23 October 2013

A versatile fungus

This blog post was written by postgraduate student Jenny Brookes as part of the course, Research Methods in Ecology (Ecol608). Jenny revisits a Lincoln University research area that look at using fungus to kill insect pests published in 2011.

Writing a blog has proved more difficult than I remembered. Having a done previous blog in 2011 entitled jennysinsectcorner, I recall it as being easier than this one!!! Or perhaps memories fade. The brief for this blog was to base it on a research paper written by a staff member or student of Lincoln University at the time of publication. The paper I chose was ‘Persistence of Beauveria bassiana (Ascomycota:Hypocreales) as an endophyte following inoculation of radiata pine seed and seedlings’ which was written by four authors, including Professor Travis Glare of Lincoln University. Reading the paper has re-enforced my view of how incredible fungi can be.
The fungal genus Beauveria has numerous species (Beauveria bassiana,1 of which I will talk about here) that are simultaneously;
1. An endophyte, a fungi within a plant, helping the plant in a specific way,
2. An entomopathogenic fungus (that is a fungus within a plant that is a pathogen to an insect but not affecting the plant.)
3. Able to not just deter but to kill insects.

 Photo 1.  Beauveria bassiana with the distinct identification formation  of ‘cotton balls’. Photo by Jenny Brookes

Beauveria bassiana (photo 1) can be endophytic in several plant species. The idea is to inoculate a target plant, for example pines trees (photo 2,) and then when the trees are attacked by insects, the fungus will kill or deter those insects. Two Beauveria bassiana isolates (F647 and F668) were found in mature wild pine trees (Pinus radiata) and were used to inoculate pine tree seedlings by two methods-Seed coating and root dipping.

Photo 2.  Beauveria bassiana isolated from within a pine needle. Photo by Jenny Brookes
This raises more interesting questions of how a fungus can kill an insect. Infection occurs when conidia (the spores) land on the insect and germinate. The spore grows a germ tube and a special blob called an appressorium (Diagram 3) which penetrates the insect cuticle at the junction of plates in the insect's exoskeleton called sclerites.

 Diagram 3; Courtesy of APSnet illustrating the infection process in a plant. The germ tube grows into the appressorium then penetrates the cells. This is in a plant but the same principle works in insects penetrating the haemocoel or insect blood system.

The fungus invades deeper into the insect and eventually causes death. This is the trigger for Beauveria to make spores (sporulate) and protrudes outside the insect to release spores to continue its life cycle. The poor unfortunate  insect is eaten from within; a long and slow death (photo.4).
It could be considered a cruel and barbaric death. The fungi steals the ‘goodies’ out of the haemocoel and spreads slowly through the insect avoiding organs that will kill the insect prematurely. Even after the insects death it will continue to spread until there is nothing left and then it will protrude outside and sporulate. If this happened to us , this could be considered torture or worse. We see in photo 4 a weta which has been killed by a natural infection of Beauveria bassiana found in the wild and given to Professor T. Glare by a colleague.

 Photo 4.  A natural infection of Beauveria bassiana protruding from the cuticle of a weta (Orthoptera).Photo by Jenny Brookes

The insect killing skills of Beauveria are now being put to good use in bio-controls worldwide. It was used by USA to control fire ants. Cornell University did a study with grasshoppers and found that at lower temperatures, mortality of the grasshoppers increased.
Regardless of how cruel the insect world may be our society prefers to have natural solutions to man-made problems. Just two of many Beauveria-based commercial products developed so far are called Beaublast and Beaugenic made by a company in the North Island, New Zealand. I believe we will see more natural products especially fungal based, what do you think? Would you hire fungal killers to kill your insect pests?

Links to more sites for Beauveria bassiana you may want to explore.

