Evidence record

What is a species?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

A judgement, not a fact: 10
Source checked: 40
Partly checked: 3
Presented as open: 2

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question about a definition, asked in biology. The page reports rival definitions and a 2007 proposal to reconcile them; it does not settle which definition is right, and the sources it rests on disagree about that.

There is one right answer to what a species is
Contested
De Queiroz argues that every current definition already shares one concept and that the rest is a matter of evidence. Others, including Freudenstein and colleagues, argue that a lineage alone is not enough and that a species also needs an ecological role.
Species are units in nature rather than conveniences of classification
Contested
Mallet quotes Darwin treating species boundaries as partly a matter of convenience, and holds that whether species are more real than other ranks is at least debatable.
One kind of definition can serve animals and microbes alike
Open
Mallet argued that genotypic clusters could give prokaryotes and eukaryotes one definition. The authors of the 2018 genome survey write that no species concept for prokaryotes is universally accepted, only working standards for naming them.

How the question is labelled

Claim: The unit that keeps moving

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s title. It follows from the page’s account of boundaries that shift with the definition used.

Context
Species Concepts and Species DelimitationFigure 1 and "The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: the different species concepts, despite sharing a common fundamental element, can nonetheless lead to different conclusions concerning which lineages deserve to be recognized as species

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Species

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: Biology counts them, protects them and mourns them,

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A figure of speech for the uses the page goes on to describe: counting, conservation and the record of extinction.

Context
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: the demarcation of species is also crucial for conservation biology

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: and has never agreed on what one is.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesisstandfirst, p. 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: we still do not all accept a common definition of what a species is
Supports
Species Concepts and Species Delimitationabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: leading to a half century of controversy concerning both the definition of the species category and methods for inferring the boundaries and numbers of species

What this does not establish

Both authors describe the disagreement as it stood when they wrote, in 1995 and 2007. De Queiroz holds that his proposal ends the argument about the definition; the page reports it as a proposal.

Later work looked for

Europe PMC, 2008 on, "general lineage concept": Freudenstein and others 2017 (abstract) open with the definition still "matters of debate"; nothing that changes it.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: More than twenty definitions of species are in use, and they disagree about real cases.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationintroduction and "Alternative Species Concepts", p. 879
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Mayden (1997) listed 24 different named species concepts, and there are even more alternative definitions ... they can lead to different conclusions concerning the boundaries and numbers of species ... Importantly, all of these concepts have advocates among contemporary biologists.

What this does not establish

The count of 24 is Mayden’s, from 1997, reported by de Queiroz. Many of the definitions are variants of a few major classes; his Table 1 lists about a dozen.

Later work looked for

Europe PMC, 2008 on, "general lineage concept" and species concepts: no newer count found; Freudenstein and others 2017 treat the debate as continuing.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: A 2007 proposal reconciles most of them by separating what a species is from how one is recognised,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: A unified species concept can be achieved by treating existence as a separately evolving metapopulation lineage as the only necessary property of species and the former secondary species criteria as different lines of evidence (operational criteria) relevant to assessing lineage separation.

Claim: which clarifies the disagreement without eliminating it.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

De Queiroz expects disagreement about where species boundaries fall to continue under his proposal, over methods and evidence rather than definitions, and the proposal itself has critics.

Context
Species Concepts and Species Delimitation"Conceptualization versus Delimitation", p. 883
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: disagreements about species delimitation should result from disagreements or differences concerning one or more of the following issues: the reliability of particular methods
Context
Biodiversity and the Species Concept: Lineages are not Enoughabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Theory · Argument
The source reads: The nature and definition of species continue to be matters of debate.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: The familiar definition is that two populations are different species if they cannot produce fertile offspring.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species DelimitationTable 1, p. 880
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Biological Interbreeding (natural reproduction resulting in viable and fertile offspring)
Supports
A species definition for the modern synthesisstandfirst, p. 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: the “biological species concept”, in which species were considered to be reproductive communities isolated from other such communities

Later work looked for

States a definition; not a finding later work revises.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: It fails for everything that does not reproduce sexually, bacteria and archaea among them,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"A Unified Species Concept", p. 883
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: a general theoretical concept of species (though restricted to sexually reproducing organisms)
Supports
A species definition for the modern synthesissection "The genotypic cluster definition", p. 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: genotypic clusters make better-defined groups of predominantly clonal organisms than definitions based on gene flow and recombination

Later work looked for

How a definition applies; not a finding later work revises.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: and it fails for a great many things that do.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "Darwin’s critique", p. 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: many good species seemed to have little in the way of sterility barriers ... strong mate choice may exist within species, while separate species can and do hybridize in nature

What this does not establish

Mallet argues this with examples; he does not count how many species hybridise.

