Additions to the Rust Fungi of Hawai'il

In a 1989 publication, the 74 species of rust fungi (order Uredinales) known to occur in Hawai'i were listed, based on newly collected material; herbarium specimens, principally those at the Bernice P. Bishop Museum (BISH); and information provided by F. L. Stevens in his 1925 publication on Hawaiian fungi. Stevens had noted an underrepresentation of this group in Hawai'i, which he attributed to the archipelago's isolation from continental landmasses. Since the time of the 1989 publication, 16 additional rusts have been recognized in Hawai'i. These include both recently introduced species, such as Coleosporium plumeriae Pat. on plumeria, and those recently discovered, such as Puccinia rugispora Gardner and P. rutainsulara Gardner on endemic Rutaceae. New host and location records and other important updating information on this well-defined group of fungi in Hawai'i are also included. THE RUST FUNGI (order Uredinales) constitute a relatively homogeneous group of obligate plant parasites, recognized by the production of morphologically characteristic, primarily windborne spores (Littlefield 1981, Cummins and Hiratsuka 1983). As a group, these fungi are noted for their virulence, causing great losses to crops on a worldwide basis, as well as for their host specificity. Perhaps the most striking characteristic of the rust fungi is the complex life cycle, which may include as many as five different spore states among macrocyclic species. Furthermore, heterocyclic rusts produce some spore states on "primary" and some on "secondary" hosts. Designation of primary and secondary hosts is an arbitrary function of the relative importance, usually economic, of each host rather than of the particular spore states produced on that host. Notwithstanding the hostspecificity of the rusts, alternate hosts typically have no taxonomic relationship to one another, with an angiosperm and a gymnosperm or a dicot and a monocot often serving as alternate hosts for a given species. With such wide diversity of hosts, determination of life cycles has presented substantial challenges. Life cycle conI Manuscript accepted 15 May 1996. 2 Cooperative Park Studies Unit, National Biological Service, University of Hawai'i at Manoa, Department of Botany, Honolulu, Hawai'i 96822. nections for many spore states remain unconfirmed, leading to the erection of form genera, such as Uredo, to accommodate particular spore states of rusts with incompletely known life cycles. In light of the above generality, it is noteworthy that few of the native or nonnative rusts in Hawai'i exhibit macrocyclic life cycles, but occur in demicyclic or microcyclic form, or as species of Uredo, in which only the uredinial state is known. Furthermore, use of alternate hosts as described above is not known to occur among either native or nonnative rusts in Hawai'i. Species that use alternate hosts to complete their life cycles elsewhere are limited to a single host in Hawai'i. For example, the aecial state of Uredinopsis hashiokai causes a serious needle disease of species offir (the primary host) in western North America (Faull 1938, Ziller 1959), but the rust occurs in Hawai'i only in the uredinial state on the secondary host, bracken fern (Pteridium aquilinum). The "repeating" ability of the uredinial state enables otherwise long-cycled rusts to survive indefinitely in tropical environments where a resistant resting, or overwintering, state is not required. In an earlier publication, Gardner and Hodges (1989) listed the rust fungi known to occur in Hawai'i, based largely on specimens on deposit at the B. P. Bishop Museum (BISH), the Animal