Spider cakes!

My graduate students are a very talented bunch – they are intelligent, creative, and have a good sense of humour.  Some of our lab group celebrated birthdays recently, and in honour of this, we had two cakes earlier this week.  The first, made by MSc student Sarah Loboda, is the VERY BEST SPIDER CAKE I have ever seen (or eaten!).  Check this out:

Spider Cake!

Of course, let’s discuss how anatomically correct that cake is!  Two body parts, pedicel, eight legs (coming from the cephalothorax, of course), and a bunch of eyes.

Spider cake! (eyes0

As you may know, most spiders in Canada have eight eyes, but since some do have six, I find it quite acceptable that this spider has six eyes.  Furthermore, not all spider eyes are identical so it is appropriate to have two kinds represented on the cake.  Well done, Sarah.

And in case that STUNNING MASTERPIECE isn’t enough, another student (Dorothy Maguire)  made a cake that is a very good approximation for the female epigynum of wolf spiders in the genus Pardosa.

Pardosa epigynum

And not just any Pardosa:  this is diagnostically similar to one of the species that graduate student Katie Sim is working on!  Incredible!

….want some proof – look at this image, taken from Dondale & Redner’s text on the Lycosidae of Canada.  Enough said.

Pardosa concinna epigynum

Seven-legged spiders walking on water

Many spiders are known to ‘walk on water‘ (including dock spiders): spiders are small enough that many species and life stages can be held by the meniscus of water.  Spiders also have eight legs but they often lose one or more of their legs (in the scientific jargon, this is ‘leg autotomy‘).   In general, this is often part of defensive behaviour, and is common in many animals.  Sacrificing an appendage is a better idea than being eaten by a predator.

So… let’s link these thoughts together- spiders run on land as well as water, and they are often missing a leg.

A wolf spider (Pardoa mackenziana). In this photo, a leg that was previously lost has been ‘re-grown’ (4th leg on right side). The cost of this spider’s lost leg must have been minimal, since it survived and moulted again!

So, next comes the research question:   what is the ‘cost’ of leg autotomy and does this cost vary depending on whether the spider is traveling on the land or on water.  This is an interesting question, and one that was addressed directly by Christopher Brown and Daniel Formanowicz Jr in a recent research paper in the Journal of Arachnology.   These authors used the wolf spider Pardosa valens as their model species, and conducted ‘speed trials’ for male and female spiders on a terrestrial track as well as an aquatic track (i.e., these were constructed in a laboratory setting).  After doing the trials with intact spiders, the authors ‘induced autotomy’ (yes, this sounds somewhat horrific, but autotomy is very common with wolf spiders, and although they lose a little of their hemolymph, they heal quickly) and ran the trials again, with the same spiders (sans legs).

Results?  Well, perhaps not surprisingly, in the first year of their study, the species ran more slowly when they were missing a leg, but in the second year of the study, this affect varied by sex (males were slower, and autotomy only affected the females).   They report some rather complicated results when comparing terrestrial to aquatic trials, but in general, the spiders tended to run more slowly on the aquatic tracks when they were missing legs.  Again, this is perhaps not a surprising result, since having seven instead of eight legs will certainly change the biomechanics when considering how the spiders interacts with the meniscus of water.

Clearly, there are some costs associated with missing legs, but it is important to note that even without legs, these wolf spiders were able to run effectively on land and water, and even if their speed was slower than when they had all eight legs, they can still move an impressive speeds.  The range of speeds in some of the trials was between  20 cm/s and 50 cm/s – this translates to  running speeds between 0.72 and 1.8 km per hour!

Leg autotomy in wolf spiders in natural habitats range from between 8% and 32% as reported by Brueseke et al. in 2001 and by Apontes & Brown in 2005.  In the present study, the authors state that natural populations of P. valens exhibit between 25% and 45% autotomy.    These numbers are in line what what I have observed, as well.  This is pretty amazing – wolf spiders exhibit leg autotomy at a very high frequency, and in some cases, half the spiders in a population are missing a leg.  What can we infer from this?   Although there are some costs associated with leg autotomy (as reported by Brown and Formanowicz), they must not be that high – otherwise, natural selection certainly wouldn’t have favoured autotomy as a means to escape predation.  Brueseke et al., research supports this as they found very few costs associated with autotomy in Pardosa milvina.  In their work, Brueseke et al. studied locomotory behaviour as well as prey capture, and found overall support for the ‘spare leg hypothesis’ (i.e., look at all of my legs!  I can manage without one!).

So, here are the take-home messages:

Wolf spiders can run quite quickly, some species can run across water and land, and they can do so with missing legs.  Although they may be a little slower without their full complement of legs, the costs must be relatively minor given the frequency of leg autotomy in wolf spiders. 

