Glossary for Biogeography

NOTE: Terms are arranged according to the following subject categories: biogeography, ecology, evolution, landscape ecology, and taxonomy. This should not be taken to mean that any term is limited in use or definition to a particular discipline; the arrangement is a pedagogical device to help the beginning student in biogeography to make associations among various words and processes. Each term also may be accessed through the index at the end of this document.

Biogeographic terminology

Alien:

a non-native species, especially one introduced to some part of the world through human action.

Altitudinal zonation:

the sorting of plant and animal species according to elevation in response to differences in temperature and precipitation patterns.

Biogeography:

the science that studies the distribution of life, past and present.

Colonization:

the establishment of a population in a place formerly unoccupied by that species. Colonization implies successful reproduction in the new area, not simply the presence of a species there.

Dispersal:

the transport of propagules beyond the limits of a species' distribution area

Distribution area:

the geographic range of a taxon.

• Allopatric: literally, "other country"; refers to distribution areas of different taxa that do not overlap.
• Circumboreal: found throughout the high latitude forests of the northern hemisphere; that is, in North America and Eurasia.
• Circumpolar: refers to a distribution area that circles either the north pole or south pole.
• Cosmopolitan: worldwide, or nearly so, in distribution.
• Disjunct: refers to a fragmented distribution area with two or more geographically separated ranges.
• Pantropical: refers to a distribution area that extends through the tropics (that is generally between 23° 30' S and 23° 30' N latitude).
• Relict: a distribution area that is a mere remnant of a formerly wider range.
Sympatric:
literally, "same country"; refers to distribution areas of different species that overlap.

Ecogeographic rule:

one of the statements from 19th century naturalists recognizing correlations between the morphology of warm blooded animals (mammals and birds) and climatic and/or latitudinal gradients.

• Bergmann's Rule: The colder the climate (thus, usually, the higher the latitude) the larger the body size of a warm blooded animal when compared to close relatives in warmer regions.
• Allen's Rule: The warmer the climate the longer the appendages (ears, legs, wings) of warm blooded animals in comparison with closely related taxa from colder climes.
• Golger's Rule: The drier the climate, the lighter the color of animals relative to closely related taxa of more humid regions. (Yellows and light browns predominate in arid regions; dark browns and blacks in humid regions.)

Endemic:

describes a taxon restricted to and native to a particular area.

Feral:

describes a species that was once tamed or domesticated and has since reverted to a free-roaming life in the wild.

Life Zone:

belts of vegetation that are similar in structure and species composition in both latitudinal and elevational expressions.

Native:

a species which is a natural member of a biotic community. An indigenous species. (The term implies that humans were not involved in the dispersal or colonization of the species.)

Propagule:

In animals, the minimum number of individuals of a species capable of colonizing a new area. This may be fertilized eggs, a mated female, a single male and a single female, or a whole group of organisms depending upon the biological and behavioral requirements of the species. In plants, a propagule is whatever structure functions to reproduce the species: a seed, spore, stem or root cutting, etc.

Vicariant:

Refers to species that occupy similar ecological niches but in geographic isolation from each other. Implies a phylogenetic relationship existing between the two species.

Ecological terminology

Annual:

a plant with a lifespan of one year.

Biennial:

a plant with a lifespan of two years. Often only flowers and sets seed during the second year.

Biodiversity:

The total variation in life, including the number of species, the degree of genetic variation within species, the different types of ecosystems, and the all ecosystem functions.

Biome:

one of the largest recognizably distinct ecosystems on earth; the plant and animal communities and associated soils that are characteristic of a given regional climate type.

Climber:

a soft- or non-woody-stemmed vine that clasps the stems or branches of trees and shrubs to raise its foliage and flowers above the ground; a type of growthform.

Community:

A group of populations of different species occupying a given place at a given time that are viewed as interdependent. An aggregation of interacting species. Sometimes used to refer to only the assemblage of populations of a particular class of organisms, such as the bird community, the herb community, and so forth.

Cushion plant:

low growing mat formed by tightly massed individuals of the same species of plant. Generally associated with tundra or high alpine communities.

Cryptogams:

nonvascular plants such as lichens and mosses that make up the ground or surface layer of vegetation.

Dispersal (sensu ecology):

the transport of propagules away from the parent.

Diversity:

a) the total number of species present;
b) some index which incorporates both the number of species and the relative abundance of each.

Ecological succession:

(according to the original theory): the development of an ecosystem through a predictable series of communities until a final, stable community (the climax community) in balance with the regional climate is attained. In its original form, the theory implied that each community altered the habitat and prepared it for invasion by the next, succeeding community.

Ecology:

the science that studies the relationships between organisms and their environment. "The study of the structure and function of nature" (Odum, 1971--Fundamentals of Ecology).

Ecosystem:

A community of species together with the surrounding environment that function together as a coherent unit to maintain a flow of energy and to acquire, store, and recycle nutrients.

Edaphic factor:

A permanent or nearly permanent condition of the substrate that influences the types of plants that grow in an area. For example, substrates may be permanently or seasonally waterlogged, droughty, deficient in essential nutrients, extremely thin, and so forth.

