Flora

The word flora has two meanings in biology. One definition means all of the vegetation of a region, such as the flora of North America; the other means a book or other work that accounts for all of the plants of a region, such as The Flora of the Great Plains or The Illustrated Flora of North Central Texas. These books and others like them catalog the plants of a region and include information on distributions and habitat requirements, taxonomic keys for plant identification, and current nomenclature for the plants. The more sumptuous floras also include plant illustrations, distribution maps, and other sources of information. The flora of a region is a dynamic thing, and through time new plants are introduced, old plants change their distributions, some plants go extinct, botanical inaccuracies must be corrected, and new nomenclature must be accounted for. A flora is never truly completed. It is necessary for botanists to revise a regional flora periodically to bring its information up to date.

Systematic botany (or taxonomy) has two notable areas of study. One is monographic (or revisionary) study, with the goal of answering questions about evolutionary relationships, species delimitations, ecological matters, and other issues. The products of these studies are monographs or revisions that are based on field and laboratory studies and that account for a natural group of plants, regardless of where they occur. In the past emphasis was placed on understanding the biological nature of each species, and many research programs incorporated greenhouse and field studies and included studies of hybridization , chromosomal variations, and genetic differences associated with the plant's distribution. Such studies (termed biosystematics ) continue to be important, but the recent past has seen the arrival of sophisticated techniques to analyze the molecular constituents of plant's genetic material, and there has been much effort spent on using molecular taxonomy to show natural relationships, that is, to untangle evolutionary history. The product of monographic or revisionary studies is an authoritative monograph, which reports the results of basic studies on a group of plants. One could say that plants do not come with their names on them. It is the monographer who works out the species and their biologies and puts the proper names on them.

Unlike monographic studies, which are concerned with the biological details of a group of related plants, a flora is concerned with all of the plants of a particular region. Floristicists (or floristicians) must have great field familiarity with their region, and they base their studies on the works of monographers, whose monographs are edited to make their data relevant to the region being studied. For plant groups that have never received monographic study, the flora writer must use his or her intuition as best as possible, based upon experience and the specimens at hand. Every floristic botanist can point out plant groups that need further study, either from an imperfect understanding of the plant's biological behavior or from inconsistent information about its ecology and distribution. Even though the knowledge of the plants in a region may be incomplete, there is still a need to communicate what is known to the other scientists in the field, who need to have accepted names for plants in hand, a means of identification for them, and readily accessible ecological information.

Systematic botanists sometimes speak of the "cascade" of botanical information, whereby the monographers do basic studies on natural plant groups. The writers of floras then synthesize these studies into books that are passed to the primary consumers of botanical information, such as applied scientists, including agronomists, foresters, environmentalists, land managers, and others. From these people, the information flows on to the ultimate consumers: farmers and ranchers, business and industrial people, and, finally, householders.

see also Biogeography; Herbaria; Identification of Plants; Systematics; Taxonomic Keys; Taxonomy.

Theodore M. Barkley

Bibliography

Diggs, G., B. Lipscomb, and R. O'Kennon. Skinner's and Mahler's Illustrated Flora of North Central Texas. Forth Worth, TX: Botanical Research Institute of Texas, 1999.

Great Plains Flora Association. Flora of the Great Plains. Lawrence, KS: University of Kansas Press, 1986.

Flora

Flora describes the assemblage of plant species that occurs in some particular area or large region. Flora can refer to a modern assemblage of plant species or to a prehistoric group of species that is inferred from the fossil record. The zoological analogue is known as fauna, although this is usually used in reference to a large region. More locally, “vegetation” refers to the occurrence of groupings of plants, often called communities, in some area or region.

Flora is also sometimes used to refer to a book that describes a taxonomic treatment of plants in some region. Floras of this sort often contain identification keys, diagrammatic and written descriptions of the species, range maps, and descriptions of habitat.

