HOME

TheInfoList




In biology, two related
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
or
populations In biology, a population is a number A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represen ...

populations
are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies
sympatric speciation Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms ...
. Such speciation may be a product of
reproductive isolation The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, ethology, behaviors and physiology, physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensur ...
 – which prevents hybrid offspring from being viable or able to reproduce, thereby reducing
gene flow In , gene flow (also known as gene migration or geneflow and flow) is the transfer of material from one to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be cons ...

gene flow
 – that results in genetic divergence. Sympatric speciation may, but need not, arise through secondary contact, which refers to
speciation Speciation is the evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes that are ...

speciation
or divergence in
allopatry Allopatric speciation (from Ancient Greek ἄλλος, ''allos'', meaning "other", and πατρίς, ''patris'', "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of ...
followed by range expansions leading to an area of sympatry. Sympatric species or taxa in secondary contact may or may not
interbreed In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
.


Types of populations

Four main types of population pairs exist in nature. Sympatric populations (or species) contrast with
parapatric In parapatric speciation, two subpopulations of a species evolve reproductive isolation from one another while continuing to exchange genes In biology Biology is the natural science that studies life and living organisms, including th ...
populations, which contact one another in adjacent but not shared ranges and do not interbreed; peripatric species, which are separated only by areas in which neither organism occurs; and
allopatric Allopatric speciation (from Ancient Greek ἄλλος, ''allos'', meaning "other", and πατρίς, ''patris'', "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of ...
species, which occur in entirely distinct ranges that are neither adjacent nor overlapping. Allopatric populations isolated from one another by geographical factors (e.g., mountain ranges or bodies of water) may experience genetic—and, ultimately, phenotypic—changes in response to their varying environments. These may drive
allopatric speciation Allopatric speciation (from Ancient Greek ἄλλος, ''allos'', meaning "other", and πατρίς, ''patris'', "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of ...
, which is arguably the dominant mode of speciation.


Evolving definitions and controversy

The lack of geographic isolation as a definitive barrier between sympatric species has yielded controversy among ecologists, biologists, and zoologists regarding the validity of the term. As such, researchers have long debated the conditions under which sympatry truly applies, especially with respect to
parasitism Parasitism is a close relationship between species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...

parasitism
. Because parasitic organisms often inhabit multiple hosts during a life cycle, evolutionary biologist
Ernst Mayr Ernst Walter Mayr (; 5 July 1904 – 3 February 2005) was one of the 20th century's leading evolutionary biologists File:Francesco Redi.jpg, Francesco Redi, the founder of biology, is recognized to be one of the greatest biologists of all ti ...
stated that internal parasites existing within different hosts demonstrate allopatry, not sympatry. Today, however, many biologists consider parasites and their hosts to be sympatric (see examples below). Conversely, zoologist Michael J. D. White considered two populations sympatric if genetic interbreeding was viable within the habitat overlap. This may be further specified as sympatry occurring within one
deme In Ancient Greece, a deme or ( grc, δῆμος) was a suburb or a subdivision of Classical Athens, Athens and other city-states. Demes as simple subdivisions of land in the countryside seem to have existed in the 6th century BC and earlier, but ...
; that is, reproductive individuals must be able to locate one another in the same population in order to be sympatric. Others question the ability of sympatry to result in complete speciation: until recently, many researchers considered it nonexistent, doubting that selection alone could create disparate, but not geographically separated, species. In 2003, biologist Karen McCoy suggested that sympatry can act as a mode of speciation only when "the probability of mating between two individuals depend olelyon their genotypes, nd the genes aredispersed throughout the range of the population during the period of reproduction". In essence, sympatric speciation does require very strong forces of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
to be acting on heritable traits, as there is no geographic isolation to aid in the splitting process. Yet, recent research has begun to indicate that sympatric speciation is not as uncommon as was once assumed.


Syntopy

Syntopy is a special case of sympatry. It means the joint occurrence of two
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
in the same
habitat In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers at the ...

habitat
at the same time. Just as the broader term sympatry, "syntopy" is used especially for close species that might hybridise or even be
sister species In phylogenetics, a sister group or sister taxon comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to eac ...
. ''Sympatric'' species occur together in the same region, but do not necessarily share the same localities as ''syntopic'' species do. Areas of syntopy are of interest because they allow to study how similar species may coexist without outcompeting each other. As an example, the two bat species ''
Myotis auriculus
Myotis auriculus
'' and '' M. evotis'' were found to be syntopic in North America. In contrast, the marbled newt and the northern crested newt have a large sympatric range in western France, but differ in their habitat preferences and only rarely occur syntopically in the same breeding ponds.


