The effect of insecticides on jumping spider personalities

This post was written by C. Buddle and R. Royaute (a PhD student in the Arthropod Ecology lab).

We are pleased to announce a recent publication from our lab, titled Interpopulation variations in behavioral syndromes of a jumping spider from insecticide-treated and insecticide-free Orchards.  As is traditional in the lab, here’s a plain language summary of the work:

Agriculture has strongly intensified in the last 60 years, causing major concerns the sustainability of biodiversity. Agricultural practices can reduce habitats available for wildlife and also release toxins in the environment through the use of pesticides. Not all organisms living in agricultural fields are harmful, and many predators, including spiders, can help to reduce pest density. We have a relatively good knowledge that the diversity of spider species in agriculture, especially under our temperate latitudes, can help reduce pest damage. However, many of the factors that influence spider predation on pests depend on the outcome of behavioural interactions and we don’t know much about that topic. Spiders are often cannibalistic and aggressive with one another and these types of behaviours may limit their efficiency for pest control. We also need to understand if these aggressive tendencies vary depending on the type of agricultural field considered, a pesticide treated field may favour very different behaviours than one that is managed organically. Another important point is that populations are composed by a multitude of individuals, each with its own behavioural tendencies. Some individuals take more risks when confronted with predators (i.e. they are more bold), others are more active and explore larger areas or consume more prey. These tendencies – often referred to as personality traits – may also be correlated with one another.

In the context of agriculture, this may mean that certain individual spiders may contribute more to biocontrol because they consume more prey, or that certain individuals are more at risk of being in contact with pesticides because they are more active. To understand, how agricultural practices, and particularly insecticidal applications, affects personality and behavioural syndromes in spiders, we focused on the jumping spider Eris militaris, an abundant and charming jumping spider occurring in apple orchards in Quebec. Here’s a lovely photo from Crystal Ernst to illustrate how attractive they are: (thanks, Crystal, for permission to post the photo here!)

Screen Shot 2013-11-26 at 3.34.45 PM

We collected spiders from pesticide-treated and pesticide-free orchards, brought them back to the laboratory, and did a number of behavioural tests on the individuals from the two populations. Compared to the insecticide-free populations, we document that individuals from orchards that did receive insecticides experienced a shift in their behaviours syndromes. The overall shape of this syndrome is multidimensional, but it suffices to say that the correlations among different behaviours (the ‘syndromes’, otherwise known as the ‘personality’) differed depending on where the population came from.

A 'mirror test' - used to study behaviour in E. militaris (photo by R. Royaute)

A ‘mirror test’ – used to study behaviour in E. militaris (photo by R. Royaute)

In sum, the personality shifts that we documented for E. militaris are potentially quite important since the relationships between different behaviours may affect a spider’s ability to be an effective generalist predator in apple orchards. We need to consider how management  (including use of insecticides) may affect specific behaviours, and more importantly, the relationships between the different behaviours.

Reference

Royaute, R., C.M. Buddle & C. Vincent. 2013.  Interpopulation Variations in Behavioral Syndromes of a Jumping Spider from Insecticide-Treated and Insecticide-Free Orchards. Ethology. doi: 10.1111/eth.12185

Tablets in the forest: using mobile technology in Higher Education

I am pleased to present a publication that came out earlier this week in Educause Review On-line. This article resulted from a pilot project done in Fall 2012, in which students in my field biology class at McGill used tablets to enhance experiential learning.  Authors on the paper included colleagues from Teaching and Learning Services at McGill (Adam Finkelstein and Laura Winer), and PhD student Crystal Ernst.

