Trophic cascades in fragmented forests

Many birds eat insects and spiders. Some of these insects and spider are themselves predators, feeding on critters lower down in the food web. Some of the insects that are fed upon by birds, or other predators, also play important roles in forest, such as munching upon the fresh, green leaves of young trees (here’s a reminder).

Munch, munch, munch. The hungry caterpillar. (photo by Sean McCann, reproduced here with permission)

Munch, munch, munch. The hungry caterpillar. (photo by Sean McCann, reproduced here with permission)

These interactions are ongoing, all the time, in forests around the world. These forests, however, are changing in important ways. Some of them are getting smaller and smaller as humans continue to encroach on the land, via urbanization or agriculture. This results in a ‘fragmented’ landscape. A landscape with small forest patches, perhaps no bigger than your back yard. A landscape with larger forests, perhaps one in which you could get lost in. These forests are themselves connected to each other –sometimes directly by a corridor or hedgerow.

This is the context for PhD student Dorothy Maguire’s research. Within that context, Dorothy tackled a fascinating project, one that was just recently published. In this work, Dorothy and co-authors (including me, an undergrad at that time, Thomas Nicole, and McGill Professor Elena Bennett) put cages around small trees in different types of forests SW of Montreal. The cages (made of chicken wire) were in place to test the effects of ‘predator exclusions’ on the insects and spiders occurring on saplings. The prediction is that if you exclude larger predators, such as birds, this may allow a ‘release’ of other insects and spiders. In turn, this release may have trickle-down effects on an important process occurring in young trees: herbivory. For example, if a predator is more common because it’s not being eaten by birds, perhaps it will eat more caterpillars, which may mean the leaves on trees will be eaten less frequently. In ecology this is dubbed a ‘trophic cascade’. Dorothy did this work in the context of fragmented forests, and she worked in forests that were either small and isolated from other forests, or in forests that were large and connected to other forests. This was done because there’s an expectation that these ecological effects will be different depending on the degree of fragmentation happening on the landscape. For example, insectivorous birds may decrease in abundance in small, isolated patches, which means their effects on insect prey (and perhaps herbivory) may be reduced relative to effects in larger patches of forest.

Dorothy Maguire, working in a forest fragment.

Dorothy Maguire, working in a forest fragment.

During one summer field season, Dorothy and Thomas wrapped up some small sugar maple trees in chicken wire, left some alone as controls, counted insects and spiders over the summer months, and measured herbivory on the trees themselves. As expected, the effects of the ‘cage’ was significant: when you put a cage around a tree, you end up with more arthropods living on those trees. This confirms other papers which report a similar effect: insectivorous birds (and perhaps other vertebrate predators) have a significant, and meaningful impact on the insects and spiders living on trees. Or, stated another way, birds eat critters living on trees, and without these birds, there would certainly be more arthropods around!

Dorothy did not uncover a strong effect on the process of insect herbivory: although more insects and spiders were living in the trees protected by chicken wire, the leaves themselves were not affected. This could be because more insect predators were around, and thus compensating for the lack of birds, and eating just as many herbivorious insects (e.g., caterpillars) as the birds might have eaten.

The lanscape of southern Quebec. Lots of agriculture, some patches of forest.

The lanscape of southern Quebec. Lots of agriculture, some patches of forest.

Scaling up to the landscape context, there were no overall significant effects of the cage treatments in relation to the forest type, nor was the level of herbivory dependent on the landscape context. The general results for large, connected patches were no different than for small, isolated patches. However, the magnitude of the effect was marginally affected by the landscape context for the cage exclusion: vertebrate predator may have a more significant impact in smaller, isolated patches.

As with all research projects, this work resulted with as many questions as answers, which is equally frustrating and fascinating. It’s clear that vertebrate predators are important in these systems, but more work is needed to fully assess whether these effects are truly affected by the degree of forest fragmentation on the landscape. The lack of effects on the process of herbivory itself was equally intriguing – there are clearly many complex interactions occurring on small maple trees. Some of these interactions involve top-down predation events, but there are likely a suite of ‘bottom-up’ effects that are also influencing the system.

Reference:

MAGUIRE, D. Y., NICOLE, T., BUDDLE, C. M. and BENNETT, E. M. (2014), Effect of fragmentation on predation pressure of insect herbivores in a north temperate deciduous forest ecosystem. Ecological Entomology. doi: 10.1111/een.12166

What is the motivation for pursuing graduate school?

