Friday, April 3, 2015

Invasion of the Beavers

Guest post by John Cherkas

Fifty years ago, Dr. Walter Howard presented his thoughts on invasive mammals at a symposium on colonizing (invasive) species, which was later turned into the volume "The Genetics of Colonizing Species." He speculated on the nature of predator-prey interactions, population growth limits and habitat disruptions. His ideas still resonate, but how well do they match up with a certain invasive mammal today.

May I bring your attention to some invasive beavers? Our national creature has been making quite a mess is the Southern most reaches of the Western Hemisphere. In the 1940s, Argentina was seeking economic improvements and imported beavers, mink and muskrat to Tierra del Fuego in an attempt to establish a fur trade. That fur trade didn't turn out as expected. Within a few years, beavers had colonized the entire island and were soon crossing channels to reach other Chilean islands, including Cape Horn, a UNESCO Biosphere Reserve.

Angry beaver -roar!

The ecological effects have been pretty well researched recently by Dr. Christopher B. Anderson. In seeing if beavers behave differently in their new habitat than back home, he’s been finding a few differences in the environment and beavers here. One of the most obvious changes is that the beaver colonies are at least twice as dense in Cape Horn. Is this for lack of predators or an abundance of food? So far, I couldn’t say, but I’d lean toward the latter. The Cape Horn forests are entirely southern beeches, which provide ample resources for the beavers’ engineering projects.

But how disruptive have beavers been to the environment: and environment that has no animal that makes such a massive environmental impact as the beaver. Howard suggested that an animal moving into a habitat where its niche doesn’t exist would have wider impacts than one who’s niche does exist. It’s fairly clear that the beaver’s landscaping projects is not something that other animals (except humans) partake in.

In the beaver situation this ecological disruption holds true. The floral assemblage in Cape Horn has never had to deal with beaver-like behaviour. The beavers foraging and building habits prevent forest regrowth, and provide a pathway for other plants to invade. It seems this beaver introduction might be a good example of invasional meltdown. The Chilean archipelago is home to quite a few invasive species already, and this synergistic effect is definitely concerning.

All the beaver-induced worries come with a grave concern for the natural environment. Cape Horn is referred to as pristine quite a bit by Anderson. Is this the place to have a deep political, socio-economic discussion about “pristine” environments? No, not today; you’ll have to read elsewhere for that. Cape Horn is certainly already at risk from invasive species. Beavers have a tremendous impact on the ecological structure of streams and forests. I am certainly one to wonder whether the eradication effort can be truly successful and both removing the beavers and reversing the environmental changes.

I surely hope that the environmental disruption can be reversed. Unfortunately we cannot look back to Howard to speculate on what happens when we remove an alien species. Just fifty years ago, species invasions were seen as a great research opportunity, not something to be extensively managed or eradicated.

Further Reading:

C.B. Anderson et al. (2006), The effects of invasive North American beavers on riparian plant communities in Cape Horn, Chile. Do exotic beavers engineer differently in sub-Antarctic ecosystems? Biological Conservation, 128: 467-474.

C. Choi, (2008) Tierra del Fuego: the beavers must die. Nature 453: 968. doi:10.1038/453968a

Monday, March 30, 2015

Divergent perspectives on biological invasions: a way forward

50 years have passed since the publishing of the seminal ecological work “The Genetics of Colonizing Species” (GCS) (Baker and Stebbins, 1965). This book covers various topics regarding the introduction of species to different regions, the effects these movements have on the species themselves and sometimes more broadly on the ecosystem into which they are introduced. After 50 years of contribution to ecological discourse, it is worth examining how GCS can help to address some contemporary ecological questions; namely, how can basic science help inform ecological management? And, how much have specific ideas or theories changes in the past 50 years?

To answer the first question, basic science has given us the ability to determine potential invasive qualities in certain species and prevent some introductions. For instance, we know to avoid introducing species that are closely related to species that are already pests or are in some way problematic. Basic science has also helped us develop species distribution maps where an introduced species is and where it could potentially spread to. These maps help us prioritize areas for protection and have helped us prevent the spread of potentially harmful species.

