| 1. |
- Pärssinen, Varpu, et al.
(författare)
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Variation in predation regime drives sex-specific differences in mosquitofish foraging behaviour
- 2021
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Ingår i: Oikos. - : Wiley-Blackwell. - 0030-1299 .- 1600-0706. ; 130:5, s. 790-797
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Tidskriftsartikel (refereegranskat)abstract
- Predation is a well-studied driver of ecological selection on prey traits, which frequently drives divergence in anti-predator performance across environments that vary in predation risk. However, predation also alters prey mortality regimes, where low predation risk often results in higher prey densities and consequently higher intensities of intraspecific resource competition. In addition, predation risk alters the foraging context, as acquiring food can be risky in the presence of predators. Thus, different predation regimes can drive divergent selection on traits associated with resource competition, such as foraging behaviours. Moreover, because sexes often differ in susceptibility to predation and limitations to their reproductive output, the intensity of the tradeoff between predator avoidance and resource competition may depend on sex. We used a laboratory experiment to assess key aspects of foraging performance in a predator-free context in Bahamas mosquitofish Gambusia hubbsi wild-caught from multiple populations that experience either high or low levels of predation risk. When competing for limited food resources at a common density, females from low-predation regimes showed higher foraging and food consumption rates than females from high-predation regimes. Males showed fewer differences between predation regimes, and an opposite pattern from females. We suggest these sex-specific effects result from females facing a greater tradeoff between predation risk and resource competition, combined with males from high-predation environments elevating foraging behaviours in the absence of nearby predators and females. Females of this species are larger than males, bear live young and show higher foraging rates in the wild than males. On the other hand, males spend more time pursuing females in the wild, and may exhibit greater flexibility in foraging behaviours based on the immediate context. Our results show that varying levels of predation risk can lead to differences in behaviours associated with resource competition, but these effects can strongly differ between sexes.
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| 2. |
- Sha, Yongcui, et al.
(författare)
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Diel vertical migration of copepods and its environmental drivers in subtropical Bahamian blue holes
- 2021
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Ingår i: Aquatic Ecology. - : Springer. - 1386-2588 .- 1573-5125. ; 55:4, s. 1157-1169
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Tidskriftsartikel (refereegranskat)abstract
- Diel vertical migration (DVM) is the most common behavioral phenomenon in zooplankton, and numerous studies have evaluated DVM under strong seasonality at higher latitudes. Yet, our understanding of the environmental drivers of DVM at low latitudes, where seasonal variation is less pronounced, remains limited. Therefore, we here examined patterns of vertical distribution in copepods in six subtropical Bahamian blue holes with different food web structure and tested the role of several key environmental variables potentially affecting this behavior. Day and night samplings showed that copepods generally performed DVM, characterized by downward migration to deeper depths during the day and upward migration to surface waters at night. Across all blue holes, the daytime vertical depth distribution of calanoid copepods correlated positively with both predation risk and depth of food resources (Chlorophyll a), but was less affected by ultraviolet radiation (UVR). A potential explanation is that since UVR is a continuous threat across seasons, zooplankton have established photoprotective pigmentation making them less vulnerable to this threat. The copepods also showed a size-structured depth segregation, where larger individuals were found at deeper depths during the day, which further strengthens the suggestion that predation is a major driver of DVM in these systems. Hence, in contrast to studies performed at higher latitudes, we show that despite the constant exposure to UVR, predator avoidance and food availability are the most pronounced drivers of copepod DVM at those low latitudes, suggesting that the main driver of DVM may vary among systems, but also systematically by latitude.
