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!
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.
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:
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.
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…
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