Integrated Pest Management. http://www.hort.uconn.edu/ipm/general/htms/bassiana.htm
Beauveria bassiana  http://www.uoguelph.ca/~gbarron/MISCELLANEOUS/nov01.htm
Know your friends. The entompopathogen Beauveria bassiana. http://www.entomology.wisc.edu/mbcn/kyf410.html


Brownbridge M., Reay S.D. Nelson T.L. Glare T.R. (2012); Persistence of Beauveria bassiana (Ascomycota:Hypocreales) as an endophyte following inoculation of radiate pine seed and seedlings. Journal of Biological Control 61:194-200. http://www.sciencedirect.com/science/article/pii/S1049964412000102

American Phytopathological Society (APS)APSnet; Glossary accessed 29/4/2013; https://www.apsnet.org/edcenter/illglossary/Article%20Images/germtube.JPG

21 October 2013

Death by chocolate - Why human food poses a danger to clever kea

This blog post was written by postgraduate student Helene Rohl as part of the course, Research Methods in Ecology (Ecol608). Helene revisits a Lincoln University research area that look at the risks that waste has for kea published in 1998.

Kea are the only true mountain parrots in the world and are endemic to (only found in) the Southern Alps of New Zealand. Kea belong to the most intelligent bird group in the world, but sometimes their cleverness is counterproductive. 

Picture by anjuli_ayer
Some smart kea, for example, have learned to open the lids of rubbish bins to get to all the 'delicious' scraps we throw away. That this isn't healthy for them is probably obvious to every reader. But, what you may not know, is that people's favorite treat, chocolate, caused the death of an innocent, healthy kea at Aoraki/Mt Cook Village. Brett Gartrell from the New Zealand Wildlife Health Centre at Palmerston North and Chris Reid from the School of Biological Sciences at Wellington found this unfortunate fact during their examination of a dead kea and published their findings in the New Zealand Veterinary Journal in 2007. Chocolate, especially the dark variety used for cooking, contains natural toxins (theobromine, caffeine and theophylline) that can be lethal, if consumed in high doses. It seems that the 20 grams of chocolate that the adult male kea had eaten, was too much for the poor chap. Although this is the first reported case of a wild parrot dying due to chocolate consumption, the toxicity of chocolate to animals is not unknown. It has already been shown that chocolate can cause death in dogs.

Rubbish bins aren't the only human food source jeopardizing kea. Other curious kea prefer to explore the places where our scraps eventually end up: rubbish dumps. This sounds even more harmful compared to just one rubbish bin which is why Mark Jarrett investigated rubbush dump dangers for kea in his Master thesis at Lincoln University in 1998 . Mark discovered that some kea at the Arthur's Pass rubbish dump suffered from lead poisoning. The source of lead poisoning isn't necessarily the rubbish dump itself. It is more likely that the attractive source for lead poisoning are nail heads in huts or other building materials which are found outside of the rubbish tips. The rubbish dumps, concludes Mark Jarrett, may pose a threat to individual kea, but don't endanger whole kea populations, since only young and unexperienced kea get injured or die.

Picture by Brent Barrett
In fact, human food is a danger to kea in several ways: First, kea are mostly vegetarians, eating mainly roots, bulbs, leaves or fruits and occasionally some insects. But the human waste that they eat contains a lot of fat and sugar, doing the kea no good (as it does, by the way, to us humans, too!). Second, if young kea don't learn how to search for natural food (because they rely on our scraps) they may starve when they can't find something eatable in winter. Third, if leftovers or rubbish are easy accessible for kea, it may act as an invitation to explore the place, leading to more mischievous behaviour and risk of accident. 

Picture by Jem Copley
Another chapter of human and kea food associations is the feeding of wild kea, especially by tourists. Kea enchant the unknowing among us with their cheekiness and beauty. And before you can say 'tasty treat' tourists end up giving cookies to these clowns of the sky, ignoring happily the 'don't feed the kea' sign.

So for the future bear in mind: Keep kea away from chocolate! They aren't bird-brained at all, but human food does them no good.

Picture by Kiwihausen


16 October 2013

Bringing home the bacon - Male kea and their unusally big beaks.

This blog post was written by postgraduate student Jenny Dent as part of the course, Research Methods in Ecology (Ecol608). Jenny revisits a Lincoln University research area that looks atthe differences between males and females published way back in 1991.

"Argh, he's attacking the thermos!!"

This particular tourist doesn't seem overly thrilled about his first kea encounter. To be fair, said kea isn't exactly making a stella first impression. Dismantling someone's lunch is never a good icebreaker. But what basis did this tourist have for assuming that the offending kea was in fact a Mr Kea? Why not a curious Mrs Kea? Chances are he had no idea (nor did he look like he cared terribly much) but he's certainly not alone. In fact, many of New Zealand's early taxonomists were in the same boat.

