IUCN Global Red List Assessments

With the introduction of Shared Taxonomy in Hortis, our primary opinion source for taxonomy is Plants of the World Online (POWO). To simplify how IUCN Red List data is integrated with Hortis, we will continue to use the POWO as a taxonomic opinion and reference backbone for IUCN Global Red List Data.

Over 20% of IUCN assessments are over a decade old, and as a consequence, some assessments refer to taxa that have since been subject to a taxonomic revision. That leaves us with nearly 8% of the assessments referring to a synonym, of which nearly 3% relate to heterotypic synonyms.

Heterotypic synonyms are names that have been independently published under different names for the same species using different reference [type] specimens. In comparison, homotypic synonyms are where species have simply changed their name.
“If two species that were once considered distinct have been merged, one of the names is retained as an accepted name, and the other is treated as a heterotypic synonym. This may affect the conservation status of the species; if an assessment was carried out on one of the original species before the merge took place, then this work will need updating.” (Antonelli, A., et al. Page, 10)

To avoid ambiguity, the IUCN Global Red List status in Hortis is derived from assessments related to accepted names or homotypic synonyms. Assessments related to heterotypic synonyms are not included. We will later explore the possibility of including red list status for heterotopic synonyms.

Below we have included a couple of examples of how assessments of heterotypic synonyms may cause confusion.

Example One: 

Example Two:


Antonelli, A., et al. (2023). State of the World’s Plants and Fungi 2023. Royal Botanic Gardens, Kew. DOI: https://doi.org/10.34885/wnwn-6s63

Havard is the author of this solution article.

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