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- 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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- Eckstein, Rolf Lutz, et al.
(författare)
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Recycling of nitrogen among segments of Hylocomium splendens as compared with Polytrichum commune : Implications for clonal integration in an ectohydric bryophyte
- 1999
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Ingår i: OIKOS. - : Nordic Society Oikos. - 0030-1299. ; 86:1, s. 87-96
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Tidskriftsartikel (refereegranskat)abstract
- Physiological integration in clonal plants, which can be assumed to be dependent on vascular connections among ramets, is associated with several potential benefits, especially in nutrient-poor environments. However, some experimental evidence indicates that ectohydric bryophytes, i.e. species lacking specialised tissues for internal water conduction, also have physiologically integrated ramets. We tested this hypothesis by analysing nitrogen dynamics and tracing movements of a 15 N label among interconnected ramets of the ectohydric Hylocomium splendens over one season. The observed patterns were compared with translocation patterns in Polytrichum commune, an endohydric species that is known to show a high degree of clonal integration. Our aims were (1) to evaluate the degree of physiological integration among segments in H. splendens and (2) to study whether the pattern of 15 N movement obtained matched those depicted by changes in total nitrogen pool size. Current-year segments (G0) of both species were identified as strong sinks for nitrogen owing to their considerable increase in the 15 N pool during the season. In P. commune all other segments types showed a net loss of 15 N from June to September, which was probably due to autumn resorption of nitrogen to subterranean structures. In H. splendens one-year-old segments (G1) increased their 15 N pool, while older green segments (G2+) lost 50% of their initially absorbed 15 N. All the label lost from these source segments could be recovered in G0 and G1 segments. We suppose that most of the recycled nitrogen is provided by degeneration of three-year-old segments, which turn brown in parallel with the reallocation of nitrogen during the season. The high degree of physiological integration in H. splendens is discussed with respect to its life history and ecosystem nitrogen cycling.
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