Going for birds: my top 6 places for bird watching in New Zealand

Posted by Daria Erastova @Kuukso

My big dream was to study New Zealand native birds. To my utter happiness, I finally joined the friendly Ecology Ngātahi labgroup under the supervision of Margaret Stanley to study ecology of urban native birds. However, I have just started my PhD project and I hope to give you some insights on that later. Instead, I will share some of my experiences birdwatching in New Zealand. Birds of a feather flock together – I found this pastime quite popular in New Zealand, so today I share my top six places to find native birds!

No. 6: Dunedin Botanic Garden, Dunedin.

The famous Dunedin Botanic Garden lies within the city’s green belt and is very big. This, along with numerous old and flowering trees growing there makes this place an excellent haven for birds. Many native species scurry here and there: tui, bellbird, silvereye, fantail etc. There is also an aviary with captive kea, kaka and kakariki.

Sylvereye

Silvereye

No. 5: Point England Reserve, Auckland.

This spacious reserve connects with other coastal reserves and is maintained, allowing you to spend a whole day there. This amazing place enables you to get  a wildlife experience while staying New Zealand’s largest city. Here you would can find a variety of shore and forest birds. I counted 25 species in a day, including natives like shelduck, kereru and rare little black shag.

Kereru

Kereru

No. 4. Urupukapuka Island, Bay of Islands.

I was not keen to go there. Urupukapuka proved I was wrong as it turned out to be an outstanding place for birdwatching. In fact, I beat my personal record and identified 27 species in 3 hours! My most interesting encounters were banded rail, New Zealand dotterel, tomtit and North Island robin.

shelduck

Shelduck

No. 3. Otago Peninsula, Dunedin.

Except for the famous Royal Albatross Colony, where you can also spot Stewart Island shag, and the Penguin Place, with grumpy yellow-eyed penguins, there are other places worth visiting. For example, the Hooper Inlet, inhabited by sacred kingfisher, white-faced heron, grey teal and swamp harrier. The other place is Portobello Bay with royal spoonbill, pied oystercatcher and the cutest little shag. Finally, go to Tomahawk Lagoon for pied stilt or spur-winged plover.

little shag

Little shag

No. 2. Tawharanui Regional Park, Auckland.

What is special about this beautiful peninsula is that it is surrounded by a pest-proof fence and has a variety of habitats, including old forests with kaka (you are highly likely to see or hear one), river thickets with spotless crake and seashores with pipits.

No. 1. Tiritiri Matangi, Hauraki Gulf.

This reserve does not need any introduction being one of the most popular tourist attractions in Auckland. After predator eradication and forest replanting the island became the bird paradise. There you all the chances to have a close encounter with species you would never or hardly ever see anywhere else, e.g. little spotted kiwi (one passed 25 cm away from me!), takahe, kokako, brown teal, stitchbird and many more.

I hope this list was useful and enjoyable for all nature lovers. It is based on my limited experience, and there are many other fantastic places, which I am eager to explore. Therefore, if you need a volunteer for your bird fieldwork or a companion on a birdwatching trip, please feel free to contact me.

 

kokako

Kokako

 

DariaphotoDaria is a PhD candidate studying the influence of garden sugar feeders on native bird behaviour and health, and whether feeders alter the contribution these birds make to pollinating indigenous plants. She is supervised by Margaret Stanley, Kristal Cain and Josie Galbraith.

 

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Coevolution in exotic herbivores and weeds

Posted by Melissa Kirk @MGKir_04

Evolution and adaptation

Exotic species have the potential to adapt and rapidly evolve in their new introduced ranges. This can have multiple consequences including changes to their host preference, defence mechanisms, growth rates and biomass, climate tolerance, fecundity and phenology. These changes can lead to an increase in abundance, range expansion, and a difference in their overall impacts.

birds evoSuch adaptations are highly likely due to the multiple new selective pressures they may encounter. For example, new selection pressures may occur as they encounter new competitors, new climates and new habitats. These adaptations and trait shift changes can occur in relatively short time periods, within a few generations. The absence of competitors and natural enemies can lead to relaxed selection, and thus a change may occur through a non-adaptive shift. A non-adaptive shift may not translate to a genetic shift initially; however, such shifts can lead to reproductive isolation and subsequently speciation.

