Assessing five decades of change in a high Arctic parasitoid community

January 29, 2013 / Chris Buddle / 2 Comments

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.

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

January 24, 2013 / Chris Buddle / 6 Comments

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 Gelis. These 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.

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 females: after 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!

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.

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

WANTED: graduate students

January 22, 2013 / Chris Buddle

Interested in arthropod ecology?

Interested in graduate school?

I’m seeking at least two graduate students. One, at the MSc level, on a project related to pollinator diversity within an agroecology context. This is a Quebec-based project, and bilingualism would be required. The second, at the PhD level, will be about Arctic arthropod biodiversity with a particular focus on temporal changes in community structure. The Arctic project will involve a combination of field and laboratory work, and will in part deal with historical specimens. Both projects will require a student with interests in both taxonomy and ecology. In other words, significant time at a microscope as well as time doing quantitative ecology. Start dates are negotiable, but there is potential for field work to commence in May/June 2013. Required skills include excellent communication skills, ability to work in a large, dynamic laboratory, passion for arthropod ecology, and abilities/interest in quantitative ecology. Experience in Entomology and/or Arachnology would be an asset.

Please do your homework: read my blog, and do research about my research; try to assess if you think you’ll be a good fit within my laboratory group.

Interested candidates should e-mail me with a brief (<200 words) statement of interest, a brief (<200 words) statement that outlines relevant experience and skills, and a brief sentence or two about your expectations in the context of graduate school at McGill University. Please submit these to me before the end of January 2013.

Misadventures in teaching: Technology Begone!

January 17, 2013 / Chris Buddle / 6 Comments

At the start of term, I discussed my continuing adventures in teaching, and I professed about how a tablet + whiteboard app would make me a better instructor, and help me deliver content more effectively in an introductory ecology class. Here’s an update.

At first, it just didn’t work. I was sure it was because I had yet to perfect the technology - the writing was sloppy, the interface was awkward, and stuff I was writing was always appearing on the wrong part of the screen. Students were chuckling in the classroom. I think the students could see the potential opportunities with the i-pad and whiteboard, especially being able to bring in complex graphs from a textbook. However, potential is one thing and reality is another. The biggest problem was that my writing on the i-pad was positively ridiculous.

Example #1:

Just admire this amazing handwriting!

So, that was lecture #1. I did not give up - I practiced in my office, worked on my penmanship, tried different i-pad apps, and kept at it. It saddens me to say that Day 2 and 3 were not much better.

Example #2:

Another problem was that when I exported the whiteboard as PDF (i.e., so students could have a record of the lecture), I realized that over the course of the lecture, my handwriting continually got bigger. Let me clarify: the whiteboard app was an ‘ever expanding’ whiteboard - so if you wrote and filled up the screen, you simply move down or sideways to expose more whiteboard, and you can continue writing. The problem is that if you aren’t careful, it’s easy to change the size of what you write without realizing it until you look at the entire whiteboard, as a PDF. The student did not, therefore, find the exported whiteboard very helpful.

Example #3:

I also tried using the typing feature a little bit - instead of writing like a 6-year old, I would sometimes bring up the keyboard and type. However, I am not much of a fan of typing on an i-pad. I need a real keyboard in order to be quick and in order to not make any mistakes (And let’s not talk about that dang auto-correct feature!). Sigh. The efforts at typing were a complete failure.

I’ll point out one final problem with the technology: there was not a 1:1 ratio between the i-pad screen and the whiteboard that was projected. This meant I would write away on the i-pad, assume everyone was following along, but would sense some unhappiness from the audience. Sure enough, when turning around to see the screen, not all that I had written was being projected. This led to more fiddling around, more wasted time, more swearing under my breath. I’m sure there was some technological fix for this, but I was out of patience.

Yesterday I went back to using the chalkboard, and the lecture went smoothly, the class was happy(ier), and most importantly, I felt the content was being delivered in a more effective manner.

Technology: BEGONE!

We need the Taxonomy Hulk

January 15, 2013January 15, 2013 / Chris Buddle / 8 Comments

The Taxonomy Hulk burst onto twitter yesterday. We need superheroes like Taxonomy Hulk. As his/her alter ego, s/he surfs the internet, working away as a taxonomist, doing things that taxonomists do - describing species, inferring their evolutionary relationships, discovering their natural history. However, if s/he spots a taxonomic mistake on a website, news story, scientific article, or blog - LOOK OUT. The Hulk goes through an impressive metamophosis. S/he gets mad and gets even. If you make a taxonomic mistake, you will be shamed. Message: DON’T MAKE A #TAXONOMYFAIL. Taxonomy Hulk points out misidentifications in images (e.g., see this website with a Harvestmen instead of a spider.. oops [although a common mistake]).

