27 July 2011
However, there may be a more elegant way of doing this: getting the answer, quite literally, at light speed (and what could be more scifi than that?). Rob Cruickshank (Lincoln University - pictured, appropriately in a red shirt) and Lars Munck (Copenhagen University) have summarised a new approach to identifying species that does not use DNA and gets us closer to 'point and click' technology. The most promising new method involves beaming near infra-red light onto the surface of the individual you wish to identify (say a beetle). You then calculate the amount of absorption/reflection of light coming off the surface. It turns out that different species of closely related species will absorb different amounts of light and have distinct 'fingerprints'. So without even collecting a sample you could identify individual species. At the moment this can only be done in a controlled lab environment and we are not sure if it will work on all sorts of different species with precision but the future is looking bright for the first 'real tricorder'! Make it so.
This article was prepared by postgraduate student Olga Petko as part of the ECOL 608 Research Methods in Ecology course.
When we hear the word “biodiversity” magnificent tigers and cute koalas, beautiful coral fish and bright parrots first come to mind. But biological diversity or, to be more precise, species richness, is not about appearance or popularity but is simply about numbers. And no other group can claim to be richer in species than the insects.
Insects can be found almost anywhere: running on sand in hot deserts or making tunnels inside icebergs, flying over tropical forest canopy or hiding behind curtains in your room. Any habitat is a home to countless six-legged dwellers, one just need to look. Little wonder that mushrooms are not an exception. To look at fungi of New Zealand to find out who exactly finds them irresistible is an adventure on its own for such a dedicated entomologist as John Marris from Lincoln University.
The woodland insects associated with the fruiting bodies of macrofungi, i.e. mushrooms, include specialist fungi-eaters, generalist detritus feeders and all their associated predators and parasitoids. Marris and his colleagues used rotted commercial mushrooms (Agaricus spp) as a bait to collect insects from native beech forest (Nothofagus spp), native mixed forest, exotic conifers (Pinus radiate or Cupressus macrocarpa) and urban restoration areas. Overal 2 429 invertabrates were collected, which mainly consisted of beetles (Coleoptera), flies and midges (Diptera), also parasitic wasps (Hymenoptera). To name just a few interesting species: a parasitoid wasp of spider eggs Idris spp (Baeini), round fungus beetles Leiodidae, Saphobius spp (Scarabaidae) and moth flies Psychoda spp (Psyhodidae). Of course, as it always happens with these tiny creatures, among collected specimens were several newly-described genera and new species.
The list of insect species that are associated with mushrooms increases our knowledge of the nature of New Zealand. Worldwide habitat-specific insect assemblages are used as indicators of site quality and conservation value, as well as measurement of anthropogenic disturbance. The survey of Marris and his colleagues showed that two conspicuous native beetles Zeanecrophilus prolongatus and Saphobius can be used as good indicators of site quality. A handy method in assessing the remnant patches of New Zealand woodland. It also became clear that monoculture plantations of exotic conifers are not a wood equivalent of a desert and can compare favorably to native forests in terms of richness and diversity of insect faunas. What is most important these plantations can provide suitable habitat for indigenous insects too.There are many restoration projects in cities and around them. And here is the good news. The research brought new evidence that despite the fact that urban nature reserves are small in comparison to remaining native forest and low in total species richness, they still play a valuable role in conservation of invertebrates, providing a refuge at a local level.
This study was first of its kind in New Zealand. The “mushroom bait” method is not ideal, not all insects are attracted by the smell of commercial Agaricus. The researchers are sure that the use of any native New Zealand fungi as bait or alternative collection techniques will widen the species list of the citizens of Mushroom City.
22 July 2011
Such a situation may occur in the last stages of speciation, as it takes numerous generations for new species to fully diverge. Repeated crossing of hybrids with parent species is termed 'introgression' and this can often have negative impacts on the parent species, such as removing local adaptational traits. Because of these impacts, organisms usually have traits for avoiding mating with hybrids or members of closely related species. Luckily, introgression does leave its mark on an organism's DNA and can be readily detected. One group of organisms with a history of introgression is the spiders.
