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Orchid phylogeny for everyone
BOOK
REVIEWS
Orchid phylogeny for everyone Phylogeny and Classification of the Orchid Family by Robert L. Dressier Cambridge University Press, 1993. $35.00 hbk (320 pages) lSBN 0 521 45058 6
T
he orchid family is not only the largest angiosperm family, with more than 20 000 species; it has probably also inspired the largest amount of specialized literature. Unfortunately, much of the literature on orchid taxonomy at the family level is somewhat eccentric, strongly discordant and very difficult to read for anybody but the orchid specialist. In contrast, Robert Dressler’s style has always been very informal, directed towards the general public rather than the scientific community. The present book is, as was his classical The Orchids - NaturalHistory and Classificationl,basically a popular scientific text. It can be read by anyone interested in the subject without previous knowledge about botany or evolution. The chapter ‘Structure and other evidence of relationship’ introduces the neophyte to such morphological concepts as sympodial versus monopodial growth habit, and defines stomata and inferior ovary. Everything is explained in a very straightforward language. Between the basic topics, however, are descriptions of morphological and anatomical details that are less well known, even to professional students of the family. In the section ‘The probable evolution of some features’ Dressler presents evolutionary scenarios in the same conversational style (‘. . .Nectaries appear to be quite lacking in both the apostasioids and the lady’s slippers.. .). The argumentation for character polarity ranges from outgroup comparison to character correlation, or sometimes just intuition. These hypotheses about character evolution are crucial for the chapters on phylogeny that follow, and will no doubt be scrutinized with critical eyes by specialists. The main part of the book is the introduction of a new orchid classification (partly revealed in previous papers in the orchid journal Lindleyana). The subfamily units are informal groups called phylads, hypothesized to be branches of the phylogenetic tree of orchids. Such units are usually called ‘clades’, but Dressler may feel that a nonstandard term like ‘phylad’ is less obliging. The system itself is of course built of groups conforming to the rules of nomenclature, but in the headings Dressier prefers more popular phrases, such as ‘Lady’s tresses and relatives, the subfamily Spiranthoideae,’
36
‘Orchis and its allies,’ ‘The Reed-stem or Epidendroid Phylad’. There has been very little consensus as to the contents and ranks of groups in orchid taxonomy, wherefore a formal name such as ‘tribe Orchideae’ contains very little information. Dressler uses cladistic argumentation throughout the discussion of relationships and summarizes the conclusions in cladograms called ‘phylogenetic diagrams’. There is, however, no attempt to carry out rigid cladistic analyses of the data used in the discussions. The ambiguity and scanty sampling of morphological data in Orchidaceae would render a computed cladogram an empty exercise in cladistic technique anyway, so Dressier’s approach is perhaps the closest we can get to a cladistic assessment of orchid evolution at the moment. It is nevertheless a radical departure from most earlier discussions of orchid taxonomy at this level, and may confuse orchid workers of the old school. Dressler does everything to introduce the (assumedly ignorant) reader to cladistic ideas very gently. Cladograms are exemplified with a cladogram of computers, with the Eniac as sister-group to all recent species! Funny, but perhaps pedagogically questionable. The final chapter reveals that Dressler is a reluctant cladist. The section ‘Theory and philosophy of classification’ contains some misunderstandings or very partisan viewpoints, and the author takes great care in dissociating himself from ‘the abstruse terminology of cladistics’, but in doing so he sometimes has to invent new terms such as ‘exophyletic’. The terminology of cladistics is really no more abstruse than, for example, that of molecular biology, but there will always be problems if one insists on translating technical terms into everyday language. The book includes a key to the genera of orchids and a systematic list of all genera recognized by the author. This list also contains a selection of synonyms, generic names that for nomenclatural or taxonomic reasons should be abandoned. This is, as is the classification itself, to some extent, a matter of judgement and likely to cause discussion. One may wish that the list had been more comprehensive. For example, Brieger2 published 21 nomenclaturally valid genera of the Dendrobium-Eria group in 1982. They are simply ignored in Dressler’s list. One may agree or disagree with the classification put forward in Dressier’s new book, but everybody interested in orchids must have it. For the professional orchid systematist, it is the latest complete system and it will be central in many scientific discussions. For the orchid amateur, it is a comprehensive survey and a very personal guided excursion into a field that otherwise is very difficult for the less-experienced