Adaptations in plant-herbivore systems

There are two key theories behind why many plant species become weeds: the ‘enemy release hypothesis’ and the ‘novel weapon hypothesis’. The theories state that either the lack of natural enemies in the new introduced area or the presence of novel defence mechanisms which allows no or low herbivory to occur in the new environment. Thus the role of coevolution between weeds and specialists herbivores has also been attributed to plants invasiveness. If a plant has escaped its specialised herbivores, there is no need to produce costly defence mechanisms and this energy and resources can be used for growth and increased competitiveness in its new introduced range. An example of this is when the wild parsnip, Pastinaca sativa invaded the US, and after many generations without its coevolved enemy the webworm, Depressaria pastinacella its levels of defence chemicals reduced. However, after the webworm became established within the US and the plant-herbivore system were reunited; rapid evolution resulted in increased levels of defence chemicals (Zangerl & Berenbaum, 2005).

Re-association: wild parsnips and webworms in New Zealand

webworm

Image source: Tarmo Lampinen, 2013

Wild parsnips also occur within New Zealand, like in the US, parsnip populations went many years without the webworms. It wasn’t until over 150 years after the establishment of the wild parsnips that the parsnip webworms were accidentally introduced into New Zealand. A previous study found that for wild parsnips in NZ, the re-association with their natural enemy the webworm did not result in an increase of defence chemicals, rather an increase in plant size (Jogesh, Stanley & Berenbaum, 2014). Therefore a switch in strategies seems to have occurred from resistance using chemical defence to tolerance via the plants size, however, whether this change is a true adaptive shift needs to be investigated.

As part of my PhD research on the ‘rapid evolution of exotic species’ I am planning on researching exotic herbivores and weed interactions, and how they can influence each other’s evolution. For this I am planning on investigating the wild parsnip and webworm interaction in NZ. I am also planning on investigating the interaction between nodding thistle and its exotic herbivores in NZ, like that of the wild parsnip it is thought that the presence of the nodding thistles natural enemies has influenced the traits and evolution of the plants growth and reproduction.

Key references:

Blossey, B., & Notzold, R. (1995). Evolution of increased competitive ability in invasive nonindigenous plants: a hypothesis. Journal of Ecology, 83(5), 887-889.

Callaway, R. M., & Ridenour, W. M. (2004). Novel weapons: invasive success and the evolution of increased competitive ability. Frontiers in Ecology and the Environment, 2(8), 436-443.

Jogesh, T., Stanley, M. C., & Berenbaum, M. R. (2014). Evolution of tolerance in an invasive weed after reassociation with its specialist herbivore. Journal of evolutionary biology, 27(11), 2334-2346.

Müller-Schärer, H., & Steinger, T. (2004). Predicting evolutionary change in invasive, exotic plants   and its consequences for plant–herbivore interactions. Genetics, evolution and biological control, 137-162.

Zangerl, A. R., & Berenbaum, M. R. (2005). Increase in toxicity of an invasive weed after    reassociation with its coevolved herbivore. Proceedings of the National Academy of Sciences, 102(43), 15529-15532.

Melissa is a PhD candidate within the Centre for Biodiversity and Biomesecurity, School of Biological Sciences at the University of Auckland. She is studying rapid evolution in exotic species, and is supervised by Darren Ward, Thomas Buckley and Quentin Paynter. Email: mkir508@aucklanduni.ac.nz

Simple Words and Storytelling: Communicating Science to a General Audience

Posted by Olivia Rooke-Devoy (BSc(Hons) Candidate)

If a tree falls in the woods and [we don’t communicate it to someone], does it make a sound?

