Taxonomic sufficiency in biodiversity research: Is it always necessary to identify species?

It’s been a successful few weeks in the lab!  Two weeks ago I promoted an exciting paper about spider silk and herbivory and just after that paper come out, another publication from our lab was published, titled: “Does species-level resolution matter? Taxonomic sufficiency in terrestrial arthropod biodiversity studies“.  This paper evolved out of a past graduate-level class in Forest Entomology at McGill, and was re-worked and re-written by post-doc Laura Timms, former Phd student Joseph Bowden, and my colleague Keith Summerville.

Let me provide a plain language summary of this work and I will also touch upon some of the controversy that has arisen because of this paper:

Biodiversity science is about the discovery and description of all the different kinds (species) of organisms living on our planet.  It is a vitally important area of research because different species play important roles in our ecosystems, and as a consequence, are important to us.  The different number of species in an area can also inform us about how we might be harming or helping ecosystems.  This is an active area of study in the context of forestry, since some forest practices (for example, cutting all the trees down in an area) can cause changes in the number of species (and whether they are rare or common) and these changes can inform us about whether our forestry practices are harming our ecosystems.  All of this kind of work, however, depends on the ability of scientists to collect, sort, and identify different kinds of species.  Since most described species on the planet are Arthropods (e.g., spiders, insects, and their relatives), these animals are often used as a way to indicate how biodiversity might be affected by environmental change.  However, there is a problem: it takes a very long time to identify different arthropods, and it is costly and difficult – requiring highly specialized training, by people known as taxonomists.  In our research project, we asked whether not you always need to know the exact differences between insects and spiders  in order to tell if a disturbance is affecting biodiversity.  We did this by looking at a series of data-sets about beetles (Coleoptera), moths & butterflies (Lepidoptera), and spiders (Araneae). These data-sets were from past research projects about how forest disturbance affects biodiversity.

Here is how we did the work: Different kinds of organisms are classified using a two-part name:  the genus and the species.  There can be many different species within one genus.  You can then classify different genera (the plural of genus) into grouping called Families.  For example, all wolf spiders are in the Family Lycosidae.  A common genus within this family is Pardosa – there are dozens of species of Pardosa in Canada; Pardosa mackenziana, Pardosa moesta, Pardosa hyperborea, etc.  We first took our big data-sets and using the lowest level of naming (the species) we asked whether forest disturbance affected biodiversity.  We then grouped all our species into their respective genera -this meant that the data-sets got smaller (i.e., there are necessarily fewer genera than species).  We did the same analysis to see if we could still get a signal about the effects of disturbance on biodiversity, but now with the ‘reduced’ data.  We did this again at the family level.  We did this because we wanted to know if you could take a short-cut. Stated another way, if you don’t have the time or ability to figure out all the species in your research project, can you still see if there is an effect of forestry on biodiversity?

A wolf spider (Lycosidae)

A wolf spider – do you need to know its name?

Our results showed that in most cases, you do not need to know the species identity to see the effects of forestry practices on the biodiversity of spiders, beetles and moths & butterflies – you do not get as clear answers when things were grouped into Families, but the datasets with species grouped into genera were almost as good as when you group things into species.  This was surprising, because an assumption in biodiversity science is that species-level identifications are necessary and should be the ‘gold standard’ for this kind of research.  We showed that in many cases, you can get your answer by identifying arthropods to the generic level:  this can save you a lot of time (and money).   Some researchers (including taxonomists) may not be thrilled with this result as it might suggest that species are not important, and specialized taxonomic knowledge is not essential to complete biodiversity research.  This is certainly not the case, which leads me to the caveats:

1) Our results do not mean species are not important!  Instead, we are saying that if there are logistical and financial constraints, you might be able to answer your research question without having to identify all the species.   If you have a project about large-scale disturbance and are looking to see whether there are any broad affects on biodiversity, our approach might work.   However, you might miss some subtle effects, so this approach must be taken with caution.  Although our suggestion is a short-cut, it would still be important to save all the samples, and at a later time (as money and expertise permits) the species could be determined.

2) Our study is specifically geared towards research about insects and spiders in relation to large-scale forestry disturbances.  We are not saying that this will work in all situations and with all different kinds of organisms! The context is important.  Related to this, if an overarching research question is about species in an ecosystem, species-level identifications are essential.  Everything depends on the research question and the research context.

