ASBS Newsletter – Book Review
Flora of Australia. Volume 48: Ferns, Gymnosperms and Allied Groups.
Melbourne: ABRS/CSIRO Australia (1998);
XXII + 766 pp, 213 figs, 609 maps.
This is about the 20th volume published of the 59 proposed volumes in the Flora of Australia series although developments in Australian botany over the past two decades have meant that the 1981 Introduction volume has now been entirely revised and re-issued as a second edition.
Volume 48 is a substantial treatise on the non-angiosperm elements in the Australian vascular flora. At 766 pages it might have been preferable to publish the volume in two parts: one for ferns and fern allies and another for gymnosperms. In any case this publication contains an imposing quantity of descriptive and distributional data for Australian lycophytes, psilophytes, ferns, conifers, and cycads. The volume contains descriptions of 582 species and includes an appendix with descriptions and typification of 22 new species, 13 new combinations, and one new genus: Revwattsia (Dryopteridaceae). Fern allies are represented in Australia by 44 species slightly outranking conifers with 43 species but lagging behind cycads with 69 species. The ranks of Australian cycads have swelled with circumscription of nine new species of Macrozamia in this volume.
Succinct circumscription of the diagnostic characters and keys for the identification for all phyla, families, genera and species are provided in this work. The keys are mostly easy to use although in a number of cases, especially at species level, they require specialized microscopic techniques (e.g., for recognition of stomata and spore-wall ornamentation) that may not be available to the interested lay botanist. In a few places (e.g., Lycopodium-Lycopodiella) the keys are a little cumbersome even without resort to microscopic techniques and clear, phylogenetically meaningful, distinctions between a few taxa are not readily apparent. Apart from the diagnostic morphological features, the distribution of each taxon is stated and aided by Australian distribution maps for each species and subspecies (609 in total). The maps provide a quick reference for regional distribution of taxa based on herbarium records and are useful for drawing attention to disjunct distribution patterns for some taxa that may require complex biogeographic and historical explanations. A point of caution, however, is that at least in one case the distribution indicated in the text does not match that in the maps. Macrozamia pauli-guilielmi (p. 652) is stated to occur in the Burnett, Darling Downs, and western Moreton districts in southeast Queensland. The corresponding distribution map (p. 702) indicates only a Burnett distribution. This appears to be a case of an error in the text as the species is stated to occur almost exclusively on siliceous beach dune sands which are not a feature of the Darling Downs. For some species additional useful comments on morphological variation, inter-species distinctions and habitat preferences are included. Key synonymy records and literature references to illustrations are provided for each species. Although not every species is illustrated in this volume, the descriptions are supported by 117 full page, multi-element, line-drawings, and 96 good-quality colour photographs. Apart from general frond habit, the line-drawings of ferns are particularly useful for illustrating the key diagnostic features of sori position and structure and stipe/rhizome scale and hair morphology. Details of megaspore and microspore morphology are only provided for Selaginella and Isoetes although broad pollen characteristics are also given for some conifer genera and families. Given the importance of spore morphology in keying out Isoetes species in particular, it would have been useful to include some scanning electron micrographs or clear transmitted-light photomicrographs of the megaspores and microspores of each species as the subtleties of the ornamentation are difficult to express in line-drawings.
A point of caution for taxonomists is that Callipteris Bory 1804 (Athyriaceae), although little used between 1804 and 1947, has priority over Callipteris Brongniart 1849, a Northern Hemisphere fossil peltasperm (seed-fern) species. Species of the latter are now mostly transferred to Autunia, but Callipteris is still widely used in the palaeobotanical literature for Late Carboniferous to Early Permian foliage. These records should not be taken to indicate generic affinity to extant Callipteris ferns (Kerp, 1986).
This volume still employs the category of Division rather than Phylum. As a concession to standardizing the codes of biological nomenclature, I would argue that the latter term should be preferred - especially where it comes to categorizing those micro-organisms where affinities to plants, fungi, or animals are not immediately clear. Apart from "Division" this volume does not employ any taxonomic categories higher than family. Such rankings (Class and Order) may lack any real meaning in our somewhat artificial classification schemes, and in any case it might be difficult to achieve consensus among a number of contributors. Furthermore, as Drinnan points out in the chapter on Classification and Phylogeny, our understanding of the relationships of fern families is likely to see dramatic improvement in the near future with the broader application of cladistic methodology and the availability of a greater range of gene sequences from a larger number of species. Erecting a detailed supra-familial classification scheme for this volume might, therefore, be premature.