Last week an interesting hashtag was floating around twitter:  #whyididaphd.  It was great to see reflections on this topic, and during our most recent lab meeting, I asked my students why they were pursuing advanced research-based degrees, and here are some of their responses:

  • Graduate school allows an opportunity for freedom to do the things you find interesting, every day.
  • Doing research means you can follow your interests and curiosity.
  • Doing a MSc is a perfect transition between an undergraduate degree and whatever might come next!
  • Doing research is an opportunity to work independently, and this is important to me.
  • Research is about gaining knowledge and learning on  your own. It’s like the best kind of drug: you can get hooked and it’s good for you, and it never ends.
  • Graduate school develops my network of collaborators, and I need this as I enter the work force.
  • I want to do things that are relevant, and are my ‘own’. Research allows this.
  • Doing an advanced degree was an important career stage, because I need it in order to do what I really want to do into the future (i.e., academic position).

These reflections were insightful, and showed that the students had wonderful motivations for pursing advanced degrees in a research-based laboratory. I agree that doing a MSc or PhD is perfect for people who are curiosity-driven, and who appreciate the independent nature of the work.

I had two responses to #whyididaphd. The first one certainly reflects my thinking now:

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The second response is a little more honest, and reflects my thinking at the time I decided to continue with research, about 20 years ago:

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Is it wrong to pursue a MSc or PhD “just because there’s nothing better to do”, or “because I don’t have another plan and I like University”?  We had a heated debate about this, and the lab was divided. One argument is that it’s a total waste of time, energy, money and resources to pursue a MSc or PhD “just because”. Sure it’s nice to stay in a University after the undergrad degree is done, but why pursue it unless you know you need that advanced degree!  Have a plan, have a career goal, and if a MSc or PhD is part of that plan, pursue graduate school.

In contrast, if you don’t have a plan, or a specific career in mind, perhaps graduate school is the *perfect* place to develop your research skills in an exciting, and familiar environment. Graduate school is a perfect transition to many, many careers, so if there is nothing else on your horizons, keep on trucking along at a University! If you are a curious person, and independent thinker, it’s an ideal learning environment.

I suspect many people fall somewhere in the middle (I think that was the case for me).  I always felt I might eventually like a career at a University, and since I seemed to like research, and be good at it, pursuing graduate school was a natural progression. So, even if the motivations for doing graduate school aren’t always based on a clear career path, those motivations can still be more than enough to give it a try.

I’ll finish by expanding that last point: “give it a try” does not mean “stick with it even when it’s not working”.  It’s important to know when to quit if grad school is not for you. It’s an awfully difficult and frustrating process if it’s not going well. Give it a try if it floats your boat, or it’s what you need. However, also know when to quit.

 

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Congratulations to the new Doctor of spider behaviour

I’m delighted to announce that lab member Raphaël Royauté successfully defended his PhD yesterday….  and he did it with grace, maturity, and poise. The defence was fair, but tough, and Raphael was able to show his breadth and depth of expertise on the broad topic of behaviour in arthropods.

Raphaël’s thesis was titled “Factors influencing behavioural variation in apple orchard populations of the jumping spider Eris militaris (Araneae: Salticidae)” and the during the defence, he was asked (not by me, remarkably!) to offer a ‘tweet’ of the his thesis. Here it is, coming in at almost exactly 140 characters.

Raph's thesis, in a tweet.

Raph’s thesis, in a tweet.

So, his research looked at behavioural syndromes in this remarkable jumping spider: Raphaël collected spiders in apple orchards, maintained them in a laboratory and ran them through a battery of behavioural test. He defined behaviours, looked at correlations among these behaviours (sometimes called ‘personality’), and how these traits varied during the development of individuals, consistency of these behaviours and whether behaviours differed depending on whether the spiders came from insecticide-free on insecticide-treated orchards.  Raphaël also looked at the direct effect of sub-lethel effects of insecticides on behaviour and will soon be publishing the ways that insecticides mess up their personalities.

Raphaël has really done incredible work – but looking back, I should not be surprised. Soon after he arrived in the lab we worked together on a short project about the activity of spiders right after snowmelt, at at that point, I was impressed with his intellectual curiosity, drive and motivation, and overall approach to scientific research.

