Meet the lab: Crystal Ernst

This is the first in a series of posts where each Arthropod Ecology lab member can introduce themselves. First up is PhD student Crystal Ernst:

I’m a Ph.D. candidate in the final stages of my program: these days I’m crunching out analyses and writing papers as I prepare to submit my thesis at the end of the term. As a community ecologist, I spend a lot of time thinking about how and why different species assemble together in space and time. These questions are foundational to the study of ecology and provide the overall framework for my research program, which uses beetles and other ground-dwelling arthropods to study the structure and determinants of terrestrial animal assemblages.

PhD student Crystal Ernst installing pan traps along the Dempster Highway (Yukon)

PhD student Crystal Ernst installing pan traps along the Dempster Highway (Yukon)

I have spent my summers conducting field research in gorgeous, remote regions of our northern territories, including Kugluktuk Nunavut and the Dempster Highway in the Yukon. My colleagues, members of the Northern Biodiversity Program, have contributed to the collection efforts as well, resulting in specimens being obtained from twelve different locations in the boreal forest, the subarctic and high arctic, spanning Canada coast to coast. I’m now neck-deep in the joy of interpreting the stories contained in my collection of specimens.

Specimens in pan trap (photo by C Ernst)

Specimens in pan trap (photo by C Ernst)

 

Sorting specimens back in the lab

Sorting specimens back in the lab

I’ve taken two approaches with this work. First, I’ve used a fairly traditional taxonomic approach to studying these animals: by identifying them morphologically (with a microscope and identification keys), I can associate each individual with a known insect species – although some new species have also been discovered! With this information I can describe the species richness (diversity) and distributions of different beetles in the north, and see which species are associated with each other at different northern locations. Secondly, I’ve looked at my arthropods from the perspective of their ecological functions – their roles in their environments. For example, some insects are responsible for pollenating plants, others are important decomposers, and others still are predators; arthropod assemblages can therefore be described in terms of the diversity and dominance of different functional groups. I am in the process of comparing taxonomic and functional assemblages found across northern Canada, and working to determine what aspects of their ecosystems (things like: temperature, wind, and sunlight; the diversity and structure of the plant community in which they live; soil characteristics) are associated with the way these assemblages are structured, and how they change over time and across space.

Three color morphs of Blethisa catenaria, a rare subarctic species (H. Goulet)

Three color morphs of Blethisa catenaria, a rare subarctic species (H. Goulet)

A fun complementary topic I’ve researched is the relationships between some high arctic ground beetles and a fascinating group of parasites called hairworms. I found a number of beetles from different locations to be infested with these worms; in one instance almost a quarter of the beetles were infected! The parasites are aquatic as adults and must first infect an aquatic insect (like a mosquito larva) before being transmitted to a terrestrial host (like a beetle) via the predation of the aquatic host by the terrestrial insect. To complete their life cycles, the worms somehow compel the beetles to enter the water, effectively forcing them to drown themselves so that the worms can emerge safely into their aquatic habitat. This discovery suggests an important link between the creatures living in terrestrial habitats and those in aquatic habitats and tells us about the arctic food chain: beetles must be eating mosquitos or other insects that have aquatic larval/immature stages. These prey items may, in fact, be a very important source of food. More work needs to be done to confirm this! In the meantime, I am excited to have found these associations – the fact that these particular species of beetles can be hosts for hairworm parasites is new information, and it appears that the parasite itself is a new species!

Pterostichus caribou with hairworms (C. Ernst)

Pterostichus caribou with hairworms (C. Ernst)

When I’m not writing my thesis or putting obscure little black beetles on pins, you can probably find me working at McGill’s Teaching and Learning Services, enjoying my time as a teaching assistant, networking on Twitter, mucking around in my vegetable garden (or putting said veggies in jars), walking my dogs, enjoying nature while canoe tripping with my partner, poking wildlife, or lifting heavy things at the gym. I’m on the hunt for a fantastic postdoctoral position that will allow me to continue studying different communities of living things in other ecosystems, and that factors that affect how they’re put together, and I’m excited about the many opportunities out there!

It’s a wrap! How about a thesis on Arctic spiders? How about two of them…?

This week I am thrilled to report that two of my MSc students have successfully completed their degrees! Both the projects are part of the collaborative Northern Biodiversity Program – a project aimed to quantify and understand ecological change with Arthropods from Canada’s north.

A BIG congratulations to Sarah Loboda and Katie Sim  - they are both tremendously talented students, excellent Arachnologists, and wonderful people to know.  Last night we had our annual Lab BBQ – and at that event, I was pleased to give Sarah and Katie a small token of appreciation.  Here’s a photo showing them both with their wolf spider photographs (photos by the incredible Thomas Shahan):

Katie Sim (l) and Sarah Loboda (r) - successful MSc students!

Katie Sim (left) and Sarah Loboda (right) – successful (& happy) MSc students!

Sarah Loboda’s thesis is titled Multi-scale patterns of ground-dwelling spider (Araneae) diversity in northern Canada. Her research focused on broad diversity patterns of ground-dwelling spiders collected from our 12 study sites, spread across Canada’s north. Our project spanned 30 degrees of latitude and 80 degrees of longitude –> yes that is a lot of land area! Sarah identified over 300 spider species from 14 families, and over 23,000 individuals.  Publications are forthcoming so I won’t give details here, except to say that we can learn a lot about diversity patterns over broad spatial scales using a study taxon such as spiders.