Later work looked for

Europe PMC, 2018 on, bears and gene flow: later genome studies (for example Kumar and others 2022 on the Asiatic black bear) add cases rather than removing any.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Where the disagreement is

Claim: Where the disagreement is

Kind: Framing. Signposting. It asserts nothing a source could check.

The definitions disagree in practice

Claim: The definitions disagree in practice

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"Alternative Species Concepts", p. 879
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In addition, many of the concepts are at least partially incompatible.

Later work looked for

See claim 5.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: Interbreeding, ecological role, evolutionary history, morphology and genetic clustering can each pick out different boundaries.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationp. 880 and Table 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: different biological properties upon which several of the alternative concepts are based; for example, intrinsic reproductive isolation ... occupation of a distinct niche or adaptive zone ... diagnosability and monophyly are fundamental for systematists. Similarly, morphological differences are central for paleontologists ... genetic ones are key for population geneticists ... Form a genotypic cluster

Later work looked for

See claim 5.

Corrected

24 September 2026. Previously: “Interbreeding, ecological role, evolutionary history, morphology and genetic distance each pick out different boundaries.” De Queiroz’s Table 1 lists genotypic clusters (a deficit of intermediates), not genetic distance, and he says the concepts can lead to different conclusions, not that they always do.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: A single group of populations can be one species under one criterion and several under another.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species DelimitationFigure 1 caption, p. 882
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: The entire set of properties forms a gray zone within which alternative species concepts come into conflict.
Context
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: studies of the same group of organisms can produce not only different species identities but also different species range and number of individuals

Later work looked for

See claim 17.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: This is not an academic problem.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement, which the consequences in claims 16 and 17 bear out.

Context
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: the demarcation of species is also crucial for conservation biology

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: How species are counted changes how many count as endangered, and how biodiversity is measured.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
The impact of species concept on biodiversity studiestitle and abstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: The impact of species concept on biodiversity studies ... surveys based on a phylogenetic species concept showing more species (48%) and an associated decrease in population size and range. We discuss the serious consequences of this trend for conservation, including an apparent change in the number of endangered species

What this does not establish

Only the abstract was read. The consequences are the authors’ discussion of their compilation, not a measured change in any legal list.

Later work looked for

See claim 17.

Corrected

24 September 2026. Previously: “Counting species determines what is protected by law, what is recorded as extinct, and how biodiversity is measured.” No cited source says anything about extinction records, and the abstract speaks of the number of endangered species and of biodiversity studies, not of what law protects.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: Groups that have been surveyed both ways come out 48% more numerous under a phylogenetic concept, each species with a smaller range and a smaller population.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: we collected instances from the literature where a group of organisms was categorized both under phylogenetic and nonphylogenetic concepts. Our results show a marked difference, with surveys based on a phylogenetic species concept showing more species (48%) and an associated decrease in population size and range.

What this does not establish

Only the abstract was read, so how the 48% was calculated, and across which groups, was not checked. It is a compilation of published cases, not a random sample of life.

Later work looked for

Europe PMC, 2005 on, "taxonomic inflation" and phylogenetic species concept with conservation: studies of single groups, no newer estimate across groups that replaces the figure.

Claim 17 · checked 24 September 2026 · AI-assisted audit

A definition built for the cases that break

Claim: A definition built for the cases that break

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Heading. Mallet’s definition is aimed at hybridising and clonal organisms, the cases where the interbreeding definition struggles.

