XVI International Botanical Congess

Thelypteris pilosa has been recongized as the sole member of the subgenus Stegnogramma in the new world. This species is common throughout central and southern Mexico, Guatemala, and Honduras, and exhibits an interesting temperate disjunction to Alabama. At least three morphotypes exist in nature and it is unclear whether these differences are due to phenotypic plasticity or genetics. Two regionally sympatric morphotypes, terrestrial with deltate fronds and epipetric with lanceolate fronds, occur throughout Mexico. These two types have been described as var. major and var. pilosa respectively. A more distinct type, described as var. alabamensis, is endemic to rockhouse habitats along a 4.5-mile stretch of the Sipsey River in Alabama. Data on ecology, gametophyte biology, crossing studies, spore morphology, and molecular biology comparing these taxa support the elevation of T. pilosa var. alabamensis to specific status.