Ptisana

Note: this tree is still under construction. It does not yet contain all known Ptisana subgroups.

Relationships after Murdock (2008a, 2008b)

Introduction

Ptisana is a Paleotropical genus, recently seggregated from Marattia by Murdock (2008b). Murdock (2008a) showed that the placement of Angiopteris and Christensenia made Marattia s.l. polyphyletic. By recognising the New World "Marattia's" as Marattia s.s. and Eupodium, the remaining Palaeotropical "Marattia's" needed a new name, because none of the previous synonyms are available due to a variety of nomenclatorial reasons. Therefore a new genus was proposed by Murdock (2008b).

Ptisana counts about 20 species. It is a genus of the wet tropics, where it is more restricted to the higher cooler areas. It occurs on stream banks, in ravines, wet mountain and cloud forests, up to an elevation of 3000 m. It can be found in tropical Africa, South and East Asia, Malaysia, New Guinea south to New Zealand, on many Pacific islands, and on Ascension Island in the Atlantic.

The generic name is derived from the Latin feminine noun ptisana meaning pearl barley or a beverage made from pearl barley, which is derived from Greek, having the same meaning. The shape of the synangium resembles pearl barley (Murdock 2008b).

Characteristics

Ptisana can be recognized by its fused, bilabiate synangia. It shares this character with Marattia, but there the synangia are vertically sulcate along the septa, which is not the case in Ptisana.

The blades are usually of a deltoid or pentagonal shape, and two to four times pinnate. The pinnae of the first order are generally opposite, though becoming alternate towards the apex. Pinnules of the second order or beyond are alternate. There are no venuloids between the veins of terminal segments.

The rhizome is often large, with an erect, usually globose, radially arranged apex. The stipules are large and when broken off can grow to become a new plant, which in some populations appears to be an important way of reproduction.

Discussion of Phylogenetic Relationships

Murdock (2008a) inferred the phylogeny of Marattioid ferns based on combined analysis of nucleotide sequence data (plastid trnS-trnG intergeneric spacer plus the trnG intron, rps4-trnS intergeneric spacer, atpB and rbcL) and morphology. He studied the crown group of Marattiales, using Danaea as outgroup. He had a broad sampling of species but was not able to include all species of his new genus in the analysis, and thus the placement of several species remains unknown.

An interesting result within the Ptisana clade is that the basal species P. fraxinea is the only African species, and P. purpurascens occurs on Ascension Island in the Atlantic, whereas the species in the crown group have their predominant distribution in Asia-Oceania.

References

Murdock, A. (2008a). Phylogeny of marattioid ferns (Marattiaceae): inferring a root in the absence of a closely related outgroup. Amer. J. Bot. 95, pp. 626-641.

Murdock, A. (2008b). A taxonomic revision of the eusporangiate fern family Marattiaceae, with description of a new genus Ptisana. Taxon 57, pp. 737-755.

Information on the Internet

• Botany Photos: Marattiaceae. Plant Images by Maarten Christenhusz.