Here are the ‘take away’ messages from the project:

  • Environmental biology students mobile devices to gather rich data in the field and to support learning through real-time interaction with their instructor and the larger research community.
  • The project included an analysis of survey and interview data to determine the impact of tablet use on student engagement once the project was complete.
  • Students recognized the value of the tablets as a research tool; however, the tablets’ most important contribution to learning was the real-time communication and feedback they enabled between students, instructors, and the scientific community.
A group using a Toshiba tablet to help identify an aquatic invertebrate

A group using a Toshiba tablet to help identify an aquatic invertebrate

Stated another way, tablets are wonderful to use, and can be effective tools in a field biology course, but the students felt connectivity (which facilitated communication) was essential: the mobile WIFI units paired with the tablets made the project successful.  Here’s a quote from the paper to further illustrate that point:  “most students (53 percent) reported that the tablets increased their interaction with the instructor and TA. This was corroborated by their responses on tool use: 72 percent of students thought that live communication with the instructor and TA helped develop their skills.”

I previously highlighted a video from that project on social media use in the class, and the video (below) is more specifically about the use of the tablets in the class.

This work was done in collaboration with Teaching and Learning Services at McGill, McGill Libraries, and the tablets were generously provided by Toshiba Canada, and Bell Mobility helped us with mobile WIFI units.  I am immensely thankful for the support and I am truly honoured to be able to explore these adventures in teaching and learning.  We are continuing with these kinds of initiatives, and a Brown-Martlet Foundation grant has allowed my Department to purchase some of the tablets originally used last year.

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.

Seasonality of Arctic Beetles

I’m excited to report on paper written by Crystal Ernst, PhD student in my lab, and well known as the “Bug Geek“. This paper is a product of the Northern Biodiversity Program (yes, it sure is great that the papers from this project are starting to appear!), and will be one of Crystal’s PhD thesis chapters. The paper is titled Seasonal patterns in the structure of epigeic beetle (Coleoptera) assemblages in two subarctic habitats in Nunavut, Canada

A very nice Arctic beetle! (photo by C. Ernst, reproduced here with permission)

A very nice Arctic beetle! (photo by C. Ernst, reproduced here with permission)

Here’s a plain-language summary of the work:

Although we often think of Arctic systems as cold and lifeless, Canada’s tundra habitats are home to a high diversity of arthropods (insects, spiders and their relatives). Beetles are important insects on the tundra – filling ecological roles as predators (feeding on other insects), herbivores (feeding on plants), mycophages (feeding on fungi), and necrophages (feeding on dead or decaying animals). In this research, we wanted to find out what happens to ground-dwelling Arctic beetles as a function of seasonality. We were curious about whether different species occurred at different times during the short Arctic summer, and whether the functions of the beetles changes over the summer. This is an important area of study because beetles perform important ecological functions, and knowing how these functions change over time may have broader implications for northern ecosystems. This is especially relevant in the Arctic since these systems have a short ‘active season’, and climate change is disproportionally affecting northern latitudes. If climate change alters an already short summer, what might happen to the beetles?

This research was done as part of the Northern Biodiversity Program (NBP) – a broad, integrative project about the diversity of insects and spiders across northern Canada. The NBP involved collecting samples at 12 sites in the Arctic, but at one of these sites (Kugluktuk, in Nunavut) we had an opportunity to do a more detailed collection over the entire summer of 2010. This involved setting out traps for the entire active season, from June through to August. These traps were plastic containers sunk into the ground – beetles that wander along the tundra fall unawares into these traps, which contain preservatives, and are trapped until a researcher collects the samples. Traps were placed in wet and (relatively) dry habitats so that we could compare the two habitats. After the collections were returned to our laboratory, the beetles were identified to species, counted, and the biomass of the beetles was estimated – biomass lets us determine what happens to the ‘amount of beetles’ on the tundra in addition to figuring out ‘how many’ (abundance) and ‘what kind’ (species) were in the traps. The beetles were also classified into their key ecological roles. The data were then compared as a function of when traps were serviced to let us assess what happens to beetles as a function of seasonality.

