Investigation of the red algal parasites Rhodophyllis parasitica sp. nov. and Pterocladiophila hemisphaerica from New Zealand

Red algal parasites are common within red algae and most parasites are closely related to their host. Red algal parasites can switch hosts and their development is unique. Red algal parasites are poorly known in New Zealand. There are only four parasites described in New Zealand and those are based on morphological characteristics. This thesis focuses on the two red algal parasites Rhodophyllis parasitica sp. nov. and Pterocladiophila hemisphaerica from New Zealand. First, development and phylogeny and distribution of an undescribed red algal parasite growing on Rhodophyllis membranacea was investigated. Microscopy, molecular markers (ITS2, cox1, cox2-3 spacer) and phylogenetic analysis, and herbarium sampling were used to address these questions. The parasite, described as Rhodophyllis parasitica sp. nov. shows a close relationship of all genomes to Rhodophyllis membranacea, which suggests that the parasite evolved from its hosts. The parasite is widely distributed throughout New Zealand. The second parasite, Pterocladiophila hemisphaerica was grouped taxonomically, based on morphology, in the order Gracilariales and parasitizes Pterocladia lucida in the order Gelidiales. Molecular marker were used to reveal the relationship of Pterocladiophila hemisphaerica to its host: if the parasite is grouped in the Gracilariales or the Gelidiales; if host switches might have occurred; and if atp8 is present in the parasite. Nuclear DNA (SSU rRNA, LSU rRNA), mitochondrial (cox1) and plastid regions (rbcL-rbcS spacer) from the parasite were sequenced and phylogenetic analysis performed. New primer were designed to amplify atp8 and genetic analysis performed. Pterocladiophila hemisphaerica evolved in the Florideophytes but neither in the Gracilariales or Gelidiales and the parasite possibly switched hosts at least two times, which was shown by three different origins of chloroplast, mitochondria and nuclear DNA. Atp8 in the parasite is present but probably a pseudogene. Rhodophyllis parasitica sp. nov. is the first described red algal parasite species in New Zealand in 55 years and Pterocladiophila hemisphaerica is the first parasite with organelles and nuclei with different histories of origin.