3) This general approach that we have discussed is highly dependent on what kind of organisms you are studying.  If you are working with a group of organisms that do not have too many different species within a genus, our approach may work.  If, however, there are many species within a single genus, our suggestion will not work as well.  Therefore, a researcher should look at the general relationship between the number of species per genus for their study organisms and use this ratio as a guide when thinking about taking the short-cut that we discussed in the research.

In sum, we are quite excited about this research – we think it will provide more opportunities for biodiversity projects to get done, and will help answer certain research questions when there are substantial constraints on time and money.  This is one way to be pragmatic about biodiversity research.

Please share your thoughts!

Reference:

Timms, L., Bowden, J., Summerville, K., & Buddle, C. (2012). Does species-level resolution matter? Taxonomic sufficiency in terrestrial arthropod biodiversity studies Insect Conservation and Diversity DOI: 10.1111/icad.12004

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.

Notes from the field: Yukon wildlife (Part 3)

Here is Part 3 from the “notes from the field” series  – an account of a recent field research trip to the Yukon.  Click here for Part 1 and here for Part 2. 

17 July, 10 AM, Dawson City, Yukon

I am back in the world of electricity, Internet, hotels, and tourists.  The layers of mosquito repellent have finally been washed off after a much-needed shower in the Hotel last night.

Arctic Pardosa wolf spiders… captured.

The big news is that the day after I last wrote, we managed to find and collect Pardosa glacialis! We woke early on July 15 and went up to the high elevation tundra habitats located exactly on the border of the Yukon and NWT (we are not even sure what Territory to write on our collection labels! – the site was, literally, on the border!).  All five of us helped Katie look for wolf spiders, and after a couple of hours of searching and collected, we found dozens of specimens – this was thrilling, as these specimens are very important for Katie’s research and we were getting anxious about not finding any. We also got a little bit lucky – within an hour of that sampling, some rather nasty weather blew in and we were forced back to camp for the afternoon.  In the rain, tundra wolf spiders tend to hunker down deep into the moss and lichens, not to be seen.

I have mixed feelings about being able to catch up on e-mails, and I certainly miss my family.  However, I am also missing the fields of cottongrass on the Arctic tundra, eating cloudberries in high mountain passes, and seeking new localities for the Arctic pseudoscorpionThe Dempster Highway is a biologist’s dream – full of wildlife, stunning vistas, amazing habitats, a unique biogeographical history, and a region that hosts a rather stunning and diverse arthropod fauna.

I will be back up here again.

The Yukon landscape.

Notes from the field: Yukon wildlife (Part 2)

Here is Part 2 from the “notes from the field” series  – an account of a recent field research trip to the Yukon.  Click here for Part 1. 

14 July, 11 PM, Rock River Campground, km 445 (Dempster Highway), Yukon

“Bag of spiders” – a nice haul of wolf spiders!

We have had a busy few days – we finally got some drier weather in Tombstone and Laura and Barb were able to do some collecting, and Crystal set some more traps.  We left Tombstone a couple of days ago to drive north, collecting en route.  We have seen some of the larger wildlife, including arctic fox, moose, and grizzly bears.   However, our sights were really set on the smaller wildlife: Barb was particularly impressed with the diversity of parasitic wasps at a place called “Windy Pass” – this area is known for hosting a lot of rare, Beringian species, and entomologists have collected at this locality for decades. We crossed the Arctic Circle yesterday, and the Rock River campground is nestled in a river valley just north of the Arctic Circle.  We are now officially in the Richardson Mountain range – the tundra habitats about 10 km north of this campground is one of the most beautiful places on the planet.  I feel very lucky and privileged to be here.

Although we had some more rain and cold weather yesterday, today was a perfect summer day at this latitude (i.e., it got just above 20C) – it was also a very windy day, which was bliss since higher winds mean that the incessant hordes of mosquitoes are kept at bay.  Fieldwork in the sub-arctic is quite challenging, in part because of the mosquitoes.

Self-portrait geared up for the biting flies.

