Glossary of evolutionary biology

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This glossary of evolutionary biology is a list of definitions of terms and concepts used in the study of evolutionary biology, population biology, speciation, and phylogenetics, as well as sub-disciplines and related fields. For additional terms from related glossaries, see Glossary of genetics, Glossary of ecology, and Glossary of biology.


1.  The dynamic evolutionary process by which biological organisms develop characteristics that allow them to survive and reproduce within their environments.
2.  The state or condition reached by a population during that process.
3.  Any characteristic or phenotypic trait with a functional role in an individual organism and which has evolved and is maintained through natural selection.

Also called functionalism.

The Darwinian view that many or most physiological and behavioral traits of organisms are adaptations that have evolved for specific functions or for specific reasons (as opposed to being byproducts of the evolution of other traits, consequences of biological constraints, or the result of random variation).
adaptive radiation
A species that does not reproduce sexually but rather by cloning.[1] Agamospecies are sometimes represented by species complexes that contain some diploid individuals and other apomictic forms—in particular, plant species that can reproduce via agamospermy.[2]
allele frequency
allochronic isolation
The isolation of two populations of a species due to a change in breeding periods. This isolation acts as a precursor to allochronic speciation, a type of speciation which results when two populations of a species become isolated due to differences in reproductive timing. An example is the periodical 13- and 17-year Magicicada species.[2]
allo-parapatric speciation
A mode of speciation where divergence occurs in allopatry and is completed upon secondary contact of the populations--effectively a form of reinforcement.[3][2]
The comparative study of the relationship between the size of an organism's body (or of a specific organ, e.g. the brain) and various other biological characteristics, such as body shape, anatomy, physiology, or behavior.
In allopatric speciation, a population becomes separated by a geographic barrier and reproductive isolation results in two separate species
allopatric speciation

Also called geographic speciation, vicariance, vicariant speciation, and dichopatric speciation.

A mode of speciation where the evolution of reproductive isolation is caused by the geographic separation of two or more populations of a single species.[4]
allopatric taxa
Specific species that are allopatrically distributed.
The phenomenon by which two or more populations of a single species exist in geographic isolation from one another.
allo-sympatric speciation
A mode of speciation where divergence occurs in allopatry and is completed upon secondary contact of the populations–effectively a form of reinforcement.[5][2]
Evolutionary change that occurs within a species lineage as opposed to lineage splitting (cladogenesis).[6]
ancestral trait

Also called an ancestral character.

area cladogram
asexual reproduction
assortative mating

Also called positive assortative mating and homogamy.

A mating system in which individuals with similar phenotypes mate with each other more frequently than would be expected in a completely random mating system. Assortative mating usually has the effect of increasing genetic relatedness between members of the mating population. Contrast disassortative mating.


Bateson–Dobzhansky–Muller model
behavioral isolation
The scientific study of the spatial distributions of biological organisms, populations, and species. It includes the study of both extinct and extant organisms.[7]
biological constraints
biological species concept
See population bottleneck.


In centrifugal speciation, the range of an original population (green) expands and then contracts, leaving an isolated fragment population behind. In the absence of interbreeding, the central population (changed to blue) evolves reproductive isolation over time.
centrifugal speciation
A variation of peripatric speciation where speciation occurs by geographic isolation, but reproductive isolation evolves in the larger population instead of the peripherally isolated population.[8]
chromosomal speciation

Also called a monophyletic group.

A phylogenetic grouping of organisms that consists of a single common ancestor and all of its lineal descendants, and which by definition is monophyletic. The common ancestor may be an individual organism, a population, a species, or any other taxon; any and all members of a clade may be extant or extinct. Clades can be visualized with cladograms and are the basis of cladistics.
An approach to biological classification in which organisms are grouped in clades defined by shared ancestry; hypothesized relationships between organisms are typically based on shared derived characters (synapomorphies) which can be traced to the most recent common ancestor and are not present in more distant ancestors or unrelated groups.
The splitting of a single species lineage into multiple lineages.[6]
A measurable spatial gradient in a single biological character or trait of a species or population across its geographic range. The nature of a cline may be genotypic (e.g. variation in allele frequency) or phenotypic (e.g. variation in body size or pigmentation), and may show smooth, continuous gradation or abrupt changes between different geographic regions.
cluster analysis
character displacement
The process by which two or more distinct populations, species, or other groups of organisms, or two or more distinct traits within a species, reciprocally affect each other's evolution through natural selection. Each party in a coevolutionary relationship exerts selective pressures upon the other, leading to the evolution of separate traits in each party.
cohesion species concept
common ancestor
competitive gametic isolation
congruent clines
convergent evolution
copulatory behavioral isolation
A type of speciation in which more than two species speciate concurrently due to their ecological associations (e.g. host-parasite interactions).[9]
cryptic species
cytoplasmic isolation



Also called Darwinian theory or Darwinian evolution.

