Browsing by Subject "STICKLEBACKS"

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  • Candolin, Ulrika; Bertell, Elina; Kallio, Jarkko (2018)
    1. Alien species are altering ecosystems around the globe. To predict and manage their impacts, the underlying mechanisms need to be understood. This is challenging in ecosystems undergoing multiple disturbances as unexpected interactions can alter the impact of individual disturbances. Such interactions are likely to be common in disturbed ecosystems, but have so far received little attention. 2. We investigated whether interactions between an invading shrimp Palaemon elegans and another human-induced disturbance, the population growth of a native mesopredator, the threespine stickleback, influences a third human-induced disturbance, the increase in biomass of filamentous algae. Increases in both the native mesopredator population and algal biomass have been promoted by eutrophication and a trophic cascade triggered by declining predatory fish stocks. 3. We used mesocosm and field enclosure experiments, combined with analyses of long-term trends in the abundance of the invader and the native mesopredator, to dissect the influence of the two species on algal biomass when alone and when co-occurring. 4. The impact of the invader on algal biomass depended on the native mesopredator; shrimp on their own had no effect on algal growth, but mitigated algae accumulation when competing with the stickleback for resources. Competition caused the shrimp to shift its diet from grazers to algae, and its habitat choice from open to vegetated habitats. The native mesopredator, in contrast, increased algal biomass irrespective of the presence of the invader, by preying on grazers and inducing a trophic cascade. 5. Our results show that the presence of a native mesopredator causes an invader to alter its behaviour and thereby its ecological impact. This demonstrates that interactions between invaders and other anthropogenic disturbances can alter the ecological impact of invaders, and, notably, that the impact of invaders can be positive and stabilize disturbed ecosystems. These results stress the importance of considering interactions among disturbances when investigating the ecological impact of alien species.
  • Priklopil, Tadeas; Kisdi, Eva; Gyllenberg, Mats (2015)
    We consider mating strategies for females who search for males sequentially during a season of limited length. We show that the best strategy rejects a given male type if encountered before a time-threshold but accepts him after. For frequency-independent benefits, we obtain the optimal time-thresholds explicitly for both discrete and continuous distributions of males, and allow for mistakes being made in assessing the correct male type. When the benefits are indirect (genes for the offspring) and the population is under frequency-dependent ecological selection, the benefits depend on the mating strategy of other females as well. This case is particularly relevant to speciation models that seek to explore the stability of reproductive isolation by assortative mating under frequency-dependent ecological selection. We show that the indirect benefits are to be quantified by the reproductive values of couples, and describe how the evolutionarily stable time-thresholds can be found. We conclude with an example based on the Levene model, in which we analyze the evolutionarily stable assortative mating strategies and the strength of reproductive isolation provided by them.
  • Montiglio, P. O.; Gotanda, K. M.; Kratochwil, C. F.; Laskowski, K. L.; Farine, D. R. (2020)
    Because genes and phenotypes are embedded within individuals, and individuals within populations, interactions within one level of biological organization are inherently linked to interactors at others. Here, we expand the network paradigm to consider that nodes can be embedded within other nodes, and connections (edges) between nodes at one level of organization form "bridges" for connections between nodes embedded within them. Such hierarchically embedded networks highlight two central properties of biological systems: 1) processes occurring across multiple levels of organization shape connections among biological units at any given level of organization and 2) ecological effects occurring at a given level of organization can propagate up or down to additional levels. Explicitly considering the embedded structure of evolutionary and ecological networks can capture otherwise hidden feedbacks and generate new insights into key biological phenomena, ultimately promoting a broader understanding of interactions in evolutionary theory. Lay Summary: Interactions are ubiquitous across biological systems. Modeling their consequences requires capturing how units are organized across biological scales: gene and protein interactions shape phenotypic traits within individuals, individuals are embedded within populations, populations within communities, and communities within ecosystems. Doing so reveals how indirect connections among units arise from the structure of connections at higher or lower levels of organization, and how effects at one level of the network propagate across neighboring levels.