The relationships of the Apostasiaceae on the basis of floral anatomy

Abstract

The Apostasiaceae is a small family of limited distribution, with about 15 species altogether, and its affinities have been controversial. The floral anatomy of nine representatives of the family is now known in detail, and its relationships are discussed on the basis of the floral vasculature. The pattern of the vascular supply to the floral organs is very similar to that of the diandrous orchids, showing the undoubted affinity of the Apostasiaceae with the Orchidaceae. The subtribe Cypripedilinae of the Orchidaceae must have evolved directly from the Apostasiaceae.

What does morphology tell us about orchid relationships?—a cladistic analysis

“…The homology of the functional stamens present in orchids has been discussed by Brown (1833), Lindley (1853), Darwin (1862), Swamy (1948), and Rao (1974). Further investigation was not undertaken here; we assume that all monandrous orchids have A 1 , all diandrous orchids have a 1 and a 2 , and triandrous orchids have A 1 , a 1 , and a 2 .…”

“…The variation seen in number of functional stamens has led to speculation about the evolution of the androecium. The identity of the functional stamens, relative to those present in a putative liliaceous ancestor, was worked out by Brown (1833), Darwin (1862), Swamy (1948), and Rao (1974). Remnants of some stamens, now nonfunctional, are believed to exist in some groups as ancillary structures on the gynostemium (Kurzweil, 1987a(Kurzweil, , b, 1988.…”

Apostasiads, systematic anatomy, and the origins of Orchidaceae

“…Studies of floral anatomy have been reviewed by Rao (1969Rao ( , 1974. His investigations showed anatomical features of Apostasiaceae to be very similar to those described for the 'true orchids', and evidence from floral anatomy pointed to a close affinity between Apostasiaceae and Cypripedilinae of Orchidaceae.…”

A phylogenetic analysis of the Orchidaceae: evidence from rbcL nucleotide sequences

“…Historically, Apostasioideae have been considered the most primitive subfamily, followed by Cypripedioideae. In fact, these two groups have been classified by some as distinct families, Apostasiaceae and Cypripediaceae, because of their multiple anthers (Rao, 1974;Dahlgren, Clifford, and Yao, 1985;Rasmussen, 1985). The three monandrous subfamilies have always been regarded as a natural group, with Spiranthoideae and Orchidoideae suggested as closest allies on account of their shared terrestrial habit, sectile pollinia, and erect anthers.…”