Context
A species definition for the modern synthesissection "The genotypic cluster definition", p. 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Thus, species defined as genotypic clusters can hybridize, as in many plants like Darwin’s cowslip and primrose, and as in ducks, orchids, and birds of paradise.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: A 1995 proposal took the opposite approach to defining a species by what keeps populations apart: it defined them by what is observed, as groups that remain genotypically distinct where they meet.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "The genotypic cluster definition", pp. 3 to 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: define species in the darwinian way as distinguishable groups of individuals which have few or no intermediates when in contact ... we are able to separate the causes of species distinctness from the observable distinctness itself

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: Gene flow then acts on a species rather than defining one, and two clusters can stay separate under a good deal of it where selection against the intermediates is strong.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "The genotypic cluster definition", p. 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: species can be affected by gene flow, selection and history, rather than being defined by these processes ... Clusters can remain distinct under relatively high levels of gene flow provided there is strong selection against intermediates

What this does not establish

Mallet’s argument, supported with examples; he does not say how much gene flow any particular pair of species can bear.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: That handles hybridising species, which the textbook definition cannot,

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissections "Wallace’s critique" and "The genotypic cluster definition", pp. 3 to 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Because no gene flow between species is conceptually possible under interbreeding concepts ... species defined as genotypic clusters can hybridize

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: and its author argued it extends to predominantly clonal organisms, giving prokaryotes and eukaryotes one definition.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "The genotypic cluster definition", p. 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: genotypic clusters make better-defined groups of predominantly clonal organisms than definitions based on gene flow and recombination ... If we all adopted a genotypic cluster method, we would have a unified species definition for eukaryotes and prokaryotes

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: It is one of the more than twenty definitions in use,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species DelimitationTable 1, p. 880
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Genotypic cluster (definition) *Form a genotypic cluster (deficits of genetic intermediates; e.g., heterozygotes) Mallet (1995)

Later work looked for

See claim 5.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: and it shows that the disagreement is about where boundaries fall, not only about words.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Under Mallet’s definition two hybridising clusters are two species; under an interbreeding definition they may be one. The page’s reading of that difference.

Context
A species definition for the modern synthesissection "The genotypic cluster definition", p. 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Thus, species defined as genotypic clusters can hybridize

Corrected

24 September 2026. Previously: “It is one of the more than twenty definitions in use, and citing it is the quickest way to see that the disagreement is substantive rather than terminological.” The old wording made a claim about citing the paper that no source carries; the new one says what the definition’s own cases show.

Claim 24 · checked 24 September 2026 · AI-assisted audit

A proposal that separates two questions

Claim: A proposal that separates two questions

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: First, the issues of species conceptualization and species delimitation are clearly separated

Later work looked for

See claim 5.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: A 2007 paper argued that all the current definitions share one concept, that a species is a separately evolving lineage, and differ on which further property a lineage must have acquired to count.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationabstract; "The Common Element" and "The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Alternative species concepts agree in treating existence as a separately evolving metapopulation lineage as the primary defining property of the species category, but they disagree in adopting different properties acquired by lineages during the course of divergence

Claim: It proposed treating those properties as evidence that a lineage has separated, rather than as part of what a species is.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"A Unified Species Concept", p. 882
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Instead, they are considered contingent properties: properties that species may or may not acquire during the course of their existence.
Qualifies
Biodiversity and the Species Concept: Lineages are not Enoughabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Theory · Argument
The source reads: We argue that biodiversity is inherently a phenotypic concept and that role, as manifested in the organismal extended phenotype, is a necessary component of the species concept.

Claim: On that view, reproductive isolation, distinct ecology and genetic divergence are not rival definitions but different lines of evidence, which appear at different times as a lineage splits.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitationabstract; "The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: the former secondary species criteria as different lines of evidence (operational criteria) relevant to assessing lineage separation ... they arise at different times during the process of speciation

Corrected

24 September 2026. Previously: “On that view, interbreeding, distinct ecology and genetic divergence are not rival definitions” The line of evidence in de Queiroz is intrinsic reproductive isolation, which lineages acquire as they diverge; interbreeding is its absence.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: Disagreements between them are informative rather than fatal: they locate a case in the middle of a split.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from de Queiroz’s gray zone: criteria conflict only between the first property acquired and the last.

Context
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: On either side of the gray zone, there will be unanimous agreement about the number of species.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: What a split looks like as it happens

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Populations separate

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species DelimitationFigure 1 caption, p. 882
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: This highly simplified diagram represents a single lineage (species) splitting to form two lineages (species).

What this does not establish

A simplified sequence, after de Queiroz’s diagram, not a record of any particular split.

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: Gene flow between them falls across a geographic barrier, or selection against intermediates starts to outweigh it.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissections "Wallace’s critique" and "In speciation studies", pp. 3 and 6; passage on hybridizing genotypic clusters
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: An external barrier to gene flow, allopatry, becomes the easiest way to imagine speciation ... To understand speciation, we need to understand when disruptive selection can outweigh gene flow between populations. Disruptive selection will dominate when gene flow is low ... ecological adaptations which select disruptively against intermediates or hybrids

What this does not establish

Two routes Mallet discusses; which one a given split followed is a separate question for each case.