The understanding of biological evolution as developed by the English naturalist Charles Darwin and others, which states that all biological organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce. Colloquially, the term is sometimes used to refer more broadly to modern evolutionary theory as a whole, though in scientific circles distinctions are usually made between Darwin's ideas and later additions to evolutionary biology.
derived trait

Also called a derived character.

developmental biology
directional speciation
disassortative mating

Also called negative assortative mating and heterogamy.

A mating system in which individuals with dissimilar phenotypes mate with each other more frequently than would be expected in a completely random mating system. Disassortative mating usually has the effect of decreasing genetic relatedness between members of the mating population. Contrast assortative mating.
divergent evolution
The process by which any phenotypic or genotypic distinction emerges between two different populations or evolutionary lineages. Divergence may occur by any of a variety of mechanisms but is often especially noticeable after the two lineages have been reproductively isolated for many generations.[6]
Dobzhansky–Muller model
See Bateson–Dobzhansky–Muller model.


ecogeographic isolation
ecological allopatry
ecological character displacement
ecological isolation
ecological niche
ecological speciation
A type of speciation in which reproductive isolation is caused by the interaction of individuals of a species with their environment.[10]
ecological species concept
The ecological state of a species being unique to a single geographic location, such as an island, nation, country, or any other clearly defined area, or to a single habitat type.
environmental gradient
error catastrophe
The extinction of a population of organisms (insofar as the population can be defined by one or more identifiable characteristics) as a result of the excessive accumulation of genetic mutations, such that the population loses self-identity because all of its mutated descendants lack the identifiable characteristics.
ethological isolation
ethological pollinator isolation
The phenomenon by which the heritable characteristics of biological populations change over successive generations. Evolution occurs when processes such as natural selection and genetic drift act on the variation in characteristics that exists between members of a population, resulting in certain characteristics becoming more or less common within the population.
evolutionary arms race
The positive feedback mechanism operating between competing sets of co-evolving genes, traits, species, or other taxa which evolve specific adaptations and counter-adaptations due to each other's presence, which may be seen as analogous with an "arms race".
evolutionary biology
The discipline of biology that studies the evolution of biological organisms and the processes by which it operates, including natural selection, adaptation, common descent, and speciation. A core element of the modern synthesis, evolutionary biology integrates concepts from genetics, systematics, ecology, paleontology, developmental biology, and numerous other fields.
evolutionary landscape
evolutionary lineage
The line of descent of a species.[6]
evolutionary species concept
Currently living or existing; still in existence and not extinct. The term is generally used to refer to the present-day state of existence of a particular taxon (such as a family, genus, species, etc.).
extended evolutionary synthesis
extrinsic hybrid inviability
extrinsic postzygotic isolation


The process by which a single allele for a particular gene with multiple alleles increases in frequency in a given population such that it becomes permanently established as the only allele at that locus within the population's gene pool. How long fixation takes depends on selection pressures and chance fluctuations in allele frequencies.
floral isolation
flowering asynchrony
founder effect
founder event
founder takes all
A hypothesis that describes the evolutionary advantages of the first-arriving lineages in a new ecosystem.[11] An example could be when a species becomes reproductively isolated on an island, as in peripatric speciation.


gametic isolation
Any segment or set of segments of a nucleic acid molecule that contains the information necessary to produce a functional RNA transcript in a controlled manner. Genes are often considered the fundamental units of heredity and are typically encoded in DNA. A particular gene can have multiple different versions, or alleles, and a single gene may influence many different phenotypes.
Gene flow is the transfer of alleles from one population to another population through the migration of individual organisms between the populations
gene flow
The transfer of genetic variation from one population to another.
gene pool
The sum of all of the various alleles shared by the members of a single population.
genealogical species concept
genetic distance
A measure of the genetic divergence between species, populations within a species, or individuals, used especially in phylogenetics to express either the time elapsed since the existence of a common ancestor or the degree of differentiation in the DNA sequences comprising the genomes of each population or individual.
genetic drift

Also called allelic drift or the Sewall Wright effect.