Sympatric speciation

The lack of geographic constraint in isolating sympatric populations implies that the emerging species avoid interbreeding via other mechanisms. Before speciation is complete, two diverging populations may still produce viable offspring. As speciation progresses,
isolating mechanisms The mechanisms of reproductive isolation are a collection of evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene ...
 – such as gametic incompatibility that renders fertilization of the egg impossible – are selected for in order to increase the reproductive divide between the two populations.


Species discrimination

Sympatric groups frequently show a greater ability to discriminate between their own species and other closely related species than do allopatric groups. This is shown in the study of
hybrid zoneA hybrid zone exists where the ranges of two interbreeding species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often ...
s. It is also apparent in the differences in levels of prezygotic isolation (by factors that prevent formation of a viable
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
) in both sympatric and allopatric populations. There are two main theories regarding this process: 1) differential fusion, which suggests that only populations with a keen ability to discriminate between species will persist in sympatry; and 2)
character displacement Character displacement is the phenomenon where differences among similar species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A s ...
, which implies that distinguishing characteristics will be heightened in areas where the species co-occur in order to facilitate discrimination.


Reinforcement

Reinforcement is the process by which natural selection reinforces reproductive isolation. In sympatry, reinforcement increases species discrimination and sexual adaptation in order to avoid maladaptive hybridization and encourage speciation. If hybrid offspring are either sterile or less-fit than non-hybrid offspring, mating between members of two different species will be selected against. Natural selection decreases the probability of such hybridization by selecting for the ability to identify mates of one's own species from those of another species.


Reproductive character displacement

Reproductive character displacement strengthens the reproductive barriers between sympatric species by encouraging the divergence of traits that are crucial to reproduction. Divergence is frequently distinguished by
assortative mating Assortative mating (also referred to as positive assortative mating or homogamy) is a mating pattern and a form of sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and ...
between individuals of the two species. For example, divergence in the mating signals of two species will limit hybridization by reducing one's ability to identify an individual of the second species as a potential mate. Support for the reproductive character displacement hypothesis comes from observations of sympatric species in overlapping habitats in nature. Increased prezygotic isolation, which is associated with reproductive character displacement, has been observed in cicadas of genus ''
Magicicada ''Magicicada'' is the genus of the 13-year and 17-year periodical cicadas of eastern North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convent ...
'',
stickleback The Gasterosteidae are a family (biology), family of fish including the sticklebacks. They are related to the pipefish and seahorses. Taxonomy FishBase recognises 16 species in the family, grouped in five genera. However, several of the species ...
fish, and the flowering plants of the genus ''
Phlox ''Phlox'' (; Greek language, Greek φλόξ "flame"; plural "phlox" or "phloxes", Greek φλόγες ''phlóges'') is a genus of 67 species of perennial plant, perennial and annual plant, annual plants in the family Polemoniaceae. They are found ...

Phlox
''.


Differential fusion

An alternative explanation for species discrimination in sympatry is differential fusion. This hypothesis states that of the many species have historically come into contact with one another, the only ones that persist in sympatry (and thus are seen today) are species with strong mating discrimination. On the other hand, species lacking strong mating discrimination are assumed to have fused while in contact, forming one distinct species. Differential fusion is less widely recognized than character displacement, and several of its implications are refuted by experimental evidence. For example, differential fusion implies greater postzygotic isolation among sympatric species, as this functions to prevent fusion between the species. However, Coyne and Orr found equal levels of postzygotic isolation among sympatric and allopatric species pairs in closely related ''
Drosophila ''Drosophila'' () is a genus of fly, flies, belonging to the family (biology), family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the character ...

Drosophila
''. Nevertheless, differential fusion remains a possible, though not complete, contributor to species discrimination.


Examples

Sympatry has been increasingly evidenced in current research. Because of this,
sympatric speciation Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms ...
 – which was once highly debated among researchers – is progressively gaining credibility as a viable form of speciation.


Orca: partial sympatry

Several distinct types of
killer whale The killer whale or orca (''Orcinus orca'') is a toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetacea Cetaceans (from la, Cetus (mythology), cetus, lit=whale, from grc, κ ...

killer whale
(''Orcinus orca''), which are characterized by an array of morphological and behavioral differences, live in sympatry throughout the North Atlantic, North Pacific and Antarctic oceans. In the North Pacific, three whale
population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ...

population
s – called "transient", "resident", and "offshore" – demonstrate partial sympatry, crossing paths with relative frequency. The results of recent genetic analyses using
mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five car ...

mtDNA
indicate that this is due to secondary contact, in which the three types encountered one another following the bidirectional migration of "offshore" and "resident" whales between the North Atlantic and North Pacific. Partial sympatry in these whales is, therefore, not the result of speciation. Furthermore, killer whale populations that consist of all three types have been documented in the Atlantic, evidencing that interbreeding occurs among them. Thus, secondary contact does not always result in total
reproductive isolation The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, ethology, behaviors and physiology, physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensur ...
, as has often been predicted.