Corrected

24 September 2026. Previously: “Geography, timing or behaviour reduces gene flow.” No cited source discusses timing or behaviour as causes; Mallet discusses geographic separation and disruptive selection against intermediates.

24 September 2026. Previously: “Gene flow between them falls, across a geographic barrier or under selection against intermediates.” Mallet does not say that selection against intermediates lowers gene flow. He frames speciation as disruptive selection coming to outweigh gene flow, which it can do while gene flow stays well above zero; the wording now follows him.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: Nothing yet distinguishes them by any criterion.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: Before the acquisition of the first property, everyone will agree that there is a single species

What this does not establish

True of the simplified diagram; in a real case the first property may be acquired early.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Differences accumulate

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: changes in these characters lead to the acquisition of a number of different properties by diverging lineages

What this does not establish

A simplified sequence, after de Queiroz’s diagram.

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: Genetic, ecological and morphological differences appear in no fixed order, which is why criteria disagree at this stage

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: The problem is that these changes do not all occur at the same time, and they do not even necessarily occur in a regular order

What this does not establish

De Queiroz’s account of why the concepts conflict; it is a model of the process, not a measurement of it.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: and each is right about something.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s gloss on de Queiroz, who treats every criterion as a real line of evidence.

Context
Species Concepts and Species Delimitationp. 880
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: They are all based on important biological properties.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: Reproductive isolation arrives

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: Others will draw the cutoff somewhat later, perhaps where the lineages develop an intrinsic reproductive barrier.

What this does not establish

Placing it third follows one illustration in de Queiroz; he says the properties arise in no regular order (claim 40).

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: The threshold the textbook definition insists on.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: under the isolation version of the biological species concept, the lineage also has to be intrinsically reproductively isolated from other lineages

Later work looked for

States a definition; not a finding later work revises.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: Where it comes after other differences, that definition counts fewer species than a phylogenetic one does.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"Alternative Species Concepts", pp. 879 to 880; "The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: adoption of the biological species concept leads to the recognition of fewer species taxa than adoption of one of the alternative species concepts ... diagnosable version of the phylogenetic species concept ... they arise at different times during the process of speciation
Context
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: surveys based on a phylogenetic species concept showing more species (48%)

Later work looked for

See claim 17.

Corrected

24 September 2026. Previously: “The threshold the textbook definition insists on, which is why it counts fewer species than the phylogenetic alternatives do.” De Queiroz reports situations in which the biological concept recognises fewer species, not a general rule; and since the order of the thresholds varies, the cause holds only where isolation comes later.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: It is not reliably the last one crossed.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Species Concepts and Species Delimitation"The Differences", p. 881
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Model
The source reads: And still others will draw the cutoff later yet, perhaps where both lineages form exclusive (monophyletic) groups in terms of multiple gene trees.

Later work looked for

See claim 5.

Claim 40 · checked 24 September 2026 · AI-assisted audit

What it costs

Claim: What it costs

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: A count is only as firm as the unit being counted.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own line, following from claims 16 and 17.

Context
The impact of species concept on biodiversity studiesabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field
The source reads: Unfortunately, different methods of diagnosing species can arrive at different entities.

Claim 42 · checked 24 September 2026 · AI-assisted audit

What to do about hybrids

Claim: What to do about hybrids

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Many species exchange genes occasionally.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The evolutionary history of bears is characterized by gene flow across speciesabstract and introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes
The source reads: some 600 mammalian hybrids are known ... Evidence for extensive inter-specific gene flow, found also in other animal species

What this does not establish

Kumar and others also note that gene flow from hybridisation has been thought rare among mammals. "Many" is not a proportion of all species.

Later work looked for

Europe PMC, 2018 on, bears with gene flow or introgression: later genomes (Barlow and others 2018 on cave bears, Kumar and others 2022 on the Asiatic black bear) add further cases; nothing that changes it.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Brown bears and polar bears mate in the wild and produce cubs,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The evolutionary history of bears is characterized by gene flow across speciesintroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes
The source reads: In bears, natural mating between grizzlies (brown bears Ursus arctos), and polar bears (Ursus maritimus) results in hybrid offspring, the grolars

Later work looked for

See claim 44.

