Puccinia embergeriae McKenzie & P.R.Johnst. ined.
Chatham Island sow thistle rust
General status: Endemic
Population: Probably <250 individuals. Known only on Embergeria grandifolia (Chatham Island sow thistle, great sow thistle), from one host population at Kaingaroa, Chatham Island. It may be more widespread, with its host.
Decline: The rust will have declined with the decline of the host plant. The host is threatened (vulnerable), being restricted to areas inaccessible to livestock.
Total area occupied: < 1 ha
Distribution: Chatham Island
Biology: Rust fungi are near obligate plant parasites. Puccinia embergeriae is probably restricted to the one host species (Embergeria grandifolia). It is doubtful that all individual plants of E. grandifolia are infected by this rust. Although a single host plant probably nurtures more than one individual of the fungus, the total rust population on one individual host plant must be considered an individual - destruction of the host means destruction of that rust population.
Both urediniospores and teliospores occur on the host. There may be an alternate host on which the rust completes its life cycle, but this is unknown.