You are looking at 1-19 of 19 entries for:
- All: subspecies x
- Environment x
Did you mean subspecies subspecies
subspecies Quick reference
A Dictionary of Ecology (5 ed.)
... Technically, a race of a species that is allocated a Latin name. The number of races recognized within a species and the allocation of names to them is something of an arbitrary procedure. Systematic and phenotypic variations do occur within species, but there are no clear rules for identifying them as races or subspecies except that they must be ( a ) geographically distinct, ( b ) populations , not merely morphs, and ( c ) different to some degree from other geographic...
polytypic Quick reference
A Dictionary of Ecology (5 ed.)
...Of a species : divided into subspecies ; varying geographically. See polytypism...
Rassenkreis Quick reference
A Dictionary of Ecology (5 ed.)
...A polytypic species, or a group of subspecies linked by clines . The word is German, meaning ‘circle of races’. See also ring species...
polytypism Quick reference
A Dictionary of Ecology (5 ed.)
...The occurrence of phenotypic variations between populations or groups of a species that are geographically distinct. It is contrasted with polymorphism , which is variation within a population or group. A species with systematic geographical variation ( subspecies or clines ) is said to be...
polytopism Quick reference
A Dictionary of Ecology (5 ed.)
... ( polytopic evolution ) A type of monophyletism ( see monophyletic ) in which a new (polytopic) taxon arises in more than one place from conspecific parents. The chances of this happening simultaneously in each instance, except perhaps in the case of subspecies , are remote; polytopic species may therefore be regarded also as polychronic...
paedomorphosis Quick reference
A Dictionary of Ecology (5 ed.)
...Evolutionary change that results in the retention of juvenile characters into adult life. It may be the result of neoteny , of progenesis , or of postdisplacement . It permits an ‘escape’ from specialization, and has been invoked to account for the origin of many taxa, from subspecies to...
vicarious distribution Quick reference
A Dictionary of Ecology (5 ed.)
...of one member of a species pair (i.e. two closely related species derived from a common ancestor) by the other, geographically (as opposed to ecologically). There are many animals and herbaceous plants with a vicarious distribution between North America and Europe. In zoology, subspecies are conspecific...
phylogeography Quick reference
A Dictionary of Ecology (5 ed.)
...The study of the geographic distribution of genealogical lineages in order to determine the evolutionary history of species , subspecies , and populations . In animals, phylogeography is largely based on mitochondrial-DNA , in plants it is based on chloroplast DNA , but other DNA sequences and markers are also...
deme Quick reference
A Dictionary of Ecology (5 ed.)
...A spatially discrete interbreeding group of organisms with definable genetic or cytological characters (i.e. a subpopulation of a species ). There is very restricted genetic exchange, if any, with other demes, although demes are usually contiguous with one another, unlike subspecies or races which are generally isolated by some geographical or habitat barrier. All possible male and female pairings within a deme have an equal chance of forming, for one breeding season at least. Populations which fulfil only one of the two key criteria (i.e. very occasional...
area-effect speciation Quick reference
A Dictionary of Ecology (5 ed.)
...speciation Speciation by the increased differentiation of two subspecies with incompatible gene complexes, so that selection is strongly against hybrids . The phenomenon is observed among slow-moving or sedentary organisms (e.g. snails and plants) occupying areas of habitat that remain unchanged for long periods (sometimes thousands of years) and within which stable local populations of particular polymorphs ( see polymorphism ) occur. As a result of strong selection for certain loci ( see locus ), particular alleles become more frequent,...
ring species Quick reference
A Dictionary of Ecology (5 ed.)
...species A group of subspecies that are contiguous along a cline . Members of each population are able to mate successfully with members of adjacent populations, but the group as a whole forms a ring, with sufficient morphological differentiation in some places to prevent interbreeding between overlapping populations. Gulls of the genus Larus comprise a circumpolar ring species in the northern hemisphere. Moving westwards from Britain, the herring gull ( L. argentatus ) occurs in North America (where one variant has developed into a distinct species, L....
species (sing. and pl.) Quick reference
A Dictionary of Ecology (5 ed.)