Within New Zealand there are four species of Dolomedes, a genus of large spiders spread around the world. Dolomedes aquaticus is found among the stones of braided riverbeds and D. minor in grass and scrub areas as well as swamps and other wet areas. Although individuals from these two species often come into contact and have the potential for interbreeding to occur, a study by Vink and Duperre found that this did not happen throughout New Zealand. Everywhere, that is, except the southern end of the range that they sampled where there was the suggestion of introgression occurring. Following up this study was the task for honours student Vanessa Lattimore with here supervisors Adrian Paterson, Rob Cruickshank (both Department of Ecology, Lincoln University) and Cor Vink (LU Entomology Research Museum and AgResearch). Vanessa sampled from braided rivers throughout the southern South Island of New Zealand and obtained Dolomedes specimens from 13 locations. She then examined a nuclear gene (actin 5C) and a mitochondrial gene (COI) for evidence of introgression.
Evidence for introgression was found with three haplotypes (versions of a gene region) from D. aquaticus being present in D. minor and this was recently published in Invertebrate Systematics, where it made the front cover! (Although I didn't buy 5 copies for my mother) Interestingly, there was no evidence for movement of genes from D. minor to D. aquaticus.
Why is the introgression only occurring in one direction? Because of the way that mitochondrial DNA is inherited, the most likely reason is that males from D. minor are willing to mate with females of D. aquaticus whereas D.aquaticus males are either too big (they are much larger than D. minor males) or more picky than D. minor males. The geographical pattern of the three haplotypes are also different which suggests that these introgression events have happened at different places and probably at different times. A major question to arise out of this research is explaining why the introgressions occur in southern braided rivers and not elsewhere in New Zealand. The authors suggest that as braided rivers are prone to variable flows (from no flow to floods in short time periods) that D. aquaticus may be forced into the surrounding vegetation where D. minor are found from time to time.
21 July 2011
It has long been thought that ammonia oxidising archaea (AOA) (single celled micro-organisms which have no nucleus or any other bound organelles) only drive the nitrogen cycle in harsh environments. However, in a paper published in Nature, Linginer and colleagues discovered that AOA may be the most abundant ammonia oxidising organisms in soil ecosystems. This questions the traditional assumption that nitrification is dominantly the role of ammonia oxidizing bacteria (AOB) and begs to question what really is driving the nitrogen cycle in the soil?
Although it has been shown that AOB dominate the nitrification process in some agricultural soils, it is interesting to see how AOA may react to nutrient changes in the soil and in the presence of an inhibitory substance.
In a recently published study in the Federation of European Microbiological Societies Microbiology from Hong Di and his team at the Centre for Soil and Environmental Research, Lincoln University, they investigated the role of AOA and AOB in differing layers of soil and determined the effects of animal urine and a nitrification inhibitor (DCD) application on the two organisms. Samples from Waikato, Canterbury and Southland were collected to gain a holistic view of New Zealand soils. They found that AOA was more abundant in the soil than AOB in both soil layers with the bacteria decreasing in the lower layer. With the addition of urine AOB greatly increased whereas AOA seemed to be inhibited. This demonstrates that AOA and AOB prefer different soil nutrient conditions with AOA favouring low-nutrient environments.
Adding nitrification inhibitor sufficiently reduced the AOB nitrification rates and hence lowered nitrate leaching and nitrous oxide production. The AOA were inhibited by the urine addition but this could have been due to the urine or DCD which were both present in the treatment. It would be useful to determine the AOA reaction to the DCD alone. However, because nitrification inhibitors work by preventing the enzyme produced from the organism rather than targeting the actual producer, Archaea would most likely react in a similar way to the bacteria and be inhibited.
