Endemism.org uses biological databases, government records, specialist taxonomic sources, conservation assessments, museum and university resources, and peer-reviewed research to document endemic species and the geographic limits of their natural ranges. Source choice depends on the type of claim being checked.
How sources are selected
No single database covers every taxonomic group, country, and type of distribution evidence equally well. A source that is suitable for an accepted scientific name may not be the best source for a national species count, conservation category, or narrow native range.
For that reason, sources are selected according to their role. Specialist taxonomic databases are used where current accepted names and synonymy matter. Government biodiversity agencies and official species accounts are used where national or regional distribution data are available. Botanical authorities are preferred for plant taxonomy and native-range treatment. Peer-reviewed checklists and institutional datasets may be used when they provide stronger coverage for a particular group or geographic area.
Source quality is evaluated claim by claim. A source is not treated as authoritative for every biological question simply because it is widely used.
Source priority
Preference is generally given to specialist and primary sources with direct responsibility for the data being reported. These can include taxonomic databases, government biodiversity agencies, official wildlife or botanical authorities, conservation databases, museums, universities, and peer-reviewed taxonomic or biogeographic research.
When a secondary page points to an original dataset, the original source is preferred where it can be accessed and interpreted directly. News reports, summaries, and general reference pages are not used as substitutes for underlying biological evidence when a stronger source is available.
Different data types are kept separate
Endemism data may be reported as species, taxa, subspecies, varieties, genera, families, assessed species, native species, threatened species, or estimated totals. These units are not interchangeable.
A source reporting 1,000 native vascular plant taxa does not automatically support a claim of 1,000 native species. A checklist of assessed species is not treated as a complete national inventory unless the source explicitly defines it that way.
Species-level counts are used only when the underlying records are actually at species rank.
Geographic scope is preserved
Every quantitative value is interpreted within the geographic area covered by its source. National, state, provincial, island, watershed, mountain, spring, cave, and aquifer datasets are not treated as equivalent.
Subnational figures can describe concentrations of endemism, but they are not promoted to national totals. Separate regional datasets are not added together unless the source structure and definitions make that calculation valid.
When a species has a well-supported range narrower than the country containing it, the narrower range is preferred in species-level records.
Native distribution determines endemic status
Endemic status is based on natural native range. Introduced, naturalized, cultivated, captive, planted, or translocated populations are not used to expand a species’ original geographic distribution.
Occurrence databases can provide useful evidence of presence, but occurrence alone does not establish endemism. A species is not classified as endemic simply because records outside an area are absent or sparse.
Taxonomic treatment
Current accepted names are preferred where a suitable taxonomic authority is available. Synonyms are linked to accepted taxa rather than counted as separate species. Recent taxonomic splits, mergers, and changes in genus placement are considered when they affect endemic status or species totals.
Different authorities may recognize different species boundaries. When those differences materially affect a count or checklist, values are kept within the taxonomic treatment used by the source rather than merged into a new synthetic figure.
National statistics
Country profiles use national-scale quantitative data where reliable figures are available. These may include endemic mammals, birds, reptiles, amphibians, freshwater fishes, plants, trees, genera, families, threatened endemic species, or endemic shares within native groups.
There is no fixed number of statistics required for a country page. The number of measures depends on the quality and compatibility of the available data. Distinct, well-defined metrics are retained; duplicate measures and weak figures are left out.
Values with different taxonomic coverage, methodology, or time periods are not added together to create an all-taxa total unless the source itself provides a defensible basis for doing so.
Derived values
A percentage or ratio may be calculated when the source provides compatible numerator and denominator values from the same dataset or taxonomic treatment.
The geographic scope, taxonomic rank, native-status definition, and time basis must match. Values from unrelated sources are not combined simply to create a percentage.
Derived figures retain the precision of the source data. Approximate inputs are not converted into overly precise decimal results.
Species checklist method
Species checklists are built from records that can be supported individually or through a source that clearly defines the included species set. Each record is checked for accepted name, species rank, broad taxonomic group, native distribution, and endemic scope.
Checklist size is not limited to a fixed sample. When more species can be verified from reliable sources, they are included. When a source gives a total but species identities cannot be resolved with adequate confidence, the total and displayed checklist are kept separate.
Duplicate accepted species are removed. Synonyms, subspecies, varieties, forms, populations, and other infraspecific records are not counted as additional species.
Conservation data
Threatened, extinct, and extinct-in-the-wild counts are used only when the conservation categories belong to a dataset that can be matched to the endemic species scope being described.
Conservation categories are not assumed to cover every endemic species in a country. Assessment coverage can differ between groups, and an unassessed species is not treated as non-threatened.
Dataset versions and updates
Datasets that are released in versions are checked for newer compatible editions. A newer release is preferred when it reports the same measure using a compatible definition.
Version changes can also alter taxonomy, geographic scope, or assessment coverage. In those cases, older and newer figures are not treated as directly interchangeable without checking the underlying definitions.
Source citations
Endemism.org uses compact source references within articles and places source details in a separate Sources section. The same source keeps the same reference number throughout a page.
References are placed beside the factual or quantitative claims they support. National statistics tables use compact citation markers next to values instead of inserting source titles, years, or external URLs into the table itself.
Limits of coverage
Biological knowledge is uneven across countries and taxonomic groups. Some groups have current national inventories, while others are documented through older checklists, regional studies, or incomplete assessments.
Where evidence does not support a national total, full checklist, or exact percentage, no value is created to fill the gap. Separately defined datasets remain separate, and uncertainty in the source is retained in the published page.