bernard roitberg
Simon Fraser University, Biology, Emeritus
Foraging models are useful tools for generating predictions on predator-prey interactions, such as habitat or diet choice. However, the majority of studies attempting to explain adaptive behaviour using optimality criteria have assumed... more
Foraging models are useful tools for generating predictions on predator-prey interactions, such as habitat or diet choice. However, the majority of studies attempting to explain adaptive behaviour using optimality criteria have assumed that there is no trait (e.g. size) variation among individual consumers or their prey. Hymenopteran parasitoids that attack the free-living stages of their host are an ideal system for studying the influence of body size on host selection because of the wide range of adult parasitoid sizes coupled with the defensive capabilities of their hosts. We report here our application of an experimentally parameterized host selection model to investigate the influence of parasitoid body size on the range of acceptable host instar classes. Using a demographic model, we compared the efficiency of parasitoids using an optimal host selection strategy against parasitoids using an indiscriminate host selection strategy over a range of different parasitoid body sizes. Net fitness accrual of parasitoids and the impact of host instar selection on aphid recruitment were assessed on different stage-structured aphid populations. Our results demonstrate that optimal host selection allows larger parasitoids to utilize a wider range of hosts. However, smaller parasitoids receive the greatest benefits from selecting hosts optimally by utilizing a restricted range of small, poorly defended hosts when they are abundant. We argue that the correlation between flexible host selection behaviour and adult body size may be a general phenomenon that applies to the majority of hymenopteran parasitoids that attack free-living, well-defended hosts. The potential of within-generation behavioural interactions to impact between-generation dynamics in host-parasitoid populations are discussed.
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Resource availability and location are expected to vary, based on use by individuals and changing ecological conditions; the response of animals to those changes is critical to their fitness. To investigate the effects of changing... more
Resource availability and location are expected to vary, based on use by individuals and changing ecological conditions; the response of animals to those changes is critical to their fitness. To investigate the effects of changing conditions on fitness, we conducted field experiments using the central-place-foraging alfalfa leafcutting bee (Megachile rotundata), examining the changes in sex allocation when presented with changes in flight distance required to obtain resources. The results suggest that changes in flight distance to resources during the year’s flight season altered subsequent allocation decisions: mothers experiencing long flight distance to resources early in the season and short flight distance later in the season generated a greater proportion of female offspring than mothers experiencing the opposite. During the second half of the season, however, it was current experimental conditions significantly impacting decisions with those mothers residing near the resources producing a greater portion of female offspring than those far from resources, regardless of flight distances experienced earlier in the year. These results show that sex allocation decisions may change dynamically during a female’s lifetime in response to ecological changes. We also looked at these results through the contradicting hypotheses marginal value theorem and sex ratio theory, finding that the latter may be in play depending on an individual’s past and/or present condition.
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... WILLEM G. VAN HERK 1,* ,; ROBERT S. VERNON 1 ,; CHANTELLE HARDING 1 ,; BERNARD D. ROITBERG 2 ,; GERHARD GRIES 2. ... is reported in various insects and is considered as an important mechanism for developing resistance to insecticides... more
... WILLEM G. VAN HERK 1,* ,; ROBERT S. VERNON 1 ,; CHANTELLE HARDING 1 ,; BERNARD D. ROITBERG 2 ,; GERHARD GRIES 2. ... is reported in various insects and is considered as an important mechanism for developing resistance to insecticides (Prokopy & Lewis, 1993). ...
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We develop an evolutionarily stable strategy theory of parent-offspring conflict in insect herbivores for the case in which offspring can choose to leave host plants on which they have been deposited by their mother. We find that a... more
We develop an evolutionarily stable strategy theory of parent-offspring conflict in insect herbivores for the case in which offspring can choose to leave host plants on which they have been deposited by their mother. We find that a fundamental parent-offspring conflict in larval leaving rates occurs because individual larvae are more related to themselves than to their siblings whereas mothers are equally related to each of their offspring. Several patterns emerge: (1) The optimal probability of movement from the mother's perspective, P*(mom), is always greater than or equal to the optimal probability of movement from the offspring's perspective, P*(off), (2) a consequence of this difference in optimal probabilities of movement is that the mother's fitness for a given clutch is always greater for P*(mom) than P*(off), (3) as the payoff for leaving a plant decreases, (i) the optimal movement rates decrease and (ii) clutches become smaller, (4) as relatedness increases, optimal movement probabilities increase and this causes an increase in optimal clutches, and (5) the clutch size that maximizes the mother's lifetime fitness will frequently diverge from that which the mother would produce were the offspring to move at her optimal rate (i.e., P*(mom)).