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| 3. |
- Sha, Yongcui
(författare)
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Zooplankton responses to multiple threats within and across generations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In their natural environments, organisms are unlikely to be distributed randomly but instead they are constantly faced with multiple and variable threats. In order to maximise survival, they need to be able to perceive the present threat level and respond accordingly. In aquatic ecosystems, two common threats for crustacean zooplankton are predation and ultraviolet radiation (UVR). Despite the growing recognition that zooplankton can plastically respond to predation and UVR within a single generation, little is known on how they evolutionarily cope with these simultaneously occurring multiple threats over generations. In this thesis, I investigate the threat responses in zooplankton when exposed to multiple threats from predation and UVR based on short-term (within a single generation) and multigenerational exposure experiments.Alteration in behavioural traits is generally the first reaction in zooplankton to changed conditions, which allows them to escape from the threats instantly after exposure. One example of a common behavioural response in zooplankton is diel vertical migration (DVM), where they spend the day in deep, dark waters and migrate up to surface waters at night. I found that low-latitude copepods in Bahamian blue holes exhibited DVM to reduce predation risk from visually hunting fish, whereas no response was found to lake-specific differences in UVR transparency. Moreover, copepods also follow their food resources, so that they stay at the depth with rich food where predation risk and UVR may decrease to a negligible level. When exposed to conflicting threats from UVR and predation from either moving pelagic or benthic predators, Daphnia are able to make different risk assessments and thereby alter their behaviour in accordance with the actual threat level. I show that two Daphnia species respond strongly to UVR, whereas only the large prey species D. magna express a predator avoidance behaviour. In addition to alterations in behaviour, D. magna can also change its body size and life-history to deal with multiple threats from predation and UVR. I demonstrate that D. magna become smaller through generations in response to fish predation, whereas they change their behaviour to avoid UVR. Individuals who have previously experienced UVR respond more relaxed when exposed to such radiation again. These individuals also produce less offspring during the first generation after exposure but the number of offspring then gradually increases through generations. Therefore, D. magna adopt divergent strategies over generations and become adapted to the local environmental conditions after about three generations. Exposure to UVR can induce plastic phenotypic changes in D. magna including alterations in behaviour and life-history shifts. However, such transgenerational effects may be modified by the evolutionary history of stress that lead to different plastic responses to UVR across generations.
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| 4. |
- Tesson, Sylvie V.M., et al.
(författare)
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Population connectivity, dispersal, and swimming behavior in Daphnia
- 2021
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:6, s. 2873-2885
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Tidskriftsartikel (refereegranskat)abstract
- The water flea Daphnia has the capacity to respond rapidly to environmental stressors, to disperse over large geographical scales, and to preserve its genetic material by forming egg banks in the sediment. Spatial and temporal distributions of D. magna have been extensively studied over the last decades using behavioral or genetic tools, although the correlation between the two has rarely been the focus. In the present study, we therefore investigated the population genetic structure and behavioral response to a lethal threat, ultraviolet radiation (UVR), among individuals from two different water bodies. Our results show two genetic populations with moderate gene flow, highly correlated with geographical location and with inheritable traits through generations. However, despite the strong genetic differences between populations, we show homogeneous refuge demand between populations when exposed to the lethal threat solar UVR.
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| 5. |
- Vinterstare, Jerker, et al.
(författare)
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Predation risk and the evolution of a vertebrate stress response : Parallel evolution of stress reactivity and sexual dimorphism
- 2021
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Ingår i: Journal of Evolutionary Biology. - : John Wiley & Sons. - 1010-061X .- 1420-9101. ; 34:10, s. 1554-1567
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Tidskriftsartikel (refereegranskat)abstract
- Predation risk is often invoked to explain variation in stress responses. Yet, the answers to several key questions remain elusive, including the following: (1) how predation risk influences the evolution of stress phenotypes, (2) the relative importance of environmental versus genetic factors in stress reactivity and (3) sexual dimorphism in stress physiology. To address these questions, we explored variation in stress reactivity (ventilation frequency) in a post-Pleistocene radiation of live-bearing fish, where Bahamas mosquitofish (Gambusia hubbsi) inhabit isolated blue holes that differ in predation risk. Individuals of populations coexisting with predators exhibited similar, relatively low stress reactivity as compared to low-predation populations. We suggest that this dampened stress reactivity has evolved to reduce energy expenditure in environments with frequent and intense stressors, such as piscivorous fish. Importantly, the magnitude of stress responses exhibited by fish from high-predation sites in the wild changed very little after two generations of laboratory rearing in the absence of predators. By comparison, low-predation populations exhibited greater among-population variation and larger changes subsequent to laboratory rearing. These low-predation populations appear to have evolved more dampened stress responses in blue holes with lower food availability. Moreover, females showed a lower ventilation frequency, and this sexual dimorphism was stronger in high-predation populations. This may reflect a greater premium placed on energy efficiency in live-bearing females, especially under high-predation risk where females show higher fecundities. Altogether, by demonstrating parallel adaptive divergence in stress reactivity, we highlight how energetic trade-offs may mould the evolution of the vertebrate stress response under varying predation risk and resource availability.
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