Taxonomy Hulk reminds us to use Latin names, not common names.

Taxonomy Hulk is also funny. We need humour - every day.

On a slightly more serious note: correct taxonomy is critically important. Other posts (e.g., see here or here) have pointed out taxonomic failures - and I especially like Bug Girl’s Flickr set!. One letter difference in Miridae (a family of plant bugs) gets you to Muridae (rodents and their relatives) - yeah those two are just a bit different. As an ecologist (although one with envy of taxonomists, and one in awe of the work taxonomists do!), I admit that I am perhaps not as careful as I should be when it comes to checking nomenclature, or ensuring spelling is always correct. I try - but given that my training is not in taxonomy, I surely make mistakes. I fear that some ecologists appreciate the importance of sound taxonomy even less than I do, and we need a watchdog. Reminders about correct taxonomy are a good idea. Taxonomy Hulk reminds us that we must be clear in what we are saying, whether it be in science journalism, writing a blog post, or working on a scientific paper.

Taxonomy Hulk is a concept not a person and this is a good thing: the humour and fun and ‘alter ego’ perspective is non-threatening, and allows taxonomic issues to be brought into the open easily and effectively. We can fix our mistakes, smile about it, and move forward.

Thank you Taxonomy Hulk. (and yes, you should follow Taxonomy Hulk on twitter)

I finish by stating that Taxonomy Hulk’s ‘regular’ persona (the Bruce Banner) is known to some of us (and s/he’s an incredibly competent taxonomist!, and a super-nice person).

But I’ll keep it quiet - it’s better that way.

Natural History: unknown.

January 10, 2013January 10, 2013 / Chris Buddle / 13 Comments

I sometimes see this statement in taxonomic papers that describe a new species:

Natural History: Unknown

Think about this… specimens have been collected, somewhere, sometime. Perhaps these specimens sat in an Entomology museum for decades until a MSc student took them out and started a revision. Perhaps the specimen was recently sorted from a bulk malaise trap sample from the Amazon basin, and sent to a taxonomic expert for identification. S/he recognized it was something different and later, while doing a taxonomic revision, included it, measured it, did a line drawing, extracted some DNA, wrote a description, gave it a name. However, when writing what is known about its natural history and biology had to write “unknown“. (by the way, discussions about defining natural history can be found here and here).

An unknown weevil with unknown natural history.

I recognize why nothing is known, but when trying to get some sense of why a particular species might be found in a particular habitat, having no information about natural history and biology can be frustrating. This is especially true for ecologists, whose research might benefit immensely from ANY natural history information. In my own work, after I key out a species of wolf spider, for example, I immediately flip to the description, and scan down to the notes about the biology of the species - these notes can confirm details about the species (hey look, I found it under rocks on a shoreline, and that is where it is reported, also!; or, indeed, it makes sense that I found that egg sac in late summer - that species is known to mate in mid-summer).

Natural history is important, as is so elegantly stated in many papers (e.g., see Greene’s 2005 paper) and the impending extinction of natural history was written about over 10 years ago by Wilcove & Eisner. The world needs natural history information, and although I recognize that having a name is clearly very important, it is also essential to have some natural history information. Such information can lead to additional research on the species, or allow others to document the species in new locations around the globe. Having some information will help future graduate students figure out when during the growing season they should find specimens, and perhaps what host plants they should look on.

So, I ask these questions, and I look forward to responses, especially from taxonomists:

Should taxonomists wait to describe a species until there are some details known about its natural history? (this will, of course, take more specimens and more time…)

and,

Under what conditions is it acceptable to state “Natural History: unknown”?

Caveats: I am coming from this question as an ecologist with an appreciation for taxonomy, but not as someone trained in taxonomy. I am, therefore, biased in my views. I also recognize that in many cases, taxonomists only have one specimen and a label to work with, and data on the label itself may be lacking, hence the need to state “natural history: unknown”. My questions are meant to be more general, and I am hoping to gain insights into whether seeking additional natural history information about species (when it is described) is a losing battle… and whether this task should be in the hands of the individuals who describe species.

References

Greene, H.W. (2005). Organisms in nature as a central focus for biology Trends in Ecology and Evolution, 20 (1), 23-27 DOI: 10.1016/j.tree.2004.11.005

Wilcove, D. and Eisner, T. (2000) The impending extinction of natural history. Chron. Higher Ed. Sept. 15, B24. Available here.

Arthropod Ecology

Writings about arthropod ecology, arachnids & academia at McGill University

Month: January 2013

Assessing five decades of change in a high Arctic parasitoid community

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

WANTED: graduate students

Misadventures in teaching: Technology Begone!

Natural History: unknown.

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