We collected over 2500 beetles, representing 50 different species – remarkably, 17 of these species represented new Territorial records. This means that 17 of the species that were identified had never before been recorded in all of Nunavut! Although many ecological functions were represented by the beetles we collected, most were predators. We documented that wet habitats had different kinds of beetle species than the drier tundra habitats, even though the actual number of species between the habitats did not differ. We also uncovered a seasonal affect on the functions of beetles in the system – as the season progressed, the beetles tended to be represented more by predators compared to earlier in the season, which was dominated by beetles representing a diversity of functions. The mean daily temperature also related to the seasonal change that was observed in the beetles.

PhD student Crystal Ernst, happily working on the Arctic tundra.

PhD student Crystal Ernst, happily working on the Arctic tundra.

This work is one of the first to carefully quantify how beetles change during short Arctic summers. We found a diverse assemblage of beetles, filling a range of ecological roles. These ecological roles, however, do not stay the same all summer long, and the shifts in the beetles were related to mean daily temperature. Given that Arctic systems will be significantly affected by climate change, this is worrisome – if temperatures increase, or become more variable, this may affect ecosystem functions that are mediated by beetles. This is more evidence supporting the need to track climate change in the Arctic, and play close attention to the small animals of the tundra.

Reference:

Ernst, C., & Buddle, C. (2013). Seasonal patterns in the structure of epigeic beetle (Coleoptera) assemblages in two subarctic habitats in Nunavut, Canada The Canadian Entomologist, 145 (02), 171-183 DOI: 10.4039/tce.2012.111

Assessing five decades of change in a high Arctic parasitoid community

As my colleague Terry Wheeler mentioned on his blog, our Northern Biodiversity Program team is thrilled to see post-doc Laura Timms‘s paper about Arctic parasitoid wasps published in Ecography!  Our team worked on Ellesmere Island, Nunavut, in 2010, and compared parasitoid wasps to historical collections from the same site that were made in 1961-65, 1980-82, and 1989-92. Parasitoid wasps are at the top of the insect food chain: they lay eggs inside or on top of other arthropods and the wasp larvae emerge after consuming their hosts – a gruesome but very common lifestyle for many types of wasps.  Species at higher trophic levels, such as these parasitoid wasps, are often the first to respond to new environmental pressures, including the climate change that is occurring rapidly in Arctic systems.

Laura identified a LOT of wasps, recorded the type of host attacked (e.g. plant-feeding hosts versus hosts that are predators), and the body size of two species of wasps that were commonly collected in all time periods.  We found no clear pattern of change in most aspects of the parasitoid wasp community on Ellesmere Island over past 50 years, even though temperature and precipitation have increased significantly during the same period. However, there were some signs that parasitoids of plant-feeding insects may be more affected more than other groups: one common parasitoid species that was abundant in 1960s hasn’t been collected since then, and the community in the 2010 study contained fewer parasitoids of plant-feeding insects than previous studies.

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Some members of the Northern Biodiversity Program working in the Yukon in 2012. (l-r, Chris Buddle, Laura Timms, Crystal Ernst and Katie Sim)

Laura takes it as a good sign that no major changes in the ecology of the high Arctic parasitoid community have been observed, but isn’t taking it for granted that the community will remain unaffected for long.  At 82°N, Ellesmere Island is relatively isolated, but other research has found that parasitoid communities further south are changing dramatically (Fernandez-Triana et al 2011).

Laura has the following comment about our work: “We hope that our findings will be used as baseline data for ongoing monitoring on Ellesmere Island”, said Timms.  “We know so little about these high Arctic insect communities, we should learn as much as possible about them while they are still intact.