Ephemeral:

an annual plant with an extremely short lifespan measured in a few weeks or very few months; characteristic growthform of desert forbs.

Epiphyte

a plant which uses a rock or host plant merely as a place of residence and obtains its moisture and nutrients directly from the air; an air plant. A type of growthform.

Environment:

the totality of physical, chemical, and biotic conditions surrounding an organism

Environmental resistance:

those factors of the environment which prevent reproduction or inhibit development of a species and hence limit the extent (or determine the borders) of its distribution area.

Forb:

a small, upright soft-stemmed or non-woody plant with broadleaves; the growthform of many common wildlfowers

Formation:

a group of communities in a single region or continent with similar physiognomy (structure) and related climatic and environmental conditions. One of several regional or continental expressions of a given biome.

Function:

refers to action, how something works. In the case of ecosystem functions we look at photosynthesis, nutrient cycling, population control, dispersal mechanisms, temporal patterns of flowering , breeding, dormancy, and so forth.

Graminoid:

an herb with grass-like morphology; a growthform typified by true grasses (Graminae) and by sedges (Cyperacaeae).

Grass:

a member of the Graminae family of flowering plants.

Growthform:

the overall morphology of a plant species, including its stature, leaf type, and habit. The most basic growtforms are trees, shrubs, forbs, and graminoids; but there are many more specialized growthforms such as epiphytes, lianas, and stem succulents.

Heath:

a member of the Ericaceae or heather family. Usually leathery-leaved shrubs preferring acidic or low-nutrient substrates and often tolerant of cold.

Herb:

any non-woody vascular plant; a category of plants including both forbs and graminoids. Hence the term "herbaceous" layer .

Landscape Ecology:

the study of patterns of ecosystems of a given area and the interactions among those various ecosystems.

Liana:

a woody-stemmed vine. Lianas are rooted in the substrate and use trees or shrubs as support; often their leaves and flowers reach the canopy of layer of the vegetation. A type of growthform.

Niche:

the total requirements and tolerances of a species; its way of life, including how it traps energy and otherwise uses its habitat or microhabitat.

Parasite:

A plant without chlorophyll that obtains its nutrients by tapping into the branches, stems or roots of living green plants

Perennial:

a plant that lives more than two years

Phreatophyte:

A desert shrub with a long trap root that enables the plant to avoid reliance on rainwater by tapping into groundwater.

Pioneer species:

a species that is an early occupant of newly created or disturbed areas. A member of the early stage communities in ecological succession.

Population:

the individuals of a given species that occupy the same locality and form the interbreeding group in that location. A group of two or more populations that regularly exchange genes is known as a metapopulation..

Rosette:

a growthform in which the leaves are arranged in concentric circles or whorls around a central bud.

Saprophyte:

a plant lacking chlorophyll that obtains its nutrients from dead organic matter. The bacteria and fungi of decay are examples, but there are also flowering plants like the white Indian pipes of eastern US Temperate Broadleaf Deciduous Forests or the giant Rafflesia of the Indo-Malyasian formation of the Tropical Braodleaf Evergreen Forest that are saprophytes.

Sedge:

any member of the Cyperacaeae, a family of flowering plants that in their growthform resemble grasses.

Strangler:

a plant that begins life as an epiphyte in the canopy of a forest and sends its roots down the trunk of a host tree and into the substrate. The roots may form a thick woody net around the host's trunk, but it is apparently the foliage of the strangler that eventually kills the host by blocking sunlight from the latter's leaves. A type of growthform found in tropical forests.

Structure:

the physical arrangement or spatial patterns of the components of an ecosystem, especially the plant life. Includes growthforms, number of canopy layers, degree of cover, distribution patterns of species within the ecosystem (patches, for example). Structure may also refer to the organization of the ecosystem in terms of trophic levels.

Succulent:

a plant that is able to store water in its tissues and then withdraw it during times of drought. Water storage tissue may be found in the stem, leaves, or roots depending on the species. Stem succlulents, leaf succulents, and root succulents are types of growthforms.

Tussock:

a hummock of grasses or sedges bound together by their roots

Weed:

a species that volunteers in artificially modified habitats and is considered undesirable by people. The same species may occur elsewhere in a wild state, or even in cultivation.
Weedy habit refers to the propensity of certain species to disperse easily and widely and to colonize disturbed habitats.

Xerophyte:

a plant well adapted to withstand prolonged drought. The typical xerophyte is a deciduous shrub with tiny leaves and a shallow root system that etends well beyond the crown of the shrub.

Evolutionary terminology

Adaptation:

a condition or character which afford fitness to a species in a particular environment.

Adaptive radiation:

evolutionary divergence of members of a single phyletic line into many different niches.

Allele:

one of two or more different chemical codes possible for a given gene. Offer variation in a given trait.

Cline:

a series of contiguous populations that exhibit gradual and continuous change of character in response to some environmental gradient.