This gives you more reasons to watch spiders – count some legs and see how many individuals are without their full complement of legs.

References:

Apontes, P., & Brown, C.A. (2005). Between-set variation in running speed and a potential cost of leg autotomy in the wolf spider Pirata sedentarius. American Midland Naturalist, 154, 115-125 DOI: 10.1674/0003-0031(2005)154[0115:BVIRSA]2.0.CO;2

Brown, C.M., & Formanowicz Jr, D.R. (2012). The effect of leg autotomy on terrestrial and aquatic locomation in the wolf spider Pardosa valens (Araneae: Lycosidae). Journal of Arachnology, 40, 234-239 DOI: 10.1636/Hill-59.1

Brueseke, M.A., Rypstra, A.L., Walker, S.E., & Persons M.H. (2001). Leg autotomy in the wolf spider Pardosa milvina: a common phenomenon with few apparent costs. America Midland Naturalist, 146, 153-160 DOI: 10.1674/0003-0031(2001)146[0153:LAITWS]2.0.CO;2

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Notes from the field: Yukon wildlife (Part 3)

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

17 July, 10 AM, Dawson City, Yukon

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

Arctic Pardosa wolf spiders… captured.

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

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

I will be back up here again.

The Yukon landscape.

Notes from the field: Yukon wildlife (Part 2)

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

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

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

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

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

Self-portrait geared up for the biting flies.

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

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

Stay tuned for Part 3, coming Friday…

 

Notes from the field: Yukon wildlife (Part 1)

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

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

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

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

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

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

PhD student Crystal Ernst installing insect traps on the Yukon Tundra

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

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

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

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

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

Canada’s largest spider …sittin’ on the dock of the bay

I just returned from a week of vacation on beautiful Stony Lake, north of Peterborough, Ontario.  A lot of time was spent sitting on docks (Note: the correct terminology should be Wharf instead of dock i.e. you ‘dock’ at a wharf; however, it is generally more commonplace to use the terminology Dock), at water’s edge.  Where there are docks wharfs, there are spiders.   The most common species on the docks tends to be the (in)famous “dock spiders”.  I am pretty sure that dock spiders are the largest spiders in Canada (if not, please correct me!).  I receive many phone calls and e-mails about dock spiders, and I suspect an impressive amount of arachnophobia can be blamed on this hairy wonder of the Arachnid world.

Dock spider (Family Pisauridae), Dolomedes sp.

Dock spiders belong to the family Pisauridae, which are closely related to wolf spiders (family Lycosidae).  Both of these families of spiders show interesting behaviours towards their young (‘spiderlings’).  Females lay eggs within a silken egg sac, and this sac is carried around by the female until it is time for the young to hatch.  Wolf spiders attach their egg sacs to the end of their abdomen, and when the spiderlings hatch they are carried around on the mother’s abdomen before embarking on a solitary life.  Pisaurid females, however, hold the egg sacs by their fangs, and it is carried underneath the female’s body – it looks like the females are carrying around a big wad of cotton by their mouths.  Pisaurids are commonly known as nursery-web spiders, as females build a silken, tent-like ‘nursery’ for their spiderlings.  Upon hatching, the young spiders live in a protected place, typically spun in and among grasses, low-growing vegetation, or between rocks around the margins of water.

A dock spider (Family Pisauridae), Dolomedes sp., in its favourite habitat

Two species, Dolomedes tenebrosus and Dolomedes scriptus are the common ‘dock spiders’.  Unfortunately it is difficult to tell these two species apart, without a microscope, forceps, and expertise. Both species are brownish-grey in colour, with black and light brown markings (‘chevrons’) on their abdomen. These spiders, especially the full-grown females, are the largest (native) spider species in Canada, and their body (including legs) can almost fill your palm – the body length (i.e., not including legs) of mature females can easily exceed 2 cm.  But do not worry!  These spiders do not bite people, and would rather eat land-dwelling and aquatic insects, and they are known to catch small minnows, which is the reason for their other common name, the fishing spider.  The spider will wait with its front legs resting in the water, and when small tadpoles or fish come near, the vibrations alert the spider to its lunch. An invertebrate eating a vertebrate is not a common occurrence in the animal kingdom!  

Dock spider habitat

Dock spiders, as their name suggests, tend to be associated with the margins of lakes, ponds, swamps and rivers, where they typically sit motionless on tree trunks, rocks, boats, and docks.  However, individuals are known to travel some distance from water, and are the reason for many alarmed people describing hairy monsters in their basements.  This mainly occurs in the autumn months when the spiders are searching for a warm place to spend the winter (under stones, leaves, or bark, or inside buildings).  After spending a winter as an immature spider, dock spiders typically mature and mate in the spring, with females carrying egg sacs for a few weeks, before the young hatch in the nursery.  Females can then go on to produce a second, or sometimes a third egg sac before the end of cottage season.  One egg sac can produce over 1,000 spiderlings.

