North American monilophyte (fern) and lycophyte richness patterns are examined at three taxonomic levels (species, genus, and family). We determine: (1) if fern richness patterns are associated with water and energy variables that are predicted by the productivity-diversity hypothesis and (2) whether the pattern or strength of the relationship varies with taxonomic level. We present species richness maps for individual families of ferns and lycophytes allowing us to identify taxa with unique distributional patterns and taxa with patterns comparable to ferns in general. To accomplish these goals, we use data from the Flora of North America project for continental North America north of Mexico plus Greenland. We construct 479 GIS fern species range maps and tabulate fern and lycophyte richness in a gridded map with 2500km² squares. We perform regressions of fern richness on water and energy climate variables (with squares as data points) in order to identify which variables most influence fern richness. We find that fern richness correlates with water and energy variables in ways consistent with the productivity-diversity hypothesis. A multiple regression model that includes mean annual temperature (MAT) and annual rainfall (RAN) explains 78.1% of the variation in fern family richness. The relationship between fern family richness and climate is stronger than the relationship between fern species richness and climate.

Although several species of ferns possess a characteristic odor, only a few published studies have described their volatile constituents. The aim of the present study was to evaluate the chemical composition of essential oils from two chemically unexplored fern species, Anemia hirsuta and Anemia raddiana. These species were collected during the day in ravine banks of Rio de Janeiro state, Brazil. Fresh leaves of the ferns were individually turbolized with distilled water and submitted to hydrodistillation in a Clevenger-type apparatus for three hours. The essential oils obtained were subjected to gas chromatography/mass spectrometry for identification. Nine compounds were identified in Anemia raddiana essential oil, accounting for 81.3% of the total oil, where the sesquiterpene β-selinene (46.8%) was the major compound. Thirteen compounds were identified in Anemia hirsuta (92.3% of the total oil) and the sesquiterpene β-caryophyllene was the major compound (48.7%). No similarity was observed between the chemical profile of essential oils obtained from A. hirsuta and A. raddiana. Likewise, extremely low similarities (≤6.2%) were observed between these species and three previously published profiles of Anemia tomentosa var. anthriscifolia.

The occurrence of helical cell wall thickenings in fern roots is not well investigated and there are few records about it in the literature. To assess the presence of thickenings and their chemical composition, we studied all species of Polypodiaceae, which grow in northwestern Argentina, using light microscopy, scanning electron microscopy, and fluorescence microscopy. Twenty of the twenty-one species studied showed the thickening in the roots. Only in Melpomene peruviana are helical cell wall thickenings absent. All thickenings have cellulose as the main compound. The structure of the thickening may be classified as simple, furcate, or anastomosing. All data presented in this paper corroborate the same structure and chemical composition of thickenings previously reported for Aspleniaceae.