Mr Kea or Mrs Kea? (Photo by Jennifer Dent 2013)
There was a widespread belief amongst New Zealand's early taxonomists that male and female kea could be told apart by their appearance. The problem was that no one was exactly sure HOW they could be told apart. They all had their theories of course, but for the most part these were vague and poorly tested. My personal favourite was the assertion that males could be identified by their "aggressive demeanour".

Surprisingly there was no quantitative assessment of the difference in size between sexes (called sexual dimorphism) in kea until 1991 when Alan Bond, Kerry-Jayne Wilson and Judy Diamond took it upon themselves to solve this conundrum once and for all. Their findings confirmed that kea do express a degree of sexual dimorphism. Males are about 5% larger overall, and, even more impressively, have upper bills which are 12-14% longer than their female counterparts. Now this difference may not seem like much, especially when you consider some of nature's more extreme examples of sexual dimorphism - but for a parrot species this is actually pretty extraordinary. Sexual dimorphism (differences between the sexes) relating to size is only found in seven of the 81 parrot genera. Furthermore, at the time of this study, only one other parrot - the Palm Cockatoo - was known to have bill size dimorphism greater than the overall difference in body size. Its no surprise then, that researchers were pretty keen to see if this uniqueness extended to the only other species in this genus, the kaka.

It would appear that it does. In 1999, Ron Moorehouse and his colleagues were able to demonstrate the presence of bill size dimorphism in the North Island Kaka. The level of dimorphism that they observed was very similar to that observed in kea, with male bills being 14% longer on average. Because of this similarity, and the rarity of the condition overall, there is thought to be a phylogenetic basis for this condition. In other words, it is assumed that kea and kaka have inherited this trait from a common ancestor.                                                                                                                        

With this new discovery in mind, researchers set about trying to explain how bill size differences could have arisen. The little evidence available seems to suggest that it may have arisen as a result of differential niche utilisation (a fancy term for the specialisation of male and females for different roles). In both kea and kaka, the females take on most of the chick-rearing responsibilities and the males assist by provisioning the female and chicks with food. Essentially Mrs Kea becomes a stay-at-home mum and Mr Kea is the breadwinner – think 1950's gender roles.

This all ties in with the bill size dimorphism because having a larger bill is thought to enhance a males provisioning ability. Food availability is strongly correlated with breeding success so natural selection would have favoured the larger billed males over time. Of course, at this stage, a lot of this is based on speculation and assumption. It will be interesting to see how this hypothesis stands up in future studies. However, if you just can't wait for these future studies and want to discover more right now, I suggest you start with these two papers:
Bond, A.B., Wilson, K.J. & Diamond, J. (1991) Sexual dimorphism in kea Nestor notabilis. EMU, 91, 12-19.                                                                                              
Moorehouse, R. J., Sibley, M.J., Lloyd, B.D.  & Greene, T.C. (1999) Sexual dimorphism in the north island kaka Nestor meridionalis septentrionalis: selection for enhanced male provisioning ability? Ibis, 144, 644-651.

14 October 2013

Can natives species make a comeback in Christchurch's urban woodlands?

This blog post was written by postgraduate student Denise Ford as part of the course, Research Methods in Ecology (Ecol608). Denise revisits a Lincoln University research area that measures the re-emergence of indigenous forest  in Christchurch published in 2004.

Can Christchurch move away from the image of an "English garden city" to a city which reflects its indigenous natural heritage?  Research on the regeneration of native species within urban Christchurch has shown definite signs that indigenous forest can reappear in the city. This move then, may well depend on changes to the cultural and aesthetic values held by many Christchurch citizens.

