Three new red algal parasites from New Zealand: Cladhymenia oblongifoliaphila sp. nov. (Rhodomelaceae), Phycodrys novae-zelandiaephila sp. nov. (Delesseriaceae) and Judithia parasitica sp. nov. (Kallymeniaceae)

2018 International Phycological Society There are over 120 species of red algal parasites (Florideophyceae) but they are often overlooked due to their small size and patchy distribution. Red algal parasites have mostly been described as independent genera but recent phylogenetic studies have shown that parasites are related to free-living relatives, often their hosts, and have been named in these genera to maintain monophyly. We investigated the morphology, distribution and phylogeny, using diverse molecular markers (mitochondrial, nuclear, plastid), of three new red algal parasites in New Zealand. We describe the parasites using morphological and anatomical observations and estimate their distribution by surveying herbarium vouchers. Analyses of reproductive structures and molecular phylogenies indicate that the closest relative of the parasite Phycodrys novae-zelandiaephila sp. nov. is its host, Phycodrys novae-zelandiae. Based on nuclear and mitochondrial markers, the closest relative of the parasite Cladhymenia oblongifoliaphila sp. nov. is its host Cladhymenia oblongifolia but plastid markers group it with Cladhymenia lyallii, suggesting that this species was a past host and the source of parasite plastids. The parasite Judithia parasitica sp. nov. groups with Judithia delicatissima but infects Blastophyllis spp., suggesting that this parasite evolved as a free-living or parasitic Judithia species, and host switching may have occurred. This study adds to our knowledge of New Zealand red algal parasites and highlights contrasting patterns of host–parasite relationships.