References

Timms, L., Bennett, A., Buddle, C., & Wheeler, T. (2013). Assessing five decades of change in a high Arctic parasitoid community Ecography DOI: 10.1111/j.1600-0587.2012.00278.x

Fernandez-Triana, J., Smith, M., Boudreault, C., Goulet, H., Hebert, P., Smith, A., & Roughley, R. (2011). A Poorly Known High-Latitude Parasitoid Wasp Community: Unexpected Diversity and Dramatic Changes through Time PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023719

Where did all the spiderlings go? A story about egg-sac parasitism in Arctic wolf spiders

This week we are in a deep freeze in the Montreal area, so it seems somewhat fitting to discuss Arctic spiders.  I’ve discussed the life-history of Arctic wolf spiders (Lycosidae) before, specifically in the context of high densities of wolf spiders on the tundra.    Much of this work was done with my former PhD student Joseph Bowden.  The latest paper from his work was published last autumn, and was titled ‘Egg sac parasitism of Arctic wolf spiders (Araneae: Lycosidae) from northwestern North America‘. In this work we document the rates of egg sac parasitism by Ichneumonidae wasps in the genus GelisThese wasps are fascinating, and we have found them to be very common on the tundra.  There are often multiple wasps in a single egg sac, and as is typical with Gelis, they leave nothing behind: all eggs within an egg sac are consumed.  After fully developed, the adult wasps pop out of the egg sac; the Gelis adults we encountered had both winged forms and wingless females, the latter superficially resembling ants.

A Gelis emerging from a wolf spider egg sac. Photo by Crystal Ernst, reproduced here with permission.

A Gelis emerging from a wolf spider egg sac. Photo by Crystal Ernst, reproduced here with permission.

The rates of parasitism of Pardosa egg sacs (by Gelis) were, at some sites, extremely high.  In some cases over 50% of the wolf spider egg sacs were parasitized.  Stated another way,  half of all the females encountered with egg sacs had zero fecundity because the female was  carrying around wasps within the egg sac instead of spider eggs.

It’s quite interesting to think about these wingless Gelis femalesafter emerging from egg sacs, they end up wandering around the tundra in search of hosts.  Spiders with egg sacs must be encountered frequently enough for the wasps to grab on to a passing wolf spider in order to parasitize the egg sac.  Recall, densities of wolf spiders can be very high in the Arctic (4,000 per hectare, at least).  Hmmm…. this is all starting to fit… high densities of wolf spiders support high rates of egg parasitism and these wasps can ‘afford’ to be wingless since their hosts are frequently encountered:  an interesting feedback loop!   We can also speculate about large-scale gradients in diversity – many Ichneudmonidae show high diversity in northern regions.  Within Gelis, it’s a good bet that they will find many suitable spider hosts in these environments.

Looking down the microscope - all those Gelis!

Looking down the microscope – all those Gelis!

So, how extreme are these rates of egg parasitism?  Looking at some of the literature, there are certainly a number of papers about  wasps that parasitize spider egg sacs.  Cobb & Cobb (2004) studied two Pardosa species in Idaho, and recorded a egg parasitism rate of about 15% (by Gelis wasps and wasps in the genus Baeus [Sceleonidae]). Van Baarlen et al (1994) studied egg parasitism in European Linyphiidae spiders and their maximum rates of parasitism were about 30%.   Finch (2005) did a detailed study of four spiders species (non-Lycosidae) and rates of egg parasitism varied between 5% up to as high as 60% in an Agroeca species.

Our documented parasitism rates for Arctic wolf spiders are certainly quite high (for Lycosidae), but not out of the range of other published studies for non-Lycosidae.  I do wonder whether we will continue to find high egg parasitism rates if more species were examined in detail – certainly a fertile area of study.  Related to this, what are the population-level consequences of this interaction?  What is the relationship between spider densities and parasitism rates?  Although Joe and I did try to speculate on this, our data are preliminary – again, a key area for future research.

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In the Arctic context, we will continue to uncover fascinating food-web dynamics.  Our research group has already been thinking seriously about this – Crystal Ernst has written a nice post about the idea of an ‘inverse trophic web’ (i.e., predator-dominated) in the Arctic, and a fair amount of my future research will pursue this avenue of research.

Pique your interest…?  Why not think about graduate school in my lab, and study Arctic arthropod biodiversity?