How important is it that scientists communicate and disseminate their ideas to the wider public?

fallentree

Credit: Miri Schroeter

Scientific communities now face climate change denial, anti-vaccination movements, ‘detox’ diets and, bizarrely, a resurgence of Flat-Earth believers. In view of these challenges, it seems that science communication is just as important as the science itself. Ultimately, by educating societies, we as researchers encourage better social and political decision making.

However, science communication is challenging. David Chambers’ well-known ‘Draw a Scientist’ test (1983) demonstrates that, from a young age, people view scientists as aloof and antisocial. My own research of urban lawns in Auckland has stirred controversy. Many people have rejected the premise immediately: “I like your idea, but I won’t stop mowing my lawn!”. Preconceived notions of science and the emotive subjects we study make for critical (and often unfriendly) audiences.

Faced with these difficulties, how do we communicate complex scientific ideas, so general audiences understand? Common techniques, such as using less jargon, sound great in theory but are hard in practice. For example, the Ten Hundred Words of Science blog challenges scientists to use the 1000 most commonly used English words to describe their research. Here’s my own attempt:

“What are the impacts of varying mowing regimes on lawn species assemblages in urban lawns?” becomes “what happens if city people cut green low-growing things less?”

Have a go at the challenge yourself.

Explaining scientific ideas in a straightforward way is difficult. However, using ‘simple’ language and crafting a science narrative makes our subjects accessible. Storytelling in science, taking the form of analogies and personal stories of successes and struggles, connects many types of people. This form of communication opens science to previously-excluded groups and makes science more inclusive and diverse.

Contemporary communication is instantaneous and global. In this modern age, what is a ‘scientist’? Overall, I believe that part of what makes a scientist is the ability to communicate ideas. If a tree falls in the woods and you don’t tell me, how can I care that it made a sound?

Further Reading:

Chambers, D. W. (1983). Stereotypic images of the scientist: The draw-a-scientist test. Science Education, 67(2), 255–265. https://doi.org/10.1002/sce.3730670213

Salmon, R., & Priestley, R. (2015). A future for public engagement with science in New Zealand. Journal of the Royal Society of New Zealand, 45(2), 101–107. https://doi.org/10.1080/03036758.2015.1023320

 

Olivia is an Honours student at the School of Biological Sciences, University of Auckland. Her research is focused on encouraging low-cost, biodiverse lawns in Auckland. She is supervised by Dr Bruce Burns. For further information regarding this research, please visit https://urbanlawnsproject.weebly.com/

Selective reporting: The abuse of statistics

Posted by Andre M. Bellve (MSc Candidate)

As a quick preface – what I am talking about in this post isn’t new or revolutionary. My intent with this blog is to package some of the facts in a more digestible form and hopefully steer my fellow biologists to better practice.

When we carry out statistical significance tests (I.e. ANOVAs, t-tests, etc) there are two types of errors associated with them: False positives: falsely rejecting the null hypothesis, H0, and; False negatives: falsely accepting H0. Every test has these two errors in them and they are inversely proportionate to each other. A significance level of 0.05 means that 5% of the time we will incorrectly reject the null hypothesis. This is the basis of selective reporting, A.K.A p-hacking. Collectively, we have (for the most part) deemed a 5% cut-off as acceptable, at least when we aren’t betting on human lives, and I tend to agree.

What if the chance was higher though? If there was a 10% or 25% chance of false positive, would you still trust your results? You might be thinking: “Well that’s silly Andre – who cuts off their p-values at anything higher than 0.05? ” Well here’s the catch: if you carry out two significance tests, and both have a cut-off for significance at 5%, then the chance that there is a false positive is no longer 5% – it is much higher. This inflating of the overall error rate is the basis of p-hacking. The chance of a false positive is also increased when making pairwise/multiple comparisons!

type1error

Credit: Statistical Statistic Memes via Facebook

Now this isn’t the end of the world – you can correct for it. The read significance level that you set as your cut-off defines the overall error rate of your experiment – both the type I and II error rates. If you are doing several tests, then you have to correct for the increased chance of a false positive. Fortunately, it’s relatively easy to do! There is the extremely conservative Bonferroni’s correction where you divide your significance level by the number of tests you are doing, which is appropriate in some cases (i.e. when it’s a case of life or death). This isn’t popular among biologists as we often deal with very noisy data and it can be hard enough to pick up a signal as it is. For this reason, the less conservative False Discovery Rate (FDR) correction works well when lives aren’t on the line, as it typically leaves at least one significant result without sacrificing the integrity of your analysis. This is not an exhaustive list and you can read more about different methods for correction here.