Without a doubt, dock spiders are impressive animals and although not small and obscure, they are still worthy of study. They should be considered friends of cottagers, boaters and home-owners.  I encourage you to watch them, observe their behaviours, and marvel at their size – it’s especially fun to do this when sitting down at the dock, having a glass of your favourite beverage, watching when the evening comes….

A few reasons to study Arctic entomology

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

Poorly understood food-web

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

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

Look at all those spiders!

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

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

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

Excellent base-line dat

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

The Arctic is changing

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

Biting flies:

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

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

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

Canada = Arctic 

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

It is beautiful

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

The stunning landscape of the Yukon Territory (Tombstone range)

You are always within three feet of a spider: Fact or Fiction?

A lovely crab spider (Thomisidae).

Last week I wrote a post about the life history of Arctic wolf spiders – and in that post I discussed how some of our recent research results show wolf spider densities in Arctic tundra habitats are just under 0.5 per square metre.  Morgan Jackson commented on that post, and asked about whether it was true that you are always within six feet of a spider.  This is one of those common myths (along with ‘do spiders bite?).

A quick scan on the Internet suggests this myth can be stated in many ways (e.g., within a metre, within six feet, within three feet, etc.)  but you get the point: are you always close to spiders? .  This ‘myth’ has been submitted to Mythbusters  as one that the show should tackle,  and ‘yahoo answers‘ has this question – some of the answers are hilarious (e.g., not when you are swimming).   So…is it fact or fiction?  When in doubt, let’s go look at the scientific evidence.

What does the scientific literature tell us?

As mentioned in my post last week, our laboratory just published a paper in the Canadian Journal of Zoology about wolf spiders in the Arctic.  In this work, wolf spiders occurred at densities of close to 0.5 per square meter.  In some of my own earlier work in Alberta (more shameless self-promotion! see Buddle, 2000), I estimated densities of wolf spiders (in a forest environment) to be between 0.5 and 1 per square meter.   Not long ago, I had a discussion with a PhD student working in Alaska, and she also had densities estimates of wolf spiders within a similar range.  Kiss & Samu published a paper in 2000 that was about densities of wolf spiders in agroecosystems in Europe, and their estimates were at a minimum of three adults per square metre.

A wolf spider (Lycosidae) – they are everywhere!

Those aforementioned estimates are for one family of spiders only (the wolf spiders, Lycosidae), and wolf spiders are active and easy to see.  I would argue that densities of other spider families are likely higher than wolf spiders.  Most spiders are quite small and easy to miss, but they are everywhere.

In a classic and seminal paper by Turnbull (1973) (all Arachnologists should read that paper!) there are a series of estimates of spider densities in a range of habitats – and these are estimates for all spiders, not just a single family.   The lowest estimate he provides is from work in a Polish meadow where densities of 0.64 spiders per square metre were reported.  The highest density was 842 spiders per square metre in an English pasture. Turnbull averaged all previous published estimates and ended with a mean of 130.8 spiders per square meter.  Turnbull does point that it is kind of a meaningless statistic, except that it helps us tackle the question of interest: Is there always a spider within three feet of you…?

So…. in most “natural” habitats, I think it is true that you are always within three feet of a spider.

There are some exceptions, of course.  Here are some:

-spiders are not nearly as common in heavily managed, monoculture habitats (e.g., turf grass, golf courses, some urban greenspaces)

-spiders are not as common in buildings as in natural habitats (although they are there, as I’ve written about in posts about the zebra spider, cellar spider, and ceiling spider)

-in Northern climates, spiders are not active in the winter months- so although you could still be close to them (i.e, they are under the snow, somewhere…), it’s quite a different context

-spiders are terrestrial, so you are not close to spiders when you are swimming!

-on the theme of ridiculous exceptions, spiders don’t tend to be common on trains, in airplanes or in trucks and cars (although have you noticed there is often a spider tucked away in your side-view mirror?)

Spiders: you gotta love them – in natural systems, they are always close to you!

Spiders – they really are everywhere – even as sculpture.

References

Buddle, C. (2000). LIFE HISTORY OF PARDOSA MOESTA AND PARDOSA MACKENZIANA (ARANEAE, LYCOSIDAE) IN CENTRAL ALBERTA, CANADA Journal of Arachnology, 28 (3), 319-328 DOI: 10.1636/0161-8202(2000)028[0319:LHOPMA]2.0.CO;2

Kiss, B., and Samu, F (2000) Evaluation of population densities of the common wolf spider Pardosa agrestis (Araneae : Lycosidae) in Hungarian alfalfa fields using mark-recapture.  European Journal of Entomology 97(2) 191-195  Link

Turnbull, A. (1973). Ecology of the True Spiders (Araneomorphae) Annual Review of Entomology, 18 (1), 305-348 DOI: 10.1146/annurev.en.18.010173.001513

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Life History of Arctic Wolf Spiders: Part 1

For those of you who follow my blog, you will notice I’m somewhat obsessed with the Arctic – in part because of our large Northern Biodiversity Program, but also because it’s an ideal  system for studying the ecology of arthropods.    It also doesn’t hurt that the Arctic is a beautiful place to work!