References:

Bowden, J., & Buddle, C. (2012). Egg sac parasitism of Arctic wolf spiders (Araneae: Lycosidae) from northwestern North America Journal of Arachnology, 40 (3), 348-350 DOI: 10.1636/P11-50.1

Cobb, LM & Cobb VA (2004). Occurrence of parasitoid wasps, Baeus sp and Gelis sp., in the egg sacs of the wolf spiders Pardosa moesta and Pardosa sternalis (Araneae: Lycosidae) in southeastern Idaho. Canadian Field Naturalist 118(1); 122-123.

Baarlen, P., Sunderland, K., & Topping, C. (1994). Eggsac parasitism of money spiders (Araneae, Linyphiidae) in cereals, with a simple method for estimating percentage parasitism of spp. eggsacs by Hymenoptera Journal of Applied Entomology, 118 (1-5), 217-223 DOI: 10.1111/j.1439-0418.1994.tb00797.x

Finch, O. (2005). The parasitoid complex and parasitoid-induced mortality of spiders (Araneae) in a Central European woodland Journal of Natural History, 39 (25), 2339-2354 DOI: 10.1080/00222930500101720

ResearchBlogging.org

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

Fear factor: spider silk reduces plant damage

Today I am excited to report on research published with Ann Rypstra, a most wonderful person and exceptional spider ecologist.  Here’s the take home message from our paper, titled  “Spider silk reduces insect herbivory” (Rypstra & Buddle 2013):

In the presence of spider silk, insect herbivores eat less plant material  – and the spider doesn’t have to be around to see this effect!

A spider’s web, made with silk. Photo courtesy of M. Larrivee (reproduced here, with permission)

Here’s a plain-language summary of the research:

Spiders are important in agricultural systems because they eat many insect pests that in turn eat valuable crops.  Spiders also leave behind silk as they move through an agricultural field – sometimes this silk is there because it was part of a web that was constructed to catch prey, or sometimes spiders leave silk in the form of a ‘drag-line’ – a kind of silk that acts as a safety-line for a spider.  Whatever the means, the agricultural landscape contains plants, their insect pests, spiders and spider silk.  In this work, we wondered whether  silk, in the absence of a spider, would still cause the insect pests to be wary, and feed differently than if there was no spider silk in their environment.  

We used laboratory and field-based experiments for this research, and we used two pest species – the Japanese beetle and the Mexican bean beetle.  These pests were allowed to eat either leaflets or whole plants of bush-style snap beans.  The plants or leaflets were either left alone, or were adorned with five strands of spider silk or with five strands of silkworm silk.  We included the silkworm silk (i.e, produced from the silkworm moth) because we were curious about whether the beetles might respond to ANY silk instead of silk produced specifically by spiders.  To extract the spider silk, we allowed a long-jawed orb-web spider to hang from its drag-line, and we wound its silk around a stick as the spider bobbed up and down – in this way we could get enough silk for the experiments. We found that when spider silk was on the plants, the insects inflicted less damage compared to when there was no silk.  The silkworm silk also caused the insects to feed less, but the effect with silkworm silk was less than with spider silk.  We also wondered whether this response could just be because the silk got in the way of the beetles, and so we did some experiments with human hair, and a strand of kevlar – these are both ‘silk-like’ strands but since they did not come from an insect or spider, would only represent the physical nature of the silk rather than have any other chemicals or smells from the silk produced by a insect or spider.  This additional experiment showed us the same results: the insect pests still ate less when on plants containing silkworm silk or spider silk compared to those with the kevlar or human hair.  

All these experiments, combined, tell us that there is something very special about spider silk, and it causes pest insects to eat less plants.  In ecology this is dubbed an ‘indirect’ effect – the spiders do not have to eat a pest insect to cause it to change its behaviour! It is also called a ‘non-consumptive effect’ – meaning the effect of the spider on its prey is not through the act of eating the prey, but rather by changing prey behaviour by other means.  This work is fascinating because it shows that spiders have a much more important role in agricultural systems than we realized before: spiders do not have to be present to cause insects pests to eat less – as long as they were there, and produced silk as they moved through their environment, their potential prey will live in a ‘landscape of fear’.  Or, the insect pest is living in fear of spiders because of their silk. 