Selective reporting happens a lot. One recent example came out of the sensory science food labs from Cornell University: Brian Wansink, director of the Food and Brand lab at Cornell, boasted online that a volunteer research assistant of his was able to take a “failed study which had null results” and produce ‘significant’ results from it (Science of Us, 2016). However, careful investigation of the published papers yielded multiple errors and inconsistencies suggesting that the research assistant had ‘p-hacked’ the data to produce these results, although it seemed she had done so unwittingly. It is this kind of behaviour that brought about an analysis by Ioannidis (2005) which found that most published research findings are actually false. The incorrect use of these methods can put at risk the objectivity of the traditional scientific method and create issues of credibility for the scientific community. With more “fake news” and anti-science rhetoric being thrown around than ever before the last thing we need are blows to our credibility or any more fuel being added to the tangerine tire fire that is my president.

tangerinetyrefire

Image Credit: politicususa.com

References

A Big Diet-Science Lab Has Been Publishing Shoddy Research — Science of Us. (n.d.). Retrieved April 8, 2017, from http://nymag.com/scienceofus/2017/02/cornells-food-and-brand-lab-has-a-major-problem.html

Ioannidis, J. P. (2005). Why most published research findings are false. PLos Med, 2(8), e124.

 

 

Don’t mention the P word

Posted by Tom Bodey

Scientists are always trying to communicate their research and ideas across a wide spectrum of media to varying degrees of success (and I can already feel the hoisting of my own petard here). Some of the difficulties arise because a researcher can apply caution and caveating to their results, whereas recipients may prefer to see a clear-cut outcome that makes for more straightforward decision-taking for example. However, scientists do not always help themselves, either by using jargon, or through the avoidance of terms because of the connotations they may imply.

For my latest research I have decided to enter one of these minefields by looking at individual variation in behavioural responses – you see, I’ve done it myself. This variation, particularly if examined across contexts, has been given a range of names within the scientific literature – behavioural syndromes, coping styles, behavioural tendencies – all of which shy away from the dreaded p word – ‘personality’. Now, of course, there are obvious reasons why a researcher may choose to avoid this word, and certainly to use it within air quotes. After all, without becoming Dr Doolittle, it’s pretty hard to get into a non-human head to actually assess their personality, and what you have instead is the examination of a handful of behaviours where individuals differ in their responses.

image1

Welcome to the office. Rakitu Island study site – you don’t get many laboratories with views like that.

However, even on these highly simplified ‘personality’ scales, it is becoming increasingly obvious that individual animals often differ substantially, and also consistently, in their behaviour. For example, some individuals from species as different as prawns, hyenas and albatross can be bolder, more active, or more social than others, and this variation can then affect other aspects of their lives such as how they find food. These differences are especially intriguing as the maintenance of variation stands in contrast to the movement of species towards a fitness peak. In order to maintain variation, there must be situations in which one set of behaviours are beneficial, and contrasting situations where different individuals prosper – any peak must shift through time or space.

Not content with dipping my toe into an area with such linguistic juggling, I thought I would combine this with invasive species – another area where terminology can take on unfortunately loaded connotations – by looking at individual variation across a range of niche dimensions in everyone’s favourite critter, the humble rat. The Chinese, of course, recognise the rat as the first animal within their zodiac cycle, embodying alertness, spirit and intelligence (as well as being timid, devious and gossipy to balance it out). New Zealand is ‘blessed’ with three species – all invasive and globally widespread – the Brown/Norway Rat Rattus norvegicus, Black/Ship Rat R rattus and the Pacific Rat/Kiore R exulans. I’ve been catching wild rats on offshore islands in the beautiful Hauraki Gulf, running them through behavioural trials in the field before releasing them in order to do it all again the next day, and the next.

image2

Taking pictures of rats in livetraps is tricky. This is a kiore.

