Browsing by Subject "PREDATION"

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  • Schrandt, Meagan N.; Stone, Laura C.; Klimek, Brian; Makelin, Saara; Heck, Kenneth L.; Mattila, Johanna; Herlevi, Heidi (2016)
    In the Baltic Sea, species diversity is relatively low and the introduction of new predator species can have large direct and indirect impacts on native species - both prey and potential competitors. The alien round goby Neogobius melanostomus Pallas, 1811 was introduced to the Baltic Sea in the early 1990s and is now well-established. We examined the feeding habits of male round gobies from the Aland Islands, Finland, where round gobies were first recorded in 2011. Specifically, we tested whether small round gobies (
  • Laanto, Elina; Mäkelä, Kati; Hoikkala, Ville; Ravantti, Janne; Sundberg, Lotta-Riina (2020)
    Phage therapy is becoming a widely recognized alternative for fighting pathogenic bacteria due to increasing antibiotic resistance problems. However, one of the common concerns related to the use of phages is the evolution of bacterial resistance against the phages, putatively disabling the treatment. Experimental adaptation of the phage (phage training) to infect a resistant host has been used to combat this problem. Yet, there is very little information on the trade-offs of phage infectivity and host range. Here we co-cultured a myophage FCV-1 with its host, the fish pathogenFlavobacterium columnare, in lake water and monitored the interaction for a one-month period. Phage resistance was detected within one day of co-culture in the majority of the bacterial isolates (16 out of the 18 co-evolved clones). The primary phage resistance mechanism suggests defense via surface modifications, as the phage numbers rose in the first two days of the experiment and remained stable thereafter. However, one bacterial isolate had acquired a spacer in its CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)-Cas locus, indicating that also CRISPR-Cas defense was employed in the phage-host interactions. After a week of co-culture, a phage isolate was obtained that was able to infect 18 out of the 32 otherwise resistant clones isolated during the experiment. Phage genome sequencing revealed several mutations in two open reading frames (ORFs) likely to be involved in the regained infectivity of the evolved phage. Their location in the genome suggests that they encode tail genes. Characterization of this evolved phage, however, showed a direct cost for the ability to infect several otherwise resistant clones-adsorption was significantly lower than in the ancestral phage. This work describes a method for adapting the phage to overcome phage resistance in a fish pathogenic system.
  • Tolvanen, Jere; Pakanen, Veli-Matti; Valkama, Jari; Tornberg, Risto (2017)
    Capsule: Mark-recapture data suggest low apparent survival and sex- and population-specific site fidelity and territory turnover in adult Northern Goshawks Accipiter gentilis breeding in northern Europe.Aims: To understand how species cope with global environmental change requires knowledge of variation in population demographic rates, especially from populations close to the species' northern range limit and from keystone species such as raptors. We analyse apparent survival and breeding dispersal propensity of adult Northern Goshawks breeding in northern Europe.Methods: We used long-term mark-recapture data from two populations in Finland, northern Europe, and Cormack-Jolly-Seber models and binomial generalized linear models to investigate sex- and population-specific variation in apparent survival, territory turnover and site fidelity.Results: We report low apparent survival (53-72%) of breeding adult Goshawks. Breeding dispersal propensity was higher in females than males, especially in northern Finland, contrasting with previous studies that suggest high site fidelity in both sexes.Conclusion: Low apparent survival in females may be mainly due to permanent emigration outside the study areas, whereas in males the survival rate may truly be low. Both demographic aspects may be driven by the combination of sex-specific roles related to breeding and difficult environmental conditions prevailing in northern latitudes during the non-breeding season.
  • Bump, Joseph K.; Murawski, Chelsea M.; Kartano, Linda M.; Beyer, Dean E.; Roell, Brian J. (2013)
  • Heikinheimo, Outi; Lehtonen, Hannu; Lehikoinen, Aleksi (2018)
    Hansson et al. (2017) concluded that competition between fisheries and piscivorous mammals and birds exists in the Baltic Sea, based on the estimation of biomass of the fish species consumed in the ICES subdivisions. We compared their results to the data and scientific knowledge from the coastal waters of Finland and show that local differences in fisheries, fish assemblages and abundance of predators should be taken into account to reliably assess potential competition. Hansson et al. (2017) did not include the piscivorous fish in their analysis, but these may be the most important predators. In the Archipelago Sea, for instance, the consumption by fish predators is considerably larger than that of cormorants.