A change in the frequency with which an existing allele occurs in a population due to random variation in the distribution of alleles from one generation to the next. It is often interpreted as the role that random chance plays in determining whether a given allele becomes more or less common with each generation, irrespective of the influence of natural selection. Genetic drift may cause certain alleles, even otherwise advantageous ones, to disappear completely from the gene pool, thereby reducing genetic variation, or it may cause initially rare alleles, even neutral or deleterious ones, to become much more frequent or even fixed.
genetic erosion
genetic variation
The genetic differences both within and between populations, species, or other groups of organisms. It is often visualized as the variety of different alleles in the gene pools of different populations.
genic speciation
genotypic cluster species
geographic speciation
Continuous evolutionary change within a species lineage.[6] See also phyletic gradualism.


habitat isolation

Also called inheritance.

The passing on of phenotypic traits from parents to their offspring through reproduction. Offspring are said to inherit the genetic information of their parents.
heteropatric speciation
Haldane's rule
A rule formulated by J.B.S. Haldane which states that if one sex of the hybrid offspring resulting from a cross between two incipient species is inviable or sterile, that sex is more likely to be the heterogametic sex (i.e. the one with two different sex chromosomes).[12]
Hardy–Weinberg principle
A principle of population genetics which states that allele and genotype frequencies of a population will remain constant from generation to generation in the absence of other evolutionary influences. In the simplest case of a randomly mating population of diploid organisms possessing a single locus with two alleles, A and a, with frequencies f(A) = p and f(a) = q, respectively, the expected genotype frequencies are f(AA) = p2 for AA homozygotes, f(aa) = q2 for aa homozygotes, and f(Aa) = 2pq for heterozygotes. In the absence of evolutionary forces such as natural selection, mutation, assortative mating, gene flow, and genetic drift, p and q will remain constant between generations, such that the population is said to be in Hardy–Weinberg equilibrium with respect to the locus in question.
A similarity between a pair of structures, traits, or DNA sequences in different taxa that is due to shared ancestry.
homoploid recombinational speciation
host race
host-specific parasite
host-specific species
The offspring that results from combining the qualities of two organisms of different genera, species, breeds, or varieties through sexual reproduction. Hybrids may occur naturally or artificially, as during selective breeding of domesticated animals and plants. Reproductive barriers typically prevent hybridization between distantly related organisms, or at least ensure that hybrid offspring are sterile, but fertile hybrids may result in speciation.
hybrid breakdown
hybrid incompatibility
hybrid inviability
hybrid speciation
hybrid sterility
hybrid swarm
hybrid zone
A geographic area in which the ranges of two interbreeding species or populations overlap, allowing them to cross-fertilize and generate hybrid offspring. The formation of a hybrid zone is one of the four outcomes of secondary contact between divergent genetic lineages.
The process by which a hybrid organism is produced from two parents of different genera, species, breeds, or varieties.


identical ancestors point
inclusive fitness
incomplete speciation
incipient species
Any population that is in an early stage of speciation.
intrinsic postzygotic isolation
isolating mechanism
isolation by distance
A reproductive strategy characterized by multiple reproductive cycles during an individual organism's lifetime. Organisms that use such a strategy are said to be iteroparous. Iteroparity is usually contrasted with semelparity.


Jordan's Law


In the Kaneshiro model of peripatric speciation, a sample of a larger population results in an isolated population with less males containing attractive traits. Over time, choosy females are selected against as the population increases. Sexual selection drives new traits to arise (green), thereby reproductively isolating the new population from the old one (blue).
Kaneshiro model
A model of peripatric speciation developed by Kenneth Y. Kanneshiro where a sexual species experiences a population bottleneck—that is, when the genetic variation is reduced due to small population size—mating discrimination among females may be altered by the decrease in courtship behaviors or displays of males. This allows sexual selection to give rise to novel sexual traits in the new population.[13]
kin selection


last universal common ancestor (LUCA)

Also called lineage-branching.

