Woodsia R.Br., Prodr.

Kessler, Michael & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. XXXI. Woodsiaceae, Phytotaxa 344 (1), pp. 80-82 : 80-81

Woodsia R.Br., Prodr. : 158, Obs. 4. 1810.

Woodsia is often confused with Cystopteris , and mixed collections of the two genera in herbaria are not uncommon. Woodsia can best be distinguished by the persistent petiole bases, multilobed, basal (subtending the sori) indusia (vs. arching or hoodlike), ± equilateral pinnae (vs. inequilateral), and obscure veins ending short of the adaxial blade margins in hydathodes (vs. ending at the margins). Most Woodsia species bear at least some acicular or glandular hairs on the axes and lamina abaxially, while Cystopteris is essentially lacking such hairs. There is also a chromosome base number difference: x = 38, 39, 41 in Woodsia , and x = 42 in Cystopteris . In regions where several species of Woodsia co-occur, identification can be difficult due to the presence of hybrids and polyploidy, but only one variable species is currently recognized for Bolivia. Woodsia has about 39 species, mostly in north-temperate regions and higher elevations in the tropics and subtropics ( Brown 1964, Shmakov 2015). Several species are circumboreal. Recent phylogenetic studies have revealed a number of welldefined clades, with the Bolivian species, W. montevidensis , belonging to a group of mainly American species ( Shao et al. 2015, Shmakov 2015, Windham 2014, 2015). In this American clade, the species all have x = 38, with diploids, many allotetraploids, and numerous interspecific hybrids ( Windham 2015); reticulate speciation appears to be an overriding theme in this genus.

The New World species, most numerous in north-temperate regions (Flora of North America Editorial Committee 1993; 10 species) and Mexico (8 species; Mickel & Smith 2004), form a related group, apart from those in eastern Asia and the Himalayas (24 species, including Protowoodsia Ching and Cheilanthopsis Hieron. ; Zhang et al. 2013), which are more numerous and diverse.

Ecologically, Woodsia is primarily a genus of rocky habitats, where it typically grows in crevices among rocks. It is one of few fern groups that appear to have completely lost the association with mycorrhizal fungi ( Lehnert et al. 2017), perhaps because fungi do not thrive in the habitats preferred by these ferns. As such, research on the adaptations of this genus to nutrient and water acquisition might be of particular interest.