Raphael and me, in 2008

Working together on Raph’s first project at McGill

After that first project, Raphaël came back to McGill to work on a PhD with me and Dr. Charles Vincent as co-supervisors. And now, many years later, he is now successfully defended a PhD. What a marvellous journey, and I can honestly say that I’ve learned far more from Raphaël than he could have learned from me.

Good luck Raph! (And you’ll be missed in the lab)

Charles Vincent (l), Raphaël (c) and me (r), just after the Defence (17 March 2014)

Charles Vincent (l), Raphaël (c) and me (r), just after the Defence (17 March 2014)

Congratulations to the lab

Last week my laboratory attended the Entomological Society of Canada’s annual meeting, held in Guelph. I was so proud of the whole lab – we had an impressive showing at the meeting, and I was especially impressed with the three undergraduate students who presented their research to Entomologists from across Canada. Wow – I don’t think I had that amount of confidence when I was an undergrad!

I am THRILLED to announce that three arthropod ecology students were recognized for their excellent presentations.

First, Master’s student Étienne Normandin was awarded first prize for his oral presentation in the Biodiversity section.  His talk was titled Biodiversity of wild bees in two urban settings: Montreal and Quebec city. He’s co-supervised by Valérie Fournier at Laval University. Here’s a photo of Etienne doing some field work:

Field work!

Field work!

Second, PhD student Dorothy Maguire was the runner up in the the same Biodiversity section. Her oral presentation was on Insect herbivory in fragmented forest landscapes: linking land use with changes in biodiversity and ecosystem function. Dorothy is co-supervised by Elena Bennett. Here’s a photo of Dory doing what she loves!

Tree climbing!

Tree climbing!

Finally, PhD student Raphaël Royauté was runner up in the student poster competition, for his work titled Does physiological state affect individual variation in boldness in a jumping spider?  Raphaël is co-supervised by Dr. Charles Vincent, from Agriculture and Agri-Food Canada.  Here’s an older photo of me and Raph, not long after he first came to the lab for a short internship.

Raphael (left) and Chris (right), working hard.

Raphael (left) and Chris (right), working hard.

My favourite spider species: a natural history story 120 years in the making

A little while ago my nephew asked me what my favourite spider was. I quickly answered “Peckhamia picata“, in part because I had recently returned from a field trip in which that species was collected (a trip to one of my favourite places in Quebec), but also because the species has the most amazing habitus: is a myrmecomorph – a species that looks a heck of a lot like an ant. Here’s a photo to illustrate this:

A species of jumping spider in the genus Peckhamia (photo by Alex Wild, reproduced here with permission)

A species of jumping spider in the genus Peckhamia (photo by Alex Wild, reproduced here with permission)

So, what does this species do? What are its behaviours? Where does it live?

I started digging around to see what literature exist on this species. There are certainly many publications that discuss its distribution – it is on many checklists (see here for a relatively complete list), and I was aware that it was originally described as Synemosyna picata (by Hentz, in 1846).

I did a search of Web of Science for publications with the species name, and came up with two hits. One was a systematics papers on a related genus of jumping spider, and the second was a paper by Durkee et al. in 2011*.  They did some laboratory studies of the species, to assess whether or not its ant-like appearance helped it avoid being eaten by predators (spoiler: the answer is yes). A little more digging on-line took me to various sites, and in some cases, I came across this statement:  “almost no information on them

What?  Really?

A Peckhamia picata, from Quebec (Photo by J. Brodeur, reproduced here with permission)

A Peckhamia picata, from Quebec (Photo by J. Brodeur, reproduced here with permission)

Peckhamia picata is a widespread species, with an incredible appearance, and it’s a jumping spider!  Salticids are the darling of the arthropod world –> the panda bears of the invertebrates: big eyes, furry, fascinating courtship behaviours, and truckloads of ‘personality’.  Surely we know SOMETHING about what I declared as my favourite species.

