Gomphocalyx and Phylohydrax (Rubiaceae): sister taxa excluded from Spermacoceae s.s., featuring a remarkable case of convergent evolution
Abstract:The genera Gomphocalyx and Phylohydrax (Rubiaceae) have been invariably placed in the tribe Spermacoceae s.s. based on the uni-ovulate ovary locules and pluri-aperturate pollen grains. Sequence data from the rps 16 intron and the rbcL gene here presented exclude Gomphocalyx and Phylohydrax from Spermacoceae s.s. The two genera are closely related and their nearest relatives are found among members of the former tribe Hedyotideae. This position may be surprising at first, because the growth form of Phylohydrax is similar to some observed in Spermacoceae s.s. A detailed survey of morphological and anatomical characters shows, however, that the character states of the two genera are largely consistent with the here-proposed position in Hedyotideae. The creeping growth form, the uni-ovulate ovaries and the pluri-colporate pollen grains of Gomphocalyx and Phylohydrax are the result of convergence between this pair of genera and Spermacoceae s.s. The taxonomic position of Lathraeocarpa, sometimes considered closely related to Gomphocalyx, is also discussed.
Document Type: Research Article
Publication date: 2005-02-01
More about this publication?
Impact Factor (2015): 2.9
Taxon electronic back issues (1950-2001) have been released in 2005
Submission of manuscripts: www.editorialmanager.com/taxon
- Information for Authors
- Subscribe to this Title
- Membership Information
- Information for Advertisers
- Regnum Vegetabile
- Taxonomic Literature online
- Taxon electronic back issues (1950-2001) hosted by JSTOR
- Ingenta Connect is not responsible for the content or availability of external websites