This study demonstrates that AOB are the hardest workers in the soil nitrogen cycle, although AOA should not be underestimated. AOA’s abundance in the soil suggests their importance, but the processes they undertake are yet to be understood. Continued research from Lincoln University will continue to decipher the roles of AOA and their potential presence in agricultural soils as well as their value in lower nutrient environments.
19 July 2011
Nature is full of wonderful and surprising phenomena. Organisms can often be linked directly or indirectly in amazing and unpredictable ways. It came as somewhat of a surprise when honeybees were discovered to have an impact on caterpillars. Common sense would suggest honeybees (Apis mellifera) and caterpillars would have little to do with one another, as honeybees increase plant fitness by pollination and caterpillars decrease plant fitness by herbivory.
Other relatives of the bees are not so benign. Wasps (Vespula spp.) are generalist predators and are natural enemies of many caterpillar species worldwide. Rapid wing movement while flying creates vibrations in the air, heard as a buzz. Previous research indicated that these vibrations stimulate special sensory hairs on caterpillars and pre-warn them that predators are present. The caterpillar will then stop moving and damage to the plant will cease, until the predator has gone. Occasionally, the caterpillars may even drop off the plant, if the predator gets too close.
Wasps could therefore be effective biological control agents to reduce pests. However wasps themselves are considered pests by many. Wasps are one of the most invasive insect pests in the world. They cause problems to agriculture, horticulture, wildlife and are a nuisance in urban environments due to their nesting and aggressive behaviour. Instead, a similar alternative buzzing insect is required. As honeybees are of high economic value and also create a buzz, they were thought to be a potential candidate. A new study was published in Current Biology by Jürgen Tautz and Michael Rostas (Lincoln UNiversity), in which they carried out an experiment to test whether particular herbivores would show the same behavioural reaction with honeybees, as occurs with wasps.
A field cage experiment was carried out using the beet armyworm caterpillars (Spodoptera exigua), as they are a generalist pest that feeds on at least 50 plant species. The caterpillars were applied to either bell pepper (Capsicum annuum), with or without fruit, or soybean (Glycine max). Honeybee hives were applied to half of the treatments, with the remaining half with no hives as controls.
When the honeybees were present, there was a significant reduction in leaf damage (60.6-69.3%). The caterpillars’ behavioural reaction to the honeybee buzz was similar to the reaction triggered by a wasp buzz. Honeybees created very similar air vibrations, at an almost identical frequency (Hz) to the wasps, which the caterpillars could not distinguish between.
These findings indicate that other caterpillar species with sensory hairs may also react to the presence of honeybees. Some smaller experiments were then carried out by Michael Rostás. The cabbage moth (Mamestra brassicae), a common European moth was then tested and did behave in a similar way in the presence of honeybees. The large white butterfly (Pieris brassicae) is another species which may potentially respond in a similar manner, as it responds to the air particle movement of hand clapping. Numerous other species worldwide could also be candidates, but future success may depend on honeybee densities in the area.
Honeybees can therefore not only perform pollination by transporting pollen from flower to flower, but also they may contribute to the reduction of plant damage by some herbivores. This unexpected interaction may prove to be a useful tool in the development of future integrated pest management programs.
07 July 2011
New toxins that are effective, humane and sociably accepted are desperately needed in New Zealand for predator control. Wildlife managers have relied upon too few toxins for broad control of many predator species. The development of a safer, humane, and predator specific toxin is highly desirable and long overdue for New Zealand predator control.
New Zealand wildlife evolved in the absence of mammalian predators. Birds (such as Kiwi, Mohua and Kokako to name a few) have particularly been impacted by the introduction of non-native predators, and this is reflected by the extinction of over 40% (Eason et al. 2010) of the pre-human land bird species.
Stoats (Mustela erminea) were introduced into New Zealand in 1884 for the control of rabbits which were reducing pasture production. Stoats moved from farmlands and into the native forests where they have become the most significant factor in New Zealand’s historic fauna decline. Their large home ranges (up to 100 hectares), excellent swimming ability, and furious appetite for any animal that moves, has made the stoat, one of the Department of Conservation’s (DoC) main targeted animals.