When gene flow between two populations is completely eliminated.[6]


Evolutionary change as it occurs at a relatively large scale, at or above the level of species, as opposed to microevolution, which occurs at a smaller scale. Macroevolution is often thought of as the compounded effects of microevolution.
mating system
mating system isolation
mechanical isolation
mechanical pollinator isolation
Allopatric speciation occurring on a small geographic scale.[14]
Evolutionary change as it occurs at a relatively small scale, typically within a particular species or population, as opposed to macroevolution, which occurs at a larger scale. Because of the convenience of observing and modeling small-scale changes in allele frequencies within discrete populations, the principles of population genetics are often conceptualized at microevolutionary scales.
mitochondrial Eve
modern synthesis
modes of speciation
A classification scheme of speciation processes based on the level of gene flow between two populations.[15] The traditional terms for the three modes—allopatric, parapatric, and sympatric—are based on the spatial distributions of a species population.[16][15]
morphological species concept
mosaic evolution
mosaic hybrid zone
A zone in which two speciating lineages occur together in a patchy distribution–either by chance, random colonization, or low hybrid fitness.[15]
mosaic sympatry
A case of sympatry in which two populations overlapping in geographic distribution exhibit habitat specializations.[15]
most recent common ancestor (MRCA)
Muller's ratchet
mutational meltdown


natural selection
niche adaptation
niche preference
noncompetitive gametic isolation
nongenetic barrier
non-geographic speciation



Also called ontogenesis and morphogenesis.

The origination and biological development of an organism within its own lifetime, as opposed to phylogeny, which refers to the evolutionary history of the organism's ancestors. In sexually reproducing organisms, ontogeny is the study of the development of an organism from the time of fertilization to the organism's reproductively mature form; the term may also be used to refer to the study of an organism's entire lifespan.


para-allopatric speciation
A mode of speciation in which divergence begins in parapatry but is completed in allopatry.[2]
parallel speciation
A diagram representing population subject to a selective gradient of phenotypic or genotypic frequencies (a cline). Each end of the gradient experiences different selective conditions (divergent selection). Reproductive isolation occurs upon the formation of a hybrid zone. In most cases, the hybrid zone may become eliminated due to a selective disadvantage. This effectively completes the speciation process.
parapatric speciation
A type of asexual reproduction in which the growth and development of embryos occurs without fertilization. In animals which reproduce by parthenogenesis, an unfertilized gamete of the female parent is capable of developing into an adult without any contribution from a male parent, resulting in offspring possessing only the mother's genetic material (the exact proportion of which depends on the parthenogenetic mechanism, of which there are numerous varieties). Some species reproduce exclusively by parthenogenesis, while others can switch between sexual reproduction and parthenogenesis under certain environmental conditions.
peak shift model
In peripatric speciation, a small population becomes isolated on the periphery of the central population evolving reproductive isolation (blue) due to reduced gene flow
peripatric speciation
A variation of allopatric speciation where a new species forms from a small, peripheral isolated population.[17] It is sometimes referred to as centripetal speciation in contrast to centrifugal speciation.
phyletic gradualism
The study of the evolutionary history and relationships among individuals or groups of organisms (e.g. species or populations within a species).
phylogenetic species concept

Also called a phylogenetic tree.

pollinator isolation
The grouping of organisms which do not share an immediate common ancestor; such groups are said to be polyphyletic. The term is often applied to groups of organisms that share characteristics which appear to be similar but are not actually closely related, frequently as a result of convergent evolution. The avoidance of polyphyletic groupings is often a stimulus for major revisions of biological classification schemes. Contrast monophyly and paraphyly.
population bottleneck
A sharp, often sudden reduction in the size of a biological population.
postmating barrier
postmating prezygotic isolation
postzygotic isolation
premating barrier
premating isolation
prezygotic isolation
punctuated equilibrium


quantum speciation
A chromosomal model of speciation that occurs rapidly when a cross-fertilizing plant species buds off from a larger population on the periphery, experiencing interbreeding and strong genetic drift that results in a new species.[18][19][20] The model is similar to that of Ernst Mayr's peripatric speciation.[21]


recapitulation theory
recognition species concept
recombinational speciation
recurrent evolution
Red Queen hypothesis
Reinforcement assists speciation by selecting against hybrids
A process of speciation by which natural selection increases the reproductive isolation between two populations of a species as a result of selection acting against the production of hybrid individuals of low fitness.[2] See also Evidence of speciation by reinforcement.
Reproductive character displacement sometimes occurs when two allopatric populations come into secondary contact. Once in sympatry, changes can be seen in mating-associated traits only in the zone of contact. This is a common pattern found in speciation by reinforcement.
reproductive character displacement
reproductive isolating barriers
The set of mechanisms responsible for speciation.
reproductive isolation
When two different species mate and cannot produce fertile offspring. Isolating mechanisms are typically classified as prezygotic (isolating barriers occurring before the formation of a zygote) and postzygotic (isolating barriers occurring after the formation of a zygote).
reproductive success
In a ring species, individuals are able to successfully reproduce (exchange genes) with members of their own species in adjacent populations occupying a suitable habitat around a geographic barrier. Individuals at the ends of the cline are unable to reproduce when they come into contact.
ring species
Connected populations of a species, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed.
The persistence of a certain phenotypic trait or characteristic in a biological system despite perturbations or conditions of uncertainty. Robustness is achieved through the combination of many genetic and molecular mechanisms which effectively preserve the integrity of a particular adaptation, and can evolve by direct or indirect selection.
runaway selection

Also called a Fisherian runaway.


