Dr. Sandra J. Walde
BSc (U Calgary)
PhD (U Calgary)

  • Teaching & Research
  • Students' Research Topics
  • Publications
  • Special Topics Chair
  • Links   
  • Teaching & Research
    Population dynamics, arthropods, dispersal, species interactions

    Stream ecology: My students and I are studying the interactions among productivity, disturbance and geomorphology with the goal of explaining the patterns of biodiversity, composition and population dynamics that we see in the coastal stream communities of western Nova Scotia.  The region is quite unique, with many short, parallel streams that drain a tilted basalt ridge (North Mountain) and flow through secondary forest into the Bay of Fundy. 

    We are looking at: (1) Large scale consequences of species interactions: (a) top-down effects of fish (brook trout) on abundances and life history traits of aquatic insects, (b) the consequences of intraguild interactions among invertebrate predators for coexistence and abundances. (2) Flood disturbance: the significance of major episodic flow events for energy availability (detritus retention). (3) Biodiversity: how energy (detritus and algal productivity) affects species richness.

    Ross Creek waterfall
    Ross Creek waterfall

    Classes in which Sandra currently teaches:
    Evolutionary dynamics and ecology of Patagonian fish: Together with Daniel Ruzzante (Dalhousie), Evelyn Habit (Chile) and Victor Cussac (Argentina),we have been studying the evolutionary dynamics and ecology of native fish in the mountain and steppe lakes of Patagonia. We are looking at causes of morphological variation within and among lakes, and the phylogeography of two of the most important families in the region (Galaxiidae and Percichthyidae).


    Examples of Students' Research Topics
    Sampling benthic invertebrates in Lago Belgrano, Argentina
    Honors BSc Students
    • Emily Sangster: Effects of agriculture on food web structure (in progress)
    • David Blanchard: Alternative food and biocontrol of Lygus (in progress)
    • Matthew Jones: Risk of predation by brook trout affects behaviour of three caddisfly species (2010)
    • Christopher Barry: Retention of detritus varies with glacial till type in small coastal streams (2010)
    • Jean Blair: Effects of land use patterns on stream communities (2009)
    • Kathleen Archibald: Effects of flood disturbance on stream Ephemeroptera (2009)
    • Jenna Disch: Leaf litter input, breakdown rate, and invertebrate predator diversity (2007)
    Graduate Students
    • Charles Wright: Intraguild interactions along a productivity gradient (MSc in progress)
    • Justin Renkema: Integrated organic management strategies for blueberry maggot in highbush blueberries (PhD in progress, co-supervised, D. Lynch)
    • Tyler Zemlak: Phylogeography of the Patagonian Galaxiidae (PhD in progress, co-supervised, D. Ruzzante)
    • Julie Sircom: Determinants of the biodiversity and composition of stream insect communities (PhD, 2009)
    • Anna Calvert: Modeling variation in stopover behaviour by migratory songbirds: temporal patterns an dimplications of climate change (PhD, 2009, co-supervised, P. Taylor)
    • Kincaid Chan: Trophic polymorphism, growth, and life history variation in Percichthys trucha (MSc 2009, co-supervised, D. Ruzzante)
    • Kurtis Trczinski.: The effect of food web structure on the population dynamics of pitcher plant microfauna. (PhD, 2003)
    • Carol Hilton: The effect of predation on life history traits of an intertidal amphipod. (MSc, 1999).
    • Julie Sircom: The effect of dispersal on predator-prey dynamics in a spatially heterogeneous environment. (MSc, 1999).
    • Qingcai Wei: Species interactions within a mite complex and their effects on biological control. (MSc, 19

      Retrieving litter bags
      Retrieving litter bags

    Selected Publications

    Habit, E., Piedra, P, Ruzzante, D.E., Walde, S.J., Cussac, V.E., Belk, M., Gonzalez, J., Colin, N. Changes in distribution patterns of native fishes in response to introduced species and other anthropogenic effects. 2010. Global Ecology and Biogeography 19: (available online).

