The application of leaf phenolic evidence for systematic studies within the genus Pelargonium (Geraniaceae)

In a leaf phenolic survey of 58 Pelargonium taxa, quercetin was almost univ ersally present. Tannins were major components, namely proanthocyanidins an d ellagitannins (in 53 % of tars) and free ellagic acid (in 50%), Myricetin (in 38%), flavone C-glycosides (in 36%) and luleolin (in 49% of taxa) were other regular constituents. A correlation was found between the presence o f myricetin and proanthocyanidins. Although no individual compound or group of compounds appears to be a useful taxonomic marker for sectional classif ication, the data do indicate which sections are homogeneous, e,g, Otidia a nd Jenkinsonia. The chemistry supports the removal of some taxa from sectio n Ligularia to the new sections Chorisma and Subsucculentia but does not di stinguish between the latter two groups and indicates that section Ligulari a is still an unnatural assemblage. Similarly, the data support the separat ion of P. reniforme me and related species from section Cortusina into the new section Reniformia but P. odoratissimum appears misplaced in the latter group, The data suggest the placement of P. rodneyanum in section Perister a with the other Australian species. From a phylogenetic point of view the presence of ellagitannins or absence of tannins may be considered a more ad vanced state than the presence of proanthocyanidins and myricetin in the ge nus Pelargonium. For example, the most primitive state was found in P. cris pum (section Pelargonium) and the most advanced in P.,multi-bracteatum (sec tion Ciconium). The chemistry also lends support for the division of the ge nus into two cytological groups based on chromosome size, in that most ella gitannin-producing species have large chromosomes while most proanthocyanid in-producing species have small chromosomes. There is agreement with the cy tological and molecular data in groupingP. existiplatum with P. album, P. r eniforme and P. sidoides. (C) 2000 Elsevier Science Ltd. All rights reserve d.