| Abstract: | ![]()
This revision deals with the system, evolution, distribution, cytotaxonomy andtaxonomic treatment of the genus Aristolochia Linn. from E. & S. Asia, which covers Japan,USSR (Far East), China, Viet Nam, Laos, Cambodia, Thailand, Burma, India, Bhutan, Nepal, Sikkim, Bangladesh and Pakistan. Total 2 subgenera, 7 sections, 4 series, 68 species and1 variety (cultivated species not included) are recognized in this treatment, of which 3 sections and 2 species are described as new. In addition, 13 new synonyms and some new records to this region are also included. Ystem Having estimated all the works dealing with the subdivision of the genus bythe previous authors, the system of O. C. Schmidt (1935) is chosen as the basis, with a changeof the sequence of the subdivisions. The subgenus Pararistolochia (Hutch. & Dalz.) O. C.Schmidt, which has indefinite stamens and gynandrous lobes, seems to be better considered asthe most primitive one in the genus, while the subgenus Siphisia (Raf.) Duch., which has definite stamens and gynandrous lobes, anthers arranged in 3 pairs and more modifications ofthe perianth, seems to be the most advanced one. The perianth of the subgenus Siphisia has differentiated into several types, and it is more rational using this character to classify sectionsthan lobes of the gynostemium. In this way, three new sections has been established. A suggested system of the genus is summarized as follows: Subgen. 1. Pararistolochia (Hutch. & Dalz.) O. C. Schmidt Subgen. 2. Aristolochia: Sect. 1. Aristolochia (2 series), Sect. 2. Gymnolobus Duch. Subgen. 3. Siphisia (Raf.) Duch.: Sect. 3. Pentodon Klotz, Sect. 4. Odontosiphisia J. S.Ma, Sect. 5. Leptosiphisia J. S. Ma, Sect. 6. Nepenthesia Klotz., Sect. 7. Obliquosiphisia J. S.Ma, Sect. 8. Siphisia (2 series). Evolution According to the character analysis of the genera of Aristolochiaceae, the evolutionary trends of the family are proposed as follows: 1, the perianth from double to single,from cup-like to tubular, 2, stamens from indefinite to definite, from separate from pistil tounited into a gynostemium with pistil, which is a major evolutionary line in the family, 3,ovary from half-superior to inferior, and 4, fruit from a follicle to a capsule. It is evidentthat the genus Aristolochia, with a tubular perianth, stamens 6, a gynostemium, an inferiorovary and a capsule, is in highly advanced position in the family. The subgenus Pararistolochia, which has more stamens and more lobes of gynostemium, is very similar to the genusThottea Rottb. and thus better considered as the most primitive subgenus in the genus. The subgenus Siphisia, which has definite stamens (6) in 3 pairs and 6 lobes of gynostemium as wellas the polyploid feature (2n=4x=28), is the most advanced subgenus. As a result of the character analysis, the evolutionary trends of the subgenera in the genus, which are in accordancewith those of the family, are proposed as follows: 1. stamens from indefinite to definite, and2. gynostemium lobes from more to less. Distribution The more primitive subgenus Pararistolochia is only distributed in WestAfrica (except 1 species in Malesia), the subgenus Aristolochia in the tropical and subtropicalregions, rarely in the temperate one, and the most advanced subgenus Siphisia occurs mainlyin E. Asia, occasionally in N. America. The result of this work shows that the HengduanMountains is the second center of distribution after South America. The second center of distribution is of following features: 1. complex composition of taxa, among 3 subgenera and 8sections, 2 subgenera and 7 sections have been recorded here, 2. rich in species, more thanhalf of the total E. & S. Asian species, i.e. about 42 species have been found in this region, and3. numerous endemics, more than 85 percent of the total number of species in the region, i.e.about 35 species, are endemic. Cytotaxonomy and taxonomic treatment The known chromosome numbers in 43species, with 34 reported by Gregory (1956) and Fedorov (1969), together with 9 species newlyreported in this work, show that Subgen. Aristolochia with 2n=2x=14, rarely 12, is apparentlymore primitive than Subgen. Siphisia with 2n=2x=28. |
