Sibling species
Encyclopedia
Sibling species are species
that are very similar in appearance, in behavior and in other characteristics, but they are reproductively isolated
. In other words, sibling species (also known as aphanic species) are pairs or groups of genetically closely related species which are often morphologically indistinguishable, but are reproductively isolated, meaning that while they may interbreed, the offspring cannot reproduce. Sibling species may arise as a result of allopatric speciation
through geographic isolation, parapatric speciation
, or sympatric speciation
. The important thing to note is that sibling species are in fact separate biological species. The Biological Species Concept, proposed by Ernst Mayr
in 1942, emphasizes reproductive isolation as the basis of defining a species. The definition states: "A species is defined as a population or group of populations whose members have the potential to interbreed with one another in nature and to produce viable offspring, but cannot produce viable, fertile offspring with members of other species." Mayr, a proponent of allopatric speciation
, hypothesized that adaptive genetic changes that accumulate between allopatric populations cause negative epistasis
in hybrids, resulting in sterility
of the offspring.
Until recently, scientists deemed pairs or groups of species as sibling species based upon morphology, biogeography, and anatomical studies, however recent advances in DNA testing and molecular phylogeny
have made it possible to better determine whether two or more species are in reality sibling species.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
that are very similar in appearance, in behavior and in other characteristics, but they are reproductively isolated
Reproductive isolation
The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...
. In other words, sibling species (also known as aphanic species) are pairs or groups of genetically closely related species which are often morphologically indistinguishable, but are reproductively isolated, meaning that while they may interbreed, the offspring cannot reproduce. Sibling species may arise as a result of allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
through geographic isolation, parapatric speciation
Parapatric speciation
Parapatry is a term from biogeography, referring to organisms whose ranges do not significantly overlap but are immediately adjacent to each other; they only occur together in the narrow contact zone, if at all. This geographical distribution is opposed to sympatry & allopatry or peripatry...
, or sympatric speciation
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...
. The important thing to note is that sibling species are in fact separate biological species. The Biological Species Concept, proposed by Ernst Mayr
Ernst Mayr
Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...
in 1942, emphasizes reproductive isolation as the basis of defining a species. The definition states: "A species is defined as a population or group of populations whose members have the potential to interbreed with one another in nature and to produce viable offspring, but cannot produce viable, fertile offspring with members of other species." Mayr, a proponent of allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
, hypothesized that adaptive genetic changes that accumulate between allopatric populations cause negative epistasis
Epistasis
In genetics, epistasis is the phenomenon where the effects of one gene are modified by one or several other genes, which are sometimes called modifier genes. The gene whose phenotype is expressed is called epistatic, while the phenotype altered or suppressed is called hypostatic...
in hybrids, resulting in sterility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
of the offspring.
Until recently, scientists deemed pairs or groups of species as sibling species based upon morphology, biogeography, and anatomical studies, however recent advances in DNA testing and molecular phylogeny
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
have made it possible to better determine whether two or more species are in reality sibling species.
See also
- Biological species
- Allopatric speciationAllopatric speciationAllopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
- Parapatric speciationParapatric speciationParapatry is a term from biogeography, referring to organisms whose ranges do not significantly overlap but are immediately adjacent to each other; they only occur together in the narrow contact zone, if at all. This geographical distribution is opposed to sympatry & allopatry or peripatry...
- Sympatric speciationSympatric speciationSympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...