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Another introduced hymenopteran
Invertebrata 21, November 2001

[It's a bit unusual for Invertebrata to reproduce an abstract from an unpublished paper, but this one has been widely circulated in the Tasmanian entomological community, and the results are of major importance. The paper may also have set a Tasmanian entomological record for Most Authors. - Ed.]

Hingston, A.B., Marsden-Smedley, J., Driscoll, D.A., Corbett, S., Fenton, J., Anderson, R., Plowman, C., Mowling, F., Jenkin, M., Matsui, K., Bonham, K.J., Ilkowski, M., McQuillan, P.B., Yaxley, B., Reid, T., Storey, D., Poole, L., Mallick, S.A., Fitzgerald, N., Kirkpatrick, J.B., Febey, J., Harwood, A.G., Michaels, K.F., Russell, M.J., Black, P.G., Emerson, L., Visiou, M., Morgan, J., Breen, S., Gates, S., Bantich, M.N. and Desmarchelier, J.M. (in press) The extent of invasion of Tasmanian native vegetation by the exotic bumblebee Bombus terrestris (Apoidea: Apidae). Austral Ecology (in press).

Abstract

Observations of the large earth bumblebee Bombus terrestris (L.) in native vegetation were collated to determine the extent to which this exotic species has invaded Tasmanian native vegetation during the first nine years of its introduction. The range of B. terrestris now encompasses all of Tasmania's major vegetation types, altitudes form sea level to 1260 m, and the entire breadth of annual precipitation in the state from over 3200 mm to less than 600 mm. Observations of workers carrying pollen, together with the presence of large number sof bumblebees, at many localities across this range indicate that colonies are frequently established in native vegetation. Evidence that colonies are often successful was obtained from repeated observations of the species during more than one year at particular sites. Unequivocal evidence of colonies was obtained from six National Parks, including four of the five in the Tasmanian Wilderness World Heritage Area (WHA). Indeed, it has been present in the WHA for at least as long as it has in the city of Hobart, where it was first recorded. In southwestern Tasmania, evidence of colonies was obtained up to 40 km from gardens, 61 km from small towns, and 93 km from large towns. Hence, contrary to previous suggestions, the species is established in the most remote parts of Tasmania and is not dependent on introduced garden plants. Given their strong record of invasion, it is likely that B. terrestris will form feral populations on the mainland of Australia and in many other parts of the world if introduced. Because of their likely negative impacts on native animals and plants, and potential to enhance seed production in weeds, the spread of bumblebees should be avoided.

A tale of two rare and threatened invertebrates
Invertebrata 21, November 2001

In March 2001, a collaborative project on two rare and threatened invertebrates in the Launceston area was started with funding from the Threatened Species Unit within the Department of Primary Industries, Water and Environment, Tasmania (DPIWE). Both invertebrates have limited distributions, are listed as rare under the Tasmanian Threatened Species Protection Act 1995 and require a damp, mossy habitat.

The project is hosted by the Launceston Environment Centre and additional funds have now been received from Hydro Tasmania, DPIWE (Threatened Species Unit and Parks & Wildlife Service) and a World Wide Fund for Nature grant to enable a twelve-month study of the two species. Partnerships have been established with the Launceston Environment Centre community volunteers, Launceston City Council, Queen Victoria Museum and Art Gallery, Conservation Volunteers 'Green Reserves' program and the University of Tasmania.

The project aims to:

        locate mossy environments (dolerite boulders, rotting wood and leaf litter) in the Launceston area, initially focusing on places where the species have already been recorded

        investigate the distribution and abundance of both invertebrates

        foster a greater understanding of threatened species conservation and management within the broader community, including direct training in habitat and species surveys and weeding trials and

        involve land and water managers in the conservation of both threatened species in areas under their jurisdiction.