Here is a more technical summary, placed within a broader ecological context:

Tetragnatha – a long-jawed orb-web spider. Photo by Lee Jaszlics, reproduced here with permission

The pest insects (the beetles) in our study system recognize the silk is coming from a potential predator (the spider), and this means they alter their behaviour, or LIVE IN FEAR!  This work fits within the broader literature about the landscape of fear (e.g. see Laundré et al. 2012), or ecology of fear sensu Brown et al. (1999). The idea here is that prey are shifting their behaviours depending on predators, and so the prey’s overall ‘landscape’ is peaks and valleys related to the strength and type of interactions (direct or indirect) caused by the predator.  To anthropomophize this even more: fear induces behavioural changes in prey; they are scared and this fear has real and measurable effects.

Although a lot of this kind of research is with vertebrates, there are some interesting examples from the arthropod world.  One recent example is by Hawlena et al. (2012) – in this work, grasshoppers that were raised in an environment of fear (via continual exposure to spiders whose chelicerae were glued shut) had different Carbon:Nitrogen ratio in their bodies relative to controls, and this affected plant litter decomposition.  So, the ‘fear factor’ changed the elemental composition of grasshopper’s bodies and eventually this affected the decomposition process!  In Hlivko & Rypstra’s (2003) work, a leaf-eating beetle, when exposed to a range of cues produced by spiders (this included feces, silk and other chemicals) ate less plant biomass compared to controls, and the strongest effect was from cues of the largest spider.   Within the context of fear – the largest (and presumably the most feared) spider, can elicit a response in its prey which results in an affect on plant biomass.  Our paper is taking this one more level, and focuses on the silk as a key ‘cue’ that induces the behavioural change in the prey.

Our results show that insect pests that feed on plants in agroecosystems may be living in a landscape of fear that is brought on by one of the most common substances produced our eight-legged friends…the silk.  This silk acts as an important cue for the insect pests and they eat less plant material because of this.   This research also shows the added value of spiders in agroecosystems; conservation of spiders, or even habitat manipulations to encourage spiders to live in agroecosystems, could have many pay-offs.

The study species in our research: Tetragnatha (photo courtesy of M. Larrivee, reproduced here with permission)

Thanks to Max Larrivee and Lee Jaszlics for permission to use their wonderful photographs!

References:

Brown, J., Laundré, J., Gurung, M., & Laundre, J. (1999). The Ecology of Fear: Optimal Foraging, Game Theory, and Trophic Interactions Journal of Mammalogy, 80 (2) DOI: 10.2307/1383287

Hawlena, D., Strickland, M., Bradford, M., & Schmitz, O. (2012). Fear of Predation Slows Plant-Litter Decomposition Science, 336 (6087), 1434-1438 DOI: 10.1126/science.1220097

Hlivko, J., & Rypstra, A. (2003). Spiders Reduce Herbivory: Nonlethal Effects of Spiders on the Consumption of Soybean Leaves by Beetle Pests Annals of the Entomological Society of America, 96 (6), 914-919 DOI: 10.1603/0013-8746(2003)096[0914:SRHNEO]2.0.CO;2

Laundre, J., Hernandez, L., & Ripple, W. (2010). The Landscape of Fear: Ecological Implications of Being Afraid~!2009-09-09~!2009-11-16~!2010-02-02~! The Open Ecology Journal, 3 (3), 1-7 DOI: 10.2174/1874213001003030001

Rypstra, A., & Buddle, C.M. (2012). Spider silk reduces insect herbivory Biology Letters, 9 (1), 20120948-20120948 DOI: 10.1098/rsbl.2012.0948

ResearchBlogging.org

Plain-language summary of research results: Mites, rotten wood, and forests

Last week I wrote a post that outlined a proposal to require plain-language summaries of all research papers. I decided that I would start to do this with my own papers to see how difficult it might be, and also to see if this could help to make the research more accessible to a broad audience.

