Natural history of canopy-dwelling beetles: More than just ‘Fun Facts’

This is the second post by undergraduate student Jessica Turgeon – she’s doing an Honour’s project in the lab; here’s her first post that introduces the project.  Since that first post, Jessica has spent a LOT of time at the microscope, and has identified over 120 species of spiders and beetles from forest canopies and understory habitats.

Every species has a different story to tell and each one of these is equally interesting. I sometimes think about natural history as ‘fun facts’: something interesting about an organism (or species) to tell children so that they can appreciate nature. As my time at McGill progressed and my knowledge of the natural world deepened, I realized that the ‘fun facts’ are actually built upon a very strong scientific foundation, and can help us understand results of research projects. Natural history can sometimes be reduced to ‘fun facts’ but it’s a whole lot more than that!

The European Snout Beetle on a pin.

The European Snout Beetle on a pin.

I decided that perhaps I should look at the natural history of some of my species and maybe this would shed light on some patterns that I’m seeing within the data. The most abundant beetle species was Phyllobius oblongus (Curculionidae) with 69 individuals. Interestingly, we only collected this species in the first half of our sampling season and they were mainly collected on black maple and sugar maple trees. To try and understand why this is so, I turned to the species’ natural history, and to the literature.

These weevils tend to eat fresh leaf shoots and prefer the soft leaves found on maple trees. Once the maple’s leaves are fully-grown, P. oblongus moves on to plants with indeterminate growth, like raspberry bushes (Coyle et al. 2010). This corresponds exactly to our data: the beetles were found on our black and sugar maples during the beginning of summer and then they taper off as the season progressed!

Beetle data: the European Snout Beetle was only collected during the beginning of the season.

Beetle data: the European Snout Beetle was only collected during the beginning of the season.

To make this even more interesting, P. oblongus is an invasive species. Its common name is the European Snout Beetle and was accidentally introduced into North Eastern North America in the early 1900s. While most invasive species are a cause for concern, both the Canadian and American governments largely ignore this species. It may inflict some damage to trees but not enough to be worried about. They’re more annoying to researchers than anything since they congregate in the trees in large numbers!

The second most abundant beetle species in the collections was Glischrochilus sanguinolentus (Nitulidae). This species is native to Canada and rather abundant. Species in this genus are called sap beetles but this species in particular is more commonly called a picnic beetle. Large groups of G. sanguinolentus swarm to picnics since they are attracted to sweet food, which ruins the picnics. In nature, they feed on the sap produced by injured trees – hopefully not an indication that the trees we were climbing were damaged!

The natural histories of species open new doors to understanding how organisms live and interact with one another. I thought that it was strange that P. oblongus completely disappeared from my samples midway through the sampling season and its natural history explained why this was so. Picnic beetles eat the exuding sap of an injured tree so in the future I’ll be on the lookout so that I don’t accidentally climb a broken tree! So really, natural history is more than just ‘fun facts’; it helps us understand patterns and to better understand how our natural world works.

References

Coyle, D.R., Jordan, M.S. and Raffa, K.F., 2010. Host plant phenology affects performance of an invasive weevil, Phyllobius oblongus (Coleoptera: Curculionidae), in a northern hardwood forestEnvironmental entomology,39(5), pp.1539-1544

Evans, A.V., 2014. Beetles of eastern North America. Princeton University Press.

Summer in the trees: Undergrad research on canopy spiders and beetles

Note: this post is written by undergraduate Honour’s student Jessica Turgeon, who is a member of the arthropod ecology laboratory. This post is part of the requirements for her project, and is an introduction to her research.

I’ve always been interested in nature and the environment but was never a big fan of insects. As time went on and I learned to appreciate all organisms big and small I realized that I didn’t really have a preferred “pet taxon” but rather was interested in ecology and community structure. I found others that my interests were shared with other members of the arthropod ecology lab, and I was able to start an Honour’s project in the lab earlier this fall.

Using a beat-sheet in the tree canopy, to collect arthropods

Using a beat-sheet in the tree canopy, to collect arthropods

I was given an opportunity to do an internship at Kenauk Nature, a 65,000-acre plot of land near Montebello, Quebec. This property is primarily used for the hunting and fishing industries, but they are branching into scientific research. Kenauk was keen to support three McGill interns to complete the Black Maple project, the pilot project for Kenauk Institute.

The Black Maple project revolves around black maples, since Kenauk is the only area in Quebec to have a black maple stand. The project consisted of three sub-projects, one for each intern and each project dealing with a different taxon. While the two other students worked on plants and birds, my project was about arthropods and their diversity in Kenauk. We wanted to characterise the community structures of beetles and spiders based on vertical stratification and tree species: this involved tree-climbing!