  • Kisdi, Eva (2015)
    Evolutionary singularities are central to the adaptive dynamics of evolving traits. The evolutionary singularities are strongly affected by the shape of any trade-off functions a model assumes, yet the trade-off functions are often chosen in an ad hoc manner, which may unjustifiably constrain the evolutionary dynamics exhibited by the model. To avoid this problem, critical function analysis has been used to find a trade-off function that yields a certain evolutionary singularity such as an evolutionary branching point. Here I extend this method to multiple trade-offs parameterized with a scalar strategy. I show that the trade-off functions can be chosen such that an arbitrary point in the viability domain of the trait space is a singularity of an arbitrary type, provided (next to certain non-degeneracy conditions) that the model has at least two environmental feedback variables and at least as many trade-offs as feedback variables. The proof is constructive, i.e., it provides an algorithm to find trade-off functions that yield the desired singularity. I illustrate the construction of trade-offs with an example where the virulence of a pathogen evolves in a small ecosystem of a host, its pathogen, a predator that attacks the host and an alternative prey of the predator.
  • Hopkins, Juhani; Lehtonen, Topi K.; Baudry, Gautier; Kaitala, Arja (2021)
    How fecundity might be traded off with mate attraction and other aspects of reproduction in females remains poorly understood. We investigated these allocation trade-offs using the common glowworm (Lampyris noctiluca), a lampyrid beetle, in which flightless, sedentary females only use resources gathered during the larval stage to attract flying males by glowing. While sexual signaling was not found to have a significant fecundity cost, a delay in successfully attracting a mate greatly increased the risk of reproductive failure, with fecundity losses being more severe in small females. These findings are among the first to show that failure to quickly attract a mate can decrease female fecundity. The results also show how the length of delay before mating can drive the evolution of female sexual ornamentation.
  • Vitale, Caterina; Kisdi, Eva (2019)
    Under the threat of predation, a species of prey can evolve to its own extinction. Matsuda and Abrams (Theor Popul Biol 45:76-91, 1994a) found the earliest example of evolutionary suicide by demonstrating that the foraging effort of prey can evolve until its population dynamics cross a fold bifurcation, whereupon the prey crashes to extinction. We extend this model in three directions. First, we use critical function analysis to show that extinction cannot happen via increasing foraging effort. Second, we extend the model to non-equilibrium systems and demonstrate evolutionary suicide at a fold bifurcation of limit cycles. Third, we relax a crucial assumption of the original model. To find evolutionary suicide, Matsuda and Abrams assumed a generalist predator, whose population size is fixed independently of the focal prey. We embed the original model into a three-species community of the focal prey, the predator and an alternative prey that can support the predator also alone, and investigate the effect of increasingly strong coupling between the focal prey and the predator's population dynamics. Our three-species model exhibits (1) evolutionary suicide via a subcritical Hopf bifurcation and (2) indirect evolutionary suicide, where the evolution of the focal prey first makes the community open to the invasion of the alternative prey, which in turn makes evolutionary suicide of the focal prey possible. These new phenomena highlight the importance of studying evolution in a broader community context.
  • Ovaskainen, Otso; Tikhonov, Gleb; Dunson, David; Grotan, Vidar; Engen, Steinar; Saether, Bernt-Erik; Abrego, Nerea (2017)
    Estimation of intra- and interspecific interactions from time-series on species-rich communities is challenging due to the high number of potentially interacting species pairs. The previously proposed sparse interactions model overcomes this challenge by assuming that most species pairs do not interact. We propose an alternative model that does not assume that any of the interactions are necessarily zero, but summarizes the influences of individual species by a small number of community-level drivers. The community-level drivers are defined as linear combinations of species abundances, and they may thus represent e.g. the total abundance of all species or the relative proportions of different functional groups. We show with simulated and real data how our approach can be used to compare different hypotheses on community structure. In an empirical example using aquatic microorganisms, the community-level drivers model clearly outperformed the sparse interactions model in predicting independent validation data.
