Thanks to the “Threatened Weta recovery plan”, the population sizes and distributions of giant weta are increasing. On this basis the habitat and potential host population size of the 3 known hosts of C. kirkii have increased since 1996 and are further expanding. With only 4 fungarium specimens, however, the knowledge of its abundance and distribution within the range of its hosts is unknown, hence also the status. It could possibly qualify for VU2 (very few localities, area of occupancy or no of mature individuals, if including an estimate of the unrecorded portion of the population). However, at this stage, we rather suggest DD.
This is a conspicuous endemic species of Cordyceps on threatened species of endemic giant weta - flightless insects.
The holotype of C. kirkii was collected in 1922, on the threatened Stephens Island weta, Deinacrida rugosa (Categorised as globally VU (Vulnerable) in 1996 by IUCN), and the next specimens were from 1975 and 2014 - with a further recent photograph (no specimen) from 2018. .
Sequence data from the 2014 specimen of C. kirkii for nSSU, nLSU, TEF, RPB1, and RPB2 was incorporated into the Sanjuan et al. (2014) phylogenetic paper on orthopteran Cordyceps of Columbia. C. kirkii is confirmed as a true Cordyceps, but phylogenetically distinct from the Colombian orthoptera-associated species. No genetic data is known for other New Zealand species of Cordyceps.
The New Zealand endemic insect pathogen Cordyceps kirkii is currently known from 4 specimens on 3 species of giant weta, endemic flightless insects that are themselves threatened - and are the subject of captive breeding and translocation programmes to ensure their survival.
Known to date from only 3 in-shore islands where rats have been eradicated, and one location on the mainland - Westland, South Island. The islands, such as 150 ha Stephens Is. are small.
Although the obligate host of the holotype specimen, D. rugosa, is present on 5 small islands and 2 islets, C. kirkii has been recorded from only 2 of these, but it may not have been searched for at these other locations. To date, it has mostly been found by entomologists looking at weta, rather than mycologists seeking the fungus.
Note that the attached KML file does not yet include the northern Hauturu/Little Barrier Island record, where its presence is based on convincing photographic evidence only - without a voucher specimen.
Population status and trend unknown. Obligate host, however, is confined to 5 rodent-free islands and 2 islets in New Zealand, plus recent translocations. - see regional status. Arguably the Cordyceps is more threatened that the “Vulnerable” (IUCN-rated) host.
Population Trend: Uncertain
On the basis of only four known specimens, the species is apparently confined to giant weta, though recorded from 3 weta species: Deinacrida rugosa (Stephens Island Giant Weta; Cook Strait Weta), D. heteracantha (wētāpunga), and Hemiandrus maculifrons. It is presumably parasitic, sporulating on dead weta. Most giant weta are now confined to New Zealand off-shore islands where rats have been eradicated, or on mainland locations with predator control.
D. rugosa, as host of the holotype specimen, prefers dense grassland and low growing shrubs in open situations. On Mana Island, they now occur in rank grass and shrubland including tauhinu (Cassinia leptophylla). Predators include reptiles and birds, and most significantly rats (unless eradicated). (from http://www.doc.govt.nz/Documents/science-and-technical/tsrp25.pdf)
Cordyceps kirkii, previously recorded in New Zealand on the Stephens Is./Cook Strait giant weta (Deinacrida rugosa) and the ground weta (Hemiandrus maculifrons), has been newly recorded on Hauturu (LIttle Barrier Island) on dead wetapunga, (Deinacrida heteracantha) [Photos Lyn Wade/David Stone/unknown]. While parasitic, this native Cordyceps is unlikely to negatively affect wetapunga at a population level.
The main threat is survival of its host. The decline of most wētā is due to three major causes:
- Predation: Wētā have evolved alongside native predators such as birds, reptiles, and bats. The introduction of predators such as rats, mustelids, cats, and hedgehogs has resulted in a sharp increase in the rate of predation.
- Habitat destruction: Caused by human impacts
- Browsers: Modification of wētā habitat caused by introduced browsers.
For example, Deinacrida rugosa is confined to certain offshore, rodent free nature reserve islands. Exotic predator-free status needs to be maintained indefinitely in these habitats. Translocations of wētā to other reserve islands and recently to mainland predator-free reserve has been successful. A population explosion of the native and also threatened reptile Tuatara, that eat weta, could also potentially diminish the wētā population at a local level.
No conservation actions have been undertaken specifically for Cordyceps kirkii.
However, there has been active conservation effort to support survival of several species of giant weta. For example, the host Deinacrida rugosa, is secure on Stephens Island (Takapourewa Nature Reserve) where 2 of our 4 specimens of C. kirkii were collected. This island holds the world’s largest population of tuatara, that naturally prey on weta and other invertebrates. Other species found there include fairy prion, seven species of lizard and the endemic Hamilton’s frog (though latter too small to consume weta).
Conservation initiatives to support the Stephens Island / Cook Strait Giant Weta (from Sherley (1998) http://www.doc.govt.nz/Documents/science-and-technical/tsrp25.pdf):
“Cook Strait giant weta (Deinacrida rugosa) A self-sustaining and expanding population has been established by translocating weta from Mana Island to Maud Island. Transfer of weta from Mana Island to Somes Island was initiated in 1996. Captive breeding techniques have been developed. Field research on dispersal behaviour and habitat use has been completed. Mice (presumed to prey on weta) have been removed from Mana Island which is considered to be the species stronghold”
“Distribution and abundance: Deinacrida rugosa is found on five rodent-free islands and two islets in the Cook Strait vicinity; North, South and Middle Trio Islands, Stephens Island, Maud Island, Matiu/Somes Island, and Mana Island. This weta is abundant on Mana Island, and healthy populations are also present Stephens and Middle Trio Island. The population on Maud Island was introduced in 1976, and is increasing (Meads and Notman 1992a). D. rugosa was introduced to Matiu/Somes Island in 1996.”
Similar data and conservation actions have been undertaken for other giant weta species, and these actions collectively are likely having spin-off benefits to secure the long-term survival of C. kirkii.
Basic understanding of biology of species, and its interaction with its host. Is the relationship parasitic, commensal, or mutualistic?
Search on other island habitats of host to evaluate distribution of Cordyceps.
Evaluate population size of C. kirkii
Phylogenetic relationships of New Zealand Cordyceps in global context
Does C. kirkii show any variation morphologically or genetically in relation to its different host weta species?
Host giant weta (dead or alive) are sought after by some collectors, but government control is reasonably tight via application of conservation permits for collection - with prosecutions likely for unpermitted holders of weta.
Cunningham, G.H. 1922: A singular Cordyceps from Stephen Island, New Zealand. Transactions of the British Mycological Society 8(1-2): 72-75
Dingley, J.M. 1953: The Hypocreales of New Zealand. V. The genera Cordyceps and Torrubiella. Transactions of the Royal Society of New Zealand 81(3): 329-343.
Sanjuan, T. et al. 2014: Entomopathogens of Amazonian stick insects and locusts are members of the Beauveria species complex (Cordyceps sensu stricto). Mycologia (in press), doi:10.3852/13-020. http://www.mycologia.org/content/early/2014/01/23/13-020.full.pdf
Sherley, G.H. (1998) Threatened Weta Recovery Plan. Threatened Species Recovery Plan no. 25. Department of Conservation, Wellington, New Zealand. http://www.doc.govt.nz/Documents/science-and-technical/tsrp25.pdf