We collected well into the NWT, getting all the way to the Peel River (located about 540 km up the Dempster).  Crystal found the most northern locality for Wyochernes asiaticus in the NWT and for that reason I will buy her a beer whenever we get back to civilization!   Unfortunately we have yet to find Katie’s wolf spider species – we have checked a few locations but have come up empty – there are certainly many other species of wolf spiders on the Tundra, but the ones we have collected have not been Pardosa glacialis.  Our team is a little anxious about this, as we only have a few more days at the Richardson Mountains before heading south.

We are now back in camp and it should be time to crawl into the tents.  At this latitude it is pretty difficult to think about going to sleep – it is light 24 hours a day, so it is hard to trick the body into thinking it is time for sleep.   It’s even harder to get to sleep knowing that Pardosa glacialis is out there…somewhere.

Stay tuned for Part 3, coming Friday…

 

Notes from the field: Yukon wildlife (Part 1)

This is the first of a three-part series that was originally published (as one article) in the McGill Reporter, as part of their “notes from the field” section – it is an account of my research trip to the  Yukon, back in July.  It is reproduced here, with permission.  For a different (yet complementary!) account of this field trip, see The Bug Geek’s blog posts, Part 1 and Part 2.

MSc student Katie Sim searching for wolf spiders in the Yukon, among fields of cottongrass

8 July 2012, 10 PM, The Westmark Hotel, Whitehorse Yukon

Our entomology research team has just arrived in Whitehorse in anticipation of our upcoming fieldwork in the Yukon.  I just returned to my room after enjoying a beer at the hotel bar where we completed our GIANT shopping list this evening. Tomorrow morning we are picking up our RV, and will be driving about 500 km NW of Whitehorse (on paved roads) before turning onto the Dempster Highway – this famous Yukon road is a dusty, gravel road that heads straight up towards the Northwest Territory, crossing the Arctic Circle, and taking you from boreal spruce forests in the south to sub-arctic tundra in the North.  The Dempster crosses the Yukon-Northwest Territory border at about kilometer 465, and then continues on to Inuvik.   It’s a big trip with few opportunities for groceries along the way.  We are all part of the Northern Biodiversity Program – a multi-University collaborative project about the diversity of insects and spiders in Canada’s North.   After months of planning, applying for research permits, and fine-tuning our methods, it is great to finally be here.  That being said, I worry that the excitement and anticipation will keep us too jittery to get a good night’s sleep tonight – too bad since after tonight, we’ll be sleeping in tents rather than hotel rooms!

10 July 2012, 3 PM, Tombstone Campground, km 72 (Dempster Highway), Yukon

We have made it up to the Tombstone mountain range, about 75 km up the Dempster Highway.  Unfortunately, the weather has not been cooperative, so we are stuck in the campground, huddling in a cook-shack with other travelers.  Most of the other campers are on vacation, so we are unusual since our trip is for research.  We are also unusual because unlike most visitors to this part of the world, we are NOT viewing large wildlife (bears, moose) but are instead spending our time searching for the tiny wildlife along the Dempster highway.

PhD student Crystal Ernst installing insect traps on the Yukon Tundra

Our team includes two graduate students from my laboratory, Crystal Ernst and Katie Sim.  Crystal has been setting out “pan traps” (yellow bowls) to collect ground-dwelling arthropods (i.e., insects, spiders).  Part of her PhD is about unraveling some of the complexities of arthropod-based food webs in the Arctic, and she is using these traps to collect critters that live on the tundra.  Thankfully, her work does not require good weather!  Katie is working on the population genetics of a high arctic wolf spider, Pardosa glacialis – and she needs some more specimens.  We know that the species occurs near the Yukon-NWT border (in the Richardson mountains), about 300 km north of us.  A post-doc, Dr. Laura Timms, is part of our team also – she studies plant-insect interactions in the North, and is focusing her research on insects that feed on Willow and Balsam Poplar trees.  Our final team member is Dr. Barb Sharanowski, an entomology professor from the University of Manitoba – she is collecting parasitic wasps, with a goal of better understanding their evolution and diversity in northern environments.  Unfortunately, Barb and Laura’s work is dependent on dry and warm weather, so they are hoping for good conditions!