  • Santangeli, Andrea; Arroyo, Beatriz; Millon, Alexandre; Bretagnolle, Vincent (2015)
    Modern farming practices threaten wildlife in different ways, and failure to identify the complexity of multiple threats acting in synergy may result in ineffective management. To protect ground-nesting birds in farmland, monitoring and mitigating impacts of mechanical harvesting is crucial. Here, we use 6years of data from a nationwide volunteer-based monitoring scheme of the Montagu's harrier, a ground-nesting raptor, in French farmlands. We assess the effectiveness of alternative nest protection measures and map their potential benefit to the species. We show that unprotected nests in cultivated land are strongly negatively affected by harvesting and thus require active management. Further, we show that protection from harvesting alone (e.g. by leaving a small unharvested buffer around the nest) is impaired by post-harvest predation at nests that become highly conspicuous after harvest. Measures that simultaneously protect from harvesting and predation (by adding a fence around the nest) significantly enhance nest productivity. The map of expected gain from nest protection in relation to available volunteers' workforce pinpoints large areas of high expected gain from nest protection that are not matched by equally high workforce availability. This mismatch suggests that the impact of nest protection can be further improved by increasing volunteer efforts in key areas where they are low relative to the expected gain they could have.Synthesis and applications. This study shows that synergistic interplay of multiple factors (e.g. mechanical harvesting and predation) may completely undermine the success of well-intentioned conservation efforts. However, identifying areas where the greatest expected gains can be achieved relative to effort expended can minimize the risk of wasted volunteer actions. Overall, this study underscores the importance of citizen science for collecting large-scale data useful for producing science and ultimately informs large-scale evidence-based conservation actions within an adaptive management framework. This study shows that synergistic interplay of multiple factors (e.g. mechanical harvesting and predation) may completely undermine the success of well-intentioned conservation efforts. However, identifying areas where the greatest expected gains can be achieved relative to effort expended can minimize the risk of wasted volunteer actions. Overall, this study underscores the importance of citizen science for collecting large-scale data useful for producing science and ultimately informs large-scale evidence-based conservation actions within an adaptive management framework.
  • Merikanto, Ilona; Laakso, Jouni T.; Kaitala, Veijo (2018)
    Background: Environmentally growing pathogens present an increasing threat for human health, wildlife and food production. Treating the hosts with antibiotics or parasitic bacteriophages fail to eliminate diseases that grow also in the outside-host environment. However, bacteriophages could be utilized to suppress the pathogen population sizes in the outside-host environment in order to prevent disease outbreaks. Here, we introduce a novel epidemiological model to assess how the phage infections of the bacterial pathogens affect epidemiological dynamics of the environmentally growing pathogens. We assess whether the phage therapy in the outside-host environment could be utilized as a biological control method against these diseases. We also consider how phage-resistant competitors affect the outcome, a common problem in phage therapy. The models give predictions for the scenarios where the outside-host phage therapy will work and where it will fail to control the disease. Parameterization of the model is based on the fish columnaris disease that causes significant economic losses to aquaculture worldwide. However, the model is also suitable for other environmentally growing bacterial diseases. Results: Transmission rates of the phage determine the success of infectious disease control, with high-transmission phage enabling the recovery of the host population that would in the absence of the phage go asymptotically extinct due to the disease. In the presence of outside-host bacterial competition between the pathogen and phage-resistant strain, the trade-off between the pathogen infectivity and the phage resistance determines phage therapy outcome from stable coexistence to local host extinction. Conclusions: We propose that the success of phage therapy strongly depends on the underlying biology, such as the strength of trade-off between the pathogen infectivity and the phage-resistance, as well as on the rate that the phages infect the bacteria. Our results indicate that phage therapy can fail if there are phage-resistant bacteria and the trade-off between pathogen infectivity and phage resistance does not completely inhibit the pathogen infectivity. Also, the rate that the phages infect the bacteria should be sufficiently high for phage-therapy to succeed.
