Seven new Serendipita species associated with Australian terrestrial orchids

<p><i>Serendipita</i> is one of the main fungal genera that form mutualistic associations with species of orchids (Orchidaceae). Seven new <i>Serendipita</i> species associated with various Australian orchid genera are described. These <i>Serendipita</i> species were originally characterized by multilocus DNA sequence species delimitation analyses (three mtDNA and four nuclear genes) and confirmed as distinct with addition of further isolates and re-analysis of the nuc rDNA ITS1-5.8S-ITS2 (ITS) and nuc 28s rDNA (28S). Morphology and micro-features of cultures of each of the species are described. Three of the new species are binucleate, whereas the other four are multinucleate. For the ITS region, the seven species have within species sequence divergence between 1.07 and 4.31 % and all but one of the species pairs are separated by interspecific divergence of at least 4.35 %. The newly described <i>Serendipita</i> species, <i>S. australiana, S. communis</i>,<i> S. occidentalis</i>,<i> S. rarihospitum</i>,<i> S. secunda</i>, <i>S. talbotii</i>, and <i>S. warcupii </i>are shown to be separate species to <i>S. vermifera</i> on the basis of comparison against a sequence from the type. Isolates originally identified by Warcup as <i>Sebacina "vermifera</i>" from <i>Caladenia</i> orchids are reidentified as belonging to three of the species newly described here. Some non-<i>Caladenia</i> isolates identified by Warcup as <i>S. </i>"<i>vermifera</i>" are also shown to be non-conspecific with the type of <i>S. vermifera</i>. On the basis of ITS sequences, 346 isolates from 26 other studies, previously identified under provisional designations, are accomodated under the novel species. The species of <i>Serendipta</i> described here associate with the Australian orchid genera <i>Caladenia, Cyanicula, Elythranthera, Ericksonella, Eriochilus, Glossodia</i>,<i> </i>and<i> Pheladenia</i>. Most of the novel <i>Serendipita</i> species occur widely across Australia, often with widely distributed hosts, but one species, <i>Serendipita rarihospitum</i>, associates with narrowly distributed orchid species.</p>