleven eastern North American species of Dryopteris (Dryopteridaceae), and examine differences in these parameters for evidence of adaptation to light availability. 2.Economic theory predicts that species from sunnier habitats should have narrower, more steeply inclined leaves, lower specific leaf area, higher stomatal density, higher rates of maximum photosynthesis, respiration, and stomatal conductance, and require more light to saturate photosynthesis. Species should show adaptive cross-over in net carbon uptake per unit leaf mass, with a relative advantage by sun-associated species at high photon flux densities (PFDs) and by shade-associated species at low PFDs. 3.Field studies allow us to begin characterizing the range of native light environments occupied by members of this group, and to examine interspecific variation in several aspects of leaf form and photosynthetic light response for evidence of adaption to light availability. We also present a novel means for incorporating phylogeny in tests of correlated evolution in a reticulate lineage. 4.Synthesis. Observed trends in physiology and morphology generally agree with qualitative predictions, but are often not statistically significant. We found no support for adaptive cross-over in mass-based carbon uptake, and thus for light availability being the most important variable driving morphological and physiological adaptation in these ferns. We propose that hydraulic factors related to water balance may have played a larger role in determining their morphological and physiological variation. Allopolyploid hybrids did not show transgression in any physiological parameter that may have allowed them to coexist regionally with their parents. The results of our phylogenetically-structured analyses highlight the importance of incorporating phylogeny into comparative studies, particularly when hybrid or polyploid taxa are present.1. 尽管蕨类植物广泛分布，且植物学家至少已默认其生理特性在陆生植物中独树一帜，但绝大多数蕨类生理研究仅聚焦于少数局部分布、通常亲缘关系较远的物种。此前尚无研究针对一类分布广泛、亲缘关系清晰且近缘的类群开展生理适应性探究。本研究针对北美东部的11种鳞毛蕨属（Dryopteris）鳞毛蕨科（Dryopteridaceae）类群，报道其叶形与生理性状测定结果，并分析这些参数的差异以探寻其对光照可获得性的适应性证据。 2. 资源分配经济学理论预测，来自向阳生境的物种应具备更狭窄、倾角更大的叶片，更低的比叶面积（specific leaf area）、更高的气孔密度、更高的最大光合速率、呼吸速率与气孔导度，且达到光合饱和所需的光照强度更高。物种在单位叶质量的净碳吸收方面应表现出适应性交叉（adaptive cross-over）：在高光量子通量密度（photon flux densities, PFDs）下，向阳物种具备相对优势；而在低PFDs下，耐阴物种占据相对优势。 3. 本研究通过野外调查，初步明确了该类群各物种所占据的原生光照环境范围，并分析了叶形与光合光响应多方面的种间差异，以探寻其对光照可获得性的适应性证据。此外，我们提出了一种全新方法，可将系统发育信息纳入网状进化类群（reticulate lineage）的协同演化检验分析中。 4. 综合与结论。本研究观测到的生理与形态性状趋势总体上符合定性预测，但多数未达到统计学显著性水平。我们未发现单位质量碳吸收存在适应性交叉的证据，因此不支持光照可获得性是驱动这些蕨类形态与生理适应性的核心变量。我们推测，与水分平衡相关的水力因子可能在塑造其形态与生理变异中发挥了更关键的作用。异源多倍体杂种（allopolyploid hybrids）未在任何生理参数上表现出性状超亲（transgression），而该现象本可帮助其与亲本物种在区域内共存。本研究采用系统发育校正的比较分析结果凸显了将系统发育信息纳入比较研究的重要性，尤其当类群中存在杂种或多倍体物种时。