Control methods for stoats currently rely on labour intensive trapping and poisoning. However, the use of 1080 (sodium fluoroacetate) is becoming increasing unpopular in New Zealand, as public fears relating to the contamination of water supplies, possible sub-lethal effects on humans, welfare impacts on targeted species, and the potential of 1080 to kill native birds and other non-target species is still embroiled in controversy. At the present time there is no stoat specific toxin available.
Para-aminopropiophenone (PAPP) was investigated in the 1980’s as an alternative to 1080 for coyote (Canis latrans) control in North America. PAPP is a red blood cell toxin. This toxin works by reducing the oxygen supply to the brain, making animals lethargic, sleepy and unconscious prior to death, which is within 1 to 2 hours. This rapid time till death gives PAPP a high humane rating when compared with other toxins used worldwide.
PAPP was trialled by Connovation in conjunction with DoC at Lincoln University facilities, under the guidance of Professor Charlie Eason. Captured wild animals were given a PAPP paste within meat baits, which caused 95-100% mortality. There were no signs of discomfort, stress or vomiting associated with poisoning, and animals became unconscious quickly following ingesting the bait.
From this study , PAPP looks extremely useful for stoat control, with no toxins currently registered for use against stoats and few effective techniques are available to control them. PAPP has relative specificity for mammals, and is lethal to stoats at low doses. PAPP would therefore be a significant advance for wildlife protection in New Zealand. With stoats continuing to have significant impacts on a wide range of threatened birds, lizards and invertebrates, PAPP is a welcome relief for wildlife managers and long overdue.
Eason C., Wickstrom M.and Gregory. 1997. Product stewardship, animal welfare, and regulatory toxicology constraints on vertebrate pesticides. Proceedings of 50th New Zealand Plant Protection Conference. Pg 206-213
Gregory N., Milne L., Rhodes A., Littin K., Wickstrom M. And Eason C. 1998. Effect of potassium cyanide on behaviour and time to death in possums. New Zealand Veterinary Journal 46 pg 60-64
Littin K., O’Connor C., Gregory N., Mellor D and Eason C. 2002. Behaviour, coagulopathy and pathology of brushtail possums (Trichosurus vulpecula) poisoned with brodifacoum. Wildlife Research 29 pg 259-267
Littin K., Gregory N., O’Connor C., Eason C. and Mellor D. 2009. Behaviour and time to unconsciousness of brushtail possums ((Trichosurus vulpecula) after a lethal or sublethal dose of 1080 and implication for animal welfare. Wildlife Research 36 pg 709-720.
New Zealand has vast areas of highly modified and fragmented, disconnected landscapes. It is important for the conservation of biodiversity to understand the ecology in these modified, human-dominated landscapes. Urbanised areas and farmland both tend to be on low-lying land that is high in nutrients and resources and previously supported biodiversity hotspots. Remnants of native forest are rare pockets of once widespread species and are important in conserving biodiversity. Both remnants and restored native vegetation are important in the conservation of other native species, such as invertebrates. To maintain and increase biodiversity we must build on such remnants by restoring native plant species in altered habitats.
Landscape-scale patterns in fragmented areas provide an important understanding of the ecological processes driving invertebrate distribution and abundance. In New Zealand there are many small patches of native trees, which are not joined to a larger patch of forest making it difficult for invertebrates to move between areas to find food or a new habitat. These patterns have been explained by Ruth Guthrie and two other Lincoln University scientists, Hannah Buckley and Jon Sullivan, in their study of cabbage tree (Cordyline australis) damage by the larvae of the endemic moth Epiphryne verriculata Feld (Lepidoptera: Geometridae) in Christchurch, New Zealand.