Jessica - getting ready to climb up!

Jessica – getting ready to climb up!

During the summer, I looked at abundance data and concluded that beetles were more abundant in the upper canopy and that spiders were more abundant in the understorey. This internship transitioned into my Honour’s project, where I plan to look at species richness and functional diversity to answer my questions on community assemblages. To my knowledge, this has never been done at Kenauk Nature and would provide great baseline data for the owners of the property.

We sampled in three sites, each containing three trees. Each site had one sugar maple (Acer saccharum), one black maple (Acer nigrum) and one American basswood (Tilia americana). Within each tree we sampled five times: twice in the understorey, once in the middle canopy and twice in the upper canopy. We also used two different types of traps: beat sheets, an active technique, and Lindgren funnels, a passive technique. Both trap types are specialized, with beating more tailored towards spiders and Lindgren funnels invented to collect beetles. When beating a branch, the arthropods fall on a 1m2 sheet and are then collected whereas Lindgren funnels are hung in a tree and passively collect arthropods that fly into it.

LindgrenFunnel

As part of our job, we learned how to use a single ropes climbing system, a one-person method of using ropes to climb a tree. All three interns caught on quickly and it easily became our favourite part of the job. However, we did have to sort through the samples, a job requirement that wasn’t nearly as fun as climbing trees. But this is what happens in ecology: you romp around in the woods to collect your data then spend time in the lab analysing them. It was nice to experience this first-hand and I must say, I liked it and am looking forward to future projects like this.

Now that the summer is over and collection is completed, I spend all of my free time in the lab identifying beetles and spiders. All of the beetles are identified and about half of the spiders are identified. From this work, Kenauk Nature can proudly say that the property supports 24 families representing 117 species of beetles! Once the Kenauk Institute officially launches, more rigorous research can be done to try and increase these numbers.

Learning Taxonomy... spider drawings (of male palps) help.

Learning Taxonomy… spider drawings (of male palps) help.

All in all, from the sampling in the summer to the identification in the lab, this has been a great experience. Here’s to hoping the second half of my honours project will be as equally fun and challenging as the first half was! Stay tuned for a blog post to be published in the spring of 2016: it will summarize the main results from this Honour’s project.

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.

image

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).

image

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.

Arthropods in the tree-tops: Canopy ecology in Quebec (Part 3)

This is the final post in a three part series about studying canopy arthropods in Quebec.  Part 1 was about canopy access and Part 2 was about patterns of diversity.  This post is about ecological interactions in the canopy. 

I had the pleasure of supervising a M.Sc. student, Kathleen Aikens, who was keen to work on a canopy project that looked deeper into some of the ecological interactions occurring in our deciduous forest canopies.  This was possible since we had, by this time, acquired a lot of base-line data on arthropods in many strata of the forest.  Kathleen’s work included using exclosure cages to see whether or not bird predation might affect arthropods in the Canopy differently than in the understorey.   This was exciting work, as it took our laboratory in a new direction, and lets us start to unravel some of the complexities of the food-webs in the tree-tops.  Her main result was that birds did have a strong top-down effect on arthropods, and that effect did differ as a function of height.  Using some bait trials, we also found that predation by arthropods on arthropods was also stratified.   This research suggests that arthropods living in trees in our region of the world are always under significant predation pressure, from both vertebrate and invertebrate predators.

A cage experiment, to assess the effect of predators on insects living in the forest canopy.

More recently, my laboratory has started to collaborate closely with another group at McGill studying “ecosystem services” – this is work done with Elena Bennett, another colleague at McGill University.  The research framework with this project is about how different ecosystem services are affected by the fragmented landscape that occurs in a large region just south of Montreal.  Elena and I co-supervise a PhD student Dorothy Maguire, who is looking at the ecosystem function of insect herbivory, and studying how herbivory varies as a function of forest size and degree of isolation (i.e., from a large contiguous forest), and she is studying herbivory in the understorey as well as the canopy.  Herbivory is closely linked to ecosystem services because of its effect on nutrient cycling, forest aesthetics, and more.  Although this project is currently underway, Dorothy is uncovering some interesting results, already.  For example, she is finding that levels of insect herbivory differ between the understorey and the canopy, and that forest fragmentation is affecting insect herbivory.

Summary

I have provided some highlights of some of the work that our laboratory has done in Quebec’s deciduous forests (and my apologies to the students who I didn’t mention!).  Although we have come a long way, and uncovered some interesting research results, I still feel that the work is just beginning.  For example, the bulk of our work has been on only two tree species (Sugar Maple and American Beech), and we have only studied a fraction of the arthropods that exist in the canopies of our forests.  I would like to expand the research to include other plant-feeding guilds, bees and wasps.  I’m also always curious about the piles of dead and decaying leaves that we find nestled between the crotches of high branches – these micro-habitats surely contain suspended soil (e.g., see Lindo & Winchester 2007), and within those “islands” there should be a host of arthropods.   Not surprisingly, the forest canopies in southern Quebec are home to a marvelous diversity of arthropods.  It’s a scientist’s model system, and a delightful system in which to work and play.