Plomley's trapdoor spider

Plomley's trapdoor spider, Migas plomleyi, was first recorded in 1987 from the Cataract Gorge Reserve and described by Raven & Churchill (1989) from three accidentally collected female specimens. The specimens are lodged at the Queens-land Museum. Their habitat was recorded as 'moss-covered boulders along the Cataract Gorge'. The conservation status of this species is Endangered under the Tasmanian criteria and Critically Endangered under the IUCN 1994 criteria at the Commonwealth level. M. plomleyi is one of three endemic mygalomorph spiders in the family Migidae found in Tasmania and the only one with an above-ground burrow. Females are stout with a body length of 6.4 mm and have a brown cephalothorax with a black abdomen. The thin parchment-like sac used for shelter (up to 2 cm long) is similar in colour to the surrounding moss or soil and is located at the moss/soil interface on dolerite boulders. The sac door is concave, thin and moss-covered, and opens directly to the outside. An above-ground, parchment-like shelter sac is typical of Migas in New Zealand but atypical for most Australian mygalomorphs. Population density is probably <3/100 m2 in suitable habitat. M. plomleyi probably lives for five to 10 years, and their presence indicates soil stability (R. Raven, pers. comm. 2001). The spider is subject to predation by native wasps (and, we suspect, also European wasps) and is prone to death by flooding of burrows and burrow dislodgement. It is likely to quickly disappear from areas which are opened up by clearing, thus lowering the humidity of the microclimate (R. Raven, pers. comm. 2001).

Plomley's trapdoor spider, Migas plomleyi
(from a photograph)

Cataract Gorge snail

The Cataract Gorge snail Pasmaditta jungermanniae was described from the Cataract Gorge in 1879 by Petterd as Helix jungermanniae. It is a small to minute punctid land snail (2-3 mm diameter), slightly frosty/glossy and jet black/bronze in colour with no flecking or striping. The shell has a sculpture of very low, close riblets with faint spiral striae. It is easily confused with the more common and widespread Planilaoma luckmanii. P. jungermanniae occurs in small, widely spaced clusters of individuals and has been recorded from mossy boulders, leaf litter and rotting wood in the Cataract Gorge Reserve (1879), Notley Gorge (1984) and possibly West Arm (?) in the Tamar area.

Results

Surveys for mossy habitat were conducted in the Cataract Gorge Reserve, Trevallyn State Reserve, Corra Linn and Notley Gorge areas and rated for their quality/lushness. These areas are now being systematically searched for both species. To date three additional female M. plomleyi have been located (identified by Lisa Boutin, QVMAG), two in the Cataract Gorge Reserve and one specimen in the Trevallyn State Reserve. Pitfall traps have been set up in the Cataract Gorge in the hope of collecting wandering males looking for a mate. P. jungermanniae has been recorded from the Cataract Gorge Reserve only.

A collaborative program for the future management of both species has been set up involving environmental volunteers from the local community supported by land and water managers. The assessment of impacts on the quality of moss habitats is underway along with weeding and revegetation trials. Those impacts could come from fire, weeds, recreation (abseiling and rock-climbing) and high water levels (in Cataract Gorge), leading to flood-scouring of mossy boulders.

Pasmaditta jungermanniae
Drawing by Rhyllis Plant from Smith, B.J. and Kershaw, R.C. (1981).
Tasmanian Land & Freshwater Molluscs. Fauna of Tasmania Handbook No. 5.
Hobart: Fauna of Tasmania Committee, University of Tasmania.

Agency stakeholders and their management issues are:

        Launceston City Council manages Cataract Gorge Reserve and is concerned with weeds, recreation and habitat protection.

        Hydro Tasmania manages water levels in the South Esk River in Cataract Gorge for power generation.

        Parks and Wildlife Service (DPIWE) manages Trevallyn State Reserve and is concerned with recreation and habitat protection.

        The Threatened Species Unit (DPIWE) is concerned with protecting the two invertebrates at both State and Federal level.

Future project direction

As the project continues we will

        Continue to assess and monitor impacts on the quality of mossy habitats and liase with the appropriate land and water managers

        Write Listing Statements for both species (including Action Plans)

        Aim for formal listing of both species at the Commonwealth level

        Engage stakeholders in formal management agreements for the protection of both species.

        Increase public awareness of threatened species with interpretive panels funded from a World Wildlife Fund grant in cooperation with the Launceston City Council

        Educate and engage environmental volunteers to enhance, restore and establish key habitats for both species (WWF grant)

        Continue to survey for both species.

Sandy Leighton
Research Officer
Launceston Environment Centre
sandyleighton@tas.quik.com.au

More information:

Raven, R.J. 1989. A new species of Migas (Araneae, Migidae), with notes on Heteromigas in Tasmania. Bulletin of the British Arachnological Society 8(1): 5-8.

Bryant, S.L. and Jackson, J. 1999. Tasmanian Threatened Species Handbook: What, Where and How to Protect Tasmania's Threatened Animals. Hobart: Threatened Species Unit, Parks and Wildlife Service.

