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Joined 2026-09-21 Message
Incoming links: Species Concepts and Species Delimitation by Kevin de Queiroz
Phylogenetic species concept 2026-10-14
Phylogenetic species concepts use ancestry and diagnostic inherited differences; versions differ over requiring a clade, an exclusive ancestry pattern at genetic loci, or a distinguishable character combination. State which criterion is intended. [ref]
Species Concepts and Species Delimitation by Kevin de Queiroz. p. 880, Table 1: distinct monophyletic, genealogical and diagnosable versions of phylogenetic criteria
For an original operational example, suppose a phylogenetic tree inferred from one genetic locus separates two sampled biological populations. Compare further genetic loci and additional local samples before interpreting that branch as a species boundary. Otherwise the test may merely identify the particular ancestry of the sampled alleles. Adding more sites from the same genetic locus improves that locus's evidence without creating an independent ancestry test.
Species concept 2026-10-13
A species concept states what should make organisms members of the same species; an operational criterion states what observations will test that claim. Reproductive isolation, distinguishable morphology and ancestry inferred through phylogenetics answer different questions. In a lineage-based interpretation, they are evidence for separation of evolving biological populations, and need not appear together. [ref]
Species Concepts and Species Delimitation by Kevin de Queiroz. pp. 880–883, Table 1, Figure 1 and “Conceptualization versus Delimitation”: distinguish defining properties from operational evidence
Species delimitation 2026-10-13
Species delimitation infers the boundaries and number of species from evidence. No single arbitrary percentage of nucleotide sequence difference is a universal boundary. Divergence within an old, widespread species can exceed divergence between recently separated species; geography and multiple kinds of evidence matter. [ref]
Species Concepts and Species Delimitation by Kevin de Queiroz. pp. 884–885, “Alternatives to the Traditional Properties”: divergence cutoffs and geographic differentiation
An original counterexample to a universal percentage rule: an assay could examine a strongly conserved gene in one comparison and a rapidly changing nucleotide sequence in another. Equal percentages then answer different historical questions. Even the denominator needs specifying: all sites, aligned sites, or only a filtered region? A threshold is an operational rule for a stated assay and group of organisms, whose errors need evaluating. It is not a definition that automatically transfers to every species.
Contrasting operational evidence for species delimitation
. Original hypothetical comparison of morphology, mating and ancestry evidence. Each observation tests a different claim; the combinations are thought experiments, not a dataset or verdicts about named species. “Not tested” does not mean absent. Details.
The diagram's hypothetical pair B has similar morphology but reduced mating and distinct ancestry evidence. A morphological species concept could miss that distinction. Pair C instead has different morphology but compatible mating and ancestry that fails to separate the samples. That combination calls for checking variation in phenotype within a species. Pair A has only a structural difference observed: the other criteria remain untested. These examples show why missing evidence, disagreeing evidence and agreeing evidence require different interpretations.