Studying cabbage tree herbivory has helped to explain the abundance and distribution of E. verriculata. The larvae eat only cabbage tree leaves (i.e. they are monophagous), which means its ability to survive is dependent on the presence of the cabbage tree. This also means that the clearly identifiable damage on cabbage trees is a straight-forward way to determine the abundance of the moth larvae. Herbivory was measured by Guthrie et al. (2008) as the percentage of damaged leaves on a cabbage tree crown. Herbivory was seen on almost all trees across all sites, indicating a widespread presence of the moth in both natural and modified areas. Damage was higher in adult trees, this is likely to be because they provide a larger food source. Herbivory was also higher when few other cabbage trees were in close vicinity, which is a likely to be result of the moth larvae being monophagous – fewer cabbage trees means they will do more damage to less trees. The skirt of dead leaves on the cabbage tree was thought to be a refuge for adult moths but the presence or absence of a skirt appeared to have no impact on the level of damage. This may indicate that larval abundance is more dependent on the availability of food rather than suitable habitat for adults. The abundance and distribution of E. verriculata can help to explain more complex landscape-scale patterns.
There appears to be a pattern across the Canterbury Plains where endemic herbivorous invertebrates are present on their host plant regardless of landscape fragmentation. In the study by Guthrie et al. (2008) this was confirmed as larvae were found on cabbage trees in all landscape types. The widespread presence of larvae indicates that the availability of suitable host tress is the determining factor for the E. verriculata moth to be able to survive in an area. Native trees in both restored and urban areas provide potential habitat and food sources for invertebrates. This emphasises the significance of native flora in modified landscapes for maintaining invertebrate diversity, providing strong motivation to ensure we continue to promote native biodiversity through restoration in modified areas.
Guthrie, R.J., Sullivan, J.J. and Buckley, H.L. 2008. Patterns of host damage by the cabbage tree monophage Epiphryne verriculata Feld (Lepidoptera: Geometridae) across urban, rural and native forest habitats. New Zealand Entomologist 31: 77-87.
04 July 2011
Determining the ecology of freshwater streams is important because it contributes to our understanding of the effects of human activities on the stream and lets us monitor remediation strategies. The health of freshwater streams is typically determined by examining the diversity and abundance of fish and invertebrates. But there may be another way of determining the health of freshwater streams, in the form of tiny, microscopic bacteria. These bacteria may be useful as highly responsive indicators of changing environmental conditions.
Freshwater streams display both temporal (time) and spatial (space) differences. Time variation is a result of seasonal influences and space variation is due to flow regime, substrate type, water solutes, suspended materials and incident light exposure. It is believed that bacterial communities are good indicators due to their rapid life cycle. However, if we can’t see them, how do we know that they are present and observe changes? Bacteria can be detected using Automated Ribosomal Intergenic Spacer Analysis (ARISA) which creates ‘fingerprints’ of microbial communities. The ‘fingerprint’ produced is just like a human fingerprint, because it is unique to a bacteria species just like a fingerprint is unique to a person.
So how is ARISA used to construct a ‘fingerprint’? Unfortunately, it isn’t as easy as dipping bacteria into ink and pressing them against paper. First, the DNA has to be extracted from the cells and then DNA sequences are identified for each species. The length of the gene region varies between different species and this difference in length allows a unique ‘fingerprint’ to be constructed for each species.
In the study “Spatial and temporal heterogeneity of the bacterial communities in stream epilithic biofilms” conducted by Gavin Lear from Lincoln University, the time variation in biofilm communities was analysed over a range of spatial scales. It was expected that the main study site, Cascade Stream, located within the Waitakere Ranges, west of Auckland, New Zealand, would have uniform water chemistry characteristics. Interstream variability was also assessed using samples from a second stream. It was hypothesised that there would be no significant bacterial variation on a spatial scale and that the temporal variation in the two streams would be similar.