Thankfully, in a filing cabinet in my laboratory, I have a series of older publications on the Salticidae, including “A Revision of the Attidae of North America” by Peckham & Peckham (1909) [available here as a PDF download – note: big file!]. The George and Elizabeth Peckham did an incredible amount of work on the Salticidae (called Attidae, previously). The Peckhams are themselves a fascinating story – some details are on their Wikipedia page  and I’ll summarize briefly: they were teachers (in Wisconsin), natural historians, behavioural ecologists and taxonomists, notably with jumping spiders.  The bulk of their work was done in the late 1800s, and they often cited and discussed Darwinian concepts. They were awesome and I would have liked to meet them.

Another stunning Peckhamia species, this one from Thomas Shahan.

Another stunning Peckhamia species, this one from Thomas Shahan.

So, back to Peckamia picata: Their 1909 tome states the following about the species “We have described in detail its mating and general habits in Vol. II, Part 1 of the Occ. Pap. Nat. Hist. Soc. Wis. pp. 4-7)”.

So, apparently 1909 does not take us far enough back in history to learn about Peckhamia picata. Their paper from 1892 had all the details, and thankfully was fully accessible on the biodiversity heritage library.

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Here is some of the lovely writings about Peckhamia picata, from the Peckhams, in 1892 (transcribed from their papers):

About appearance:

While picata is ant-like in form and colour, by far the most deceptive thing about it is the way it which it moves. It does not jump like the other Attidae [Salticidae], nor does it walk in a straight line, but zig-zags continually from side to side, exactly like an ant which is out in search of booty. This is another illustration of which Wallace has shown in relation to butterflies ...”

(note: The Peckhams give a node to that Wallace guy….)

About feeding behaviour:

Spiders commonly remain nearly motionless while they are eating; picata, on the other hand, acts liks an ant which is engaged in pulling some treasure-trove into pieces convenient for carrying I have noticed a female picata which, after getting possession of a gnat, kept beating it with her front legs as she ate, pulling it about in different directions, and all the time twitching her ant-like abdomen

Regarding courtship:

From the Peckham's 1892 publication.

From the Peckham’s 1892 publication.

His abdomen is lifted vertically so that it is at right angle to the plane of the cephalothorax. in this position he sways from side to side. After a moment he drops the abdomen, runs a few steps nearer the female, then then tips his body and begins to sway again. Now he runs in one direction, now in another, pausing every few moments to rock from side to side and to bend his brilliant legs so that she may look full at them.”

In sum, this journey of discovery has made me fall in love with Peckhamia picata even more. It’s also reminded me that OLD literature is essential to our current understanding of the species we identify. There is a wealth of information in these “natural history” papers – although the writing is in a different style, it is scientific, it is the foundation of current biodiversity science.  We cannot ignore these older books and “Occasional papers”. We can’t rely on quick internet searches and we certainly can’t rely on literature indexed on Web of Science.

We must dig deep and far into the past. There are ‘treasure-troves’ aplenty.

—————–

*The oldest paper cited in Durkee et al. is from 1960. They did not cite the Peckhams.

Another Peckhamia species, courtesy of Matt Bertone (reproduced here, with permission)

Another Peckhamia species, courtesy of Matt Bertone (reproduced here, with permission)

References:

Durkee, C. A. et al. 2011. Ant Mimicry Lessens Predation on a North American Jumping Spider by Larger Salticid Spiders. Environmental Entomology 40(5): 1223-1231

Peckham, G.W., and E.G. Peckham. 1892. Ant like spiders of the family Attidae Occ. Pap. Nat. Hist. Soc. Wis. II, 1 .

Peckham, G.W., and E.G. Peckham. 1909. Revision of the Attidae of North America. Trans. Wis. Academy of Sci., Arts & Letters. Vol. XVI, 1(5), 355-646.

The art of delegation: Perspectives from Academia

The talented graduate student (and all-around great guy) Morgan Jackson recently posted a question on twitter, asking for advice on the art of delegation, from an Academic perspective. This question really struck me as important, for graduate students who are pursuing academic careers and for tenure-track academics.  The reason why is pretty obvious: without learning how to delegate, burnout is inevitable.

To delegate means to entrust (a task or responsibility) to another person, typically one who is less senior than oneself.