Right now I just have a lot of home video, but ultimately this work should provide insights into ecological theory – for example, the ways in which interference competition affects niche space occupancy at individual and species levels. It should also have applied applications for invasive species management. New Zealand, like many oceanic islands, is in the position of having no native terrestrial mammals, and thus can manage invasive mammals, should they choose to do so, in relatively straightforward and robust ways. However, elsewhere management must avoid harming native mammal species. Triaging of the system, making adjustments to maximise the chances of catching the individuals with the greatest potential to cause harm, would be the most cost-effective way forward if eradication is not possible or desirable. And if eradication is the goal, then you need to know there aren’t individuals that will avoid all control mechanisms. Either way, identifying those individuals with a ‘troublemaking personality’ (as any press release might say but any scientific paper would not) is key.

The Challenges of Invertebrate Conservation

Posted by Simon Connolly

Invertebrates are (ironically) the backbone of every ecosystem in New Zealand, providing multiple essential services. It is troubling to note then that in NZ over 1000 invertebrate species are classified as Threatened or At Risk (full lists can be found here).  However, despite evidence they can benefit from conservation action, they are often ignored in conservation policy.

There are exceptions to this rule. Notably, the Cromwell Chafer Beetle was saved from extinction by the world’s first nature reserve dedicated to the protection of an invertebrate species (read more about this here).

The simplest reason for the lack of invertebrates in conservation work is the fact that they are very difficult to study, because of their staggering species diversity. The bane of entomologists is the ‘taxonomic impediment’, meaning that there are so many invertebrate species that we do not have names for all of them yet. I’m sure you can imagine the impossibility of trying to come up with recovery plans for species that aren’t even known to science. This diversity also increases the need for specialist work in terms of distinguishing threatened species from common close relatives.

Wetapunga

A large and iconic Weta being large and iconic.

To classify a species as threatened requires a lot of knowledge about its populations, range, and other related factors. Such data are not as easy to gather as they are for vertebrate species, given that invertebrates are often hard to see, making it difficult to come to any conclusions at all. It is no coincidence that the Weta, easily the most iconic group in NZ invertebrate conservation, are also the largest and most noticeable.

A more uncomfortable truth is that we as human-beings like to play favourites. Charismatic and cute vertebrates tug at our heartstrings, and, for most, invertebrates will never hold the same lustre despite their importance to the world. Inevitably, the species we care about more receive more conservation resources.

What can be done? Well, research in the scientific space is looking at whether we can more effectively use the data we have. This includes using known locations of invertebrates to build up a picture of their climatic preferences or looking at a species’ physical traits to speculate on the threats it may face in the wild. Hopefully, you’ll hear more about this at the end of my Master’s project (fingers crossed). Is this a magic bullet? Certainly not, but hopefully it’s a step in the right direction.

Ngaio_Weevil

The Nationally Critical Ngaio Weevil

For now, I hope when you think of threatened species you will remember that there are hundreds of species that need our attention and some of them are much less cute, but no less important than others.

Simon is a Masters Student at the School of Biological Sciences, University of Auckland. His research is focused on threatened insects and he is supervised by Darren Ward.

Taking the graveyard shift for science

Posted by Tynan Burkhardt @TynanBurkhardt

Bias is a thorn in the side of any researcher, whose goal it is to discern general effects and phenomena in the environment. The most commonly quoted of these biases is the hemispheric bias, in that there is a lot more research occurring in the northern hemisphere, where 88% of the worldly population resides. Another bias, which I have encountered in my research, is the diurnal to nocturnal bias. My research considers the patterns of nocturnal transpiration (night-time water loss) between seasons and between drought and non-drought years. By choosing to study nocturnal transpiration I have effectively taken the graveyard shift, taking leaf-scale measurements all through the night on multiple occasions and depriving myself (and others… for which I thank my volunteers greatly!) of sleep. Apparently, and I have no idea why, other researchers choose to study processes which can be measured at normal working hours, meaning day-time ecology is more frequently documented.

sleepy

Me sleeping on the job, while volunteer Helen does all the hard work.