Chromosome:

rod-shaped bodies in the nuclei of cells that consist of a string of genes and maintain the structure or arrangement of the genetic code (DNA).

Convergence:

phenotypic similarity in distantly related (or unrelated) forms, presumably in response to similar selective pressures.

Evolution:

a change in the allele frequencies within a population

Fitness:

the measure of a species ability to survive and reproduce

Founder Principle:

a few individuals starting a new population may represent an atypical sample of the parent species' gene pool. This "sampling error" leads to the founder effect: rapid changes in allele frequencies in the colonizing population and divergence from the parent population.

Gene:

the segment of DNA at a particular locus on a particular chromosome that controls production of proteins and enzymes and influences the development of a specific trait.

Gene flow:

the transfer of genes (actually, alleles) from one population to another.

Gene pool:

the totality of genetic information in a given population at a given time

Genetic drift:

allele frequency changes in populations caused by random events rather than by natural selection, especially the effects of sampling error on the gene pool of small populations.

Genotype:

the genes (or alleles) present in an individual

Geographic isolation:

the separation of a population from the rest of its species due to some physical barrier, such as a mountain range, an ocean, or great distance.

Individual variation:

phenotypic diversity within a population.

Locus:

a specific place or location on a given chromosome. The genetic information encoded there is a gene.

Phenotype:

the totality of characteristics of an individual: the expression of the genotype.

Phyletic gradualism:

the belief that evolution (and especially speciation) occurs over considerable time through a slow accumulation of new alleles and changing allele frequencies.

Phylogeny:

the evolutionary history of a taxon. The graphic representation of a phylogeny is called a phylogenetic tree.

Punctuated equilibrium:

the belief that evolution proceeds by spurts of change interspersed with long periods of stasis (genetic stability) where selection favors no change.

Reproductive isolation:

a condition in which interbreeding between populations is prevent by intrinsic factors of the species themselves.

Speciation:

the process by which new species arise. The process by which discontinuities between populations occur due to the development of mechanisms creating the reproductive isolation of one population from the other.

• Allopatric speciation: species formation that occurs during geographic isolation of populations. Generally believed to be the most common way in which new species arise, especially among the higher animals.
• Sympatric speciation: the formation of new species without geographic isolation; the acquisition of reproductively isolating mechanism among individuals coexisting in the same area. Not infrequent in plants.

Landscape Ecology

Boundary:

the line or zone formed by the edges of two adjacent ecosystems.

Corridor:

a linear strip of habitat type that differs from that on either side of it.

Edge:

that part of an ecosystem near the perimeter that is influenced by the environment of the adjacent ecosystem so that it differs in some characteristics from the center of the ecosystem. Edge effect refers to changes in species composition, distribution and/or abundance found in the edge relative to the interior.

Landscape:

a mosaic of repeated ecosystems in a given geographic area. The land is heterogeneous, but there are structural and functional relationships among the matrix and the various patches and corridors.

Matrix:

the background land use or vegetation in a landscape: that ecosystem-type which is most extensive so that others appear as patches or corridors within it.

Patch:

a nonlinear habitat type that differs from the surrounding vegetation.

Taxonomic terminology

Clade:

in cladistics, a group with a common set of shared derived characteristics persumed inherited from a common ancestor

Cladistics:

a methodology for reconstructing evolutionary relationships of taxa, both living and extinct, by using the distribution of shared derived characters.

Cladogram:

in cladistics, a graphic depiction of evolutionary relationships based on shared derived characters

Congeners:

refers to species belonging to the same genus

Conspecific:

refers to individuals or populations of the same species

Derived (character):

in cladistics, a feature shared among members of smaller groups or clades that is believed to have evolved at a later date than primitive features. Also called advanced.

Fauna:

the animal life of a given area. A list of all species of animals found in a given area

Flora:

the plant life of a given area. A list of all species of plants found in a given area., often listing diagnostic features.

Taxon:

any one of the levels in the taxonomic hierarchy:

• Kingdom: One of the major subdivisions of life; based upon basic similarities in cell structure. Five kingdoms are recognized: Monera, Protoctista, Fungi, Animalia, and Plantae.
• Phylum: A subdivision of a kingdom encompassing all forms of life with the same distinctive body plan. [plural = phyla].
• Class: a higher taxon consisting of one or more orders and distinct from other taxa of similar rank
• Order: a higher taxon consisting of one or more families and distinct from other taxa of similar rank.
• Family: a taxonomic level including one or more genera of common phylogenetic origin and distinct from taxa of the same rank. [The Latin names of animal families end in "-idae".]
• Genus: a taxonomic category including one or more species with a presumed recent common ancestor.
• Species: groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. The lowest taxonomic rank and presumably only real taxonomic unit in nature.
• Subspecies: a geographically defined aggregate of local populations which differ phenotypically from other such subdivisions of a species in other geographic areas.

Primitive (character):

in cladistics, a character shared among and defining members of a large group or clade and believed to have arisen early in the group's evolution.

Taxonomy:

the science of classifying and identifying organisms. The modern classification of organisms reflects their presumed phylogeny.

Index