 In regards to the second question, I’m a bit more hesitant to answer. We still don’t have an adequate answer as to why certain species can establish and be very successful, while others don’t. We’ve come up with many hypotheses to try and explain it, such as enemy release (Colautti et al. 2004), novel weapons (Mitchell et al. 2006), empty niche (Elton, 1958), etc. but we still haven’t been able to generalize these ideas. We simply fit these hypotheses in a case by case manner, so really has there been much progress in the past 50 years? To answer this I’ll turn to a current debate where two schools of thought have divergent views on this topic.

On one side, Mark Davis and colleagues (2011) seem to think that we’ve made progress but not enough. With their controversial Nature Comment, they call for the end of invasion biology, stating that the native versus non-native dichotomy within this field is a hindrance to progress as it can promote xenophobia and bias the views of scientists and the public. Davis points out that within this field there is a large emphasis on negative impacts of non-natives, which can take away from the potential positive influences they could have. These researchers are embracing the idea of “novel ecosystems”, which are systems that are rapidly changing as a result of climate change, land use, and increasingly through the introduction of non-natives (Thompson and Davis, 2011).  Moreover, these researchers describe how non-natives have the potential to contribute to conservation goals as they are more likely than native species to persist and provide ecosystem services within these novel ecosystems (Schlaepfer et al. 2011)

Leading the charge from the opposing side is Dan Simberloff ,who believes that within the short span of its existence (about 25-30 years) invasion biology has made significant progress, especially in terms of technological improvements to help prevent or stop the spread of invasive species (Simberloff , 2011; Simberloff et al. 2013). In contrast to Davis and colleagues, Simberloff doesn’t believe that attempting to stop invasions is a lost cause and is able to provide various examples of invasive species that have either been eradicated or brought down to manageable population densities through the continued work of researchers and community efforts (Simberloff and Vitule, 2014). He believes that Davis is downplaying the severity of the impacts non-natives can have, especially when there are no visible effects on the ecosystem (Simberloff and Vitule, 2014). All in all, Simberloff sees great potential in the development of new technologies, but in order to develop them we must have scientists working on these projects, and public support to ensure that there is funding for these projects. 

To learn more about the debate I would highly recommend checking out the webcast of their debate (Conservation Science Webinar - scroll down to Native and Non-native Species: How much attention should managers be paying to origins?). In regards to where I stand with all of this I am unfortunately on the fence. From the GCS I read the chapter titled: “Establishment Aggression, and Cohabitation of weedy species”, authored by John Harper. I very much enjoyed Harper’s chapter as he emphasizes the fact that the introduction of species is non-random. It is the “specialized” species that are capable of moving around the world. Harper points out that these species tend to have particular dispersal or germination traits that are allowing them to establish within new regions. I believe Harper’s views on introduced species mirrors what we currently think. The world is becoming increasingly connected so it is logical that species taking advantage of this connectivity would be the most likely to move around and establish in new areas.

 I think that the “specialized” traits of these species gives us predictable patterns to look for, and that this predictability based on traits plays well into Simberloff’s views of being wary about newly introduced species. An incredible amount of work must be put in to accurately characterize a species, so it’s practically impossible to know everything about a newly introduced species that you’ve just encountered. Therefore, we should be extremely cautious if the introduced species has any “specialized” characteristics. More simply, if the species has any of the 4 risk factors: good dispersal ability, fast reproduction rate, lacks predators or pathogens in the new range, or if it’s primary resource is readily available in the new range, then we should play a more active role in stopping it from establishing (Lerdau and Wickham, 2011).

In general, I’m slightly indecisive about this topic as while I do agree with most of Simberloff’s views I also see the merit with Davis’ idea of “novel ecosystems” since the world is changing so rapidly. With a rapidly changing environment many new questions come to mind, for me the simplest one would be: are species changing (ie adapting and evolving) to better fit the new or “novel” environment?  Using the plant species native to Europe, St. John’s Wort, Maron et al (2004) were able to demonstrate that this species is capable of adapting to a new environment. In the introduced range in North America this invader was becoming better fit to the broad scale abiotic conditions, and was thus experiencing rapid adaptive evolution as this was occurring within the last 150 years. 