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: ducks and birds of paradise hybridise,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "The genotypic cluster definition", p. 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Review of the field
The source reads: species defined as genotypic clusters can hybridize, as in many plants like Darwin’s cowslip and primrose, and as in ducks, orchids, and birds of paradise

What this does not establish

Named as examples in a 1995 review, without data.

Later work looked for

Europe PMC, 2005 on, "taxonomic inflation": Mallet 2008 on hybridisation and the nature of species (record only) continues the argument; nothing found that changes it.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: and bear genomes show gene flow among several other species too, not only between close relatives.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
The evolutionary history of bears is characterized by gene flow across speciesabstract; results on D-statistics
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes
The source reads: genome analyses using different statistical methods show that gene flow is not limited to closely related species pairs. Strong ancestral gene flow between the Asiatic black bear and the ancestor to polar, brown and American black bear

What this does not establish

The gene flow was among the ursine bears; the study detected none between them and the spectacled bear. Some of the signal is ancestral rather than recent.

Later work looked for

See claim 44.

Corrected

24 September 2026. Previously: “and gene flow runs across the whole bear family rather than between the two species that look alike.” Kumar and others found no gene flow between the spectacled bear and the ursine bears, so not the whole family; and brown and polar bears are not two species that look alike.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: Our own lineage is in the same position:

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The comparison is the page’s: as with the bears, two lineages that exchanged genes.

Context
A draft sequence of the Neandertal genomeabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Measurement
The source reads: suggesting that gene flow from Neandertals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: Neandertals shared more variants with present-day people in Europe and Asia than with people in sub-Saharan Africa.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A draft sequence of the Neandertal genomeabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Measurement
The source reads: We show that Neandertals shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa

What this does not establish

The 2010 comparison used five present-day genomes.

Later work looked for

Europe PMC, 2019 on, Neandertal ancestry in Africans: Chen and others 2020 (Cell, abstract) find a stronger Neandertal signal in African individuals than thought, from back-migration, without reversing the difference; wording narrowed to what Green measured.

Corrected

24 September 2026. Previously: “Neandertals share more variants with present-day people outside Africa than with people inside it.” Green and others compared Eurasians with sub-Saharan Africans, not everyone outside and inside Africa.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: A definition built on complete isolation cannot accommodate that.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
A species definition for the modern synthesissection "Wallace’s critique", p. 3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: Under interbreeding concepts, species “cohesion” is due to interbreeding or gene flow within species and an absence of gene flow between species, by definition.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: What is not agreed is how much gene flow a boundary can survive while remaining a boundary.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Supports
The evolutionary history of bears is characterized by gene flow across speciesabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes
The source reads: necessitates shifting the attention from speciation processes achieving genome-wide reproductive isolation to the selective processes that maintain species divergence in the face of gene flow
Context
Species Concepts and Species Delimitation"Conceptualization versus Delimitation", p. 883
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Argument
The source reads: and cases of incomplete lineage separation

Claim 51 · checked 24 September 2026 · AI-assisted audit

How to count microbes

Claim: How to count microbes

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Bacteria and archaea exchange genes across enormous distances in the family tree, between prokaryotes and eukaryotes as well as among themselves,

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Horizontal gene transfer: building the web of lifeabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Research in microbes · Review of the field
The source reads: HGT is a widely recognized mechanism for adaptation in bacteria and archaea ... using examples of HGT among prokaryotes, between prokaryotes and eukaryotes, and even between multicellular eukaryotes

What this does not establish

Only the review’s abstract was read. It establishes that such transfer happens, not how often across any given distance.

Later work looked for

Europe PMC, 2016 on, reviews titled horizontal gene transfer: later reviews (Husnik and McCutcheon 2018 on bacteria to eukaryotes, Arnold and others 2022; titles only) extend it; nothing that changes it.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: which raises the question of whether they form discrete species at all or a continuum.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: One such question is whether bacteria (and other microbes) form discrete clusters (species), or, due to high frequency of horizontal gene transfer (HGT) and slow decay kinetics, a continuum of genetic diversity is observed instead.

Later work looked for

See claim 58.