    Zemlak, T.S, Habit, E.M., Walde, S.J., Carrea, C. Ruzzante, D.E. 2010. Surviving historical Patagonian landscapes and climate: molecular insights from Galaxias maculatusBMC Evolutionary Biology 10: 67
    [online: http://www.biomedcentral.com/1471-2148/10/67)]

    Calvert, A.M., Walde, S.J., Taylor, P.D. 2009. Seasonal drivers of population dynamics in long-distance migrants: conservation parallels across taxa. Avian Conservation and Ecology 4(2) [online] URL: http://www.ace-eco.org/vol4/iss2/art5.

    Sircom, J. and S.J. Walde. 2009. Intraguild interactions among stream invertebrate predators and large-scale population patterns. JNABS 28: 649-658.

    Calvert, A.M., Bonner, S.J, Jonsen, I.D., Flemming, J.M., Walde, S.J. & Taylor, P.D. 2009. A hierarchical Bayesian approach to multi-state mark-recapture: simulations and applications Journal of Applied Ecology 46: 610-620

    Sircom, J. and S.J. Walde.  2009. Catchment-level and within-stream structuring of an invertebrate predator guild in streams. Hydrobiologia 620: 181-190.

    Calvert, A.M., P.D. Taylor, S.J. Walde.  2009. Cross-scale environmental influences on migratory stopover behaviour. Global Change Biology 15: 744-759.

    Trzcinski, K., Walde, S.J. & P. Taylor. 2008. Spatial variation in population growth rate and community structure affects local and regional dynamics. Journal of Animal Ecology 77:1153-1161.

    Zemlak, T.S., Habit, E.M., Walde, S.J., Battini, M., Adams, E.D.M., Ruzzante, D.E. 2008. Across the southern Andes on fin: glacial refugia, drainage reversals and a secondary contact zone revealed by the phylogeographical signal of Galaxias platei in Patagonia. Molecular Ecology 17: 5049-61.

    Paterson, IG, Walde, SJ, Cussac, VE, Habit, E, Ruzzante, DE.  2008. Isolation and characterization of 13 microsatellite loci for Percichthys trucha (Percichthyidae). Molecular Ecology Resources 8: 907-909.

    Ruzzante, D.E, Walde, S.J., Gosse, J.C., Cussac, V.E., Habit, E., Zemlak, T.S., Adams, E.D.M. 2008. Climate control on ancestral population dynamics: Insight from Patagonian fish phylogeography. Molecular Ecology 17:2234-2244.

    Buria, L., Walde, S.J., Battini M., Macchi P.J., Alonso, M., Ruzzante, D.E., & Cussac, V.E. 2007. Movement of an endemic perch (Percichthys trucha) in a montane Patagonian lake during spawning and pre-spawning periods. Journal of Fish Biology, 70:215-230.

    Ruzzante, D.R., Walde, S.J., Cussac, V.E., Dalebout, M.L., Seibert, J., Ortubay, & S., Habit, E. 2006. Phylogeography of the Percichthyidae (Percichthys spp. and Percilia spp.) in southern South America: roles of orogeny, glaciation, and volcanism. Molecular Ecology, 15:2949-2968.

    Milano D, D.E. Ruzzante, S.J. Walde, V.E. Cussac, & P.J. Macchi. 2006. Latitudinal and ecological correlates of morphological variation in Galaxias platei (Pisces: Galaxiidae) in Patagonia. Biological Journal of the Linnean Society 87:69-82.

    Trzcinski, M.K., Walde, S.J. & Taylor, P.D. 2005. Local interactions in pitcher plant communities scale-up to regional patterns in distribution and abundance. Environmental Entomology 34:1464-1470

    Trzcinski, M.K., Walde, S.J. & Taylor, P.D. 2005. Stability of pitcher-plant microfaunal populations depends on food web structure. Oikos 110: 146-154.


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