With both sides of this debate I find that despite their differing views Davis and Simberloff are still fighting for the same thing: the acquisition of knowledge. Superficially there will always be a debate between the idea of the origin of an introduced species versus the impact of that introduced species. But really underneath it all everyone is still trying to answer the same fundamental questions: How did you get here, and what are you doing?

 So referring back to that second question: how much have specific ideas or theories changed? I don’t think our ideas have really changed, realistically I think we’re still where we started, but we have more information both on the species and the environment, so I do think we’re on our way to a big change. Charles Elton, the founder of this field had written 60 years ago, “we require fundamental knowledge about the balance between populations, and the kind of habitat patterns and interspersion that are likely to promote an even balance and damp down the explosive power of outbreaks and new invasions.” (Elton, 1968)  Invasion biology has only formally been a field of study for about 25-30 years; we’re still at a stage where we’re gathering knowledge. It’s my opinion that its way too early for us to call it quits, but it is the perfect time for us to push the field and make giant leaps. We’re scientists! We can revolutionize this field. We have the technology. We have the curiosity. We can make the world better than it was. More sustainable, more functional, more diverse.


Baker, G.H & Stebbins, J.L. (Eds.) (1965). The Genetics of Colonizing Species. Academic Press Inc

Colautti, R. I., Ricciardi, A., Grigorovich, I. A., & MacIsaac, H. J. (2004). Is invasion success explained by the enemy release hypothesis?. Ecology letters,7(8), 721-733.

Davis, M. A., Chew, M. K., Hobbs, R. J., Lugo, A. E., Ewel, J. J., Vermeij, G. J., ... & Briggs, J. C. (2011). Don't judge species on their origins. Nature,474(7350), 153-154.

Elton, C. S. (1958). The ecology of invasions by animals and plants. University of Chicago Press.

Harper, J. L. 1965. Establishment, Aggression, and Cohabitation of Weedy Species. In H. G. Baker &  J. L. Stebbins (Eds), Genetics of Colonizing Species (pp 245-263). Academic Press Inc.

Lerdau, M., & Wickham, J. D. (2011). Non-natives: four risk factors. Nature,475(7354), 36-37.

Maron, J. L., Vilà, M., Bommarco, R., Elmendorf, S., & Beardsley, P. (2004). Rapid evolution of an invasive plant. Ecological Monographs, 74(2), 261-280.

Mitchell, C. E., Agrawal, A. A., Bever, J. D., Gilbert, G. S., Hufbauer, R. A., Klironomos, J. N., ... & Vázquez, D. P. (2006). Biotic interactions and plant invasions. Ecology Letters, 9(6), 726-740.

Schlaepfer, M. A., Sax, D. F., & Olden, J. D. (2011). The Potential Conservation Value of NonNative Species. Conservation Biology, 25(3), 428-437.

Thompson, K., & Davis, M. A. (2011). Why research on traits of invasive plants tells us very little. Trends in ecology & evolution, 26(4), 155-156.

Simberloff, D. (2011). Non-natives: 141 scientists object. Nature, 475(7354), 36-36.

Simberloff, D., Martin, J. L., Genovesi, P., Maris, V., Wardle, D. A., Aronson, J., ... & Vila, M. (2013). Impacts of biological invasions: what's what and the way forward. Trends in Ecology & Evolution, 28(1), 58-66

Simberloff, D., & Vitule, J. R. (2014). A call for an end to calls for the end of invasion biology. Oikos, 123(4), 408-413.

Thursday, March 26, 2015

Ecology in evolutionary times

Ecological and evolutionary perspectives on community assembly. 2015. Gary G. Mittelbach, Douglas W. Schemske. Trends in Ecology and Evolution.

Phylogenetic patterns are not proxies of community assembly mechanisms (they are far better). 2015. Pille Gerhold, James F. Cahill Jr, Marten Winter, Igor V. Bartish and Andreas Prinzing. Functional Ecology

Community assembly has always provided some of the most challenging puzzles for ecologists. Communities are complex, vaguely delimited, involve multi-species interactions, and assemble with seemingly immense variation. Thousands of papers have been dedicated to understanding community assembly, and many have proposed different approaches understanding communities. These range from the ever popular abiotic/biotic filtering concept, functional traits, coexistence theory, island biogeography, metacommunity theory, neutral theory, and phylogenetic patterns. It is probably fair to say that no one existing approach is adequate to completely describe or predict community assembly.