I am here to find a small (< 4 mm) and curious Arachnid known as the “Arctic pseudoscorpion“.  Pseudoscorpions are relatives of other Arachnids, and resemble scorpions, but without a tail.  They are predators (of other invertebrates) that live in soil, leaf-litter, under bark, and under rocks.  The species Wyochernes asiaticus lives under rocks beside creeks and rivers in the Yukon.  It is a Beringian species, meaning it exists in North America in regions that were unglaciated during the last ice age, including many regions in the Yukon. The Dempster Highway travels directly through a lot of these regions.   I have previously collected this species in the Yukon, and on this trip, I am hoping to gather more specimens to further understand its full distribution, and to collect data about its biology and life-history.

This morning, despite the rain, our team traveled to a half-dozen streams further south from this campground, and we had great success in pseudoscorpion hunting!  Numerous specimens were found under rocks beside creeks, including females with their eggs held under their abdomen.

We are now drying out and I am about to finish preparing a seminar that our team will deliver tomorrow at the campsite.  The Tombstone Park staff are keen to have researchers discuss their work with the general public – it’s a nice opportunity to share our research stories with other people traveling the Dempster.  I am always thrilled that all types of audiences show keen interest and enthusiasm about insects and spiders.

Stay tuned…later this week will be Parts 2 and 3

A few reasons to study Arctic entomology

I’m a big fan of the Arctic, and I am on a mission to get more people interested in studying northern ecosystems.  In this post, I wanted to share some of the reasons why:

Poorly understood food-web

Arthropod-based food-webs in the Arctic are largely unknown.  This is a great research opportunity – our laboratory is working on this, and I am trying to put together an Arctic food-web from an arthropod perspective.    My PhD student Crystal Ernst is also thinking a lot about how high Arctic food webs are structured, and has some interesting ideas and thoughts in one of her previous posts.

Some of Crystal’s thinking about high arctic food-webs (reproduced here, with permission)

Look at all those spiders!

As most terrestrial Arctic biologists know, spiders are among the most common of the Arctic animals.  Our lab has documented that wolf spiders on the tundra occur at a high density, and the biology of Arctic wolf spiders is amazing.

An Arctic wolf spider (Lycosidae) female with egg sac, living on scree slopes of high elevation slopes, Bylot Island (Nunavut)

So, if you are an aspiring Arachnologist…head north!

Excellent base-line dat

Arctic Entomology has a long history of excellence.  Canada has been sending entomologist up to the Arctic for decades, perhaps most notably the Northern Insect Survey of the 1940s, 50s and 60s  – some information on that survey can be found here .  There has also been a lot of research at Lake Hazen, at the tip of Ellesmere Island (above 81 degrees N)  – earlier work reports over 200 species of Arthropods up at Hazen and a recent article in the Biological Survey of Canada’s newsletter, found here, does a nice job of summarizing the insect studies at Hazen (including our own work with the Northern Biodiversity Program).  These past studies provide an excellent baseline for current and future projects related to Arctic entomology – and you need a baseline to move forward.

The Arctic is changing

The Arctic is a very fragile and special environment, and one that is changing rapidly, in part because of climate change.  Permafrost is melting, tree-line is changing, glaciers are melting, and plant and animal assemblages are facing dramatic changes to their environments.  We must strive to document, quantify, and study the biology of life in the Arctic, and given the dominance of arthropods (i.e, diversity and abundance) in the north, they are a priority.  The time is NOW for Arctic entomology.

Biting flies:

If you have an interest in biting flies (and many people do, believe it or not!), the Arctic is the place for you.  Emerging from the tundra are thousands of flies, per hectare.  Many of them want your blood, and if they don’t get you during the day, they will be there at the end of the day, in your tent.

A host of biting flies, sitting between my tent and the tent fly. Just waiting for me to exit the tent and have a feast.

…and a couple of other reasons that have less to do with entomology:

Canada = Arctic 

We are a northern country, eh?  However, few of us spend much time in the “REAL” north.  From a biogeographic standpoint, we are a country without roads and people, but with a lot of boreal forest, tundra, and high arctic landscapes.

It is beautiful

The north is stunning; awesome landscapes, vistas that never end, big sky, large rivers, glaciers and mountains.

The stunning landscape of the Yukon Territory (Tombstone range)

A walk in the woods

Last week I had the opportunity to visit my PhD student Dorothy Maguire at her field sites south of Montreal.  It was a glorious summer day, and given the construction holiday in Quebec, the travel time was quick and effortless (for Montrealers, you know what I am talking about!).  I have briefly described Dorothy’s research in a previous post, and during the field visit, I was able to see Dorothy and her two field assistants ‘in action’.  This included checking samples from an aerial malaise trap, beating the foliage (for herbivores) in the forest canopy, and checking contents of a Lindgren funnel (set up in the canopy to collect flying insects, including beetles).

