Conservation Genetic Studies

Testing of species limits for Knobbled weevils (Hadramphus stilbocarpae)

Conservation genetics of Chessemania, 'Chalk Range'

Testing of species limits for Knobbled weevils (Hadramphus stilbocarpae)

Biology and background

Knobbled weevils (Hadramphus stilbocarpae) are among the largest of New Zealand's flightless endemic weevils at 20-25 mm (Meads, 1990). Although originally described from islets around Stewart Island and from the Snares (Kuschel 1971) where they are host specific to Stilbocarpa polaris, in 1986 they were found on islets in Fiordland's Breaksea Sound Fiordland and subsequently on Resolution Island (Thomas et al. 1992) and at Puseygur Point (Bruce Thomas Pers. Comm.). A recent discovery of a Hadramphus population has been made on Chalky Island (Eric Edwards, Pers. Comm.).

Reduction of invertebrate fauna in Fiordland has apparently occurred due largely to rodent predation over the past 200 years (Bremner et al. 1984) and the demise of H. stilbocarpae on Big South Cape Island was attributed to predation by rats (Kuschel 1971). Other factors such as habitat degradation and destruction due to various agricultural practices and browsing by stock and further reduction in size and extent of host plant populations by goats and deer, also posed threats to populations of H. stilbocarpae (Meads 1990). H. stilbocarpae was added to the protected fauna list in the Seventh Schedule of the Wildlife Amendment Act 1980 and is listed by Molloy and Davis (1994) as a priority C species for conservation.

Following successful eradication of Norway rats from Hawea Island in 1986 and Breaksea Island in 1988 (Taylor and Thomas 1989, 1993) and as an integral part of an ongoing island restoration research programme in Breaksea Sound, forty specimens of H. stilbocarpae were translocated from 'OG3' (an unnamed islet near Hawea Island) to Breaksea Island in March 1991 (Thomas and Meads 1990, Thomas et al. 1992). The success of this experimental transfer has been confirmed but regular monitoring of Knobbled weevil populations in Breaksea Sound indicates that long-term viability of some Hadramphus populations is in doubt. A study of the population dynamics of H. stilbocarpae on 'OG3' revealed that, like the closely related coxella weevil H. spinnipenis on Mangere Island in the Chatham's (Shcöps 1988), Knobbled weevils in Fiordland have the capacity to over-exploit their host plant causing a complete collapse of their habitat. In several island situations this unusual phenomenon is exacerbated by increasing populations of seals suppressing regeneration, permanently reducing or annihilating large areas of weevil habitat (Bruce Thomas Pers. Comm.).

Evolution of Hadramphus stilbocarpae

Hadramphus from Breaksea Sound are currently considered conspecific with the Knobbled weevil around Stewart Island and the Snares (Thomas et al. 1992). However, feeding habits and geographical separation suggest considerable variation among these weevils (Thomas et al. 1992, Craw 1999). While Fiordland Knobbled weevils feed exclusively on Anisotome lyallii, all other populations are host specific on Stilbocarpa polaris, despite both host plant species occurring on the Snares. In an experiment by Meads (1992), ten Snares Knobbled weevils held in captivity refused to feed on Anisotome.

Fossil evidence suggests that H. stilbocarpae may once have co-existed with Stilbocarpa in the South Island. Islands in Fiordland and islets around Stewart Island were created with rising sea levels at the end of the Pleistocene. The host plant change from Stilbocarpa to Anisotome in the Fiordland populations is likely to have occurred at this time. Anisotome is closely related to Apiaceae species from the subfamily Apioideae (Mitchell et al. 1998). Stilbocarpa, traditionally classified as Araliaceae, is in fact more closely related to members of the Apiaceae, subfamily Hydrocotyloideae Mitchell et al. 1999). Thus the host change from Stilbocarpa to Anisotome has apparently occurred between relatively distantly related Apiaceous species in recent geological times.

Genetic data will play an important role in estimating the diversity in H. stilbocarpae. The advantage of analysing the DNA directly is that environmental and other influences are avoided. If genetic, morphological and physiological data supports the unique status of H. stilbocarpae from Fiordland, then urgent consideration should be given to determining an appropriate conservation status for this taxon.

Objectives

The primary objective of this work will be to aid in the conservation of the range of genetic diversity present within and among populations of Southern Hadramphus by:

1. Determining the genetic variation within and between populations of Hadramphus from the Snares, Stewart Island and Fiordland
2. Making recommendations, based on the genetic makeup of southern Hadramphus, that will contribute towards the maintenance of a gene pool containing the maximum genetic diversity.