  • Björklund, Heidi; Parkkinen, Anssi; Hakkari, Tomi; Heikkinen, Risto K; Virkkala, Raimo; Lensu, Anssi (2020)
    Intensive management of boreal forests impairs forest biodiversity and species of old-growth forest. Effective measures to support biodiversity require detection of locations valuable for conservation. We applied species distribution models (SDMs) to a species of mature forest, the northern goshawk (Accipiter gentilis, goshawk), that is often associated with hotspots of forest biodiversity. We located optimal sites for the goshawk on a landscape scale, assessed their state under intensified logging operations and identified characteristics of goshawks' nesting sites in boreal forests. Optimal sites for the goshawk covered only 3.4% of the boreal landscape and were mostly located outside protected areas, which highlights the importance of conservation actions in privately-owned forests. Furthermore, optimal sites for the goshawk and associated biodiversity were under threat. Half of them were logged to some extent and 10% were already lost or notably deteriorated due to logging shortly after 2015 for which our models were calibrated. Habitat suitability for the goshawk increased with increasing volume of Norway spruce (Picea abies) peaking at 220 m(3) ha(-1), and with small quantities of birches (Betula spp.) and other broad-leaved trees. Threats to biodiversity of mature spruce forests are likely to accelerate in the future with increasing logging pressures and shorter rotation periods. Logging should be directed less to forests with high biodiversity. Continuous supply of mature spruce forests in the landscape should be secured with a denser network of protected areas and measures that aid in sparing large entities of mature forest on privately-owned land.
  • Helenius, Laura K.; Padros, Anna Ayma; Leskinen, Elina; Lehtonen, Hannu; Nurminen, Leena (2015)
    Planktivorous fish can exert strong top-down control on zooplankton communities. By incorporating different feeding strategies, from selective particulate feeding to cruising filter feeding, fish species target distinct prey. In this study, we investigated the effects of two species with different feeding strategies, the three-spined stickleback (Gasterosteus aculeatus (L.)) and roach (Rutilus rutilus (L.)), on a low-diversity brackish water zooplankton community using a 16-day mesocosm experiment. The experiment was conducted on a small-bodied spring zooplankton community in high-nutrient conditions, as well as a large-bodied summer community in low-nutrient conditions. Effects were highly dependent on the initial zooplankton community structure and hence seasonal variation. In a small-bodied community with high predation pressure and no dispersal or migration, the selective particulate-feeding stickleback depleted the zooplankton community and decreased its diversity more radically than the cruising filter-feeding roach. Cladocerans rather than copepods were efficiently removed by predation, and their removal caused altered patterns in rotifer abundance. In a large-bodied summer community with initial high taxonomic and functional diversity, predation pressure was lower and resource availability was high for omnivorous crustaceans preying on other zooplankton. In this community, predation maintained diversity, regardless of predator species. During both experimental periods, predation influenced the competitive relationship between the dominant calanoid copepods, and altered species composition and size structure of the zooplankton community. Changes also occurred to an extent at the level of nontarget prey, such as microzooplankton and rotifers, emphasizing the importance of subtle predation effects. We discuss our results in the context of the adaptive foraging mechanism and relate them to the natural littoral community.
  • Fraixedas, Sara; Linden, Andreas; Meller, Kalle; Lindström, Åke; Keiss, Oskars; Kålås, John Atle; Husby, Magne; Leivits, Agu; Leivits, Meelis; Lehikoinen, Aleksi (2017)
    Northern European peatlands are important habitats for biological conservation because they support rich biodiversity and unique species compositions. However, historical management of peatland habitats has had negative consequences for biodiversity and their degradation remains a major conservation concern. Despite increasing awareness of the conservation value of peatlands, the statuses and ecological requirements of peat land species have remained largely understudied. Here, we first analysed temporal trends of Northern European peatland birds to document the status of their populations using bird data from five different countries. Second, we used Finnish monitoring data to assess habitat preferences of peatland bird species, hence helping to target conservation to the most relevant habitat types. There was a general decline of 40% in Northern European peatland bird population sizes in 1981-2014 (speed of decline 1.5%/year) largely driven by Finland, where populations declined almost 50% (2.0% annual decline). In Sweden and Norway, peatland bird populations declined by 20% during 1997-2014 (1.0% annual decline). In contrast, southern populations in Estonia and Latvia, where the majority of open peatlands are protected, showed a 40% increase during 1981-2014 (1.0% annual increase). The most important habitat characteristics preferred by common peatland species in Finland were openness and low tree height, while wetness proved to be an important feature for waders. Drainage of peatlands had clear negative effects on the densities of many species, with the only exception of rustic bunting, which specializes on edge habitats. Our findings call for more effective conservation actions in Northern European peatland habitats, especially in Finland where peatland drainage represents a major threat to biodiversity.
