Phylogenetics of Prescottiinae Dressler and systematics of Gomphichis Lindl. (Orchidaceae).

摘要

The phylogenetics of the subtribe Prescottiinae (tribe Cranichideae, family Orchidaceae) and the systematics of the genus Gomphichis were investigated.; Cladistic analyses of nucleotide sequences from psaB, atpB, rbcL, trnL intron, trnL-F spacer, and ITS, found that the Prescottiinae as delimited by Dressler (1990, 1993) and Szlachetko (1995) are paraphyletic and consist of two highly supported clades: "the high elevation Prescottiinae" (Aa, Altensteinia, Gomphichis, Myrosmodes, Porphyrostachys, and Stenoptera) and "the low elevation Prescottiinae" (Prescottia and Pseudocranichis). The recovered clades of the Prescottiinae show an affinity to Spiranthinae rather than to Cranichidinae. Prescottia is paraphyletic because Pseudocranichis is nested within it. These results support the transfer of Pseudocranichis to Prescottia and the re-classification of the subtribe Prescottiinae.; Gomphichis, as monographed here, consists of at least 17 species ranging from Costa Rica to Bolivia with disjunct populations in the Guayana Highlands. Three unnamed taxa may represent novelties in Gomphichis, but additional material and analyses are needed before formal descriptions are proposed. Gomphichis is distinguished by its unusual strongly reflexed flower, held at a right angle with the ovary, its sigmoid column, and saccate fleshy labellum. Phylogenetic analyses using DNA sequence data from trnL intron, trnL-F spacer, and ITS, found Gomphichis to be monophyletic and nested within a clade comprising "the high elevation Prescottiinae". Within this clade, Gomphichis is resolved as sister to Porphyrostachys, Myrosmodes, and Aa; Altensteinia is sister to these genera and Stenoptera is sister to all of them. The morphological resemblance of Gomphichis to Stenoptera is due to symplesiomorphic characters rather than common ancestry. Most species of Gomphichis fall into one of three clades characterized by either weakly- or distinctly 3-lobed labellum.; Demographic studies indicate that populations of Gomphichis crassilabia in three selected habitats of the Estacion Biologica Guandera of Ecuador (primary forest with open and closed canopy and secondary forest) follow the reverse J-curve since there are more seedlings and juveniles present than adult plants. As a result the studied populations are reproducing well. Furthermore, field experiments show that G. crassilabia reproduce by facultative out-breeding, in which, the flowers self-fertilize in the absence of pollinators late in the season.