Plant biogeographers have divided Earth and its regions into floristic units on the basis of their distinctive assemblages of plant species. The species of these large regions (sometimes called biomes, especially in the ecological context) are segregated on the basis of two complexes of factors: (1) geographic variations of environmental conditions, especially climate and to a lesser degree, soil, and (2) physical and ecological barriers to migration, which prevent the distinctive species of floras from mixing together.

In cases where regions have been physically separated for very long periods of time, their differences in plant species are especially great. In particular, isolated oceanic islands often have unique floras, composed of many endemic species of plants that occur nowhere else. For example, islands of the Hawaiian archipelago have been isolated from the nearest mainland for millions of years, and are estimated to have had an original flora of about 2,000 species of angiosperm plants, of which 94.7–98% were endemic. Unfortunately, many of these unique species have become extinct since these islands were discovered and colonized by humans, first by Polynesians and, more recently and with much greater ecological damages, by Europeans.

In cases where the physical isolation is less ancient, there can be a substantial overlap of genera and species in the floras of different regions. For example, eastern Siberia and the Alaska-Yukon region of North America were physically connected by a land bridge during the most recent era of glaciation, which abated about 14,000 years ago. Reciprocal movements of plants (and some animals, including humans) occurred across that land bridge, and this is indicated today by numerous examples of the occurrence of the same plant species in both regions. For this reason, these regions are considered to have a floristic affinity with each other.

See also Biome; Fauna.

Flora

Flora is a word used to describe the assemblage of plant species that occurs in some particular area or large region. Flora can refer to a modern assemblage of plant species , or to a prehistoric group of species that is inferred from the fossil record. The zoological analogue is known as a fauna , although this word is usually used in reference to a large region. More locally, "vegetation" refers to the occurrence of groupings of plants, often called communities, in some area or region.

The word flora is also sometimes used to refer to a book that describes a taxonomic treatment of plants in some region. Floras of this sort often contain identification keys, diagrammatic, and written descriptions of the species, range maps, and descriptions of habitat .

Plant biogeographers have divided Earth and its regions into floristic units on the basis of their distinctive assemblages of plant species. The species of these large regions (sometimes called biomes, especially in the ecological context) are segregated on the basis of two complexes of factors: (1) geographic variations of environmental conditions, especially climate and to a lesser degree, soil , and (2) physical and ecological barriers to migration , which prevent the distinctive species of floras from mixing together.

In cases where regions have been physically separated for very long periods of time , their differences in plant species are especially great. In particular, isolated oceanic islands often have unique floras, composed of many endemic species of plants that occur nowhere else. For example, islands of the Hawaiian archipelago have been isolated from the nearest mainland for millions of years, and are estimated to have had an original flora of about 2,000 species of angiosperm plants, of which 94-98% were endemic. Unfortunately, many of these unique species have become extinct since these islands were discovered and colonized by humans, first by Polynesians and, more recently and with much greater ecological damages, by Europeans.

In cases where the physical isolation is less ancient, there can be a substantial overlap of genera and species in the floras of different regions. For example, eastern Siberia and the Alaska-Yukon region of North America were physically connected by a land bridge during the most recent era of glaciation, which abated about 14,000 years ago. Reciprocal movements of plants (and some animals, including humans) occurred across that land bridge, and this is indicated today by numerous examples of the occurrence of the same plant species in both regions. For this reason, these regions are considered to have a floristic affinity with each other.

See also Biome; Fauna.

flo·ra / ˈflôrə/ • n. (pl. flo·ras or flo·rae / ˈflôrē; ˈflôrī/ ) the plants of a particular region, habitat, or geological period: the desert flora give way to oak woodlands the river's flora and fauna have been inventoried and protected.Compare with fauna. ∎  a treatise on or list of such plant life.

flora (adj. floral, floristic) All the plant species that make up the vegetation of a given area. The term is also applied to assemblages of fossil plants from a particular geologic time, or from a geographical region in a former geologic time. Examples of all three types of usage, respectively, are: British flora,Carboniferous flora, and Gondwana flora. Compare FAUNA.