One response to this problem is the growing demand to expand the lens of “community” to cover greater spatial and temporal scales. This owes a lot, directly and indirectly, to Robert Ricklefs’ influential Sewall Wright Award lecture on the Disintegration of the Ecological Community. There is also a strong trend towards re-integrating evolutionary history into studies of community ecology. Coincidentally, or perhaps not, this is occurring as so-called ‘eco-phylogenetic’ approaches have been increasingly criticised. If nothing else, eco-phylogenetics provided a path for, and popularized, the idea of reintegrating evolution into community ecology.

I’ll highlight two particular papers that address this re-integration in surprisingly convergent ways. Both have macroevolution slants (that is, they focus on the impacts and drivers of speciation and extinction, sympatry, allopatry, etc), and an interest in the feedbacks between community interactions and these processes. The first, from Pille Gerhold, James F. Cahill Jr, Marten Winter, Igor V. Bartish and Andreas Prinzing, positions itself as the phoenix from the ashes of eco-phylogenetics (as seen in their particularly enthusiastic title :) ). Evolutionary history, captured by phylogenies, was originally of interest to ecologists not for what it was, but because it could (sometimes, maybe) act as a proxy for species traits and niches. This paper does an excellent job of laying out the various hypotheses that went behind this type of approach and showing why they are not reliably true. If for no other reason, it is worth reading the paper for its clear critique of the foundation of eco-phylogenetics. Using patterns in phylogenies as proxies for the outcomes of particular ecological processes being clearly suspect, the authors argue that explicitly thinking of phylogenetic patterns as the result of both ecological and evolutionary processes is far more informative. [I’ll return to this in a bit with their examples below].

The second paper is written by two big names in their respective fields: Gary Mittlebach (ecology) and Doug Schemske (evolution). The title is a bit vague (“Ecological and evolutionary perspectives on community assembly”), but it turns out that they too have converged on the importance of considering evolutionary history in order to understand community assembly. In particular they focus on the problematic nature of the species pool: species pools are nearly always treated as a static object changing little through time or space and are notoriously difficult to define. However, the species pool underlies null model approaches used to test communities for differences from a random expectation. So defining it correctly is important.

From the early days, Elton and others defined the species pool as the group of species that can disperse to and colonize a community. However, the species pool may be dynamic, and they note “To date, relatively little attention has been focused on the feedback that occurs between local community species composition, biotic interactions, and the diversification processes that generate regional species pools.”

This paper does an excellent job of explaining how macroevolutionary processes can alter a regional species pool. The most obvious example is the process of adaptive radiation in island-like systems, where competition for resources drives ecological divergence and speciation. Darwin’s finches, Anolis lizards, and cichlid fishes provide well-known examples of this rapid expansion of the species pool through inter-specific interactions. On mainland systems, speciation may be more likely to occur in allopatry, and the rate limiting step for range expansion (leading to secondary sympatry and only then increasing a species pool) is often interspecific interactions. One study found that secondary sympatry took 7my on average, though speciation alone took only 3my. So the species pool is the outcome of constant feedbacks between species interactions and evolutionary processes.
From Mittlebach & Schemske. Figure illustrating the feedbacks between evolution and ecological interactions, in producing the species pool.
Both papers provide useful examples of how such incorporating evolution into community ecology may prove useful. As a simple example, Mittlebach and Schemske point out that evolution can greatly alter the utility of Island Biogeography Theory: given enough time, speciation events including adaptive radiations, greatly increase the (non-mainland) species pool and would strongly alter predictions of diversity, especially for distant islands.

The Gerhold et al. paper provides the below illustrations as additional possibilities for how evolution and community interactions may feedback.
From Gerhold et al. Two examples of how evolution and communities might interact.