A sudden and large mutational change from one generation to the next which is sufficient to cause rapid or immediate speciation. Various forms of saltation, such as by polyploidy in plants, have often historically been interpreted as evidence for certain theories of mutationism, in contrast to Darwinian gradualism.
secondary contact
The process by which two allopatrically distributed populations of a species are geographically reunited. Contact between divergent populations may renew the potential for gene flow between them, depending upon how reproductively isolated the populations have become.
The four outcomes of secondary contact:
1. An extrinsic barrier separates a species population into two but they come into contact before reproductive isolation is sufficient to result in speciation. The two populations fuse back into one species.
2. Speciation by reinforcement.
3. Two separated populations stay genetically distinct while hybrid swarms form in the zone of contact.
4. Genome recombination results in speciation of the two populations, with an additional hybrid species. All three species are separated by intrinsic reproductive barriers.[22]
See natural selection.
selective pressure
selective sweep
The process by which strong positive selection of a new and beneficial mutation within a population causes the mutation to reach fixation so quickly that nearby linked DNA sequences also become fixed via genetic hitchhiking, thereby reducing or eliminating the genetic variation of nearby loci within the population.
A reproductive strategy characterized by a single reproductive episode during an individual organism's lifetime, especially one in which the programmed death of the organism immediately after the reproductive event constitutes part of an overall strategy that includes putting all available resources into maximizing the probability of reproductive success, at the expense of the organism's future life. Organisms that use such a strategy are said to be semelparous. Semelparity is usually contrasted with iteroparity.
semi-geographic speciation
semipermeable species boundary
The idea that gene flow can occur between two species but that certain alleles at particular loci can exchange whereas others cannot.[15] It is often used to describe hybrid zones and has also been referred to as porous.[15]
sexual reproduction
sexual selection
The evolutionary process by which populations evolve to become distinct species.
speciation experiment
An experiment that attempts to replicate reproductive isolation in nature in a scientifically controlled, laboratory setting.
speciation in the fossil record
Speciation that can be detected as occurring in fossilized organisms.
speciation rate
The basic unit of biological classification, a taxonomic rank, and a unit of biodiversity that has no universally agreed upon, satisfactory definition.
species complex
species concept
species problem
The difficulty in precisely defining what a species is and in determining the placement of an organism within a particular species.[23]
stasipatric speciation
A species lineage that experiences little phenotypic or genotypic change over time.[6]
stepping-stone speciation
survival of the fittest
suture zone
swamping effect
sympatric speciation


temporal isolation
tension zone
type species


unit of selection


vicariance biogeography
A biogeographic approach to species distributions that uses their phylogenetic histories—patterns resulting from allopatric speciation events in the past.[24]
vicariant speciation
A biogeographic term meaning the geographic isolation of two species populations (as in allopatric speciation).


Wahlund effect
A phenomenon by which a reduction of heterozygosity at a particular genetic locus within a population as a whole is observed when two or more subpopulations have different allele frequencies at that locus, even if the subpopulations themselves are each in Hardy–Weinberg equilibrium.
Wallace effect


Y-chromosomal Adam

See also[edit]