So… here it goes. This is a summary of paper written with my former MSc student Andrea Dechene, about mites, forests and fallen logs:

         Mites are small animals, closely related to ticks and spiders. They are so small that it is very difficult to see them without the help of a magnifying glass or microscope. There are many kinds of mites, and they are found almost everywhere, including forests. Mites are important in forests because they can affect how leaves and rotten wood decompose on the forest floor. 

          In this research, we studied whether certain kinds of mites were associated with logs that were decomposing on the forest floor, and we did this work in north-western Quebec. We collected mites living in the wood, on the ground near the wood, and on the forest floor about 1 m away from logs. Mites were collected by taking a handful of soil, leaves or rotten wood, putting this in a zip-lock bag, and then the samples were taken to a laboratory. In the lab, these handfuls of soil, leaves and wood were placed on a bench below a light. Mites do not like bright lights and they try to get away by moving away from the light – in this case, they move downward where they think it is safe. The samples are on a screen, however, and the mites fall through the screen and into a jar that contains a liquid that will kill them. These jars are taken to a different lab where the mites are inspected with the help of a microscope. With the help of books and other resources, we could figure out all the different kinds of mites and sort them into their different varieties.  Some kinds had names while other ones did not 

         We discovered 80 different kinds of mites and over 15,000 mites, in total, fell into the jars. That means a lot of mites live in forests! We also discovered that different kinds of mites live in the rotten wood compared to the forest floor and compared to the leaves. We found that the most different kinds of mites actually lived in the leaves that were over top of very, very rotten wood. This is an exciting result because nobody figured this out before, and it means that long after wood decomposes, there are still animals that ‘remember’ the wood was there and are using it as a suitable place to live. Lots of scientists have worked on rotten wood and it is well known that wood is very important for many animals and plants in a forest. Our work is different because we looked at some of the tiny animals in forests and they are also telling us that rotten wood is a good place to live. Next time you see a fallen tree, remember that many kinds of mites depend on that tree and you should leave it where it is.

Mites live here.

Phew.

By the way, here is the actual Abstract from that paper:

The removal of timber during harvesting substantially reduces important invertebrate habitat, most noticeably microhabitats associated with fallen trees. Oribatid mite diversity in downed woody material (DWM) using species-level data has not been well studied. We investigated the influence of decaying logs on the spatial distribution of oribatid mites on the forest floor at the sylviculture et aménagement forestiers écosystémique (SAFE) research station in the Abitibi region in NW Québec. In June 2006, six aspen logs were selected for study, and samples were taken at three distances for each log: directly on top of the log (ON), directly beside the log (ADJ) and at least one metre away from the log and any other fallen wood (AWAY). Samples ON logs consisted of a litter layer sample, an upper wood sample and an inner wood sample. Samples at the ADJ and AWAY distances consisted of litter samples and soil cores. The highest species richness was collected ON logs, and logs harboured a distinct oribatid species composition compared to nearby forest floor. There were species-specific changes in abundance with increasing distance away from DWM, which indicates an influence of DWM in structuring oribatid assemblages on the forest floor. Additionally, each layer (litter, wood and soil) exhibited a unique species composition and hosted a different diversity of oribatid mites. This study further highlights the importance of DWM to forest biodiversity by creating habitat for unique assemblages of oribatid mites.

The Extractor – getting mites from the samples

Thoughts? –I kind of like the plain-language summary.

The plain language summary was not easy to write and it took a lot of words to explain certain things. Despite the challenge, I’m convinced it was a worthwhile use of time.  Please consider doing this with your own papers!  