  • Lai, Tin-Yu; Lindroos, Marko; Groenbaek, Lone; Romakkaniemi, Atso (2021)
    Multispecies bio-economic models are useful tools to give insights into ecosystem thinking and ecosystem-based management. This paper developed an age-structured multispecies bio-economic model that includes the food web relations of the grey seal, salmon, and herring, along with salmon and herring fisheries in the Baltic Sea. The results show that the increasing seal population influences salmon fisheries and stock, but the impacts on the harvest are stronger than on the stock if the targeted management policies are obeyed. If seal population growth and a low herring stock occur simultaneously, the salmon harvest could face a serious threat. In addition, scenarios of the multispecies management approach in this paper reveal a benefit that our model can evaluate the performance of different fisheries with identical or different management strategies simultaneously. The results show the most profitable scenario is that both fisheries pursuit aggregated profits and reveal a trade-off between herring fisheries and salmon fisheries. Our model indicates that the herring harvest level and the approaches to managing herring fisheries can influence the performance of salmon fisheries. The study also demonstrates a way to develop a multispecies bio-economic model that includes both migratory fish and mammalian predators.
  • Jokimäki, Jukka; Selonen, Vesa; Lehikoinen, Aleksi; Kaisanlahti-Jokimäki, Marja-Liisa (2017)
    Because the amount of urban areas has increased, it is important to investigate the abundance of wildlife species in relation to urban environments. Analyzing the impact of urbanization on the presence of forest-dwelling mammals is of interest due to the possible effects of urbanization on human-wildlife relationships and urban biodiversity. The Eurasian red squirrel (Sciurus vulgaris) is a declining forest species, and its occurrence in urban environments has been inadequately studied. The loss and fragmentation of forests due to urbanization may be detrimental for squirrels, whereas the abundant and predictable food resources and the low number of natural predators in urban areas may encourage squirrels to invade towns. We used large-scale data collected by volunteer bird watchers along a 950 km south-north gradient to study whether the winter abundance of squirrels in Finland is dependent on urbanization, while controlling for effects of habitat type, food abundance (spruce cone crop; number of winter feeding sites), predator abundance (northern goshawk, Accipiter gentilis; feral cat Felis catus), season and latitude. We found that squirrel abundance increased with human population density, number of feeding sites and spruce cone crop and decreased with latitude and season. Feral cats showed weak negative connection with squirrel numbers, but there were no effect of goshawks. Relative squirrel abundance was approximately twice as high in urban habitats than in forests. Artificial feeding rather than a low number of predators may attract squirrels in urban environments. Planting spruce trees in urban environments will also benefit squirrels. Our results indicate that urban areas are an important habitat for the red squirrel even along the northern edge of their distribution range, where natural forest areas are still widespread. We conclude also that a citizen science - based bird survey protocol associated with mammal surveys seems to be a good large-scale monitoring method to study the urbanization of squirrels.
  • Vasko, Ville; Blomberg, Anna S.; Vesterinen, Eero J.; Suominen, Kati M.; Ruokolainen, Lasse; Brommer, Jon E.; Norrdahl, Kai; Niemelä, Pekka; Laine, Veronika N.; Santangeli, Andrea; Lilley, Thomas M. (2020)
    Bats utilize forests as roosting sites and feeding areas. However, it has not been documented how bats utilize these habitats in the boreal zone with methods afforded by recent technological advances. Forest structure and management practices can create a variety of three-dimensional habitats for organisms capable of flight, such as bats. Here, we study the presence of boreal bats in a forest forming a mosaic of different age classes, dominant tree species, canopy cover, soil fertility, and other environmental variables, throughout their active season in the summer using passive ultrasound detectors. Our results indicate a preference for mature forest by Eptesicus nilssonii and a pooled set of Myotis bats. Both groups of bats also showed temporal changes in their habitat use regarding forest age. In June and July, both groups occurred more often in mature than young forests, but from August onwards, the difference in occurrence became less evident in Myotis and disappeared completely in E. nilssonii. In addition, E. nilssonii was more often present in forests with low canopy cover, and its occurrence shifted from coniferous forests to deciduous forests during the season. The results reflect the within-season dynamics of bat communities and their ability to utilize different types of forest as environmental conditions change. Yet, the results most importantly emphasize the importance of mature forests to bat diversity and the need to conserve such environments in the boreal zone.