Corrected

24 September 2026. Previously: “which makes a lineage a fuzzier object than it is in animals.” No cited source compares lineages in microbes with lineages in animals; Jain and others state the question transfer raises.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: Working definitions fall back on genome similarity.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesResults
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: In previous taxonomic studies, 95% ANI cutoff is the most frequently used standard for species demarcation.
Supports
Reply to: "Re-evaluating the evidence for a universal genetic boundary among microbial species"opening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Argument
The source reads: The ~10,000 species that have been described to date and have sequenced representative genomes in the public databases in order to be included in our analysis (out of a total 17,000 described species) are largely consistent (>95% of the cases) with the application of the 95% ANI criterion

Later work looked for

See claim 58.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: A comparison of seventy genomes in 2005 found that about 94% average nucleotide identity matched the DNA reassociation standard the older definition had used.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Genomic insights that advance the species definition for prokaryotesabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: we have compared the gene content of 70 closely related and fully sequenced bacterial genomes ... ANI values of ≈94% corresponded to the traditional 70% DNA–DNA reassociation standard of the current species definition
Supports
Genomic insights that advance the species definition for prokaryotesResults and Discussion, on Fig. 1C
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: ANI shows a strong linear correlation to DNA–DNA reassociation values, and the 70% DNA–DNA reassociation standard corresponds to ≈93–94% ANI
Context
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesResults
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: In previous taxonomic studies, 95% ANI cutoff is the most frequently used standard for species demarcation.

What this does not establish

The seventy were closely related bacterial genomes, and the match is a fitted correlation, about 93 to 94%, not an exact equivalence. Later work standardised on 95%, the figure used below.

Later work looked for

Europe PMC, 2006 to 2012, "average nucleotide identity" with "DNA-DNA hybridization": Goris and others 2007 (abstract) put 70% reassociation at 95% ANI, Richter and Rosselló-Móra 2009 (abstract) at about 95 to 96%; the 2005 figure stands as what that study found.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: The threshold started as a match to that older convention.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Genomic insights that advance the species definition for prokaryotesabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: ANI values of ≈94% corresponded to the traditional 70% DNA–DNA reassociation standard of the current species definition
Supports
Genomic insights that advance the species definition for prokaryotesResults and Discussion, on Fig. 1C
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: the 70% DNA–DNA reassociation standard corresponds to ≈93–94% ANI
Supports
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesIntroduction, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: Nevertheless, it closely reflects the traditional microbiological concept of DNA–DNA hybridization relatedness for defining species

What this does not establish

The 2005 study put the match at about 93 to 94%; the 95% in common use came after it.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: A 2018 analysis found that it seemed to mark something: across eight billion pairs of prokaryotic genomes, 99.8% sat above 95% identity within a named species or below 83% between species, with very little between.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesabstract; Results, "Large-scale pairwise comparison indicates genetic discontinuity"
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: Our results reveal clear genetic discontinuity, with 99.8% of the total 8 billion genome pairs analyzed conforming to >95% intra-species and <83% inter-species ANI values.
Qualifies
Re-evaluating the evidence for a universal genetic boundary among microbial speciesmain text, paragraph on the 0.2% in the gap
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Model
The source reads: Our result shows that the low density of ANI values in the gap region does not necessarily indicate a genetic boundary.

What this does not establish

The genomes are those in NCBI in March 2017, which over-represent some species. Whether the gap reflects nature or sampling is disputed (claims 59 and 60).

Later work looked for

Crossref and Europe PMC, 2019 on, "universal genetic boundary among microbial species": Murray and others 2021 contest the gap and Rodriguez-R and others 2021 defend it; page updated to report both. A 2022 preprint by Rodriguez-R and others (record only) reports a further gap within species.

Corrected

24 September 2026. Previously: “The threshold started as a match to that older convention, and then turned out to mark something. Across eight billion pairs of prokaryotic genomes, 99.8% sat either above 95% identity or below 83%, with very little between.” The page stated the 2018 gap as settled. Murray and others (2021) argue it is produced by biased sampling, and the original authors dispute that; the page now reports both sides, and states the 95% and 83% as Jain and others do, within and between named species.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: A 2021 critique argued that the gap comes from sequencing many near-identical genomes of favoured species, and that it thins when each species is represented by its most different genomes.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Re-evaluating the evidence for a universal genetic boundary among microbial speciesopening paragraph and discussion of Fig. 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Model
The source reads: resulted from the substantial biased sampling in genome sequencing ... when we reduced the within-species sampling bias by selecting two phylogenetically representative genomes from the same dataset, the distribution flattened near the end

What this does not establish

Murray and others say their simulation does not disprove a universal boundary; it shows that sampling bias alone could produce the pattern.

