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Taxon vs Material: deciding where assertions apply

In EukTrait, every assertion must be anchored to a biological entity. That entity can be:

  • a taxon (an abstract biological concept), or
  • a material (a concrete biological instance such as a culture, strain, or isolate).

Choosing the correct level is critical for accurately representing biology and preserving context.

Taxon-level assertions

Taxon-level assertions describe traits that are generalized across all members of a taxon or for which no specific material evidence exists.

Use taxon-level assertions when:

  • the trait applies broadly to the species or higher rank,
  • no specific strain or culture was examined,
  • multiple observations from different materials support a general statement,
  • the assertion describes taxonomy, nomenclature, or type designations.

Examples

- trait: parent_taxon
  value: Bicosoecida
  qualifiers:
    rank: order
    authority: Karpov, 1998

- trait: etymology
  value: "Rictus = 'opened mouth'"
  qualifiers:
    name_part: genus

These assertions describe the taxon concept itself and do not refer to a specific specimen or culture.

Material-level assertions

Material-level assertions describe traits observed or measured on a specific biological instance.

Materials can be:

  • cultures or strains,
  • environmental isolates,
  • or voucher specimens.

Use material-level assertions when:

  • the observation is made on a specific strain or isolate,
  • the trait varies between strains or conditions,
  • experimental or environmental context is important,
  • you want to capture intraspecific variability.

Example

applies_to:
  material_id: RCC299
feature: organism
trait: feeding_mechanism
value: phagotrophy
qualifiers:
  life_stage: active
  evidence_method: light_microscopy
  environment: freshwater

This assertion makes it clear which biological instance was observed, under what conditions, and how.

How qualifiers interact with taxon and material levels

Qualifiers are always attached to assertions to describe context. Their role is the same regardless of taxon or material level:

  • Life stage, environmental conditions, or evidence type can be recorded at both levels.
  • Material-level assertions often require more detailed qualifiers, since the instance may have been measured under specific laboratory conditions.
  • Taxon-level assertions can have qualifiers indicating generality, inferred status, or sources used to make a generalized claim.

Example: taxon-level inference

- trait: energy_source
  value: chemotrophy
  qualifiers:
    assertion_type: inferred
    evidence_basis: morphology
    generality: species-wide

This distinguishes a generalized, inferred statement from a direct measurement on a material.

Practical guidelines

  1. Ask what was actually observed.
    If it was a specific strain or culture, assert at the material level.

  2. Ask whether the trait is generalizable.
    If multiple sources, materials, or observations consistently indicate the trait, it can be asserted at the taxon level.

  3. Use qualifiers liberally.
    Life stage, environment, evidence type, and inference status clarify applicability and confidence.

  4. Never assume taxon-level applicability from a single material.
    Only generalizations explicitly supported by multiple observations or sources should be asserted at the taxon level.

Summary

  • Materials = concrete, observed, context-rich.
  • Taxa = abstract, general, historical/conceptual.
  • Qualifiers = describe the conditions and context that shape the observation.

Using these distinctions consistently ensures that EukTrait reflects both the real biological variability and the conceptual structure of taxonomy, while keeping assertions precise, traceable, and interpretable.