The spectrum of botanical literature
Publication of species names
Scientific names have to be published before they are considered valid. Although some early botanical literature - notably Linnaeus’ Species Plantarum (1753) – involved massive syntheses of known and new plant names, or were catalogues of useful plants, nowadays new species names are often published a few at a time in journals, or sometimes in the other types of botanical publications. Scientific plant names have to be published formally, implying copies in publicly available, printed media. Unfortunately, this does not mean that all species descriptions are easily available throughout the world, even in the age of the internet.
The most useful reference for any plant name, though, is an actual specimen of a plant. When published, a ‘type specimen’ is deposited in a herbarium and a short description, in Latin, has to appear in a journal referring to the type specimen and giving it the name. This, and other rules of taxonomy are outlined in the ‘International Code of Botanical Nomenclature’. Winston (1999) provides a friendly synopsis, and a useful guide to the whole task of naming a species. Obtaining original descriptions and type specimens are major hurdles and expenses to taxonomy, and will normally involve you or a colleague working in a well resourced botanic institution.
Strictly, the only plant without question that has a particular name is the individual plant from which the type specimen was clipped. Botanists use these type specimens as reference beacons in the spectrum of plant life. Anything that looks sufficiently similar to the type specimen is then identified with that name, and of course the meaning of ‘sufficiently similar’ is the basis of much taxonomic debate. It surprises even some regular users of scientific names that they are open to interpretation, and therefore in practice somewhat subjective. Plants vary over time and space, so their names are not as fundamental as, for example, the names of chemical elements.
Periodically, a plant is found that looks nothing like any existing type specimen, matching none of their published descriptions. A botanist will then invent a new name for this plant, and define a new type specimen. Over the last few decades, about 2500 new plant names were invented per year globally (Prance, 2001), that is almost 1 per year for every 100 species that have a scientific name already. Even for America, north of Mexico, 60 flowering plant species were described every year between 1975 and 1994, a rate which shows no sign of slowing down (Hartman and Nelson, 2003). Tropical vegetation is particularly rich in plants with no name.
For the place of publication of names of vascular plants, whether synonyms or accepted ones, users can consult Index Kewensis or, on the Internet, the International Plant Names Index (http://www.ipni.org/). These sources exclude infraspecific taxa and (Index Kewensis) ferns and their allies, and most frustratingly do not mention synonymy.
Type specimens are often not very accessible but there is an increasing number of ‘virtual herbaria’ with detailed images of type specimens on the internet (see links or search for “type, specimens, virtual, herbarium” on the internet to find the ones relevant to you)
New species have to be named in a way that distinguishes them reliably from all other plants in the world, and for this reason taxonomists tend to focus most strongly on fertile characters. The fact that fertile characters are not always available in plants met in the field contributes to a continuing demand for field guides.
As your field guide will probably cover a limited area, you do not need to distinguish your species from all its close relatives in the rest of the world, so small fertile characters are usually not as important as they are in a monograph or Flora. Species rediscovered in the field often have surprisingly distinctive, but unrecorded features - like long plank buttresses, or a strong smell - which the author of the name was unaware of in the herbarium.
Taxonomic monographs and revisions: ‘spring-cleaning’ in taxonomy
Periodically, taxonomists review all the species that have been created in a genus or other group of related species, together with the new specimens collected since publication, and publish a synoptic paper. At its simplest, this is a ‘revision’, that may appear in botanical journals: revisions themselves often include new species names as a sort of conclusion of the work. With a larger amount of study and background information, a complete book about a particular group may be published, which is then normally referred to as a monograph.
The check-list, Flora, Field Guide spectrum
Botanists identifying new specimens in herbaria often follow opinions of earlier experts recorded on the original specimen label or preferably on the most recent determination slip (a ‘det. slip’ is a small label on which a specialist simply records their identification of a specimen), rather than relying on original descriptions, but when new species are recorded in an area, botanists must rely on the literature.
Various types of publication exist to help a region develop a more consistent application of scientific names than is possible with many people independently working with type specimens and original descriptions, or copying earlier determinations for similar specimens in herbaria. Revisions and monographs summarise all plants described of a particular genus, family or other plant group. For more practical use in a particular region, synopses are made of all the available monographs and other publications for all families of plants (usually restricted to a very broad set of plant families such as ‘Trees’, ‘Flowering Plants’ or ‘Mosses’). These regional syntheses include checklists, Floras, and, of course, field guides. Frodin (2002) has summarised the content of many of these types of publication, particularly Floras.
Checklists are, at their simplest, lists of plants in a particular region, and usually the first step in producing other regional synopses. Checklists become more like Floras as more and more diagnostic information is added, but usually a checklist writer will avoid the task of identification altogether. A checklist is usually an early step towards the Flora or field guide.
Floras are detailed descriptions of all (usually higher) plants in a region, taking care to summarise all necessary taxonomic details, and in theory allow precise identifications of plants, if you have in your plant specimen(s) all the required details. They are primarily intended for use by other botanists in the herbarium, although they are often used in other situations. The Floras of the world are reviewed by Frodin (2002).
Floras tend to be the field guide writers’ most useful reference books; if none is available for your area, there may be one for a nearby country that is better than nothing.
Field guides are also primarily to help plant identification, but are designed for field use, so are generally portable, and are also often designed for use by non-botanists. They have less taxonomic detail than Floras, and more field-related information. It is not uncommon for a field guide to exclude some of the species from the target group, whereas this would run against the spirit of a checklist or Flora.
Electronic identification tools represent a dramatic change of style for botanical literature, potentially confusing the boundaries (Access methods).
Simple Flora -sophisticated field guide
We made a first attempt at a working definition of a field guide but there is really no clear boundary between a simpler, user-friendly Flora and a complex field guide. From a historic perspective, herbals represent the ancestor of the modern field guide. They are also the common ancestor of other botanical works.
On the borderline in modern times between field guides and Floras are series like the Tree Flora of Sabah and Sarawak (Soepadmo & Wong, 1995-) : either a specialist Flora because it is in several volumes (unlike any self-respecting true field guide); because it has ‘Flora’ in the title; has detailed morphological descriptions of flowers, and takes many years to write. However, as it deals with only trees (and not all other members of the families); there is a separate Flora (Malesiana) for the area; and it mentions field characteristics, this ‘Tree Flora’ has many of the features of a field guide. Its Flora credentials outweigh its field guide ones, especially its weight and volume, averaging 150 pages per family, but we include it for the sake of discussion in our “Tree Flora” heading below.
Types of field guides: the spectrum continues
The spectrum from Flora to field guide continues into a rainbow of types of field guide; from intense, heavy and technical, to light, pretty and information-poor; from encyclopaedias of regional field identification to tourist brochures for single parks