Later work looked for

See claim 58.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: The original authors replied that populations sampled straight from the environment, without culturing, show a similar gap.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Reply to: "Re-evaluating the evidence for a universal genetic boundary among microbial species"section "The ANI genetic boundary among microbial species is robust"
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Argument
The source reads: when one examines the patterns emerging from metagenomic datasets, which is an isolation-free approach, a similar ANI boundary is observed

What this does not establish

In the environmental samples they describe, the gap is between about 85 and 95%, not 83 and 95%.

Later work looked for

See claim 58.

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: Whether that gap is the kind of boundary a species concept needs is a separate question from whether it is there.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Supports
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesDiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Measurement
The source reads: The biological mechanisms underlying this genetic discontinuity are not clear but should be subject of future research for a more complete understanding of prokaryotic species.
Supports
Reply to: "Re-evaluating the evidence for a universal genetic boundary among microbial species"opening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in microbes · Argument
The source reads: Note that there is no universally accepted species concept for prokaryotes (i.e., what a species is)

Claim 61 · checked 24 September 2026 · AI-assisted audit

What was read

Species Concepts and Species Delimitationde Queiroz, Systematic Biology · Published PDF, Syst. Biol. 56(6):879–886, from a course reading list at faculty.uca.eduRead in full, 24 September 2026 · Copyright; quoted briefly
A species definition for the modern synthesisMallet, Trends in Ecology and Evolution · Author’s preprint (mallet95tree.preprint.pdf), Internet Archive copy of the author’s UCL page, 17 April 2007 captureRead in full, 24 September 2026 · Copyright; quoted brieflyThe preprint, not the printed version; page numbers are the preprint’s.
The impact of species concept on biodiversity studiesAgapow and others, The Quarterly Review of Biology · Europe PMC record, PMID 15232950Abstract only, 24 September 2026 · Copyright; quoted brieflyThe journal is closed and no repository copy could be fetched (BYU ScholarsArchive and UCL Discovery refused this environment; no Wayback capture). The method behind the 48% figure was not read.
The evolutionary history of bears is characterized by gene flow across speciesKumar and others, Scientific Reports · Europe PMC full text, PMC5395953Read in full, 24 September 2026 · CC BY 4.0Supplementary information not read.
A draft sequence of the Neandertal genomeGreen and others, Science · Author manuscript, NCBI PMC5100745 via E-utilitiesRead in full, 24 September 2026 · Copyright; author manuscript; quoted brieflyThe supplementary text (SOM) was not read.
Horizontal gene transfer: building the web of lifeSoucy, Huang and Gogarten, Nature Reviews Genetics · Europe PMC record, PMID 26184597Abstract only, 24 September 2026 · Copyright; quoted brieflyThe review is closed; only the abstract was read.
Genomic insights that advance the species definition for prokaryotesKonstantinidis and Tiedje, PNAS · PMC549018, the article page at pmc.ncbi.nlm.nih.gov, read in full 2026-09-24 (E-utilities returns only the abstract for it)Read in full, 24 September 2026 · Copyright 2005 National Academy of Sciences; free to read at PMC; quoted brieflyThe PNAS site and the PMC PDF refused this environment; the PMC article page served the full text.
High throughput ANI analysis of 90K prokaryotic genomes reveals clear species boundariesJain and others, Nature Communications · Europe PMC full text, PMC6269478Read in full, 24 September 2026 · CC BY 4.0Supplementary figures not read.
Re-evaluating the evidence for a universal genetic boundary among microbial speciesMurray, Gao and Wu, Nature Communications · Europe PMC full text, PMC8263626Read in full, 24 September 2026 · CC BY 4.0A Matters Arising on Jain and others 2018. Supplementary figures not read.
Reply to: "Re-evaluating the evidence for a universal genetic boundary among microbial species"Rodriguez-R and others, Nature Communications · Europe PMC full text, PMC8263725Read in full, 24 September 2026 · CC BY 4.0The reply by the authors of Jain and others 2018 to Murray and others 2021.
Biodiversity and the Species Concept: Lineages are not EnoughFreudenstein and others, Systematic Biology · Europe PMC record, PMID 28173602Abstract only, 24 September 2026 · Copyright; quoted brieflyRead as an abstract only; cited as a rival view, not as support.