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Questions and Answers
What is an herbarium?
An herbarium (plural: herbaria) is a collection of preserved plant and fungal specimens maintained for scientific purposes. Most specimens are carefully pressed, dried, mounted on rigid paper, and filed in metal cabinets, using techniques perfected over several centuries. Other specimens are preserved in liquid (alcohol or formalin) or dried three-dimensionally. Properly prepared and protected, herbarium specimens will last indefinitely. All specimens are accompanied by data indicating where they were collected, when, and by whom.
How do we get specimens?
Specimens accessioned into herbaria are collected not only by staff members, but by a wide diversity of amateurs and non-academic professionals, including agency biologists and environmental consultants. Many of our most valuable specimens have been collected by native plant enthusiasts who are familiar enough with their local flora to know what is noteworthy. Other specimens have been received as gifts sent for identification by in-house specialists (e.g., Latin American ferns). University-affiliated expeditions, such as the several expeditions to the Andes by the UC Botanical Garden earlier this century, resulted in an abundance of invaluable collections.
As a common practice, collectors generally prepare several duplicates of each collection, depending on how common the plants are. The best specimen is kept at the home institution, while the duplicates are exchanged for duplicates collected at other institutions from around the world. This system allows participating institutions to amass much more diverse collections than they would have otherwise been able to do, with a vastly increased payback for minimal additional effort. It also provides a level of "insurance", diminishing the scientific impact if a catastrophe destroys any one institution.
Who uses herbarium specimens?
At UC Berkeley, herbarium specimens are routinely used as display material in botany classes, providing convenient examples of diversity in the plant and fungal kingdoms. The collections are also consulted by a wide diversity of visitors, in both public and private sectors, who need comparative material in conjunction with plant identification. By far the most significant use, however, is by plant systematists, not just at UC but throughout the world, in the preparation of monographs and floras.
What do herbarium specimens represent?
Each and every herbarium specimen is a voucher documenting a plant growing at a certain site at a certain time. As such, herbarium holdings worldwide collectively provide the raw data underpinning our scientific knowledge of what kinds of plants exist, what their diagnostic features are, what range of variation exists within each, and where they occur. If herbaria ceased to exist, our monographs and floras would consist of hypothetical abstractions, no longer tied to the concrete data from which they were derived. In this light, the herbaria at UC Berkeley represent an integral part of humanity's scientific heritage, over which the University has custodial responsibility.
Why keep more than one of each?
Just as no one person can in and of themselves represent Homo sapiens, multiple specimens are necessary to document the full range of variation in any species, both morphological and geographical. Plants furthermore tend to display a much greater plasticity than animals, with morphology dramatically affected by growing conditions, time of year, and age of plant. For example, a leaf growing in the sun can look very different from one growing in the shade, even on the same tree.
What is a type specimen?
By accepted convention, a single specimen of each species is designated as the "type specimen". The type specimen gains its importance in its role of anchoring nomenclature. It is the name-bearer, providing an unequivocal way of linking a name (and abstractions connected to that name) with a single representative of the species. All other specimens are linked to the name secondarily, by virtue of their acceptance as members of the same species. If, for example, what was considered to be one species is determined to be two, then the name goes to the subunit that includes the type specimen.
It is important to realize that the type specimen is not necessarily more "typical" than is any other specimen, any more than one person can be considered more "typical" than everybody else. In fact, there are numerous examples of decidedly "atypical" type specimens, collected at the margin of the species' range (where it was most likely to be first encountered)!
Why do the names keep changing?
Names of plants are changed for one of three reasons. First, there are the legalistic reasons involving the accepted rules of nomenclature; e.g., an earlier validly published name comes to light. Second, there are changes resulting from shifts in taxonomic philosophies, such as those exemplified by "splitters" and "lumpers", or a rejection of paraphyly. Third, and most important, however, are those changes resulting from an increased understanding of the species themselves, which can be perceived as hypothesis. Initial hypotheses on what species exist, and what their diagnostic characteristics are, are often based on only a handful of specimens. The hypotheses are tested whenever more specimens become available for examination, or when novel characters are examined (including molecular evidence). Sometimes the initial hypotheses are supported, other times they need to be modified to reflect the new evidence. This in turn can affect the appropriate nomenclature. The on-going name changes accordingly do not indicate simple equivocation on the part of taxonomists, but rather are an accurate reflection of the dynamic nature of our scientific understanding of the plant and fungal kingdoms.