Collaborators

A. Mitchell, R. Emberson, B. Thomas, R. Craw, E. Edwards, K. Shcöps

References

Bremner, A. G., Butcher, C. F., Patterson, G. B. 1984. The density of indigenous invertebrates on three islands in Breaksea Sound, Fiordland, in relation to the distribution of introduced mammals. Journal of the Royal Society of New Zealand. 14: 297-386.

Craw, R. C. 1999. Molytini (Insecta: Coleoptera: Curculionidae: Molytinae). Fauna of New Zealand 39. Manaaki Whenua Press.

Kuschel, G. 1971. Entomology of the Aucklands and other islands south of New Zealand: Coleoptera: Curculionidae. Pacific insects monograph 27: 225-259.

Meads, M. J., 1990. Forgotten fauna, the rare, endangered, and protected invertebrates of New Zealand. DSIR Publishing, Wellington. 96 p.

Mitchell, A., Wagstaff, S., Webb, C. 1998. Phylogenetic relationships of species of Gingidia and related genera (Apiaceae, subfamily Apioideae). New Zealand Journal of Botany. 36: 417-424.

Mitchell, A., Meurk, C., Wagstaff, S. 1999. Evolution of Stilbocarpa Gray, a megaherb from New Zealand's sub-antarctic islands. New Zealand Journal of Botany. 37: 205-211.

Shcöps, K. 1998. Metapopulattion dynamics and behaviour of the endangered weevil, Hadraphus spinipennis in relation to its host plant Aciphylla dieffenbachii on the Chatham Islands, New Zealand. Unpublished Ph.D thesis, Lincoln University, 126 pp.

Taylor, R. H., Thomas, B. W., 1993. Rats eradicated from rugged Breaksea Island (170 ha), Fiordland, New Zealand. Biological Conservation. 65: 191-198.

Taylor, R. H., Thomas, B. W., 1989.  Eradication of Norway rats (Rattus norvegicus) from Hawea Island, Fiordland, using brodifacoum. New Zealand Journal of Ecology. 12: 23-32.

Thomas, B. W., Meads, M. J. 1990. A proposal to reintroduce knobbled weevils (Hadramphus stilbocarpae) and flax weevils (Anagotus fairburni) to Breaksea Island, Breaksea Sound, Fiordland. Unppublished Report, DSIR Land Resources, Nelson. 8 p.

Thomas, B. W., Meads, M. J., and Notman, P. R. 1992. A report on the restoration of knobbled weevils (Hadrampus stilbocarpae) and flax weevils (Anagotus fairburi) to Breaksea island, Breaksea Sound, Fiordland. DSIR Land Resources Technical Report. 79.

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Conservation genetics of Chessemania, 'Chalk Range'

Background and Rationale

Cheesemania 'Chalk Range' is a habitat-specific, range-restricted member of New Zealand's endemic Brassicaceae that is considered critically endangered (Cathy Jones; Pers Com.). According to molecular analyses of the New Zealand Brassicaceae based on ITS sequence data (Mitchell and Heenan, 2000), Cheesemania 'Chalk Range', C. fastigiata, and C. stellata represent a very closely related species complex. Although the taxonomic status of the close relatives have been studied based on morphology (Heenan and Garnock-Jones 1999), the status of C. 'Chalk Range' entity has not been investigated. The genetic variation and gene flow within and between populations of C. 'Chalk Range', C. fastigiata, and C. stellata are unknown.
Genetic data will play an important role in estimating diversity within this closely related complex. The advantage of analysing the DNA directly is that environmental and other influences are avoided (Mitchell 2000). If genetic, morphological and physiological data supports specific status for C. 'Chalk Range', then we need to act urgently to maximise the chances of this taxon surviving.

Collaborators

A. Mitchell, C. Jones, P. Heenan, C. Hargraves

References

Heenan, P. B. and Garnock-Jones, P. J. 1999. A new species combination in Cheesemania (Brassicaceae) from New Zealand. New Zealand Journal of Botany. 37: 235-241.

Mitchell, A. 2000. Plant conservation genetics - are we missing the boat? ConScience. Conservation Science Newsletter.36. 1-3.

Mitchell, A., Heenan, P. 2000. Systematic relationships of New Zealand endemic Brassicaceae inferred from rDNA sequence data. Systematic Botany. 98-105.

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