What is "jamesonia"

Jamesonia \Jamesonia\ prop. n. A genus of xerophytic ferns of South America.

Syn: genus Jamesonia.

Eriosorus and Jamesonia are two closely related genera in the taenitoid group of the core pteridoid ferns. They have long been recognized as being closely related, and recent genetic evidence has demonstrated that they are both paraphyletic genera, but only in regards to each other. Thus, they must be combined as a single larger genus, or have the generic boundaries redefined. The two genera are being temporarily considered here under Jamesonia, because 1) this is the older genus name, and 2) the core genus forms a clearly defined monophyletic group considered by itself, while there is no such clear clade for Eriosorus.

A new genus name, Eriosona, was described in 1977 to recognize the hybrids between these two genera. These hybrids are noted below. The frequency of such hybrids clearly points to the close relationships found in this group.

Eriosorus species are found in the cooler regions of Central and South America, mainly in the Andes Mountains. The type species of Eriosorus is apparently Eriosorus aureonitens.

Jamesonia species are also found in cooler regions, but extending from Mexico to Bolivia and upland Brazil. The type species of Jamesonia is Jamesonia pulchra (or possibly Jamesonia imbricata, if this is found to be the same as J. pulchra).