...to occur. Where barriers to gene flow arise (e.g. physical barriers, such as sea, or areas of unfavourable habitat) this reproductive isolation may lead by either local selection or random genetic drift to the formation of morphologically distinct forms termed races or subspecies . These could interbreed with other races of the same species if they were introduced to one another. Once this potential is lost, through some further evolutionary divergence, the races may be recognized as species, although this concept is not a rigid one. Most species cannot...
hybrid Quick reference
A Dictionary of Ecology (5 ed.)
...of differing genotypes . Strictly, most individuals in an outbreeding population are hybrids, but the term is more usually reserved for cases in which the parents are individuals whose genomes are sufficiently distinct for them to be recognized as different species or subspecies . Good examples include the mule, produced by cross-breeding an ass and a horse (each of which can breed true as a species) and Spartina townsendii , produced by cross-breeding Spartina maritima (British cord grass) and the North American species Spartina alterniflora ...
Wildlife Management Reference library
The Oxford Companion to Global Change
...such as deer, elk, and bison that competed with livestock, and predators such as wolves, bears, and cougars, and by 1900 most such animals were greatly reduced. Several species were exterminated, including the eastern and Oregon bisons, the eastern wapiti (elk), and several subspecies of grizzly bear. Until about 1870 , predators were eliminated to assist livestock raisers. After that time such “control” was also promoted as a way to increase game animals. Commercial take of wildlife began early: the fur trade, for example, played a major role in...
Mountains Reference library
The Oxford Companion to Global Change
...many species have been extirpated in adjacent lowlands, but also because many mountains provide the last habitats for relic species from the last ice age, and the complexity and diversity of ecological niches provide particular opportunities for the evolution of species and subspecies. Many of the mountain areas with the greatest biological and landscape diversity have been recognized by their designation as protected areas (national parks, nature reserves, etc.), often with additional international status awarded by UNESCO: some 70 natural and “mixed”...
Earth History Reference library
Encyclopedia of Global Change
...yet another ice house, culminating in the great glaciations of the Pleistocene epoch. Modern mammals such as the horse and camel evolved during Cenozoic times, the age of mammals. The oldest known hominid fossils are around 4.4 million years old. The first members of our own subspecies, Homo sapiens , appeared around 120,000 years ago. Embedded in the fossil record of the Phanerozoic eon is a history of rapid adaptation and recovery following catastrophic episodes ( mass extinctions ) in which many species became extinct within a geologically short time. One...
Mountains Reference library
Encyclopedia of Global Change
...many species have been extirpated in adjacent lowlands, but also because many mountains provide the last habitats for relic species from the last ice age, and the complexity and diversity of ecological niches provides particular opportunities for the evolution of species and subspecies. Many of the mountain areas with the greatest biological and landscape diversity have been recognized by their designation as protected areas (national parks, nature reserves, etc.), often with additional international status awarded by United Nations Educational, Scientific,...
Elephants Reference library
Encyclopedia of Global Change
...genera originated in sub-Saharan Africa but, while Loxodonta species never ranged outside the African continent, Elephas expanded its range into Asia on two separate occasions, a mid-Pleistocene form culminating in the present-day Asian elephant. There are considered to be two subspecies of African elephant, the savanna or bush elephant (L. africana africana) and the smaller forest elephant (L. africana cyclotes) of central Africa. The geographic range and numbers of both species have been greatly reduced during the second half of the twentieth century, and the...
Valuation of Species Preservation Reference library
Robert P. Berrens and Therese Grijalva
The Oxford Encyclopedia of Environmental Economics
...and complications to listing species under the ESA compared with lists that are not legally binding (e.g., IUCN Red List). Under the ESA, an at-risk species (including a subspecies or a distinct subpopulation) is listed as threatened if it is “likely to become endangered in the foreseeable future throughout all or a significant portion of its range”; a species (or subspecies) can be listed as endangered if it is “in danger of extinction throughout all or a significant portion of its range” ( U.S. Fish and Wildlife Service [USFWS], 2003 , p. 1). As...