Odd tales from the overstorey
Invertebrata 21, November 2001

Your editor attended the joint conference of the Society of Australian Systematic Biologists and the Australasian Evolution Society in Melbourne in July. Invertebrates featured in 35 of the 80-odd talks and posters, but for me the highlights of the meeting were three presentations about gum trees. All three came from a eucalypt genetics research group at the University of Tasmania. Because the work of this group is so little known in the zoological community, I'm offering here an abbreviated and (hopefully) not too technical overview of their recent results. Be warned: your mind is about to be stretched.

Mt Arrowsmith

For some 40 years local botanists have known about a spectacular morphological gradient in the 'yellow gum complex' on Mt Arrowsmith, near Lake St Clair. Going downhill 1.5 km from the summit, the alpine shrub Eucalyptus vernicosa grades into the small tree E. subcrenulata, then into a much taller tree lower down which is sometimes classified as E. subcrenulata and sometimes as E. johnstonii. In southeast Tasmania the 'yellow gum complex' is spatially divided. E. vernicosa populations on top of Mt Picton and Hartz Mountain, for example, are well-separated from mid-elevation stands of E. subcrenulata, which on both of those mountains grades downslope into E. johnstonii.

How did this complex evolve? Did yellow gums at lower elevations give rise to E. vernicosa shrubs separately on each mountain? Or did E. vernicosa arise just once from a yellow gum ancestor and disperse across the State over time?

To find out, the UniTas group took leaf samples from yellow gums on all three mountains and analysed them both morphologically and genetically (McGowen et al. 2001). The genetic testing was based on electrophoretic separation of microsatellite DNA from leaf cell nuclei. In both analyses, the yellow gums grouped themselves into two classes: high-elevation E. vernicosa and E. vernicosa/E. subcrenulata intermediates, and lower-elevation E. subcrenulata and E. johnstonii.

In other words, E. vernicosa on Mt Arrowsmith is more closely related to E. vernicosa on Mt Picton than it is to the taller Mt Arrowsmith yellow gums. The idea that this shrub eucalypt evolved separately on each mountain isn't supported.

And the gradient on Mt Arrowsmith? Well, what looks like gradual variation in a single lineage is no such thing. Instead, there's a mountaintop yellow gum and a lower-elevation yellow gum. They meet at middle elevations and converge to the same morphology from different directions.

Sharing

The Mt Arrowsmith story warns us that the appearance of a eucalypt isn't a reliable indicator of its evolutionary history. From here on, the genetic results reinforce that idea and are very strange indeed.

McKinnon et al. (2001) looked at the DNA in eucalypt leaf chloroplasts, or 'cpDNA' for short. Like mitochondrial DNA, cpDNA is maternally inherited. A eucalypt's cpDNA comes from its seed 'Mum', not its pollen 'Dad'.

The UniTas group extracted cpDNA from 17 species in the subgenus Symphyomyrtus, which in Tasmania are the black, white, yellow, blue and alpine white gums. Leaves were sampled across the range of each species in the State. A particularly variable stretch of the chloroplast genome, the J_LA region, was sequenced, and the relatedness of the sequences from different samples was analysed using molecular genetic measures.

The group found that their 157 samples contained 15 different J_LA sequences, or haplotypes. These could be grouped into four families: J_c, J_s, J_i and J_et. If the conventional 'branching tree' model of evolution applied here, you would expect these four to be sorted out neatly by branches.

They aren't. Instead, the four families are scattered unpredictably among the 17 species. More remarkably, the haplotype families are geographically patterned. J_s, for example, is found in 12 of the 15 Symphyomyrtus species in Tasmania's southeast, but is completely absent from the north and west. Eucalypt species which carry J_s in the southeast carry J_c, J_i or J_et elsewhere. The J_i family lives in the southwest, where it's shared by E. globulus, E. ovata and E. vernicosa. J_et occurs on the east coast north to St Marys and west to Lake Augusta on the Central Plateau; it's carried by E. archeri, E. barberi, E. globulus, E. gunnii, E. rubida and E. viminalis.

Something very odd is going on. If cpDNA is passed from seed parent to seed parent, how can haplotypes jump across species boundaries - and why do they respect geographical ones?

Reticulation

The explanation favoured by the UniTas group is that there has been extensive past hybridisation in Tasmanian eucalypts.