Here's where the Northern Biodiversity Program took our field teams!

Here’s where the Northern Biodiversity Program took our field teams.

Katie’s work (co-supervised by Prof. Terry Wheeler) had a different slant, but was still on Arctic spiders. Her thesis is titled:  Genetic analysis of Pardosa wolf spiders (Araneae: Lycosidae) across the northern Nearctic. The first part of Katie’s thesis was about understanding the phylogeographic history of the Arctic spider Pardosa glacialis, with particular attention to post-glacial dispersal patterns, as inferred by population genetics. The second part of her thesis was focused on whether or not there is enough evidence to suggest two northern Pardosa species should remain as separate species, or be merged into one – based on both molecular and morphological characters.  Let’s just say that Katie had to be a ‘field genius‘, ‘lab genius‘ and ‘spider genitalia genius‘.  Here’s an example of what she looked at, a lot:

The epigynum of a wolf spider species, (part of) the topic of Katie's research.

The epigynum of a wolf spider species, (part of) the topic of Katie’s research.

In sum, I am thrilled to see Sarah and Katie finish up their work, although their success also comes with a touch of sadness, as I will miss their daily presence in the laboratory.  Stay tuned… we shall soon report all the details from their research.

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

The greatness of pseudoscorpions

As you know, I’m quite passionate about Arachnology, from spiders, to harvestmen and Pseudoscorpions.  These are all some of the creatures that fall into the category of the ‘obscure and amazing‘.  On the topic of pseudoscorpions, a few very fun and interesting things have happened recently, and enough to warrant a short blog post.  I also promised that I would post a few more videos related to some research activities on the hunt for pseudoscorpions in the Yukon.

1. Just look at this SEM of a pseudoscorpion!

A little while ago, my Arachnid friends and colleagues from Alberta, Heather Proctor and Dave Walter, forwarded me a stunning image of a pseudoscorpion taken with a scanning electron microscope (SEM).  Dave was kind enough to give me permission to share it here:

SEM of a pseudoscorpion (Chernetidae) - copyright D. Walter (reproduced here with permission)

SEM of a pseudoscorpion (Chernetidae) – copyright D. Walter (reproduced here with permission)

There really is something lovely about getting up close and personal with these little Arachnids. I don’t know this species, but it’s definitely in the family Chernetidae – a relatively diverse family, quite common across Canada.  My favourite Yukon species, Wyochernes asiaticus, is also a Chernetid.   Dave Walter really does some magic with his SEM images, and you are encouraged to check out is macromite blog (his home bug garden blog is also worth a peek!).

2.  Just look at these videos about collecting pseudoscropions in the wild! 

Speaking of my favourite Yukon species, I took a lot of videos of field work in the Yukon last summer and I wanted to share a few with you, here.  Although our larger purpose for the trip was to complete some follow-up field work for the Northern Biodiversity Program, I also wanted to collect additional specimens of a wonderful pseudoscorpion species.  The first video provides some context to the work, and gives you a bit of a flavour of the landscape up near the Yukon – Northwest Territory border in Canada:

Typically, pseudoscorpions are not that commonly encountered.  In my experience, when they are encountered, you tend to see one or two.  What is truly amazing is the sheer abundance of this species found under rocks in creek/river beds in the Yukon.  Furthermore, you can see and collect multiple life stages, including females with eggs.  This short video gives a taste for this abundance.

The third and final video is a big goofy, and highlight the ‘collecting gear’ and appropriate field attire for becoming a “pseudoscorpion hunter“.  I am continually on a crusade to help generate enthusiasm for Arachnids, whether it is dispelling myths, or trying to inspire others to become Arachnologists (you know, we do need Arachnologists in Canada!).

One important caveat:  you may NOT simply run to the Yukon and flip rocks to collect pseudoscorpions – many parts of the world, including the Yukon, have strict guidelines about what you can collect.  Permits are required, and be sure to check into this before you plan on becoming an Arachnologist!

3.  Just look at this pseudoscorpion necklace!

To further illustrate my rather quirky obsession, I managed to find a wonderful person on Etsy who was able to make me a pendant with a pseudoscorpion design:

The pseudoscorpion necklace.  You want one.

The pseudoscorpion necklace. You want one.

Not only that, this design is actually from a photography I took a few years ago, and is an accurate depiction of the cosmopoliton species Chelifer cancroides.

Chelifer cancroides - my photo which was used to design the pendant

Chelifer cancroides – my photo which was used to design the pendant

I KNOW you want to get yourself one of these… start a conversation with Lynn.  Get yourself one of these necklaces and stand proud with other pseudoscorpionologists!

In sum, I do hope you find this post interesting, hopefully fun, and has whetted your appetite from more information about curious critters.

Stay tuned… I will continue to post more about Arachnids…

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.

Screen shot 2013-01-28 at 10.52.40 AM

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.

Screen shot 2013-01-23 at 12.20.40 PM

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

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.