Great spotted cuckoo and magpie: brood parasitism

The parasitic great spotted cuckoo (''Clamator glandarius'') and its
magpie Magpies are birds of the Corvidae family. Like other members of their family, they are widely considered to be intelligent creatures. The Eurasian magpie, for instance, is thought to rank among the world's Animal cognition, most intelligent crea ...

magpie
host, both native to Southern Europe, are completely sympatric species. However, the duration of their sympatry varies with location. For example, great spotted cuckoos and their magpie hosts in Hoya de Gaudix, southern Spain, have lived in sympatry since the early 1960s, while species in other locations have more recently become sympatric. Great spotted cuckoos, when in South Africa, are sympatric with at least 8 species of starling and 2 crows,
pied crow The pied crow (''Corvus albus'') is a widely distributed African bird species in the crow genus. Structurally, the pied crow is better thought of as a small crow-sized raven, especially as it can hybridise with the Somali crow (dwarf raven) wher ...

pied crow
and
Cape crow The Cape crow or black crow (''Corvus capensis'') is slightly larger (48–50 cm in length) than the carrion crow#REDIRECT Carrion crow {{Redirect category shell, 1= {{R from move {{R from other capitalisation ... and is completely black w ...

Cape crow
. The great spotted cuckoo exhibits
brood parasitism Brood parasites are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...
by laying a mimicked version of the magpie egg in the magpie's nest. Since cuckoo eggs hatch before magpie eggs, magpie hatchlings must compete with cuckoo hatchlings for resources provided by the magpie mother. This relationship between the cuckoo and the magpie in various locations can be characterized as either recently sympatric or anciently sympatric. The results of an experiment by Soler and Moller (1990) showed that in areas of ancient sympatry (species in cohabitation for many generations), magpies were more likely to reject most of the cuckoo eggs, as these magpies had developed counter-adaptations that aid in identification of egg type. In areas of recent sympatry, magpies rejected comparatively fewer cuckoo eggs. Thus, sympatry can cause
coevolution In biology, coevolution occurs when two or more species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined ...
, by which both species undergo genetic changes due to the selective pressures that one species exerts on the other.


''Acromyrmex'' ant: isolation of fungal gardens

Leafcutter ant Leafcutter ants, a non-generic name, are any of 47 species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often define ...

Leafcutter ant
s protect and nourish various species of fungus as a source of food in a system known as ant-fungus mutualism. Leafcutter ants belonging to the genus ''
Acromyrmex ''Acromyrmex'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...
'' are known for their mutualistic relationship with
Basidiomycete Basidiomycota () is one of two large division (mycology), divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. More specifically, Basidiomycota includes ...
fungi. Ant colonies are closely associated with their fungus colonies, and may have co-evolved with a consistent vertical lineage of fungi in individual colonies. Ant populations defend against the
horizontal transmission Horizontal transmission is the transmission of organisms between biotic and/or abiotic members of an ecosystem that are not in a parent-progeny relationship. This concept has been generalized to include transmissions of infectious agents, symbiont ...
of foreign fungi to their fungal colony, as this transmission may lead to competitive stress on the local fungal garden. Invaders are identified and removed by the ant colony, inhibiting competition and fungal interbreeding. This active isolation of individual populations helps maintain the genetic purity of the fungal colony, and this mechanism may lead to
sympatric speciation Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms ...
within a shared habitat.


See also

*
Evolutionary pressure Any cause that reduces or increases reproductive success in a portion of a population potentially exerts evolutionary pressure, selective pressure or selection pressure, driving natural selection Natural selection is the differential survi ...
*
Ring species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...

Ring species
*
Selection Selection may refer to: In science: * Selection (biology) Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is ill ...
* Syntopy *
Pieris oleracea ''Pieris oleracea'', or more commonly known as the mustard white, is a butterfly in the family Pieridae native to a large part of Canada and the northeastern United States. The nearly all-white butterfly is often found in wooded areas or open plai ...


References


Bibliography

* * * * * * * * * {{Authority control Ecology Evolution