It is certainly interesting to see this shift towards how we envision and study communities. The historical focus on local space and time no doubt reflects ecologists' attempt to limit the problem to a manageable frame. But there is some logic behind expanding our definition of communities to larger spatial scales and greater time periods, especially since there are usually no true boundaries defining communities in space and time. Answering which specific time scales and spatial scales most useful to understanding communities is difficult: if we increase the time or space we consider, how and when does the additional information provided decline? The next step is to consider evolution in this fashion for real organisms, and evaluate the true utility of this approach.  

Saturday, March 14, 2015

The fruits of our labour: the evolution of crops

#Guest post by Francesco Janzen.

Have you ever wondered how much work and time has been put into producing the food you eat today: that juicy apple, or that fresh loaf of bread? In modern times, we can easily recognize fruits and vegetables such as tomatoes, corn, and bananas, but would it surprise you that these foods have not always looked the way they do? Like all parts of the living world, food crops have changed much over time, and this change is directly linked to human efforts (Purseglove, 1965; Allaby et al., 2015). 

Agriculture began approximately 11,000-12,000 years ago, and has originated in several parts of the world (National Geographic, 2015). Humans domesticated wheat in the Fertile Crescent, or Near East approximately 8,000-9,000 years ago. (Nevo, 2014; National Geographic, 2015). In China, rice is proposed to have been domesticated 10,000-20,000 years ago (Gross & Zhao, 2014; National Geographic, 2015). Across the ocean, squash was domesticated about 10,000 years ago in what is known today as Mexico, and the beginning of sunflower cultivation began in North America around 5,000 years ago (Janick, 2013; National Geographic, 2015). All of these domestications began with wild progenitors of today’s crop species (Gross et al., 2014; Allaby et al., 2015).  

But how did the wild crops of ancient times develop into the modern ones we know today? John William Purseglove, a former tropical agricultural officer and director of the Singapore Botanic Gardens, discussed the ways in which humans have changed crop species over time in a chapter of “The Genetics of Colonizing Species” (1965). In his chapter, “The Spread of Tropical Crops”, Purseglove (1965) states that humans would have begun the first agricultural crops with a subset of desired plants from the original wild population. This subset would not possess the genetic diversity of the original population, essentially producing a genetic bottleneck effect (Purseglove, 1965). Furthermore, certain desired traits would be selected for in this new population, so breeding strategies would overtime change the traits expressed, such as larger fruit, seedless fruit, lack of defense mechanisms, etc. (Purseglove, 1965). Although they benefit humans, these changes could potentially decrease the competitive ability of these new plants. This intrinsically ties their survival to human assistance (Purseglove, 1965). 

Humans have not only changed the physical characteristics of crop plants; they have altered their geographic distributions as well. Compared to their wild ancestors, most crop plants are now grown in areas far removed from their origin, such as with vanilla (Vanilla planifolia). Vanilla originated in Mexico, but is now grown in large numbers in Madagascar (Purseglove, 1965). In fact, vanilla and most other crops are much more successful in their new environments, but why is this so? Purseglove (1965) proposed that by moving a crop plant into a new habitat where predators or disease are absent, little would control population sizes, and increase crop yields. 

Visible difference between a wild strawberry (Fragaria virginiana, left) and a domestic strawberry (Fragaria x ananassa, right), from

The new environments that domestic crops are exposed to may further increase the genetic gap with their wild ancestors. Under new, adverse environmental conditions, a population of a crop may be culled, save for a few individuals possessing recessive genes that confer a benefit to coping with the altered conditions (Purseglove, 1965). The remaining individuals reproduce, which shifts the next generation’s genotypic frequency (Purseglove, 1965). In addition, this can effectively expand the range of the domestic crop, whereas the wild type remains restricted to its original range (Purseglove, 1965). 

Science has come a long way since Purseglove proposed his ideas 50 years ago, and the advent of DNA has helped improve our understanding of evolution. With respect to the evolution of crops, DNA allows for testing of certain theories proposed, one such being the bottleneck effect. A study conducted by Gross et al. (2014) investigated whether perennial crop species, specifically the apple (Malus x domestica) showed a decrease in genetic diversity when compared to closely related wild species. They expected that there would have been a narrowing of genetic diversity at two moments in history. Firstly, during a domestication bottleneck, similar to that proposed by Purseglove (1965), and secondly during an improvement bottleneck, where desirable traits in the crop species were selected for to produce elite cultivars (Gross et al., 2014). 

