New Zealand Gigartinaceae (Rhodophyta): Resurrecting Gigartina grandifida endemic to the Chatham Islands

Abstract The red alga Gigartina grandifida J. Agardh (Rhodophyta, Gigartinales) was described in 1876 from collections made in the Chatham Islands by H. H. Travers, but was later reduced to synonymy pro parte with species of Sarcothalia and Gigartina from mainland New Zealand. Recent collecting expeditions to the Chatham Islands targeting Gigartinaceae have found a species growing in the low intertidal to upper subtidal zones that can be distinguished by morphology and habitat from other members of the family. Molecular sequence data and phylogenetic analyses have revealed that this species is genetically distinct from all other New Zealand and Chatham Islands Gigartinaceae. This species is consistent with the original concept of the Chatham Island endemic species G. grandifida J.Agardh.