enthusiast. It is also a pleasure to page through, with clear drawings and colour photographs of orchids not usually illustrated in orchid books. Finn N. Rasmussen Botanical Laboratory, University of Copenhagen, Gothersgade 140, DK-1123 Denmark
References 1 Dressler, R.L.(1981) The Orchids: Nafuml History and Classification, HarvardUniversityPress 2 Brieger, F.G. (1982) in Die Orchideen (3rd edn),
(Brieger, F.G., Maatsch, R. and Senghas, K. eds), pp. 636-752, Rudolf Schlecter
Landscape ecology Riparian Landscapes by George P. Malanson Cambridge University Press, 1993. $35.00 hbk (x + 296 pages) ISBN 0 521 38431 1
B
eing only familiar with the tamed tributaries of the Rhine in The Netherlands, confined between fixed dykes leaving the inner landscape with nothing but historical connections to its main creative force the river - it was an imaginative experience to read this book. It incorporates a wealth of information (mostly originating from research done in the USA) on more-or-less naturally functioning river systems into the concepts of landscape ecology. Malanson tries to rebuild the landscape out of its components of hydrology, geomorphology and ecology. Landscape principles and their application to riparian systems are outlined in two introductory chapters. The complex structures and processes among and within riparian landscapes are presented from different angles in the next four chapters. First, the structure of the integral landscape is presented in its relation to the surrounding matrix. Emphasis is on the longitudinal (corridor) aspect of these landscapes. The expression of this and other features is discussed in relation to hydrological characteristics, determined by past and present climate conditions, and human land-use. Next, the internal structure is discussed in terms of the composing landscape elements and their functions in the integral landscape. This chapter has a complex structure because of the difficulty in distinguishing structural elements from their underlying processes, which are the subjects of the two following chapters on cascades of materials and energy, and on species dynamics. These chapters deal TREE
vol. 9, no. I January
I.994
REVIEWS
Orchid phylogeny for everyone Phylogeny and Classification of the Orchid Family by Robert L. Dressier Cambridge University Press, 1993. $35.00 hbk (320 pages) lSBN 0 521 45058 6
T
he orchid family is not only the largest angiosperm family, with more than 20 000 species; it has probably also inspired the largest amount of specialized literature. Unfortunately, much of the literature on orchid taxonomy at the family level is somewhat eccentric, strongly discordant and very difficult to read for anybody but the orchid specialist. In contrast, Robert Dressler’s style has always been very informal, directed towards the general public rather than the scientific community. The present book is, as was his classical The Orchids - NaturalHistory and Classificationl,basically a popular scientific text. It can be read by anyone interested in the subject without previous knowledge about botany or evolution. The chapter ‘Structure and other evidence of relationship’ introduces the neophyte to such morphological concepts as sympodial versus monopodial growth habit, and defines stomata and inferior ovary. Everything is explained in a very straightforward language. Between the basic topics, however, are descriptions of morphological and anatomical details that are less well known, even to professional students of the family. In the section ‘The probable evolution of some features’ Dressler presents evolutionary scenarios in the same conversational style (‘. . .Nectaries appear to be quite lacking in both the apostasioids and the lady’s slippers.. .). The argumentation for character polarity ranges from outgroup comparison to character correlation, or sometimes just intuition. These hypotheses about character evolution are crucial for the chapters on phylogeny that follow, and will no doubt be scrutinized with critical eyes by specialists. The main part of the book is the introduction of a new orchid classification (partly revealed in previous papers in the orchid journal Lindleyana). The subfamily units are informal groups called phylads, hypothesized to be branches of the phylogenetic tree of orchids. Such units are usually called ‘clades’, but Dressler may feel that a nonstandard term like ‘phylad’ is less obliging. The system itself is of course built of groups conforming to the rules of nomenclature, but in the headings Dressier prefers more popular phrases, such as ‘Lady’s tresses and relatives, the subfamily Spiranthoideae,’