Studying a topic at night-time and in the southern hemisphere got me thinking… how will biases such as these change in future with technological and socio-economic advancements? For example, remote regions are very much understudied due to inaccessibility. Perhaps in time, when flying cars are common place or sampling robots like the curiosity rover are more affordable, this bias could be completely rectified… at least on a global scale. Likewise, a large contributor to the hemispheric research bias is that the largest populations of the southern hemisphere are within Southern Africa, Indonesia and South America. These regions contain a disproportionate amount of the world’s poverty-stricken people who do not have the resources to contribute to scientific research as readily as the populations of North America and Europe. Fortunately, living conditions worldwide are improving and young people throughout the aforementioned regions are increasingly becoming the first of their lineage to acquire a university degree. So long as this trend continues, which we should all hope it will for reasons other than scientific utility, the southern to northern hemisphere literature gap will surely be reduced.

Biases will always be a part of science as they arise from circumstance, but an important role for the scientific community is to identify the drivers of these biases, whether they be socio-economic, technological or geographic. Scientists already account for bias when making models and statements about the natural world, but nothing can replace an increased sample size!

img_7437.jpg

Tynan is a Masters student at the University of Auckland’s Ecology Ngatahi lab group. He is studying Nocturnal Transpiration in kauri trees and is supervised by Cate Macinnis-Ng.
email: 
tbur187@aucklanduni.ac.nz

You think writing a thesis is hard? Try writing one in another language!

Posted by Carolina Lara Mendoza @carislaris

Doing a PhD is hard. Writing a thesis in English when English is not your first language is harder. According to the Organisation for Economic Co-operation and Development (OECD) in 2015, more than four million students were enrolled in higher education programs outside their home countries. Since 2005, international PhD students at the University of Auckland, New Zealand, have contributed to 45% of all PhD students. This means that from the period 2014-2016, approximately 2,552 students have enrolled in the doctoral program at Auckland Uni. That’s great! And it illustrates the good work that the University and the government have done to reduce fees and make more scholarships available. At the end of the day, we live in an era of globalisation and English is its language.

Before enrolling in a doctoral program overseas, every PhD student must prove they are proficient in English. This is measured through either a TOEFL test, an IELTS test or by an internal English examination. But does passing those tests mean we are ready to write a dissertation in English? From my experience, I must say that is not enough. Furthermore, PhD students who are non-native English speakers are expected to complete the degree with all the struggles while still learning advanced English (academic English). I’m not discounting the efforts of the University of Auckland, because we’re provided with workshops aiming to improve PhD student’s academic English, but think it shouldn’t just be up to the institution and the student. Supervisors of students for whom English is not their first language also play an important role in providing adequate and constructive written feedback, and need to be aware this will likely take time and patience. Raul Pacheco-Vega recently tweeted something of great importance “For those of you who supervise doctoral dissertations in English to be written by non-native English speakers; particularly those of you whose first language IS English: please remember and check your privilege: you get to write in your own language. They may lack the background”.