The study found that the differences in bacterial communities were greater between streams than within the same stream. Significant spatial variation observed in the principle study site suggests that the hypothesis stating that there would be no significant bacterial variation on a spatial scale must be rejected. Greater variation was observed on the same rock than between sections of rocks and this indicates that reduced community similarity with increased physical distance was not observed.
So spatial variation was observed, but what about temporal variation? It was found that temporal variation was greater than spatial variation. The microbial communities not only changed over time, they never returned to their original composition over the duration of the study.
Now that we know that both spatial and temporal variation were observed we need to know why. The study concluded that water temperature and irradiance had the greatest influence on the bacterial communities. The most significant variation occurred when the warmest air and water temperatures were recorded.
In conclusion, ARISA was successfully used to determine spatial and temporal variation in bacterial communities in a freshwater stream with temporal variation having the most significant effect. Water temperature was identified as causing the greatest variation. Overall, the use of bacteria as indicators of freshwater ecology looks promising and should prove to be a sensitive technique of understanding the effects of human activities on freshwater systems and monitoring remediation strategies.
Lear, G., Anderson, M. J., Smith, J. P., Boxen, K. & Lewis, G. D. (2008). Spatial and temporal heterogeneity of the
bacterial communities in stream epilithic biofilms. FEMS Microbiology Ecology, 65. 463-473. Retrieved from
Morgan, J. (2009). May the stream be with you. Retrieved May 22, 2011, from
01 July 2011
Communities around New Zealand are becoming more aware of the state of natural areas in their community and how they are becoming degraded from pollution. This awareness has resulted in restoration projects that begin with good intentions and enthusiasm but come to a halt because of a lack of understanding of ecological knowledge about the ecosystem that is being restored.
The Styx River originates in the suburb of Harewood, Christchurch. Springs feed the river as it moves north-eastwards through residential, horticultural, agricultural, and lifestyle developments as well as conservation reserves before it empties into the Brookland Lagon. The Styx River has two main tributaries, Smacks Creek and Kaputone Stream. The Styx Living Laboratory is a community restoration project that has a mixed board of scientists that help the community to keep going in their restoration project. Kelly Walker, senior tutor in biology at Lincoln University, is one of the scientists working on the Styx Living Laboratory Trust restoration project by contributing her knowledge of fresh water invertebrates to the community and is on the board of management.
The aim of the trust is to restore the Styx river catchment in 40 years to an urban nature reserve by creating a living green corridor from the top of the Styx river catchment to where the river empties into the Brookland lagoon. Restoring the Styx river catchment includes both riparian plantings and in-stream restoration. A living green corridor is the area surrounding a focal feature, e.g. river, track etc; that is planted in native plant species which allows wildlife to either live in or pass through it.
The Styx River is a spring feed water system that is suffering from a sedimentation issue. The springs are drying up due to urban development which is increasing the amount of sedimentation in the river and then causes problems for fresh water invertebrate’s living in the river. There has been no indication that the recent earthquakes have caused the springs to dry up, as the springs had started drying up before the earthquakes occurred. There are six monthly samplings in the Styx River and its tributary waterways, collecting data on water quality, invertebrate species and spring status.
Kelly helps the community members when they survey the Styx River and its tributary waterways in identifying the invertebrates that have been collected. This work keeps the community involved in the restoration project by up-skilling the community group, which keeps them interested and makes them feel that their work is valuable to the restoration project. This enables there to be a closer relationship between the scientists and the community members which helps everyone keep the restoration project going.
Kelly also looks after the summer studies conducted by Lincoln University students on different topics in the catchment area. Previous studies have been on fresh water invertebrates, assessing the restoration of Radcliffe Drain which was a box drain, terrestrial arthropod abundance and diversity, lizard abundance and diversity of algae in the Styx River. These studies have produced interesting and useful results, including a new species of algae. The work done by the Styx Living Laboratory trust, community and the summer students has produced data that can be used as an indicator of how healthy the Styx River catchment is and shows how communities working with scientists can increase their knowledge and skills to take on a major urban restoration project.