Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South Box 951606, Los Angeles, California 90095-1606, USA.
Am J Bot. 2011 Jun;98(6):956-66. doi: 10.3732/ajb.1000237. Epub 2011 May 31.
Hawaii is home to 238 native and 35 alien fern and lycophyte taxa distributed across steep gradients in elevation and resource availability. The fern flora spans a wide range of growth forms, with extraordinary diversity in morphology and plant size. Yet the potential factors underlying this diversity have remained enigmatic.
We used a trait database generated from the most recent and comprehensive survey of Hawaiian ferns and lycophytes to test hypotheses of size-scaling and trait associations with environment and growth form as factors underlying this diversity. We also tested relationships among morphology, taxon abundance and distribution and identified key differences between native and alien taxa.
Strong trait-trait relationships included geometric scaling of plant dimensions with a tendency for more divided fronds in larger ferns. Trait-environment relationships independent of size included more divided fronds at higher elevation, longer blades in shaded habitats, and fronds with shorter stipes and fewer pinnae in drier habitats. Growth forms differed in mean size with epiphytic and epipetric taxa smaller than terrestrial ferns. Plant size was independent of taxon abundance and distribution across islands, and native and alien ferns did not differ in mean size. Alien taxa were more abundant, especially at lower elevations, apparently due to human land use.
These relationships point to linkages of fern form and demography with biogeography and highlight potential flora-scale physiological and morphological adaptations in ferns across contrasting environments.
夏威夷拥有 238 种本地蕨类植物和 35 种外来蕨类植物和石松类植物，分布在海拔和资源可用性的陡峭梯度上。蕨类植物群跨越了广泛的生长形态，在形态和植物大小上具有非凡的多样性。然而，这种多样性背后的潜在因素仍然是个谜。
我们使用了从最近和最全面的夏威夷蕨类植物和石松类植物调查中生成的特征数据库，以测试大小比例和特征与环境和生长形态的关系的假设，这些因素是多样性的基础。我们还测试了形态、分类群丰度和分布之间的关系，并确定了本地和外来分类群之间的关键差异。
强烈的特征-特征关系包括植物尺寸的几何比例，大蕨类植物的叶片更具分裂性。与大小无关的特征-环境关系包括海拔较高的叶片更具分裂性、遮荫生境的叶片更长、干燥生境的叶片梗较短、裂片较少。生长形态的平均大小不同，附生和附生类群比陆生蕨类植物小。植物大小与分类群丰度和岛屿分布无关，本地和外来蕨类植物在平均大小上没有差异。外来类群的丰度更高，特别是在较低的海拔，这显然是由于人类的土地利用。
这些关系表明蕨类植物形态和种群动态与生物地理学之间存在联系，并强调了蕨类植物在不同环境下潜在的全植物范围的生理和形态适应。
