SIX PAPERS THAT SHOOK...

Richard Saunders

During my undergraduate degree I developed an interest in plant structure, particularly in relation to function. Although I conscientiously read textbooks and research papers during this period, l cannot remember being 'shaken' by any publication until I encountered a paper by K. Bremer & M.E. Wanntorp (Phylogenetic systematics in botany, Taxon 27 (1978), 317-329). Theories of phylogenetic reconstruction (initially developed by W. Hennig in his book Grundzuge einer Theorie der phylogenetischen Systematik in 1950) had been developed by zoological systematists during the late 1960s and 1970s, but had been largely overlooked by botanists. The paper by Bremer & Wanntorp was an attempt to convince the botanical taxonomists that they should reassess the value of cladistics for the analysis of plant evolution. They demonstrated the procedures of cladistics, and outlined the taxonomic consequences of strict adherence to Hennigian principles (including the necessity to abandon well established taxa such as the Dicotyledonae, which is paraphyletic, and the Bryophyta, which is polyphyletic). l was aware at the time I was first reading the paper (sometime around 1985) that plant systematics was undergoing a revolution, and that many systematists had heeded Bremer & Wanntorp and were indeed using cladistic techniques in developing plant classifications. Taxonomy is far from being static and unchanging.

I was also fascinated by this topic because it was my first true exposure to open scientific discussion of opposing views. Although cladistic methodology has now been extensively adopted by plant taxonomists, numerous papers were published in the late 1970s and 1980s that argued against it. One such paper was by W.C. Burger (Cladistics: useful tool or rigid dogma?, Taxon 28 (1979), 385-386), written in response to Bremer & Wanntorp's paper. Burger argued that cladistics was an inappropriate tool for botanists, in part because plant evolution does not necessarily follow a dichotomously diverging pattern due to the occurrence of hybridisation.

The journal Taxon also had an impact on me in a different way. l remember browsing through several issues, and being aghast that taxonomists published papers on topics as seemingly pointless as the typification or orthography of a species name, or on the date of publication of an obscure eighteenth century Flora. As the author of such papers, I now realise their scientific objective (not quite as pointless as I previously thought). I have always been fascinated by the relationship between history and taxonomy: as a retrospective science, taxonomy is inevitably tied to the actions of previous taxonomists, and an understanding of their actions within the conceptual framework prevalent at the time they were working is essential. My third choice of a paper that 'shook' me is therefore a long forgotten paper from the 'nomenclature' column of an issue of Taxon published sometime in the early to mid 1980s: whatever the paper was about, it helped me to understand the relationship between taxonomy and history a little better.

Although I do not have any particular interest in the Cyperaceae, I was greatly impressed by a paper by O. Seberg (Taxonomy, phylogeny, and biogeography of the genus Oreobolus R. Br. (Cyperaceae), with comments on the biogeography of the South pacific continents, Botanical Journal of the Linnean Society 96 (1988), 119-195. This paper was effectively my second supervisor during my PhD, and provided me with much valuable advice regarding layout and presentation of taxonomic data. It is an immaculately executed paper. Seberg discusses the genus Oreobolus not only in terms of patterns of morphological variation, but also includes a cladistic study which is used to interpret the historical biogeography of the genus. Seberg evaluates the three biogeographical theories which are based on phylogenetic systematics (progression rule biogeography; panbiogeography; and vicariance or cladistic biogeography) and discusses the thorny issue of falsifiability in biogeography.

M.W. Chase (together with 41 other authors) recently published a paper summarising the phylogenetic interpretations of variation in the chloroplast rbcL gene (Phylogenetics of seed plants: an analysis of nucleotide sequences from the plastic gene rbcL, Annals of the Missouri Botanical Garden 80 (1993), 528-580). This study encompasses 499 species of seed plant, representing all the major taxonomic groups. Although the authors caution that the tree topologies are necessarily approximate, the paper presents a series of cladograms that form a reasonably sound basis for the interpretation of other data, both molecular and morphological. A similar paper has recently been published by D.E. Soltis (with 15 other authors) for 18S sequences (Angiosperm phylogeny inferred from 18S ribosomal DNA sequences, Annals of the Missouri Botanical Garden 84 (1997), 1-49), and other similar papers can be expected in the future. Thankfully, there is a general congruence between the rbcL and 18S phylogenies.

The Flora of the British Isles (by A.R. Clapham, T.G. Tutin and E.F. Warburg) was first published in 1952 (with subsequent editions in 1962 and 1987). This gave rise to the Excursion Flora of the British Isles (3rd ea., 1981, Cambridge University Press), which was an abridged version intended for field use. The latter book is my final choice: it was the book which introduced me to taxonomic keys and descriptions (albeit short descriptions), and it was always my preferred choice for identifying the British flora. Although both books are still in print, the larger Flora has now been superseded by C.A. Stace's New Flora of the British Isles, which gives greater emphasis to hybrids and introduced species. The first volume of a new five-volume Flora of Great Britain and Ireland (by P.D. Sell & G. Murrell) has furthermore just been published. Although I have not seen this book yet, it promises to give "an extensive account of all the large apomictic genera for the first time" (although large apomictic genera and the taxonomists that write papers on them are two of my pet hates). The Excursion Flora is the only British Flora that I know of that is specifically intended for field use, and I only hope that it hasn't been abandoned for a Flora which treats the aggregate species 'Taraxacum officinale L.' as 250 agamospecies.

P.19

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