A visual depiction of the bottleneck effect, where the bottleneck represents stochastic (random) events, from
By sequencing specific DNA regions of 11 varieties of apple cultivar (both ancient and modern), and that of three wild species, Gross et a. (2014) sought to demonstrate that domesticated cultivars show less genetic diversity than wild species. The regions selected were areas where each species show a variable amount of repeated sequence length, known as microsatellites, allowing for easy comparison of genetic quality (Gross et al., 2014). What they found, contrary to what was expected, was that domestic apples have not undergone a significant reduction of genetic diversity, either at the domestication or improvement phases (Gross et al., 2014). This evidence shows that not all theories produced 50 or more years ago withstand the test of time, especially when new tools to test these theories become available.   

So how does any of this information impact management practice of controlling invasive species? Purseglove (1965) stated in his chapter that by understanding the evolution of crop species, we gain insight into the success of introduced weed species. Although weeds do not require any human assistance in survival, the forces acting on them may be the similar to those acting on agricultural crops. Just as crops experience a release from predators and disease when removed from their native habitats, weeds may also undergo this release, contributing to their widespread success (Purseglove, 1965). This parallel could be quite useful in the understanding and management of weedy species.  


Allaby, R.G., Gutaker R., Clarke, A.C., Pearson, N., Ware, R., Palmer, S.A., Kitchen, 
J.L., and Smith, O. 2015. Using archaeogenomic and computational approaches to unravel the history of local adaptation in crops. Philosophical Transactions Royal Society  370: 20130377.

Gross, B.L., Henk, A.D., Richards, C.M., Fazio, G., and Volk, G.M. 2014. Genetic 
diversity in Malus × Domestica (Rosaceae) through time in response to domestication. American Journal of Botany 101(10): 1770-1779.   

Gross, B.L. & Zhao, Z. 2014. Archaeological and genetic insights into the origins of 
domesticated rice. Proceedings of the National Academy of Sciences 111(17): 6190-6197. 

Janick, J. 2013. Development of New World crops by indigenous Americans. 
Horticultural Science 48(4): 406-412.   

National Geographic Society. 2015. The development of agriculture. Retrieved from 

Nevo, E. 2014. Evolution of wild emmer wheat and crop improvement. Journal of 
Systematics and Evolution 52(6): 673-696. 

Purseglove, J.W. (1965). The spread of tropical crops. In H.G. Baker, and G.L Stebbins 
(Eds.). The Genetics of Colonizing Species. New York: Academic Press.

Tuesday, March 10, 2015

Scientific Presentations: the Dos and Don'ts

With the ESA submission deadline just passing, the Cadotte Lab decided that it would be helpful to dish out a few tips on how to make a presentation that is both enjoyable for your audience and fun for you to give. Presenting in front of people is never easy; giving a presentation about your own study can be even harder since you have to condense months (or even years) worth of information into a 15 minute time period. So with this in mind here are a few tips for each of the main sections of a presentation:

Note, the percentage by each section heading indicates the relative amount of time you should spend on that section.

Title Slide (5%)

This is the first chance you’ll get to catch your audience’s attention, so be interesting!

The title of your presentation depends on the type of audience you’ll be presenting to, so gauge it accordingly. If your audience is a bunch of people with only general biology backgrounds or people that are from completely different fields then don’t complicate things using heavy jargon.

Generally for the title, you want to:
  • Be witty and interesting
  • Convey the main message or main result from your study

If you’re speaking to a broad audience it could be helpful to have a broad title and then separate it from a more specific title.

Besides the title you’ll also want to include your name and affiliation. Depending on the type of talk, for instance an honors thesis, you should also include your supervisor’s name. If you are collaborating with many people on a study you should also include their names. However, make sure that your name is on the first slide, since you are the presenter, and then on a second slide include a special acknowledgement of the other people involved. It’s also recommended that you acknowledge these people throughout the talk, such as in the methods. 