Christchurch Botanical Gardens and the Avon River (by Steel Wool)
The city of Christchurch was a planned English settlement and, in the 150 plus years since the arrival of the first settlers, it has developed into a typical western urban centre. The need for familiarity, nostalgia and shelter on an exposed Canterbury site meant that much of the urban habitat became reflections of English country gardens and parks. The indigenous flora was replaced by exotic species. Trees from Europe, North America, Australia, Asia and Africa now dominate the woodlands of the city. Some pre-colonial plants survived in small pockets in and around the city but in a much reduced form.
Riccarton Bush (by Steel Wool))
In 1993 the Christchurch City Council recognized the high ecological value of many of these remnant patches and designated them as ecological heritage sites. The Kahikatea (Dacrycarpus dacrydioides) forest at Riccarton Bush is one site identified. The bush is a small remnant of podocarp forest which has survived Polynesian settlement and 150 years of urbanisation. In the last decade over a million indigenous trees, shrubs, tussocks and wetland plants have been planted in the city, not without controversy from some sectors of the community. The Christchurch City Council is actively involved in the protection and restoration of remnant areas, Travis Wetland being one example. The ongoing restoration of such sites and the inclusion of native plants in public and private land along with earlier plantings of native podocarps form a seed source from which dispersal and regeneration can occur.

Glenn Stewart and his colleagues,  Maria Ignatieva, Colin Meurk and Richard Earl, examined the exotic and indigenous shrub and tree components of urban Christchurch and how it affected the food and habitat of native birds. Their investigations of records kept by the Christchurch City Council showed that over 80% of the 50,000 plus trees planted in the cities parks and streets by local government were exotic. Most of these exotic trees are dry fruit bearing and have no or little value as a high energy food for native wildlife. In contrast to public areas, suburban gardens contained a greater proportion of native woody plants.  The majority of native plants in the city are those that produce fleshy fruits and nectar which are important food sources for native birds, lizards and invertebrates.
Regeneration of native seedlings
 (Coprosma robusta)
 ( by Elisa Ruiz used with permission)
Glen and his colleagues were also interested in the regeneration rates of exotic and indigenous vegetation within the city. They sampled parks and suburban gardens, finding a significantly higher number of indigenous seedlings than exotic woody species. This difference may be explained by seed dispersal in which wind and birds play an important role.

Many wind dispersed exotics in the city have poor dispersal ability, whereas native species, such as lowland ribbonwood (Plagianthus regius) and akeake (Dodonaea viscosa), have light seeds that can travel long distances. Seedlings are quite often found under trees where birds have perched and passed the fruit they have eaten. Only 26% of exotic species have edible fruit compared with 78% of indigenous species.

With an available seed source and the regeneration ability of indigenous species there are positive indications that the re-emergence of an indigenous-dominant woodland forest is possible. Of course sociological factors will also come into play; many citizens are comfortable with the English nature of our city and are reluctant to see a dominance of indigenous species.

This study is very pertinent to Christchurch in 2013 given the abandonment of land in the residential red zone following a series of major earthquakes in 2010 and 2011.
Map of the Residential Red Zone. The land in red has been deemed unsuitable for rebuilding.
Sourced: http://www.fix-it.co.nz/index.asp?s1=news&s3=Christchurch%20articles

In September 2012 a survey of indigenous and exotic seedling regeneration was conducted in nine suburbs (a total of 90 properties) in the red zone. The results of this survey indicated that seedling regeneration was following the preliminary seedling study done by Glenn and his colleagues in 2004. The number of indigenous seedlings found was considerably higher that the number of exotic seedlings. The two most numerous seedlings were indigenous; Kohukohu Pittosporum tenuifolium, and Cabbage trees (Cordyline australis) With the abandonment of properties, gardening practices such as weeding and mowing no longer occur. This 'neglect' has allowed, in some cases, the proliferation of indigenous species.

Is this an opportunity, with control of aggressive exotics, to see the transformation of a Christchurch urban woodland "to a new kind of indigenous-dominant forest biotype" as envisaged by authors of the 2004 paper? The red zone opportunity will not only benefit the indigenous plant biodiversity of the city but will allow our native wildlife to make a comeback. I am looking forward to a city that represents the  natural fauna and flora of the area and the cultural sense of being that it will bring.

Check out Glenn's blog Natural disasters and the nature of cities regarding the Canterbury earthquakes and subsequent vegetation dynamics in the residential "red zone".