The northern Yukon landscape: spider habitat

I am very excited to write about the latest paper published from our laboratory, titled Life history of tundra-dwelling wolf spiders (Araneae: Lycosidae) from the Yukon Territory, Canada.  This has just recently been published in the Canadian Journal of Zoology, with Dr. Joseph Bowden as the lead author.  Dr. Bowden graduate from my laboratory just over a year ago, and is now living in California with his family.  Although the climate is somewhat warmer in California compared to the Yukon, he’s still actively working on research related to the biology of Arctic arthropods.   Dr. Bowden was a terrific student in my laboratory, and has already published some work about the community ecology of Arctic spiders: he has one paper in the journal Arctic and another in Ecoscience.

Dr. Joseph Bowden, working in the Yukon and ready for the biting flies!

In the CJZ paper, Joseph studied three species of tundra-dwelling  wolf spiders (family Lycosidae) and asked whether body size or condition better explained variation in fecundity and relative reproductive effort (defined as the ratio of female body mass to clutch mass).  He also tested whether  a trade-off exists between investment in offspring size and number.  The field work for this research was really enjoyable, as it involved collecting spiders by visual surveys and dry pitfall traps – after collection, Joseph set up a laboratory in a local campground shelter to do measurements on the species:

Dr. Joseph Bowden in a Northern “laboratory”

One of the main findings was that body size explained well the variation in offspring number.  Stated another way, larger female wolf spiders produced more eggs, a finding well supported in the literature.   A second main finding was that females with a lower condition allocated relatively more to offspring production than did females in better condition. This makes some sense – if the going is tough (i.e., poor condition), the females primary objective (from a fitness perspective) is to invest in offspring.  A third key finding was that  we found a negative relationships between egg size and number.    These trade-offs may in part be because of variation in resource availability at some of the study sites in the Yukon tundra.

An Arctic Pardosa (Lycosidae) female, with egg sac

Joseph also calculated tundra wolf spider densities.  Here’s the text of the CJZ paper that describes the methods (straightforward but time consuming):

Densities of the three focal species were estimated using a ring of hard plastic measuring 1.13 m in diameter (1 m x 1 m area) and about 12 cm high. The ring was haphazardly and firmly placed on the tundra surface in each site and all wolf spiders collected inside the ring were identified and counted. This protocol was adapted from Buddle (2000).

Results? Well… the most common species Pardosa  lapponica averaged about 0.4 spiders per square metre.  Some simple calculations will tell you just how common wolf spiders are on the Tundra:  4000 wolf spiders per hectare.  Don’t forget – wolf spiders are only part of the Arachno-fauna in the Arctic.  With confidence, this estimate of 4000 spiders per hectare represents a minimum.  There are a LOT of Arachnids living on the tundra!

In sum, this paper by Joseph is about studying some good old-fashioned natural history of a fascinating group of animals.  The methods are straightforward, but the findings are significant.  It’s pretty difficult to progress in ecology without a deep understanding of a species’ biology and life-history.  Life-history studies are the cornerstone of biology, and I’m thrilled that Joseph recognized that fact and did this research on Arctic wolf spiders.

    You will see that this post is titled Part 1:  some more work will hopefully be published soon – stay tuned for Part 2…

References

Bowden, J., & Buddle, C. (2012). Life history of tundra-dwelling wolf spiders (Araneae: Lycosidae) from the Yukon Territory, Canada Canadian Journal of Zoology, 90 (6), 714-721 DOI: 10.1139/z2012-038

Bowden, J., & Buddle, C. (2010). Determinants of Ground-Dwelling Spider Assemblages at a Regional Scale in the Yukon Territory, Canada Ecoscience, 17 (3), 287-297 DOI: 10.2980/17-3-3308

Buddle, C. (2000). LIFE HISTORY OF PARDOSA MOESTA AND PARDOSA MACKENZIANA (ARANEAE, LYCOSIDAE) IN CENTRAL ALBERTA, CANADA Journal of Arachnology, 28 (3), 319-328 DOI: 10.1636/0161-8202(2000)028[0319:LHOPMA]2.0.CO;2

Bowden, J. & Buddle, C. (2010). Spider assemblages across elevational and latitudinal gradients in the Yukon Territory, Canada.  Arctic 63(3): 261-272 http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/1490

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