Write-consistently

In the meantime, here are some tips that have helped me to write my thesis in English:

  • Be proud of yourself and celebrate small achievements. Sounds hard while doing a PhD but it is important. Remember you’re doing something great by writing a thesis in a second language! You wrote a whole section? Celebrate. You wrote two sentences? Celebrate. Everything is a success!
  • Embrace feedback from supervisors. After 3.5 years of doing a PhD I still find this challenging. Getting feedback on a manuscript makes me feel anxious and quite often I feel like I’ve failed. It cannot be further from the truth. Feedback is the only way we can improve our written academic English!
  • Practice writing as much as you can. And don’t leave it until you start writing your thesis. For me writing grant applications at the early stages of my PhD (some of them have been successful!) was very useful, as was writing blog entries throughout, which was good for learning how to target my writing to different audiences.
  • Have a friend in your field proof-read your writing. Getting feedback from someone other than your supervisors is a good idea and helps you gain practice (and confidence).
  • Use the available tools. Either at your institution, books or even online. I’ve found that thesaurus.com is incredibly useful when I can’t think of a synonym or when looking for a word’s meaning.
  • Don’t give up. If you’re consistent and patient, you’ll get there. Rome wasn’t built in a day.

 

CalisCarolina Lara M. is a PhD Candidate within the Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. Her research interests focus on seed dispersal networks within fragmented landscapes. She is supervised by Margaret StanleyJason Tylianakis, Karine David, and Anna Santure.

The ants are coming

Posted by Darren Ward @nzhymenoptera

Ants are among the most invasive animals on the planet. Over 240 species have been recorded as being transported by humans to new geographic locations, and 19 of those are considered invasive.

L humile -antweb

Caption. The Argentine ant, a globally invasive species. Photo by Philip Herbst. Image available from Ant Web.

But not all invasions occur as the result of direct transport. Some species have managed to invade one place, survive, and then migrate to another—a process known as the “bridgehead effect”. In a new paper, just published in Proceedings of the National Academy of Sciences, we investigated these secondary invasions, and show bridgehead effects are a major driver of new invasions.

We looked at interception data, that is, records of what ant species have been intercepted at the border. Two large and long-term datasets were examined, one from the USA covering the years 1914 to 1984 and containing 51 ant species, and the second from New Zealand covering the years 1955 to 2013 with 45 ant species.

The most surprising result was that most of the interceptions did not originate from species’ native ranges but instead came from already invaded areas. In the United States, 75.7% of the interceptions came from a country where the intercepted ant species had been previously introduced. In New Zealand, this value was even higher, at 87.8%.

Interceptions also increased when they came from countries that were physically closer (Latin America for species intercepted in the United States and Oceania for species intercepted in New Zealand). Additionally, ant species that travelled the most tended to be more successful in invading a secondary location. This created a positive feedback loop between the introduction and establishment stages of the invasion process, in which initial establishments promote secondary introductions.

Overall, these results reveal that secondary introductions act as a critical driver of increasing global rates of invasions. Consequently, it is not enough simply to account for the original location of an invasive species. To better understand pathways of invasive species, we also need to follow the dynamics of spread throughout their entire range.

 

Cleo Bertelsmeier, Sébastien Ollier, Andrew M. Liebhold, Eckehard G. Brockerhoff, Darren Ward, and Laurent Keller. Recurrent bridgehead effects accelerate global alien ant spread. PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1801990115

 

and if you really like ants, then another really great related paper is

Cleo Bertelsmeier, Sébastien Ollier, Andrew Liebhold & Laurent Keller. Recent human history governs global ant invasion dynamics. Nature Ecology & Evolution (2017). doi:10.1038/s41559-017-0184

 

Darren Ward is an entomologist, Head Curator at the New Zealand Arthropod Collection at Landcare Research, and a senior lecturer at the School of Biological Sciences, University of Auckland.

Social Wasp Invasion on New Zealand’s Offshore Islands

     Watch my vlog on social wasp invasion on New Zealand’s offshore islands
– some of the last refuges for endangered species – below:

 

Julia Schmack is a PhD student at the Centre for Biodiversity & Biosecurity, School of Biological Scinyences, University of Auckland. She is researching the ecology and control of social wasps, supervised by Jacqueline Beggs, Darren Ward and Mandy Barron (Landcare Research). Her PhD is funded by the Biological Heritage National Science Challenge. Download the Highlights 2017 report by the Biological Heritage National Science Challenge here.

twitter_pixabay.com @julia_schmack

email_commons.wikipedia.org j.schmack@auckland.ac.nz