Once upon a time there were separate cpDNA lineages. The climate deteriorated, and for thousands of years the separate lineages lived close to each other in small refuges in the landscape. The lineages couldn't swap chloroplast genes, but they could hybridise and share the genes carried by pollen. These pollen genes are nuclear and include those which determine morphology. Eucalypt A passed its cpDNA from generation to generation, but after many generations of being rained on by eucalypt B pollen, the hybridised descendants of A began to look like B, and to share B's habitat preferences.

This process happened repeatedly during the glacial/interglacial cycles of the Pleistocene. During interglacials, the hybridised lineages left their refuges and sorted themselves in the landscape according to their pollen ancestry. E. globulus near St Marys may look like E. globulus near Hobart, but its seedline history means it may contain residual genes of the semi-alpine E. gunnii.

With the shuffling of eucalypts among refuges during successive glacial/interglacial cycles, cpDNA sharing could even occur between morphological species A and C, which cannot hybridise, by a 'stepping-stone' model in which A hybridises with B, which later hybridises with C.

This is reticulate evolution on a massive scale, a mixing of lineages through time like the mixing of water currents in a braided stream. It would be interesting enough in a pair of species. In 14 of of our 17 gums, it's extraordinary. There is also genetic evidence (McKinnon et al. 1999) for reticulate evolution in the Tasmanian ash and peppermint eucalypts.

Blue gums from where?

Another cpDNA study looked at E. globulus throughout its range in Tasmania and in parts of Victoria (Freeman et al. 2001). A larger region of the chloroplast genome was sequenced ('J_LA+', 987 base pairs), yielding a data matrix with 40 variable characters in 270 samples. The matrix was analysed using phylogenetic methods.

Results confirmed previous studies using smaller molecular data sets. There are three major cpDNA lineages in Tasmanian blue gum: J_c, J_s and J_et. The J_c lineage also occurs in mainland Australian populations, along with two haplotypes not found here.

I mentioned above that J_s and J_et are geographically restricted in Tasmania. Analysis of the much more widespread J_c family uncovered a fascinating geographical substructure. One J_c subgroup is restricted to mainland Australia and the Furneaux Group in eastern Bass Strait. A second subgroup occurs in the Otways in Victoria, on King Island in western Bass Strait and in mainland Tasmania, but not in the Furneaux Group. In southeast Tasmania, J_c subgroups are regionalised, with narrow transition zones.

The genetic and spatial patterns suggest that the J_s and J_et lineages haven't moved very far from glacial refuges in the southeast and on the east coast, respectively. The J_c data indicate that the most recent land contact between Tasmania and Victoria was through western Bass Strait. Down that path came J_c blue gums. When they reached southern and eastern Tasmania, they hybridised with J_wt (Port Davey), J_s and J_et eucalypts, creating blue gum 'look-alikes' from non-blue gum seed donors.

Back to bugs

The work of the UniTas group is revealing extraordinary and unexpected patterns in eucalypt evolution in Tasmania. Most of the geographical patterning, however, looks pretty familiar to those of us who study slow-dispersing invertebrates like land snails, millipedes, landhoppers and stag beetles. Shared patterns indicate a shared history. While eucalypts were hybridising in refuges, invertebrates were living in their leaf and woody litter, and when the gum trees left the refuges, the invertebrates followed. An interesting question now arises: which of those invertebrates are 'good' species, and which - like our eucalypts - are reticulate mixtures of lineages?

Bob Mesibov
Queen Victoria Museum and Art Gallery

More information:

Freeman, J.S., Jackson, H.D., Steane, D.A., McKinnon, G.E., Dutkowski, G.W., Potts, B.M. and Vaillancourt, R.E. 2001. Chloroplast DNA phylogeography of Eucalyptus globulus. Australian Journal of Botany 49:589-596.

McGowen, M.H., Wiltshire, R.J.E., Potts, B.M. and Vaillancourt, R.E. 2001. The origin of Eucalyptus vernicosa, a unique shrub eucalypt. Biological Journal of the Linnean Society 74 (in press).

McKinnon, G.E., Steane, D.A., Potts, B.M. and Vaillancourt, R.E. 1999. Incongruence between chloroplast and species phylogenies in Eucalyptus subgenus Monocalyptus (Myrtaceae). American Journal of Botany 86: 1038-1046.

McKinnon, G.E., Vaillancourt, R.E., Jackson, H.D. and Potts, B.M. 2001. Chloroplast sharing in the Tasmanian eucalypts. Evolution 55: 703-711.

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