The issue of how to delegate is, of course, common and widespread in the business community but academia is a bit peculiar. Let me explain my perspective: In some cases, delegation is straightforward, especially if a staff member is paid to do a particular job and if roles and responsibilities are well defined. Although these kinds of hierarchies exist in Universities and research institutes, these environments often include a high amount of volunteerism and some aspects of Universities (and research more generally) are run on collegiality and community-minded thinking.  Scientific societies would disintegrate if people didn’t share the work-load, and if society president’s weren’t able to delegate work to (often unpaid!) treasurers, web-masters and scholarship committees.  Universities wouldn’t operate effectively if Professors didn’t agree to sit on committees, often delegated by the Chairperson. Research laboratories would be unhappy places if some of the chores weren’t delegated, from making sure coffee supplies are well stocked, to ordering supplies – sometimes a paid technician does this work, but not always….

Academia is also full of “reverse hierarchies” – sometimes a more junior person has to ask a more senior person do take on a responsibility or task – this happens all the time: from seeking help putting together a symposium at a conference, to getting people to agree to sit on an editorial board.  Bottom line: there are COUNTLESS tasks in Academia that depend on delegation and often the tasks, roles and responsibilities don’t fit neatly into one person’s formal (paid) job description, and often the ‘senior to junior’ hierarchy isn’t straightforward .

And perhaps the most important point of all….  one of the biggest obstacles to delegation is the fact that many Academics are perfectionists. Academics, by in large, like to be in control of ALL THE THINGS, from preparing a CV, to setting up committee meetings, to driving a car to a field site. Professors, in general, have got to their position because of their ability to DO ALL THE THINGS and do them well. You can’t publish good papers without knowing how to write; you can’t publish papers without solid research funding, so you have to perfect the art of writing grants; you can’t get a post-doc position of tenure-track position without being able to put together a top-notch presentation and deliver it with the skills of a seasoned orator; you can’t get good teaching scores without investing time and energy into perfecting Powerpoint slides and learning the content….  etc., etc., etc.

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However, as Peter Adler wrote over at Dynamic Ecology recently, it doesn’t get any easier. In fact, the job gets more demanding on time, expectations on productivity remain, teaching can be time-intensive, and the Academics are expected to do some administration. From a personal perspective, I am far busier now than I have ever been in the past (but I try not to complain about it).  Good time management skills are not enough to get everything done. What’s needed is an ability to delegate. Again, without effective delegation, burnout is inevitable.

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With that backdrop, how do you delegate?

1) Know the players. Delegation requires knowing your community and knowing the skills and abilities of people within your community, whether it be a graduate student secretary, the treasurer of a scientific society, or a colleague down the hall. Before you can even think of delegation, realize that delegating any kind of work has a real, profound affect on somebody and on how they spend their time. It’s about people, so you must get to know these people! This means networking, whether it be around a coffee maker at work, over twitter, or attending a poster session at a conference.  Pay close attention to everyone you interact with, listen to them, learn their passions, learn what they like to spend their time doing.

2) Play nice. In addition to knowing your community, don’t be a jerk to your community! I mentioned Morgan Jackson at the start of this post; he’s an example of someone who is always willing to lend a hand, say a kind word, and be a team player. He plays nice. I am always happy to help Morgan in return, even though I am (in academic terms) his ‘senior’. This seems SO obvious, but I also know that not everyone plays nice. Some people are selfish, ignore those they deem as ‘inferior’, and require you to grovel to get an answer to an email.  It’s a tough world, and there are big personalities in Academia, and everyone has their own agendas.  This can be difficult to navigate, and politics in Academia can be fierce. However, a strategy that always wins is to play nice. Be collegial, polite, and try not to burn bridges. It’s hard to delegate if there’s nobody left that respects you.

3) Prioritize. Delegation is an art, and one of the trickiest parts is learning what to delegate and what to keep on your own plate. It’s also important to avoid delegating everything. Some things are too close to your own expertise, part of your job description and/or are tasks that you just love too much to give up. However, some tasks can be shared effectively among others, and can move away from your to-do list. Write down ALL that you have to do, and put a star beside those that you cannot see anyone else doing (ahem, if there are stars next to all of the tasks, you will burn out. Start again, and see point #6, below). If your are lead-author on a paper, you sure ought to read over those final page proofs! However, maybe your co-author could do a final check over all references, especially if s/he hasn’t contributed as much to the paper..?