Reference:

Dechene, A. and C. M. Buddle. 2010. Decomposing logs increase oribatid mite assemblage diversity in mixedwood boreal forest. Biodiv. Cons. 19: 237-256. http://www.springerlink.com/content/r3681l0185620311/

Science outreach: plain-language summaries for all research papers

1) Scientists do really interesting things.

2) Scientists have a responsibility to disseminate their results.

3) Scientists do not publish in an accessible format.

This is a really, really big problem.

Scientific research is largely funded by public money, and it can be argued that scientists have a responsibility to make their work accessible to the public (and scientists are particularly well suited for outreach activities!).  The main platform for disseminating research results is the peer-reviewed journal paper and this is not ideal.  Let’s be honest – these kinds of publications are often very specialized, full of jargon, and unreadable to most (even other scientists).  Many papers are also behind pay-walls, making them even less accessible to people outside of certain institutions.

Earlier this week I attended a scientific conference (the annual meeting of the Entomological Society of Canada) and as part of this conference I was invited to speak in a symposium that was about social media in science.  It was a great session and some of my favourite social media mentors were also speaking at the symposium, including Adrian Thyssemacromite, the Bug Geek, and Biodiversity in Focus.   As I was preparing that talk the week before, I was also madly finishing a grant application, and in that application I was require to write a plain-language summary of my proposed research.  The granting agency uses this ‘summary for public release’ as a way to communicate research to the public.  Taxpayers fund the research and they might want to know where their money is going; the granting agency has found one way to communicate this information in a clever and effective manner.

…………………………..Eureka!

Here is the proposal:  Every scientific paper published in a peer-reviewed journal must be accompanied by a short, plain-language summary of the work.

This summary would be placed on-line, free for everyone to read.  It would be concise, clear, free of jargon, and highlight why the work was done, how it was done, and what was discovered.

Here are some examples of how these plain-language summaries could be used:

1. Media: Media offices at Universities are constantly interested in promoting fantastic work by their Professors.  This work, however, is often not accessible and it can be a lengthy process to put together a press release (how easy is it to track down a researcher?).  A plain-language summary written by the researcher would be readable, clear, accessible, and an easy way to start the process of promoting research activities occurring at Universities.

2. Blogging: I am a regular blogger, and always happy to promote the research occurring within my laboratory, the laboratories of colleagues, or just discussing interesting scientific papers that I have read.  If I had plain-language summaries to access, it would make the process that much easier, and help facilitate timely communication with the public about recently published work.  Other science bloggers could also pick up on these summaries for their own writing.

3. Publishers & Editors:  As an editor-in-chief for a scientific journal, I sometimes look for ways to promote great papers, and promote the journal to a larger audience.  If I was able to peruse the summaries for public release,  this would make the process much easier.  Publishers could also take text from these summaries, put together a press release or blog post, and also promote research results from their journals based on particularly interesting papers and findings.

4. For Everyone: In my experience, people outside my area of expertise are always keen to hear about research activities.    It’s sometimes a challenge for me to explain my research results, and if I was always doing plain-language summaries, this would get easier.    The audience for research results can be as big as you can imagine: high school students, friends, family, colleagues, Departmental chairs, graduate students, journalists, libraries, etc…  Finally,  the Bug Geek has a great post about the challenges of talking science to 10-year olds:  it is hard to do, but important.  We need practice.  These summaries will help.

The procedure for getting plain language summaries could be quite simple.  When an author submits the final revisions on a scientific publication, they would be required to write a short plain-language summary.  I would like to think that publishers would be willing to incorporate this (simple) step into the on-line systems for manuscript processing, and be willing to post these, as open-access, on their websites, possibly paired with Abstracts.   These summaries would not diminish the value of the actual peer-reviewed papers – it would probably help increase readership since these summaries would help people find the work they are actually looking for, and give them a doorway into the scientific literature.

Let’s make this happen.  

It will be an effective way to do science outreach.

 Please comment, share the idea, and let’s see this idea grow.