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The preference of the predatory midge, Feltiella acarisuga (Vallot), for adult male and female twospotted spider mite, Tetranychus urticae Koch, was examined using functional response models. The midge exhibited a type-II functional... more
The preference of the predatory midge, Feltiella acarisuga (Vallot), for adult male and female twospotted spider mite, Tetranychus urticae Koch, was examined using functional response models. The midge exhibited a type-II functional response to each prey. Handling time was estimated to be much higher for the female mites than for the males (1.52 vs. 0.40 h). Estimated instantaneous search rates for the female and male mites were similar (1.32 vs. 1.28). A preference index of 1.03 was calculated using the ratio of the instantaneous search rates. Feltiella acarisuga was found to exhibit no preference for either female or male mites; when both prey were present in equal numbers, midge larvae killed as many females as males.
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... Colleen R. ALMA1,*, Mark S. GOETTEL1,2, Bernard D. ROITBERG1 and David R. GILLESPIE1,3 1Department of Biological Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada; 2Lethbridge Research Centre, Agriculture and Agri-Food... more
... Colleen R. ALMA1,*, Mark S. GOETTEL1,2, Bernard D. ROITBERG1 and David R. GILLESPIE1,3 1Department of Biological Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada; 2Lethbridge Research Centre, Agriculture and Agri-Food Canada, PO Box 3000 ...
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Research Interests: Biology, Multidisciplinary, Nature, Sex Pheromone, Insect, and 3 moreRhagoletis, Pheromone, and Maggot
This chapter emphasizes the physiological, anatomical and life history characteristics of tephritids that determine their role in agroecosystems, and the ecological and evolutionary basis of fly behaviour that allows them to adapt to... more
This chapter emphasizes the physiological, anatomical and life history characteristics of tephritids that determine their role in agroecosystems, and the ecological and evolutionary basis of fly behaviour that allows them to adapt to their environment (both their internal and external states).
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There are several biopesticides based on entomopathogenic fungi available in the market for use against insect pests in greenhouse ecosystems.Although most are compatible for use with predators and parasitoids in greenhouse... more
There are several biopesticides based on entomopathogenic fungi available in the market for use against insect pests in greenhouse ecosystems.Although most are compatible for use with predators and parasitoids in greenhouse ecosystems,much more research is needed to ...
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Compensatory growth (CG) appears common in biology and is defined as accelerated growth after experiencing a period of unfavorable conditions. It usually leads to an increase in biomass that may eventually equal or even surpass that of... more
Compensatory growth (CG) appears common in biology and is defined as accelerated growth after experiencing a period of unfavorable conditions. It usually leads to an increase in biomass that may eventually equal or even surpass that of sites not experiencing disturbance. In forestry, with sufficient time the stand volume lost in a disturbance such as a thinning operation could match or even exceed those from undisturbed sites, respectively called exact and overcompensation. The forest sector could benefit from enhanced productivity and associated ecosystem services such as carbon storage through overcompensation. Therefore, detection of CG in different types of forests becomes important for taking advantage of it in forest management. However, compensatory growth has not been reported widely in forestry, partially due to the paucity of long-term observations and lack of proper indicators. Legacy forest projects can provide a suitable data source, though they may be originally design...