Thomas and Camille checking the contents of the aerial malaise trap

It was an amazing day for natural history.  In fact, I sometimes think my graduate students cannot stand spending time in the field with me, since I tend to walk slowly, vial in hand, stopping all the time to pick up a spider or beetle, or to turn over a log to search for pseudoscorpions.    I’m probably much more of a burden than a help in the field, and this probably leads to some resentment (ha ha).

Anyway – it was great to get into the forest again after time in the Arctic, and I was thrilled at all the biodiversity starting me in the face.

What did I see?

A dozen or more species of trees, including shagbark hickory, ironwood, and the usual suspects (American beech, sugar maple, red maple, some oaks)

Some stunning underwing moths (Catocala) (although they were somewhat less stunning than usual since they were dead, in a Lindgren funnel!)

The BIGGEST horsefly that I have ever seen (probably Tabanus atratus).  Yikes – I captured it before it bit me – it could have hurt.  A lot.

The big, nasty horse fly (Tabanidae)

Butterflies, butterflies, butterflies!  Including the beautiful great spangled fritillary (Speyeria cybele) and the northern pearly-eyed (Enodia anthedon)- the latter is one of the few shade-loving butterflies in this part of the world

Hundreds of sap beetles (family Nitidulidae) – these were very common in the aerial malaise traps, but were also flying into us much of the day

Some GIANT Scarabaeidae beetles – I don’t know the species but they were robust and impressive; masters of their universe.

Dozens of Harvestmen (Opiliones), which I later identified as Leiobunum aldrichi – I have now started a colony at home (much to my children’s delight).

Female (l) and male (r) Gypsy moth, caught in the act.

Gypsy moth (Lymantria dispar) – a lot of gypsy moth.  This species in an invasive, introduced species.  Gypsy moth caterpillars can feed on hundreds of species of trees, including our beloved Sugar maple.  This is one species that I am not happy about seeing, and its numbers this year are certainly higher than last year.

And to top it all off.. Antlions (Neuroptera: Myrmeleontidae).  Yes, Antlions!!  These are among the most fascinating of the insects -the larvae build conical sand-pits and await ants that happen to slip into the pit and fall down into the waiting predator.  I have lived in the Montreal area for over 10 years and I had no idea that Antlions existed this far north.  Wow.

Quebec Antlion “trap”, photographed just south of Montreal

This is only part of the list, but one thing is clear – a hot, mid-summer day in a Montreal-area forest is full of the wonders of Nature.  I didn’t have to look very far, and I didn’t have to look very hard.  Furthermore, most of what I mentioned was all from a rather small forest fragment surrounded by agricultural lands.   We must study, document, quantify the biodiversity within these forest fragments – they are very special, and they host a diverse and fascinating flora and fauna.

 Take a walk in your local woods, and see what you can find under leaves, bark, climbing up trees and catching a few rays of sun in a small clearing.  It’s a nice way to spend a summer day.

Why I study obscure and strange little animals

I sometimes find myself defending why I study obscure and strange little animals.  Questions such as “what good are they” are asked of me.  I sometimes get weird looks when I describe what it is like discovering new distribution records of a tiny jumping spider, or the thrilling anticipation of turning over a rock to see what hides underneath.  I have to remind myself that not everyone is fascinated by the natural world.  I also think it is worthwhile reminding myself why I study small animals. Here is a list:

The Arctic pseudoscorpion Wyochernes asiaticus (copyright C. Ernst, reproduced here with permission)

I study these animals because they are there even if we can’t always see them.

I study these animals because they are unknown, and stir up a sense of curiosity, wonder and awe; their biology is as amazing as any other species.

I study these animals because they play important roles in their ecosystems; roles that we have yet to fully understand.

I study these animals because they are one piece of a giant biodiversity puzzle – they are as interesting and fascinating as primates, blue whales, oak trees, honey bees, or coral reefs.  

I study small animals because they are giants in their own world; size is relative.

I study these animals because they are beautiful; they are a landscape painting; they are a a Bach Cello Suite; they are millimetres of perfection.