Just as plant groupings periodically change status, so too geologists periodically change the status of stratigraphic terms. In 1997 the International Commission on Stratigraphy resolved to drop the use of the term 'Tertiary' System/Period and replace it with the Paleogene and Neogene Systems/Periods (previously of sub-system/sub-period status). The succeeding Quaternary System/Period retains its status. The use of 'Tertiary Period' throughout the text of this volume is now redundant and in most cases can simply be replaced with 'Cenozoic Erathem/Era' (incorporating the Palaeogene, Neogene, and Quaternary).
A review of the available palaeobotanical data by Hill & Jordan provides a succinct summary of the continent's ferns and fern ally fossil record. Their review focuses mainly on the relatively recent fossil record (last 100 million years) of direct relevance to the extant flora, although it should be noted that for some groups (e.g., Isoetes) there are records of plants (variably assigned to Isoetes or Isoetites) with close affinities to extant representatives in much older rocks of Triassic to Early Cretaceous age (Walkom, 1944; Retallack, 1997). Hill & Jordan summarize the fossil record for 10 fern families. Although the fossil record of spore-producing plants is difficult to summarize in a few pages there are a few additional families that could also be mentioned in this summary. For example, several fossil fronds from the Australian Early Cretaceous have been assigned to Gleichenites (or Microphyllopteris) with inferred gleicheniaceous affinities. However, recent studies (Cantrill, 1998) suggest that at least some of these should be reassessed as possible representatives of Lophosoria - now restricted to the Americas. Megaspores referred to Arcellites from the mid-Early Cretaceous of Victoria (Douglas, 1973) also indicate the early appearance of heterosporous aquatic ferns in Australia not long after their oldest (earliest Cretaceous) records from the Northern Hemisphere (Kovach & Batten, 1993). The Dipteridaceae also has a long fossil record in Australia extending back to at least the Middle Triassic although it is likely that they became regionally extinct during the Late Cretaceous and that the single extant representative of this family in Australia, Dipteris conjugata, may be derived from tropical Malesian stock that entered northern Australia during the Cenozoic.
The introductory section to the gymnosperms by Ken Hill and the chapters on the fossil record of conifers by Bob Hill and Leonie Scriven and the fossil history of cycads by Bob Hill include useful summaries of the history of gymnosperm systematics and the Australian palaeobotanical record of these groups. A couple of slight discrepancies between the information presented in different chapters were noted. Just as a small example, on page 514 the Araucariaceae are stated to first appear in the fossil record during the Early Cretaceous but on page 527 a Late Triassic origin is indicated. A similar discrepancy is noted for the origin of cycads. While these are relatively minor points and may result from different interpretations of the primary data, they are a little distracting for the reader and could have been picked up during the editing process.
Inclusion in the text of doubtful records (e.g., Christensenia aescilifolia: Marattiaceae), taxa of uncertain affinity (e.g., 'Oenotrichia tripinnata'), and the notable concentration of many species to eastern moist forests (many restricted to small areas) suggests that there is much work yet to be done on Australian fern systematics. Judging from the recent increase in recognized cycad species, there is probably a substantial number of undescribed, geographically restricted, fern and allied taxa awaiting discovery and description particularly in the wet tropics. This volume represents a sound foundation for future research on Australian non-angiosperm vascular plant systematics.
Despite the relatively minor problems mentioned above, this volume will be a valuable aid to systematists, biogeographers, palaeobotanists, and ecologists studying the Australian vascular flora. It will also be of substantial benefit to lay botanists interested in identifying native pteridophytes and gymnosperms. At $60 for the softback edition and $95 for the hardback this volume is reasonably priced for its detailed content and the breadth of its focus.
Reviewer: Stephen McLoughlin
Cantrill, D.J. 1998. Early Cretaceous fern foliage from President Head, Snow Island, Antarctica. Alcheringa, 22: 241-258.
Douglas, J.G. 1973. The Mesozoic flora of Victoria. Geol. Surv. Vict. Mem., 29: 1-185.
Kerp, J.H.F. 1986. Withdrawal of proposal to conserve Callipteris Brongn. (Fossiles). Taxon, 35: 370-371.
Kovach, W.L. & Batten, D.J. 1993. Diversity changes in lycopsid and aquatic fern megaspores through geologic time. Paleobiology, 19: 28-42.
Retallack, G.J. 1997. Earliest Triassic origin of Isoetes and quillwort evolutionary radiation. J. Paleont., 71: 500-521.
Walkom, A.B. 1944. Fossil plants from Gingin, W.A. J. Roy. Soc. W.A., 28: 201-207.