36
‘Orchis and its allies,’ ‘The Reed-stem or Epidendroid Phylad’. There has been very little consensus as to the contents and ranks of groups in orchid taxonomy, wherefore a formal name such as ‘tribe Orchideae’ contains very little information. Dressler uses cladistic argumentation throughout the discussion of relationships and summarizes the conclusions in cladograms called ‘phylogenetic diagrams’. There is, however, no attempt to carry out rigid cladistic analyses of the data used in the discussions. The ambiguity and scanty sampling of morphological data in Orchidaceae would render a computed cladogram an empty exercise in cladistic technique anyway, so Dressier’s approach is perhaps the closest we can get to a cladistic assessment of orchid evolution at the moment. It is nevertheless a radical departure from most earlier discussions of orchid taxonomy at this level, and may confuse orchid workers of the old school. Dressler does everything to introduce the (assumedly ignorant) reader to cladistic ideas very gently. Cladograms are exemplified with a cladogram of computers, with the Eniac as sister-group to all recent species! Funny, but perhaps pedagogically questionable. The final chapter reveals that Dressler is a reluctant cladist. The section ‘Theory and philosophy of classification’ contains some misunderstandings or very partisan viewpoints, and the author takes great care in dissociating himself from ‘the abstruse terminology of cladistics’, but in doing so he sometimes has to invent new terms such as ‘exophyletic’. The terminology of cladistics is really no more abstruse than, for example, that of molecular biology, but there will always be problems if one insists on translating technical terms into everyday language. The book includes a key to the genera of orchids and a systematic list of all genera recognized by the author. This list also contains a selection of synonyms, generic names that for nomenclatural or taxonomic reasons should be abandoned. This is, as is the classification itself, to some extent, a matter of judgement and likely to cause discussion. One may wish that the list had been more comprehensive. For example, Brieger2 published 21 nomenclaturally valid genera of the Dendrobium-Eria group in 1982. They are simply ignored in Dressler’s list. One may agree or disagree with the classification put forward in Dressier’s new book, but everybody interested in orchids must have it. For the professional orchid systematist, it is the latest complete system and it will be central in many scientific discussions. For the orchid amateur, it is a comprehensive survey and a very personal guided excursion into a field that otherwise is very difficult for the less-experienced
enthusiast. It is also a pleasure to page through, with clear drawings and colour photographs of orchids not usually illustrated in orchid books. Finn N. Rasmussen Botanical Laboratory, University of Copenhagen, Gothersgade 140, DK-1123 Denmark
References 1 Dressler, R.L.(1981) The Orchids: Nafuml History and Classification, HarvardUniversityPress 2 Brieger, F.G. (1982) in Die Orchideen (3rd edn),
(Brieger, F.G., Maatsch, R. and Senghas, K. eds), pp. 636-752, Rudolf Schlecter
Landscape ecology Riparian Landscapes by George P. Malanson Cambridge University Press, 1993. $35.00 hbk (x + 296 pages) ISBN 0 521 38431 1
B
eing only familiar with the tamed tributaries of the Rhine in The Netherlands, confined between fixed dykes leaving the inner landscape with nothing but historical connections to its main creative force the river - it was an imaginative experience to read this book. It incorporates a wealth of information (mostly originating from research done in the USA) on more-or-less naturally functioning river systems into the concepts of landscape ecology. Malanson tries to rebuild the landscape out of its components of hydrology, geomorphology and ecology. Landscape principles and their application to riparian systems are outlined in two introductory chapters. The complex structures and processes among and within riparian landscapes are presented from different angles in the next four chapters. First, the structure of the integral landscape is presented in its relation to the surrounding matrix. Emphasis is on the longitudinal (corridor) aspect of these landscapes. The expression of this and other features is discussed in relation to hydrological characteristics, determined by past and present climate conditions, and human land-use. Next, the internal structure is discussed in terms of the composing landscape elements and their functions in the integral landscape. This chapter has a complex structure because of the difficulty in distinguishing structural elements from their underlying processes, which are the subjects of the two following chapters on cascades of materials and energy, and on species dynamics. These chapters deal TREE
vol. 9, no. I January
I.994