I study these animals because they have a history; a history as great as their larger cousins; they are evolution exemplified.

I study these animals because nobody else does.

The Arctic pseudoscorpion Wyochernes asiaticus (copyright C. Ernst, reproduced here with permission)

What are your reasons for studying small, strange animals?

(thanks to Crystal Ernst for the stunning photographs of Wyochernes asiaticus – these photos were taken on our recent field trip to the Yukon)

 

Holistic views of ecosystems: linking salmon and butterflies

Beautiful Anchorage, Alaska

I’ve spent most of my week in beautiful Anchorage, Alaska.  I was attending a workshop that brought together scientists from Northern countries to discuss an Arctic Terrestrial Biodiversity Monitoring Plan. The goal of this ambitious plan is to include all key taxa, include all northern countries, and find ways to standardize methods and harmonize data.   There were a half dozen bird experts around the table, numerous experts on Arctic vegetation, a large contingent of mammal experts, and one arthropod expert (me).  This is a situation I have been in before, and will be in again in the future – largely because arthropods are not “charismatic” nor do they typically fall into management plans.  Regardless, I welcomed the opportunity to discuss ways that Arthropods can and should fit into large-scale, and long-term monitoring plans in the Arctic (there are, by the way, some tremendous arthropod monitoring programs underway – the Zackenberg research station in Greenland, for example, has been collecting arthropods using standardized protocols for almost 20 years)

The workshop was exciting, challenging, motivating, and overall a wonderful opportunity to discuss the interdisciplinary concept of biodiversity monitoring.   A great example of an interdisciplinary approach was a presentation we heard about using traditional knowledge to understand the Natural Indicators of the Salmon run in the Yukon River, a river that drains out to the ocean in Alaska. This was organized/facilitated by the Yukon River Drainage Fisheries Association.  This presentation highlighted a project where Elders were asked about what helped them understand the Salmon run in the river – a critically important process for people living in this part of Alaska.  I was amazed to hear that for some Elders, the appearance and activity of certain species of butterflies (and sometimes biting flies) was one of the indicators that was used to predict when the Salmon would run.

An Arctic Butterfly

Yes, you read correctly: Butterfly activity indicates the Salmon run.   The claim that activity of insects relates to the Salmon run is not a direct connection as the insect activity was considered as a “Correlative indicator”.  The observation is that when certain insects appeared and were active, so were Salmon, hence the correlation.  This does make some biological sense as many of the environmental factors affecting butterflies are probably also important to salmon.

The Yukon River Drainage Association went on help to produce a children’s book titled When Will the Salmon Come?. This is a richly illustrated, beautiful book that discusses all the Natural Indicators that Elders use to know when Salmon will appear on the river, and the insect activity is highlighted.   A children’s book is a wonderful way to connect with a broad audience.

When will the salmon come? (the book cover)

Being a skeptical scientist, I went and searched the literature for anything ‘published’ on the topic of Salmon and butterflies, and I could not find anything.  This does NOT mean it’s not a real and important observation. It means that it is a truly fascinating and curious correlation that was observed by Elders living close to the river, and by people who likely approach nature from a holistic standpoint.  I need to do this more; we all need to do this more. Natural systems are interdisciplinary yet we often study them in silos, defined by a specific taxon or system.

In sum, I was most pleased to be the lone entomologist in a large interdisciplinary workshop  about biodiversity monitoring in the fragile Arctic – my horizons were certainly broadened.  The story of butterflies and salmon made me take a step back and consider how different groups of people can bring different perspectives and all are equally valid.  In other words, keep an open mind, and think of this story when you see some butterflies passing by…they could be telling you an important story – you just have to listen.

Rethinking guild classifications for insect herbivores

This is the start a (somewhat) regular series of blog posts highlighting some of my favourite research papers in the discipline of Arthropod ecology – I’ll call this category “must-read research papers”.  These posts will force me to look critically at some of the great research papers I have read in the past little while, figure out the ‘take home messages’ from these papers, and articulate this message.  I also hope these posts can inspire others to think about the best papers within their discipline and to share their opinions and ideas to a broad audience.  That is what science communication is all about! 