4) Have a vision (& communicate it!). Delegation will not be successful if those you delegate to are not sure what role they are playing in the ‘big picture’.  No matter the size of the task, it is being done for some reason. Having someone give a guest lecture is pretty obvious: the guest lecture helps achieve the learning objectives of the class and gives students a new perspective on the content. Sure, that makes sense. But did you communicate that to both the students and the person giving the lecture? EVERYONE involved needs to understand the ‘why’ behind the jobs and tasks at hand. This means effective delegation requires carefully assessing why tasks are being done, and working to communicate this. If people are part of a vision (even one they may not 100% agree with), it’s a lot easier to get them to take part.

5) Ask and Explain. Sometimes it’s as easy as asking (nicely). This goes much smoother if you have a vision and that you have communicated this vision, as mentioned above. In addition to asking, it’s essential that the tasks you are delegating are clearly defined. A volunteer might agree to sort specimens if you ask them. However, a simple ask may result the job getting done, but perhaps with a lot of mistakes. Asking, and then giving someone a 1 hour tutorial and access to resources on-line will result in fewer errors. Preparing a living document that explains your protocols for sorting and letting them refine and improve the document is even better!  All tasks, regardless of their size, need to be defined. Just because you think it’s easy to do, straightforward, and simple doesn’t mean everyone else will.

6) Let go. (TRUST) I have noticed that many Academics (myself included!) don’t delegate because they say “Ah heck, I already know how to do that, it’ll take too much time to explain or show them how to do it…” or “I’ll do that myself, it’ll be faster“. There are a few problems here. First, if you say this about everything, burnout is inevitable. Second, as an Academic / Researchers/ Post-doc, etc, you are responsible for sharing knowledge and training others, and this takes time. In the time it takes you to ‘just do the task’ five times, you could have trained someone else. Third, this may indicate that you don’t ‘trust’ anyone else to do the job. You must let go of this! Be a perfectionist at the right times, but let some things go. There are errors in everything we do, so sharing them around is fine, for some tasks.  Remember, you have developed a network, you are team player, and you have shared your visions and prioritized, and defined the tasks. It’s time to let go.

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7) Verify. Letting go does not mean letting go forever. There must be follow-up and discussion to ensure the job is done well. Accountability is key. Review the job, first on your own, and then with the person to whom the work was delegated. You must provide constructive feedback, but also listen to ideas, complaints and comments. This will help you redefine the task in the future, and they will feel more responsibility and ownership over the task. This also starts the amazing process of creating someone who can later become a delegator of tasks. This is what mentoring is all about… in your laboratory or classroom, you want people to walk away with confidence in what they do, and with an ability to take their skills sets and pass them along to others.

8) Reward. It’s absolutely essential that you reward those to whom you have entrusted a task or responsibility. If people do not feel their work is valued, and that they have not contributed in an important way, you have failed in effective delegation. If you reward, your vision will grow, your team will respect you, your (positive) network will increase. Rewards can be small or big: A few kind words, a big “THANK YOU”, some homemade cookies, a promotion, or a letter of reference. Here’s an example: I often get graduate students to give guest lectures in my courses. This saves me time, and helps me out when I’m overwhelmed. When students do these lectures, I offer to write them letters or recommendation specifically about their abilities in the classroom. Most take me up on this, and it’s a kind of reward. I also ensure to pass along kind words from the students in the class.

9) Get some training. The art of delegation is seldom on an Academic’s CV. It’s often learned by trial and error, and sometimes never really perfected. Like any skill, training is required. In some cases, informal training is enough. This can be via sitting on committees in scientific societies, learning from effective mentors, or just practicing. However, I think that most Academics are not very good at delegation, and more formal training is required. This could be in the form of workshops, perhaps for all incoming Profs at a University, or as part of a research conference. I would like to see these kinds of ‘management’ skills as part of EVERY graduate student’s program, as perhaps part of the seminar/course work often required during a graduate degree. WE MUST DELEGATE ergo WE MUST HAVE TRAINING.

10) Be a leader. Don’t shy away from leadership. Everything mentioned above is about leadership.  Professors are leaders, perhaps a leader in front of the classroom, as a research leader within your institution, a leading expert in an op-ed piece, or a leader on a committee about academic programs. Effective leaders are effective at delegation; in fact, I might argue it’s impossible to be a leader without being effective at delegation.  Behind every good leader is an even better team. It’s so cliché, but also so very true.

