Nancythalia humilis gen. et sp. nov. and Abroteia suborbiculare (Delesseriaceae, Rhodophyta) from New Zealand

Abstract

Critical examination of the type specimens of Nitophyllum? suborbiculare, Abroteia orbicularis, Myriogramme oviformis and M. parvula has shown that all four taxa belong to A. suborbiculare, which is consequently the only known species of the New Zealand endemic genus Abroteia. Within the type material of A. orbicularis, there are specimens of two different genera. Although both genera share almost identical habits and are both obligate epiphytes on the New Zealand endermic fucalean algae Carpophyllum and Landsburgia, one has monostromatic blades in which tetrasporangia and spermatangia form prominent, nerve-like sori; this alga corresponds to Harvey's and J. Agardh's intended characterization of Abroteia. The second, hitherto undescribed, genus has polystromatic blades that, when fertile, are completely covered by tetrasporangia or spermatangia; Nancythalia humilis A. Millar & W.A. Nelson gen. et sp. nov. is described to encompass these algae. Both Abroteia and Nancythalia share procarps consisting of a four-celled carpogonial branch and two one-celled, sterile cell groups, and both share cystocarps in which a carposporophytic fusion cell forms candelabra-like gonimoblastic arms that bear chains of carposporangia. Abroteia and Nancythalia are thus considered to belong to the tribe Schizoserideae within the Delesseriaceae. It is unique to Nancythalia that the supporting cell of the carpogonial branch is cut off from a cortical ceil, and not from a primary central cell as in most Delesseriaceae.