Typical herbivory by a “leaf chewing” insect

For the first in this series, I wanted to highlight a paper by Novotny (and fifteen other co-authors) published in 2010 in the Journal of Animal Ecology.  This work is titled “Guild-specific patterns of species richness and host specialization in plant–herbivore food webs from a tropical forest.”   This paper was discussed in my Insect Diversity class last autumn (co-taught with Terry Wheeler), and was used as an example of assumptions we make when considering what it means to be a herbivore.    From my biassed perspective (working mostly in north-eastern deciduous forests and the Arctic), when I think about herbivores, I automatically classify herbivores into a few pretty obvious categories: leaf chewers, leaf miners, gall-makers, and a suite of ‘piercing-sucking’-type herbivores.  My off-the-cuff estimate of the number of herbivore guilds would be much less than a dozen.

Novotny et al.’s paper really shook up my view of what it means to be a herbivore.  Using their considerable data and expertise from work in Papua New Guinea, the authors refine plant-herbivore food webs and, quite simply, explode the concept.    The authors classified insect herbivores by their main mode of feeding (chewing, sucking), developmental stages (larvae, adult), where they feed (internally, externally), and by the plant part which is fed upon (leaves, flowers, fruits, xylem, phloem, etc).    Their system resulted in 72 classifications – which they reduced down to more manageable 24 – still over double what my initial estimate was.  Their system certainly includes the classic guilds (e.g., leaf chewers) but also included some wonderfully detailed interactions that are easily overlooked (especially by someone who studies spiders…).  For example, fruit chewers, flower chewers, and xylem suckers.   As an aside, and for some eye candy, here’s a nice photo of a caterpillar from The Bug Geek (reproduced here, with permission)

A cryptic caterpillar, (c) C. Ernst

The authors then took their new and detailed classification system and completed a food web analysis for their tropical system in Papua New Guinea, focusing on 11 main guilds.  Their resulting 11 food-web diagrams are a lovely depiction of multivariate data in 2-dimensions, as they show the frequency with which each host plant is consumed by herbivores, the herbivore abundance and the frequency of each interaction – and they present this for 9 standardized plant species, for each of the 11 guilds.   Their research depicts “6818 feeding links between 224 plant species and 1490 herbivore species drawn from 11 distinct feeding guilds”. WOW!  They also show that 251 species of herbivores are associated with each tree species within their study system.  There are clearly a lot of different ways for herbivores to make a living.

This paper represents a major undertaking, and it is a bit sobering to see the results and see that despite the efforts, relatively few ‘generalities’ exist – that is to say, there are examples of extreme host specificity, extreme generalist feeding, and everything in between.   Here’s a quote from that paper to illustrate that point:

“We documented a wide range of host specificity patterns among herbivorous guilds: host specificity measures spanned almost the full range of theoretically possible values from extreme trophic generalization to monophagy. These results demonstrate the importance of taxonomically and ecologically comprehensive studies, as no single guild can be designated as ecologically representative of all herbivores.”

Mealybugs: another type of herbivore. (c) C. Ernst, reproduced with permission

What’s the take-home message?  

For me, this is a strong paper that depicts effectively the complexity of plant-herbivore food-webs and illustrates (once again!) that diversity in tropical forests is stunning. More than that, the work shows this diversity from a functional, food-web perspective, and illustrates how guilds behave differently.   From a more practical perspective, this paper is forcing me to rethink how I view herbivores – i.e., they are more than leaf-chewing caterpillars and aphids.  They are also root-feeders, fruit chewers, flower chewers, and specialized xylem suckers.  Novotny et al. suggest researchers use their 24 guild system for classifying insect herbivores, and I agree – their classification system is still manageable, yet much more comprehensive than what many researchers use.

If the topic of food-webs, plant-insect interactions, and the biodiversity & ecology of tropical forests interests you, this is a must-read paper.

Reference:

Novotny, V., Miller, S., Baje, L., Balagawi, S., Basset, Y., Cizek, L., Craft, K., Dem, F., Drew, R., Hulcr, J., Leps, J., Lewis, O., Pokon, R., Stewart, A., Allan Samuelson, G., & Weiblen, G. (2010). Guild-specific patterns of species richness and host specialization in plant-herbivore food webs from a tropical forest Journal of Animal Ecology, 79 (6), 1193-1203 DOI: 10.1111/j.1365-2656.2010.01728.x