Browsing Faculty of Science by Author "Walde, Sandra Joan"
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Estimation of Temporal Variability in Populations
STEWARTOATEN, A.; MURDOCH, WW; Walde, Sandra Joan (1995-10)A common measure of the temporal variability of a population is the standard deviation of the logarithms of successive estimated population sizes, In(D-t). This measure overestimates true temporal variability (the standard ... -
How quality of host plant affects a predator-prey interaction in biological control
Walde, Sandra Joan (1995)In cases of successful biological control the pest population is maintained at low densities by a natural enemy, but the mechanisms by which the predator or parasitoid manages to control the pest are often unknown. This ... -
Intraguild interactions and large-scale population patterns
Sircom, Julie; Walde, Sandra Joan (2009-09)Competitive interactions, including interference and intraguild predation, occur in many aquatic food webs and influence large-scale patterns of abundance, especially in lentic habitats. In a study of small coastal streams ... -
Invertebrate predation and lotic prey communities: Evaluation of in situ enclosure/exclosure experiments
Walde, Sandra Joan; Davies, R. W. (1984)The influence of the stonefly Kogotus nonus on prey communities was assessed by varying the predator density within small enclosures in a first-order stream in southwestern Alberta. Experimental containers with natural ... -
Nonbreeding-Season Drivers of Population Dynamics in Seasonal Migrants: Conservation Parallels Across Taxa
Calvert, Anna M.; Walde, Sandra Joan; Taylor, Philip D. (2009-12)For seasonal migrants, logistical constraints have often limited conservation efforts to improving survival and reproduction during the breeding season only. Yet, mounting empirical evidence suggests that events occurring ... -
Patch Dynamics of a Phytophagous Mite Population Effect of Number of Subpopulations
Walde, Sandra Joan (1991)I conducted a field test of the hypothesis that the dynamics of a predator-prey interaction should be affected by the number of interacting subpopulations within an assemblage. I used a "successful" biological control ... -
Prey Exchange Rates and the Impact of Predators on Prey Populations in Streams
Cooper, S. D.; Walde, Sandra Joan; Peckarsky, B. L. (1990)We present four lines of evidence that the magnitude of prey exchange (=immigration/emigration) among substrate patches has an overwhelming influence on the perceived effects of predators on prey populations. (1) An extensive ... -
Refuge dynamics and metapopulation dynamics: An experimental test
Murdoch, WW; Swarbrick, SL; Luck, RF; Walde, Sandra Joan; Yu, DS (1996-03)Red scale, an insect pest of citrus, is under control by the parasitoid Aphytis melinus in many areas, and in our study area the interaction appears dynamically stable. The bark on the interior branches and trunk of trees ... -
A Refuge for Red Scale the Role of Size-Selectivity by a Parasitoid Wasp
Walde, Sandra Joan; Luck, R. F.; Yu, D. S.; Murdoch, W. W. (1989)The presence of a physical refuge (an area where mortality due to parasitism is very low) has been demonstrated for California red scale, a pest of citrus. Density of red scale is very high, and parasitism by the principal ... -
A Refuge for Red Scale Under Control by Aphytis - Structural Aspects
MURDOCH, WW; LUCK, RF; Walde, Sandra Joan; REEVE, JD; YU, DS (1989-12)No abstract available. -
Regulation of an Insect Population Under Biological-Control
MURDOCH, WW; LUCK, RF; SWARBRICK, SL; Walde, Sandra Joan; YU, DS; REEVE, JD (1995-01)California red scale is suppressed to very low densities by the parasitoid Aphytis melinus. The system also appears stable. We report on an experimental test of the hypothesis that stability is caused by a refuge for scale. ... -
Surviving historical Patagonian landscapes and climate: molecular insights from Galaxias maculatus
Zemlak, Tyler S.; Habit, Evelyn M.; Walde, Sandra Joan; Carrea, Cecilia; Ruzzante, Daniel E. (2010-03)Background: The dynamic geological and climatic histories of temperate South America have played important roles in shaping the contemporary distributions and genetic diversity of endemic freshwater species. We use ...