Me (Chris Buddle) above the canopy at Mont St Hilaire!

Arthropods in the tree-tops: Canopy ecology in Quebec (Part 2)

Part 1 of this series highlighted how our laboratory accesses the forest canopy.  This post is about our projects related to understanding patterns of Arthropod diversity in Quebec’s forest canopies.

I will first highlight some work done by my former PhD student Dr. Maxim Larrivée.   Max started in my lab at the exact time that I received the grant for the mobile lift platform, and he become an expert at this machine, and he proved to be an immensely talented student.  His project was focused on understanding the spatial patterns of spider diversity in three deciduous forest sites located within an hour drive of the Island of Montreal.  In the first part of his dissertation, Max collected almost 14,000 spiders representing 82 species (Larrivée  & Buddle 2009).  The spider fauna of the canopy was markedly different from the fauna from the understorey, and it is likely that different mechanisms structure the assemblages in the two habitats.

Overall fewer spiders and fewer spider species were found in the canopy compared to the understorey, but at a species-specific level, there were some spiders that seemed to have a preference for living in tree-tops.  For example, the lovely jumping spider (Salticidae) Hentzia mitrata was significantly more common in the canopy.   We were also most excited to document the species Mastophora hutchinsoni (Araneidae) in the canopy – this is the famous “bolas spider” and we believe our canopy record may be the most northern record for the species.  The Bolas spider hunts by swinging a strand of silk at its prey, and this strand has a “bolas” of sticky capture thread at the end.  This species is truly fascinating, and in our system, it is a species that likes the canopy.

Max demonstrating the methods of using a beat-sheet to collect spiders in the forest canopy. Here, he is about 25 m above the forest floor.

The follow-up work to this baseline study was focused on understanding dispersal potential of spiders in the canopy as compared to the dispersal potential of understorey species.  Most spiders in our system are small, so we predicated that their main mode of dispersal was via ballooning (i.e., releasing a small strand of silk and letting the wind carry the spider away).  We had also hypothesized that dispersal might be one of the mechanisms behind the aforementioned patterns community structure in the canopy compared to the understorey.  Max collected live spiders in the canopy and understorey and set them up in a wind-tunnel in the laboratory.  He then documented each species’ propensity to disperse by looking at the frequency by which they showed ‘tip-toe’ behaviour (a pre-ballooning condition).  In the paper resulting from this research, we reported that the spiders in our system do have high dispersal potential, but that this potential did not differ depending on whether the spider was collected in the canopy as compared to the understorey (Larrivee & Buddle 2011).   This was a fascinating area of study, and we are left with as many questions as we started with!   For example, if dispersal potential doesn’t differ between canopy and understorey species, what mechanism drives the differences in community structure between the two habitats?

Our laboratory has been studying beetles as well as spiders – although I am personally very interested in spiders, I do recognize the beauty of beetles, and their important ecological roles in virtually all ecosystems.  One of Max’s field assistants (Brianna Schroeder) was keen to complete a small project about beetles so she set Lindgren funnels in the canopy and in the understorey.  Over 170 species were collected, and once again, the fauna from the canopy was differentiated from that of the understorey (Schroeder et al. 2009).

Max up in the canopy crane!

Two other field assistants that worked with Max (Kristen Brochu and Katleen Robert) also worked on their own projects, and together with my colleague at McGill University (Prof. Terry Wheeler), we are close to finishing up a manuscript to describe more patterns of arthropod diversity as a function of vertical stratification in Quebec’s deciduous forests – this work includes beetles as well as flies (Diptera).  Although the responses are not the same for the different groups of insects, we are finding that both beetles and flies show vertical stratification in our study sites.

Stay tuned for Part 3, which will focus on ecological interactions occurring in the Canopy.

Arthropods in the tree-tops: Canopy ecology in Quebec (Part 1)

This blog post is reproduced here, with permission, from the Spring-Summer 2012 Newsletter of the International Canopy Network.  Given the length of the article, I have split the newsletter into three separate blog posts – this is Part 1. 

Canopy research in most parts of eastern Canada is in its infancy, which is somewhat surprising because I think many Canadians feel a significant connection to forests and to trees – you might even argue it’s part of our culture, along with ice hockey and maple syrup.   I have spent a lot of time doing research on arthropods in forests, but only relatively recently began to shift my focus upwards to the canopy.  The reason is quite straightforward:  when studying the biodiversity of insects and spiders in forests, you just can’t ignore the canopy!