  1. ^ Oxford Reference (2008), agamospecies, Oxford University Press
  2. ^ a b c d e f Jerry A. Coyne; H. Allen Orr (2004), Speciation, Sinauer Associates, pp. 1–545, ISBN 978-0-87893-091-3
  3. ^ Guy L. Bush (1994), "Sympatric speciation in animals: new wine in old bottles", Trends in Ecology & Evolution, 9 (8): 285–288, doi:10.1016/0169-5347(94)90031-0, PMID 21236856
  4. ^ Howard, Daniel J. (2003). "Speciation: Allopatric". Encyclopedia of Life Sciences. eLS. doi:10.1038/npg.els.0001748. ISBN 978-0470016176.
  5. ^ Guy L. Bush (1994), "Sympatric speciation in animals: new wine in old bottles", Trends in Ecology & Evolution, 9 (8): 285–288, doi:10.1016/0169-5347(94)90031-0, PMID 21236856
  6. ^ a b c d e f g Vaux, Felix; Trewick, Steven A.; Morgan-Richards, Mary (2016). "Lineages, splits and divergence challenge whether the terms anagenesis and cladogenesis are necessary". Biological Journal of the Linnean Society. 117 (2): 165–76. doi:10.1111/bij.12665.
  7. ^ M. V. Lomolino & J. H. Brown (1998), Biography (2 ed.), Sinauer Associates, Sunderland, MA., pp. 3, ISBN 978-0-87893-073-9
  8. ^ Sergey Gavrilets; et al. (2000), "Patterns of Parapatric Speciation", Evolution, 54 (4): 1126–1134, doi:10.1554/0014-3820(2000)054[1126:pops];2, PMID 11005282
  9. ^ Page, Roderick DM. (2006). "Cospeciation". Encyclopedia of Life Sciences. eLS. doi:10.1038/npg.els.0004124. ISBN 978-0470016176.
  10. ^ Howard D. Rundle and Patrik Nosil (2005), "Ecological Speciation", Ecology Letters, 8 (3): 336–352, doi:10.1111/j.1461-0248.2004.00715.x
  11. ^ Waters JM, Fraser CI, Hewitt GM (2013). "Founder takes all: density-dependent processes structure biodiversity". Trends in Ecology & Evolution. 28 (2): 78–85. doi:10.1016/j.tree.2012.08.024. PMID 23000431.
  12. ^ Turelli, M; Orr, H.A. (May 1995). "The Dominance Theory of Haldane's Rule". Genetics. 140 (1): 389–402. PMC 1206564. PMID 7635302.
  13. ^ Anders Ödeen & Ann-Britt Florin (2002), "Sexual selection and peripatric speciation: the Kaneshiro model revisited", Journal of Evolutionary Biology, 15 (2): 301–306, doi:10.1046/j.1420-9101.2002.00378.x, S2CID 82095639
  14. ^ B. M. Fitzpatrick; A. A. Fordyce; S. Gavrilets (2008), "What, if anything, is sympatric speciation?", Journal of Evolutionary Biology, 21 (6): 1452–1459, doi:10.1111/j.1420-9101.2008.01611.x, PMID 18823452, S2CID 8721116
  15. ^ a b c d e f Richard G. Harrison (2012), "The Language of Speciation", Evolution, 66 (12): 3643–3657, doi:10.1111/j.1558-5646.2012.01785.x, PMID 23206125, S2CID 31893065
  16. ^ B. B. Fitzpatrick, J. A. Fordyce, & S. Gavrilets (2009), "Pattern, process and geographic modes of speciation", Journal of Evolutionary Biology, 22 (11): 2342–2347, doi:10.1111/j.1420-9101.2009.01833.x, PMID 19732257, S2CID 941124CS1 maint: multiple names: authors list (link)
  17. ^ Michael Turelli, Nicholas H. Barton, and Jerry A. Coyne (2001), "Theory and speciation", Trends in Ecology & Evolution, 16 (7): 330–343, doi:10.1016/s0169-5347(01)02177-2, PMID 11403865CS1 maint: multiple names: authors list (link)
  18. ^ Verne Grant (1971), Plant Speciation, New York: Columbia University Press, p. 432, ISBN 978-0231083263
  19. ^ Douglas J. Futuyma (1989), "Speciational trends and the role of species in macroevolution", The American Naturalist, 134 (2): 318–321, doi:10.1086/284983
  20. ^ Loren H. Rieseberg (2001), "Chromosomal rearrangements and speciation", Trends in Ecology & Evolution, 16 (7): 351–358, doi:10.1016/s0169-5347(01)02187-5, PMID 11403867
  21. ^ L. D. Gottlieb (2003), "Rethinking classic examples of recent speciation in plants", New Phytologist, 161: 71–82, doi:10.1046/j.1469-8137.2003.00922.x
  22. ^ Hvala, John A.; Wood, Troy E. (2012). Speciation: Introduction. eLS. doi:10.1002/9780470015902.a0001709.pub3. ISBN 978-0470016176.
  23. ^ William P. Hanage (2013), "Fuzzy species revisited", BMC Biology, 11 (41): 41, doi:10.1186/1741-7007-11-41, PMC 3626887, PMID 23587266
  24. ^ M. V. Lomolino & J. H. Brown (1998), Biography (2 ed.), Sinauer Associates, Sunderland, MA., pp. 352–357, ISBN 978-0-87893-073-9