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Additional file 2. Comparison of fitted modelsâ residuals of mosquitoes collected in the hut over time. Treatment groups correspond to duration of mosquito starvation treatments (0, 24, 48 hrs). a) Model 0, leaving rate is independent of... more
Additional file 2. Comparison of fitted modelsâ residuals of mosquitoes collected in the hut over time. Treatment groups correspond to duration of mosquito starvation treatments (0, 24, 48 hrs). a) Model 0, leaving rate is independent of energy state; b) Model 1 or 2, individuals leave gradually based on energy state; c) Model 3 (constrained, see text), some proportion of individuals leave immediately, while others leave gradually based on energy state; d) Model 4, leaving rate depends on both energy state and time.
Additional file 1. Evaluation of mosquito leaving rates based on starvation treatment and experiment end time using logistic regression.
Rapid deforestation leads to loss and degradation of avian habitat. Reforestation and natural regeneration create secondary forests that may play an important role in maintaining avian biodiversity. In the tropics, many understory... more
Rapid deforestation leads to loss and degradation of avian habitat. Reforestation and natural regeneration create secondary forests that may play an important role in maintaining avian biodiversity. In the tropics, many understory insectivores are absent from secondary forests; however the mechanisms responsible for this pattern are unknown. Differences in foraging behavior can be used to identify changes to the insect community, which may contribute to this pattern. We investigated foraging behavior in a common understory insectivore, the Black-crowned Antshrike ( Thamnophilus atrinucha ), across three forest-age groups to test the hypothesis that insect (prey) communities differ with forest age. We observed no difference in attack or foraging success rates by Black-crowned Antshrikes, suggesting equal foraging effort during focal observations. However, individuals consumed less high-quality (large) prey in secondary forest. Additionally, foraging range shifted downwards from 8.5 ±...
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Compensatory growth has been observed in forests, and it also appears as a common phenomenon in biology. Though it sometimes takes different names, the essential meanings are the same, describing the accelerated growth of organisms when... more
Compensatory growth has been observed in forests, and it also appears as a common phenomenon in biology. Though it sometimes takes different names, the essential meanings are the same, describing the accelerated growth of organisms when recovering from a period of unfavorable conditions such as tissue damage at the individual level and partial mortality at the population level. Diverse patterns of compensatory growth have been reported in the literature, ranging from under-, to compensation-induced-equality, and to over-compensation. In this review and synthesis, we provide examples of analogous compensatory growth from different fields, clarify different meanings of it, summarize its current understanding and modeling efforts, and argue that it is possible to develop a state-dependent model under the conceptual framework of compensatory growth, aimed at explaining and predicting diverse observations according to different disturbances and environmental conditions. When properly app...
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Based on the premises that we called upon above (action studies on insect conservation and our love for all things six-legged), we hope this collection can stimulate research and social initiatives that protect insects. (2021) analysed... more
Based on the premises that we called upon above (action studies on insect conservation and our love for all things six-legged), we hope this collection can stimulate research and social initiatives that protect insects. (2021) analysed the literature to determine the extent of biases (including taxonomic and geographic biases) that inform our assessment of insect decline, and detail how just scattered insect records are. Insects are declining worldwide. [Extracted from the article] Copyright of Ecological Entomology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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Abstract: Insects are notoriously variable in their behavioral response to chemical substances. Much of this variability often is explained best by defining the context under which these substances are encountered and developing... more
Abstract: Insects are notoriously variable in their behavioral response to chemical substances. Much of this variability often is explained best by defining the context under which these substances are encountered and developing hypotheses that incorporate the ...
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The effects of various ecological factors, such as the probability of finding mates and hosts and of successfully obtaining a blood meal, on the mating and feeding strategies of domestic female anopheline mosquitoes was investigated using... more
The effects of various ecological factors, such as the probability of finding mates and hosts and of successfully obtaining a blood meal, on the mating and feeding strategies of domestic female anopheline mosquitoes was investigated using theoretical models. The models calculated the mean fitness of 1,000 nonblood-fed, anautogenous, virgin anophelines. One model simulated females that always mate before blood feeding, whereas another simulated females that are able to feed opportunistically if a host was detected before they mated. The models demonstrated highest fitness for mosquitoes capable of opportunistic feeding under nearly all simulated conditions. This advantage increased as the probability of finding hosts and mates decreased as a function of host and mate availability.
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ABSTRACT
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ABSTRACT