XVI International Botanical Congess

Expressions such as the endangered species act," species-rich countries" are common in biodiversity parlance. Here, 'species' is used as designating an objective, real unit existing in nature. It is now commonly acknowledged that different species have different biological realities. However, the majority of the species we recognize are the products of monographic revisions of herbarium collections, far removed from their biological context. Issues that affect species circumscription, such as availability of collections, changing taxonomic concepts, and intensity of work in different taxonomic groups are discussed. Actual total numbers of species are dependent on aspects such as fate of taxonomic species names, conflict in species delimitation in local vs. regional treatments, and the discovery" of new species. It is argued that the history of taxonomic practice plays a significant role in the circumscription of species.