In sum, delegation is about empowerment and leadership. It’s about giving someone else ‘ownership’ over a task that is part of something bigger. Delegation will help you work on things that YOU need to work on, and help you avoid burnout. It’s a required skill for success in Academia.

(BIG thanks to twitter-folks to took part in the conversation about delegation, especially Morgan, Terry, Chris, Staffan, and others)

Lunch in the tree-tops for the birds and the bugs

A few weeks ago, our laboratory published a paper in PeerJ (an open-access journal) titled “Vertical heterogeneity in predation pressure in a temperate forest canopy“. This work resulted from a project by former Master’s student Kathleen Aikens. She graduated a little while ago, and although we published one of her thesis chapters in 2012, it took another year to get this paper out, in part because Kathleen and I both become too busy.  Thankfully, post-doc Dr. Laura Timms agreed to help us finish up the paper, and she worked with me and Kathleen to re-analyze the data, re-write some sections, and whip it into shape.

As is now traditional for my laboratory, here’s a plain-language summary of the paper:

Tree canopies, including those in deciduous forests in southern Quebec, are important for many different animals, including insects and spiders. These small, marvelous creatures crawl up and down trees with regularity, feed upon the leaves of trees, feed upon each other, and are food for animals such as birds and bats. Past research has shown that many species of insects and spiders live in tree canopies, and in general, more insects and spiders are found closer to the ground compared to the very tops of the trees. This makes sense, since deciduous tree canopies often need to be recolonized each spring, and tree canopies are relatively harsh environments – they are windy, hot, and often-dry places as compared to the forest floor.  What we don’t know, however, is whether the insects and spiders avoid the tree canopies because they may be eaten more frequently in the canopy as compared to the understory. The objective of this research was to test this question directly, and find out whether insects and spiders are arranging themselves, vertically, because predators may be preferentially feeding on them along this vertical gradient. This is a very important area of study since biodiversity is highly valued and important in forests, but we cannot fully appreciate the status of this diversity without discovering what controls it.

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Our mobile aerial lift platform. TO THE CANOPY!

We did this work by using two experiments that involved manipulating different factors so we could get at our question in the most direct way possible. In the first experiment, we made ‘cages’ out of chicken wire and enclosed branches of sugar maple trees in the cages. We did this at the ground level all the way to the tops of trees, using a ‘mobile aerial lift platform’. These cages acted to keep out large predators, such as birds, but allowed insects and spiders to live normally on the vegetation. We counted, identified, and tracked the insects and spiders both within these cages, and in adjacent branches that did not have cages (the ‘control’). By comparing the control to the cage, we could find out whether feeding activity by larger vertebrate predators affected insects and spiders, and whether this differed when comparing the ground to the top of the trees. In the second experiment, we used small pins and attached live mealy worms (larvae of beetles) to the trunks of trees, and we did this in the understory all the way up to the canopy. We watched what happened to these mealy worms, and compared what happened during the day and overnight. This is called a ‘bait trial’, and let us figure out what sort of predators are out there in the environment, and in our case, whether they fed more often in the canopy compared to the ground-level. This second experiment was designed for seeing the effects of insect and spider predators along a vertical gradient whereas the first experiment was focused more on vertebrate predators (e.g., birds).

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Munch munch. Carpenter ants feeding on mealworms.

Our results from the first experiment showed that the cages had an effect: more insects and spiders were found when they were protected from predation by birds. Birds are playing a big role in forest canopies: they are feeding on insects and spiders, and in the absence of vertebrate predators, you might speculate more insects and spiders would occupy trees. Our second experiment showed that ants were important predators along the tree trunks, and overall, the most invertebrate predators were found in the lower canopy. Both experiments, together, confirmed that the understory contained the most insects and spiders, and was also the place with the highest amount of predation pressure.  The take-home message is that there is an effect of predation on insects and spiders in deciduous forests, and this effect changes if you are in the understory as compared to the top of the canopy. We also learned and confirmed that insects and spiders remain a key element of a ‘whole tree’ food web that includes vertebrates such as birds, and that predators in trees tend to feed on insects and spiders along a gradient. Where there is more food, there is more predation pressure! Our work was unique and novel because this is the first time a study of predation pressure was done along a vertical gradient in deciduous forests. It will help better guide our understanding of forest biodiversity, and the processes that govern this diversity.

A more detailed discussion of this work is posted on the PeerJ blog.