This blog is based on the journal article:
Stewart, G. H., Ignatieva, M. E., Meurk, C. D., & Earl, R. D. (2004). The re-emergence of indigenous forest in an urban environment Christchurch, New Zealand. Urban Forestry & Urban Greening, 2, 149-158.

10 October 2013

The origin of the faeces: snail tales of earthworm dinners

The view from Stockton Plateau
'Scrubs' is one of my favourite comedy series. I really enjoyed the (often extremely) odd jokes and situations. Scrubs was around long enough that they qualified for a musical episode, called My Musical. Many long running series eventually have an episode where the cast sings. The concept suited Scrubs as in the episode a patient has a brain tumour which means she hears everyone singing. There are eight great songs, including 'Guy Love' but the one that I remember best is 'Everything comes down to poo'. This song basically says that doctors learn a huge amount about a patient through their bowel movements. The song includes the great line "Your number one test is your number two". Certainly, as ecologists, although not everything comes down to poo, there is a lot of information that we can retrieve from this great organic resource. Finding faeces in the field can tell you where an organism has been and what habitat it has utilised, maybe how many there are, and, obviously, what it has been eating (which can also tell you about other species that are in the area). We can tell what has been eaten by looking at distinctive hard bits of prey, like otoliths or fur, or chemical signatures or DNA. DNA is particularly useful for diet species that are soft-bodied or mainly liquid.

New Zealand is home to carnivorous snails, mostly in the Powelliphanta genus. Although it is hard to imagine a snail moving fast enough to catch prey, Powelliphanta make a good living catching other slow moving species, like earthworms, and slurping them down like spagetti. Powelliphanta are often large (sometimes as big as your hand) and many species are found in north western South Island. Being so large also makes Powelliphanta a target for other, often introduced, carnivores and many of these snail species are threatened or endangered. One such species is Powelliphanta augusta which is found on the Stockton Plateau on the West Coast. Unfortunately, it's habitat overlaps significant coal measures which are accessed through open cast mining. In order to preserve this species while accessing the coal, over 6000 adult snails have either been relocated to adjacent undisturbed habitat or cultured in captivity for eventual release back to the remediated site. One of the key pieces of knowledge to help with the success of this project is understanding what the diet of these snails is made up of. Powelliphanta are largely nocturnal and cryptic and the best way forward was to collect their poo and sort out the origin of the faeces.

Stephane Boyer from Lincoln University has worked closely with the relocation process. A new paper in PLOS One details his work on establishing the diet of P. augusta. Snails were collected at Stockton and individually placed in plastic containers for 48 hours. Faecal strings produced during this time were collected for DNA analysis. There were few to no hard parts in the faeces. In order to look at the potential food available about 1500 earthworms, over a period of two years, were collected from Stockton. DNA was obtained from 139 worms and 18 species were identified. The earthworm DNA provided a library of earthworm species found in the area that could be compared to the snail diet. This comparison would allow Stephane to test whether P. augusta is a generalist (feeding on any earthworms they can find) or a specialist (needing certain species of earthworms to survive). Faeces from 46 snail individuals were analysed. Earthworm DNA was detected in 75% of the snails. Around three to four different worm species were usually found in each faeces string with one species, Deinodrilus gorgoni, making up 40% of the earthworm samples. D. gorgonis was found in almost all snails (that had earthworm DNA) and overall there were five worm species that were in more than half of the snails. Six of the worm species were found rarely (less than 10% of the snails) and two were not found at all. The pattern of abundance of the earthworm species in the environment was similar to the proportions in the snail diet (e.g. if they were rarely found at Stockton they were rarely found in the snail faeces) which suggests that P. augusta forages randomly through the leaf litter (i.e. eating common things more often than rare things).

Powelliphanta high tea... "soft & wriggly"

The diet study reveals that P. augusta is a generalist predator of earthworms and are happy to eat anything they find as long as they are soft and wriggly. This is good news for conservation of P. augusta as they are not tied to a having to eat specific species of earthworms which would also have to be carefully preserved. The prospect of successfully re-introducing the snail back to its remediated site looks a lot more likely to work. This finding could only have been discovered looking at DNA in the faeces. As the song says "It may sound gross, you may say shush,but we need to see what comes out of your tush"! Advice for the ages...thanks Scrubs!