POWO follows these authorities in synonymising this name:
Govaerts, R. (1999). World Checklist of Seed Plants 3(1, 2a & 2b): 1-1532. MIM, Deurne. [Cited as Coprosma grandifolia.]
Govaerts, R. (2003). World Checklist of Selected Plant Families Database in ACCESS: 1-216203. The Board of Trustees of the Royal Botanic Gardens, Kew. [Cited as Coprosma grandifolia.]
Also see: https://onlinelibrary.wiley.com/doi/10.1002/tax.12993
and: https://onlinelibrary.wiley.com/doi/full/10.1002/tax.13151 (Link)
Unintended disagreements occur when a parent (B) is
thinned by swapping a child (E) to another part of the
taxonomic tree, resulting in existing IDs of the parent being interpreted
as disagreements with existing IDs of the swapped child.
Identification
ID 2 of taxon E will be an unintended disagreement with ID 1 of taxon B after the taxon swap
If thinning a parent results in more than 10 unintended disagreements, you
should split the parent after swapping the child to replace existing IDs
of the parent (B) with IDs that don't disagree.
