Alooideae—Asphodelaceae And The Genera Thereof by M Bruce Bayer Reprinted from Alsterworthia International Special Issue No 4 My fascination with Haworthia has presented me with many problems in the way the genera in the Alooideae have been discussed, appraised and modified in and subsequent to G. D. Rowley's analysis (1967). Parr (1971) coalesced Astroloba, Haworthia and Poellnitzia and I refuted this in 1972 when I also wrote a rebuttal of Rowley's paper. My remarks did not deter Mrs Obermeyer-Mauve (1973) following and accepting Parr, nor in adding Chortolirion to Haworthia. Rowley (1976) quite pragmatically discussed the Aloid genera, but in 1980 suggested the incorporation of Poellnitzia in Aloe. He implemented this proposal in 1981 and promoted it again in 1985. Smith and van Wyk (1991) published a cladistic analysis of the Alooideae which I felt was unacceptable because of the fallacious character states and sets that were used there. Despite that paper and at least four others (Smith 1991, 1994, 1995; Smith & van Wyk 1992) generally supporting the unispecific status of Poellnitzia, Manning and Smith (2000) incorporated the genus in Astroloba. My objection to this manipulation of the genera is that the supporting arguments have been incorrect and that it essentially has not addressed or considered what I perceived to be the stumbling block to arriving at a better delimitation of the genera in the sub-family. This is the relationship within the genus Haworthia where it is quite evident to me that it comprises three distinct sets of species (the subgenera of Bayer ex Uitewaal). The floral and morphological differences for those three sets are absolute, and I am sure will need to be seen so in any way in which Aloe is configured. This is because the floral similarities within those subgenera are so minimal. I consider these floral differences to be as dramatic for genus delimitation as any of the character states covered in Rowley's (1967) analysis. It would alarm me if the result of a DNA study produced any other result. The sets also appear to me to be "behaviorally" different and with this consideration the genera (even if unispecific) Poellnitzia, Chortolirion, Astroloba are of similar status. This is not to imply that I do not recognise the problems with many other oddities in the Alooideae which require re-evaluation of the generic arrangement. Adam Harrower of NBI asked me to identify an Haworthia he had collected near the Potberg (cf H. heidelbergensis). In view of his interest I asked him to lookout for H. limifolia on a trip he was to undertake to the eastern Transvaal. On his return he presented to me a plant he took to be that species. It was in fact Chortolirion angolense. However, he produced photographs of another species at which I exclaimed “This is a new genus". Here I recognize the irony of this reaction when the generic arrangement in Aloe is so questionable. The plant that Harrower collected has thin, slender, spineless, hyacynthoid leaves (Figs 1–2) with very pronounced bulbous bases. There seem to be few accumulated dry bulb scales as in Chortolirion and the plants have not displayed deciduousness as does that species. The blades ofthe older leaves dehisce leaving fleshy bulbous bases and these are spirally arranged in the lowest order of the Fibonacci series viz. 2, 3 or 5 (Fig 2). The roots seem rather sparse and are the yellowish color of Aloe. The flower intrigues me more (figs 3 & 4). The free terminal portions of the flower are not channeled but are flared in the style of the sub-genus Haworthia. The midribs of the inner petals remain exposed and the margins of the outer petals adhere close to the mid-rib of the inner. This is the case in the subgenus Hexangulares and Chortolirion, as well as in this “new genus". The lower petals are more undershot than is the case in either the Hexangulares or subgenus Haworthia. The geographical location is the high-lying escarpment between the ranges of the species H. koelmaniorum and H. limifolia of the Haworthia subgenus Hexangulares. Why I have stated so categorically that this is a “new genus" is largely because of the historical (mal) treatment of the genera of Alooideae and the failure of students and commentators of Haworthia to exhibit any rational species concept. Such a concept appears to be missing for the genera as well. These shortcomings, coupled with the name changes which would ensue, have discouraged me from ever trying to formalize three distinct genera for Haworthia. What has troubled me in recent times is the emerging belief that molecular study will provide the basis for a real and irrefutable phylogenetic classification. We have now a paper published in Taxon 52:193 (2003) (see reprint pages 6–21) by Treutlein et al which will enable one to see to what extent these expectations are being met. What strikes me immediately about the paper is firstly a statement in the abstract, and secondly the unfortunate selection of study material. The abstract summarizes the results of the work done and this is: “The current taxonomic system does not reflect the phylogenetic affinities and relationships among the succulent genera Aloe, Chortolirion, Gasteria, Haworthia and Poellnitzia." I find this extraordinary as it has never occurred to me that it did, and I would have expected this sentence to be worded in such a way as to form a key question to be answered by the study rather than as a conclusion. Similarly Treutlein's closing paragraphs of his discussion should have been used as key questions to be answered by the study and not have been derived from it. One sentence reads "complete sampling… needed". The selection of material I take to be somewhat irresponsible given the past history of classification of the group and the literature. I would have expected some kind of predictive approach to the selection of material. The inclusion of unknown hybrids such as H. ryderiana, H. kewensis, and H. icosiphylla can tell us nothing. Ignorance of the actual taxonomic position of H. geraldii is similarly curious. The material is virtually entirely ex hortus and given my experience with identification, even voucher specimens are hardly likely give such material much credibility. I do think more thought and consideration should have been given to the species used in relation to the problems they present to their classification. Putting these considerations aside, I would comment as follows on
View Full Document
Unlocking...