| 1. |
- Brodin, Tomas, et al.
(författare)
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Conflicting selection pressures on the growth/predation risk trade-off in a damselfly
- 2004
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 85:11, s. 2927-2932
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Tidskriftsartikel (refereegranskat)abstract
- Activity is an important behavioral trait that in most animals mediates a trade-off between obtaining food for growth and avoiding predation. Active individuals usually experience a higher encounter rate with food items and predators and, as a consequence, grow faster and suffer higher predation pressure than less active individuals. We investigated how predator-induced mortality and growth of the damselfly Coenagrion hastulatum depend on activity at the level of the genotype. Larvae from six different C. hastulatum families were reared in two different predator treatments: predator present or absent. Families differed in activity, and active families grew to a significantly larger size than less-active families. Within families there was a plastic response to predators. Larvae reared without predators were more active and grew larger than larvae reared with a nonlethal predator. In the presence of a lethal predator the active families experienced higher mortality than the less active families. The results illustrate that the growth/predation-risk trade-off was mediated by activity and clearly show a cost of antipredator behavior. They also suggest that variation in activity level might be genetically regulated and could explain why C. hastulatum are abundant in aquatic systems both with and without potential predators.
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| 2. |
- Nilsson-Örtman, Viktor, et al.
(författare)
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Competitive interactions modify the temperature dependence of damselfly growth rates
- 2014
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 95:5, s. 1394-1406
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Tidskriftsartikel (refereegranskat)abstract
- Individual growth rates and survival are major determinants of individual fitness, population size structure, and community dynamics. The relationships between growth rate, survival, and temperature may thus be important for predicting biological responses to climate change. Although it is well known that growth rates and survival are affected by competition and predation in addition to temperature, the combined effect of these factors on growth rates, survival, and size structure has rarely been investigated simultaneously in the same ecological system. To address this question, we conducted experiments on the larvae of two species of damselflies and determined the temperature dependence of growth rate, survival, and cohort size structure under three scenarios of increasing ecological complexity: no competition, intraspecific competition, and interspecific competition. In one species, the relationship between growth rate and temperature became steeper in the presence of competitors, whereas that of survival remained unchanged. In the other species, the relationship between growth rate and temperature was unaffected by competitive interactions, but survival was greatly reduced at high temperatures in the presence of interspecific competitors. The combined effect of competitive interactions and temperature on cohort size structure differed from the effects of these factors in isolation. Together, these findings suggest that it will be challenging to scale up information from single-species laboratory studies to the population and community level.
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| 3. |
- Nilsson-Örtman, Viktor, et al.
(författare)
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Generalists and specialists along a latitudinal transect : patterns of thermal adaptation in six species of damselflies
- 2012
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 93:6, s. 1340-1352
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Tidskriftsartikel (refereegranskat)abstract
- Tropical organisms colonizing temperate environments face reduced average temperatures and dramatic thermal fluctuations. Theoretical models postulate that thermal specialization should be favored either when little environmental variation is experienced within generations or when among-generation variation is small relative to within-generation variation. To test these predictions, we studied six temperate species of damselflies differing in latitudinal distribution. We developed a computer model simulating how organisms experience environmental variation (accounting for diapause and voltinism) and performed a laboratory experiment assaying thermal sensitivities of growth rates. The computer model showed opposing latitudinal trends in among-and within-generation thermal variability: within-generation thermal variability decreased toward higher latitudes, whereas relative levels of among-generation thermal variability peaked at midlatitudes (where a shift in voltinism occurred). The growth experiment showed that low-latitude species were more thermally generalized than mid- and high-latitude species, supporting the prediction that generalists are favored under high levels of within-generation variation. Northern species had steeper, near-exponential reaction norms suggestive of thermal specialization. However, they had strikingly high thermal optima and grew very slowly over most of the thermal range they are expected to experience in the field. This observation is at present difficult to explain. These results highlight the importance of considering interactions between life history and environmental variation when deriving expectations of thermal adaptation.
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