Introduction (10-15%)

Don’t make this section too long. Give just enough background that the audience can understand the concepts that you’ll be discussing and how it relates to the question you are trying to answer.
Generally for the introduction, you want to:
  • Have the background information displayed in a simple to understand way
    • You could use info-graphs here to reinforce an idea
  • By the 2nd or 3rd slide you’ll want to state your study objectives or hypotheses
    • You could create ‘toy’ graphs to describe your hypotheses / predictions

Methods (10-15%)

Be very concise with this section. Everyone understands that a lot of work went into performing your study; however, you don’t want to overwhelm your audience with all the nitty-gritty things you had to do. Give enough detail that people understand what you did and if possible try and summarize your methods in a simple figure.

Generally for the methods, you want to talk about:
  • The treatments used, sample size, the measurements taken and how they were done, and the statistics that you performed

A note on statistics: try to steer clear of very complicated statistics. Most likely your audience will have a basic understanding of stats, but you may lose people if you get too complicated. When talking about your stats, make sure that you can give an easy to understand explanation of how they work.

Results (50%)

This is the biggest and best section; it’s where you get to show people all the cool and exciting things you’ve done! However, the only way you can convey how awesome your results are is by clearly explaining them.

Generally for the results, you want to:
  • Stick to the main results
    • You may have a lot different results but always make sure that what you are describing relates directly to the main message of your study
    • Don’t overwhelm your audience
  • Always thoroughly describe your graphs
    • Describe what variables were you examining (the axes)
    •  Why is the graph important?
      • What is the relationship that the graph is showing?
        • The title of the slide could be used to state what the result is
    • You’ve spent a lot of time making these graphs and analyzing them - so you know them very well, but your audience doesn’t yet. Take time to walk them through the graphs.
    •  If you’re showing several graphs in sequence, make sure to note if the axes are changing
      •  If the graphs are very similar it might be helpful to have a break between slides or to use an animation.
  •  Don’t show too many stats
    •  Just state the p-values and which stats were used
  • Avoid tables if possible
    •  Summarize all the information in an easy to follow figure
    •  If you can’t avoid using a table make it as appealing as possible
      •   Highlight key parts or add arrows to show trends if they exist

Discussion (20%)

Now start bringing everything back together. Your audience may have gotten lost during your results section, so now is the time to refocus them so that they can see the big picture.
Generally for the discussion, you want to:
  • Restate your hypotheses
  • Restate you main results
  • Describe how you could improve your study
  • Describe the next steps for your work and the field in general

In the end you’ll want to describe the broader implications of your work and give the audience a take home message so that they know that your work is bettering the field in some way.  

Acknowledgements (5%)

Don’t forget to thank everyone who has helped you through this whole process! This includes your supervisor, people who helped you with data analysis or revising your paper, or all the volunteers you helped you conduct your field work or lab work. You’ll also want to acknowledge your institution as well as anyone who provided funding to your project.

General tips

Here’s a quick list of tips to use throughout your presentation:
  • Use large text font
    • Don’t be flashy, make sure it’s easy to read
  • Don’t put too much text on a slide
    • This distracts the audience
  •  Don’t put any important point (text or an image) at the bottom 1/3rd of a slide
    • Depending on the room you are presenting in it may be very hard for the audience to see it
    • In general, try and keep everything within the top 2/3rd of the slide
  • Don’t put too many animations on a slide
    • This can be very distracting for the audience
  • Don’t read off your slides
    •  Use presenter view if you can’t memorize everything
  • Including outlines
    •  Not necessary in a short talk, but could be helpful in a longer talk
  • If you run out of time
    • Panic on the inside not the outside!
    • Acknowledge that you’re running out of time and start wrapping things up
      • Start talking about the broad implications of your work and maybe future directions you plan to take
      • If you have more slides, skip over them but tell the audience what you were planning on showing. If they ask questions about what you were going to show you can go back to those slides
  • Don’t talk too fast!
    • Everyone gets nervous! Take a deep breath and calm yourself down, the calmer you are the easier it is for your audience to follow you