Beta Diversity Turnover Between Faunas

Compare aligned abundance faunas using raw and equal-total relative Bray–Curtis. Raw-count difference is partitioned into 2*min(positive,negative) balanced change and absolute net gradient on the same total-count denominator; unlike Harrison incidence turnover, abundance rather than shared richness is used.

Description

Abundance dissimilarity differs from presence-absence turnover.

Abundance dissimilarity differs from presence-absence turnover. Equal-total normalization removes a change in total sample size from relative composition.

When to use Beta Diversity Turnover Between Faunas

Use this tool to compare aligned abundance faunas using raw and equal-total relative Bray–Curtis. Raw-count difference is partitioned into 2*min(positive,negative) balanced change and absolute net gradient on the same total-count denominator; unlike Harrison incidence turnover, abundance rather than shared richness is used.

Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.

How to use Beta Diversity Turnover Between Faunas and understand its results

Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.
Enter alignedTaxonCountsFaunaA, alignedTaxonCountsFaunaB using the field table and calculation rules, then run the tool.
Read rawAbundanceBrayCurtisDissimilarity, relativeAbundanceBrayCurtisDissimilarity, balancedAbundanceDifferenceComponent, abundanceGradientComponent. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
alignedTaxonCountsFaunaA	Aligned taxon counts fauna a	list of number	Required
alignedTaxonCountsFaunaB	Aligned taxon counts fauna b	list of number	Required

Align nonnegative integer taxon counts and require each fauna total positive. Return raw and normalized relative dissimilarity. Partition raw difference into twice the smaller directional excess and absolute net excess, each divided by the same pooled total.^[1]

Paired lists must be nonempty and have equal lengths.

raw Bray–Curtis = Σ|A−B|/(ΣA+ΣB)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
rawAbundanceBrayCurtisDissimilarity	Raw abundance Bray Curtis dissimilarity	number
relativeAbundanceBrayCurtisDissimilarity	Relative abundance bray curtis dissimilarity	number
balancedAbundanceDifferenceComponent	Balanced abundance difference component	number
abundanceGradientComponent	Abundance gradient component	number

json

{
  "input": {
    "alignedTaxonCountsFaunaA": [
      1,
      3,
      0
    ],
    "alignedTaxonCountsFaunaB": [
      0,
      2,
      2
    ]
  },
  "output": {
    "rawAbundanceBrayCurtisDissimilarity": 0.5,
    "relativeAbundanceBrayCurtisDissimilarity": 0.5,
    "balancedAbundanceDifferenceComponent": 0.5,
    "abundanceGradientComponent": 0
  }
}

Limitations and assumptions

Balanced and gradient components sum to raw dissimilarity; taxon alignment and comparable recovery are assumed.

Numbers and computed results must be finite; overflow produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Extinction Magnitude Percent Taxa: Compare distinct before/after observed taxa with comparable detection, separating lost/surviving/new records; absent observations do not themselves establish biological extinction. For a complementary task, use Good's U Sample Coverage: Compute Good’s U=1-f1/N on positive observed abundance counts; coverage estimates sampled individual probability mass, not species completeness or a guarantee that rare taxa were found.

References

Beta Diversity Turnover Between Faunas — tool.io

Similar or alternative tools

Extinction Magnitude Percent Taxa
Compare distinct before/after observed taxa with comparable detection, separating lost/surviving/new records; absent observations do not themselves establish biological extinction.
Good's U Sample Coverage
Compute Good’s U=1-f1/N on positive observed abundance counts; coverage estimates sampled individual probability mass, not species completeness or a guarantee that rare taxa were found.