PhD student Dorothy Maguire demonstrates “Single Rope Technique” for accessing the canopy.

As I moved (up) into canopy research, I had originally planned on doing some process-oriented, experimental food-web research in the tree crowns.  I was optimistic that I could go to the literature to find some base-line inventories and those studies would provide a starting point for my research.  I quickly realized, however, that literature on arthropod diversity in “northern” canopies was virtually non-existent (with the notable exceptions being the excellent research done in the temperate rainforest system of western Canada, e.g., Lindo & Winchester 2007, 2008 and related publications). It therefore became clear that the first years of this new research direction would be focused on descriptive biodiversity research.  This is not a bad thing as it allows for the kind of work entomologists and arachnologists love to do:  trap some bugs, identify them, complete a faunal list, and investigate diversity patterns.

Canopy Access

Our laboratory has used two main methods of canopy access over the past six years: a mobile aerial lift platform, and single rope technique.  The mobile lift was acquired by a grant from the Canadian Foundation for Innovation.  It provides a safe way to get people into the canopy (its maximum height is about 26 m – which in our system, takes us to the upper canopy).  Its main limitation is that the lift platform has to be driven into a field site, meaning there must be a 2 m wide trail for access.  This means that selection of field sites, and individual trees, can be somewhat biased and limiting.  You could also argue that all our trees are on soft forest edges.    For that reason, we have more recently starting accessing canopies using the well-known single-rope technique.  It has the benefit of getting you to any tree you like, but can be limiting if the researcher needs to complete complicated tasks at the ends of branches.  However, we are finding the single-rope technique a valuable method for getting our work done in Quebec forests.

Our laboratory’s “mobile aerial lift platform” used to access the canopy.

Stay tuned for Part 2, which will be about spatial patterns of diversity.

A classy canopy-dwelling jumping spider: Hentzia mitrata

I have just returned from a week of field work in the Yukon – and will report on that in some detail soon.  However, in the interim here is a short story about a lovely jumping spider (Family Salticidae).  This is a story that started quite a few years ago, with my graduate student at the time, Maxim Larrivée.  Max documented that the spider fauna of canopies of the forests around Montreal hosted fewer spiders than the understorey, and a lower number of species than the understorey (Larrivée & Buddle 2009).  However, he also noticed and documented that there were a handful of specific spider species that were more frequently encountered in the canopy compared to the understorey, including a stunning jumping spider Hentzia mitrata.  Here’s a photo, courtesy of Thomas Shahan .  (you can view more of Thomas’ amazing photographs here):

Hentzia mitrata, copyright T. Shahan, reproduced here with permission

Just recently our laboratory had a publication come out in The Canadian Entomologist on another study of spiders (and beetles) in the canopy of forests at the Morgan Arboretum (Aikens & Buddle 2012). This was work done by my former MSc student Kathleen Aikens.  As one part of her work, Kathleen asked whether there was vertical stratification in beetle and spider assemblages – there was, and in addition to that finding, Kathleen again documented that Hentzia mitrata was more common in the canopy as compared to the understorey – here’s a figure from that paper showing those data:

We have now published this finding three times – in Max’s work on foliage dwelling spiders (Larrivée & Buddle 2009), his work on bark-dwelling canopy spiders (Larrivée & Buddle 2010), and now with Kathleen’s work.  This is a convincing body of evidence: Hentzia mitrata has a strong affinity for tree canopies.  

But why?  Why is this species more common in the canopy compared to the understorey?  What does it eat in the tree-tops?  Where does it overwinter?  (our deciduous forest are bare, cold and snowy in the winter!).  As is typical, I have no idea.  We have yet to embark on any life-history study of Hentzia mitrata in the canopy, but it would be well worth pursuing.  In my experience, this species is not all that common in understorey habitats at our latitude, yet there it is, watching us with its big, curious eyes as we enter its tree-top realm:

Hentzia mitrata, copyright T. Shahan, reproduced here with permission

References

Aikens, K.R. & C.M. Buddle. 2012. Small-scale heterogeneity in temperate forest canopy arthropods: stratification of spider and beetle assemblages. The Canadian Entomologist, in press.  doi:10.4039/tce.2012.51

Larrivée, M.  & C.M. Buddle.  2009. Diversity of canopy and understorey spiders in north-temperate hardwood forests.  Agricultural and Forest Entomology 11: 225–237 DOI: 10.1111/j.1461-9563.2008.00421.x

Larrivée, M.  & C.M. Buddle.  2010. Scale dependence of tree trunk spider diversity patterns in vertical and horizontal space. Ecoscience 17:400-410 DOI 10.2980/17-4-3403