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• Sadykova, Dinara; Johnson, Andrew C.; Qu, Yueming; Henrys, Peter A.; Jürgens, Monika D. & Keller, Virginie D.J. [Vis alle 14 forfattere av denne artikkelen] (2025). The relative importance of multiple environmental factors on river macroinvertebrate abundance across different groups based on a nationwide dataset from England. Water Research. ISSN 0043-1354. doi: 10.1016/j.watres.2025.125270. Fulltekst i vitenarkiv Vis sammendrag

  Many countries are concerned by and wish to arrest or reverse what is termed a biodiversity crisis in invertebrates. To understand the issues facing riverine invertebrates in England, a fully integrated dataset where macroinvertebrate monitoring sites were aligned in space and time with physical, geographic, habitat, and chemical factors from 2003 to 2018 (quantitative abundance data being universally available from 2003) was brought together for statistical analysis. Over this period the median abundance either did not change or for some groups actually increased. The aim was to identify what the principal factors were that influenced Ephemeroptera (Mayflies), Plecoptera (Stoneflies), Trichoptera (Caddisflies), Odonata (Dragonflies and Damselflies), Diptera (True Flies), Coleoptera (Beetles), Hemiptera (True Bugs), and Gastropoda (Snails) abundance over this 16-year period. The dataset was examined using an ensemble framework within two modelling approaches: generalised linear mixed-effects models with permutation-based variable importance, as well as non-linear generalised additive mixed models to assess the percentage of deviance explained by each variable. The range of approaches aimed to offer different perspectives on variable importance, providing a more comprehensive understanding of the data and highlighting how model selection can influence ecological data interpretation. For most groups, physical factors, such as altitude, distance from source, slope, bed substrate and flow discharge, were strong predictors of abundance, likely reflecting natural habitat preferences shaped by evolutionary history. Land cover was also influential, with seminatural areas generally supporting higher abundances and urban land cover associated with lower abundances. Some chemical and ecological factors – such as wastewater and nutrient content, were particularly important for Ephemeroptera, Plecoptera, and Trichoptera abundance. For Coleoptera, Hemiptera, Trichoptera, Diptera and Gastropoda, metal levels played a role in their abundance, whilst for Odonata, mean temperature appeared to be important. Diptera appeared to be relatively insensitive to the factors examined. This statistical examination of large monitoring datasets, with no a priori assumptions, is vital in resolving a key challenge in bioassessment: identifying what influences invertebrate abundance when data are sparse. The results can provide policy options to improve ecological conditions, and the approach is transferable to other regions.

• Sadykov, Alexander; Farnsworth, Keith; Sadykova, Dinara & Stenseth, Nils Christian (2022). The transfer function method reveals how age-structured populations respond to environmental fluctuations with serious implications for fisheries management. Population Ecology. ISSN 1438-3896. 64(3), s. 190–204. doi: 10.1002/1438-390X.12124. Fulltekst i vitenarkiv Vis sammendrag

  Fluctuations in wild fish populations result from interaction between population dynamics and environmental forcing. Age-structured populations can magnify or dampen particular frequencies of these fluctuations, depending on life cycle and species traits. The transfer function (TF) gives a detailed analytical description of these phenomena. In this study, we derive a generalized form of TF to investigate the fluctuations of fish populations in response to species traits and environmental noise characteristics. We found that for semelparous species, fluctuations in fish stocks log-size are directly proportional to the recruitment elasticity and inversely proportional to the age of maturity, and for iteroparous species, fluctuations in fish stocks log-size are inversely proportional to the adult lifespan. In addition to the already known effect of cohort resonance (increased sensitivity to environmental fluctuations on cohort timescales in the elastic range of recruitment elasticity), we find a stock resonance effect (increased sensitivity to environmental fluctuations on double cohort timescales in the inelastic range of recruitment elasticity). These results were then applied to fisheries management. The relationship between fishing mortality and species-specific variability of fish stocks was formalized. In accordance with this analysis, precautionary levels for different catches were estimated.

• Sadykov, Alexander & Farnsworth, Keith D. (2021). Model of two competing populations in two habitats with migration: Application to optimal marine protected area size. Theoretical Population Biology. ISSN 0040-5809. 142, s. 114–122. doi: 10.1016/j.tpb.2021.10.002. Fulltekst i vitenarkiv Vis sammendrag

  The standard model of a single population fragmented into two patches connected by migration, was first introduced in the 1970s by Freedman and Waltman, since generating long-term research interest, though its full analysis for arbitrary values of migration rate has only been completed relatively recently. Here, we present a model of two competing species in a two-patch habitat with migrations between patches. We derive equilibrium solutions of this model for three cases of migration rate resulting in isolated, well-mixed and semi-isolated habitats. We evaluate the full range of effects of habitat, life-history and migration parameters on population sizes. Finally, we add harvesting mortality and define conditions under which introduction of a no-harvesting (protected) area may lead to increased maximum sustainable yield. The results have applications in mixed fishery management and the design of wildlife protection zones, including marine protected areas (MPAs).

• Sadykova, Dinara; Scott, Beth E.; Dominicis, Michela De; Wakelin, Sarah L.; Wolf, Judith & Sadykov, Alexander (2020). Ecological costs of climate change on marine predator–prey population distributions by 2050. Ecology and Evolution. 10(2), s. 1069–1086. doi: 10.1002/ece3.5973. Fulltekst i vitenarkiv Vis sammendrag

  Identifying and quantifying the effects of climate change that alter the habitat overlap of marine predators and their prey population distributions is of great importance for the sustainable management of populations. This study uses Bayesian joint models with integrated nested Laplace approximation (INLA) to predict future spatial density distributions in the form of common spatial trends of predator–prey overlap in 2050 under the “business‐as‐usual, worst‐case” climate change scenario. This was done for combinations of six mobile marine predator species (gray seal, harbor seal, harbor porpoise, common guillemot, black‐legged kittiwake, and northern gannet) and two of their common prey species (herring and sandeels). A range of five explanatory variables that cover both physical and biological aspects of critical marine habitat were used as follows: bottom temperature, stratification, depth‐averaged speed, net primary production, and maximum subsurface chlorophyll. Four different methods were explored to quantify relative ecological cost/benefits of climate change to the common spatial trends of predator–prey density distributions. All but one future joint model showed significant decreases in overall spatial percentage change. The most dramatic loss in predator–prey population overlap was shown by harbor seals with large declines in the common spatial trend for both prey species. On the positive side, both gannets and guillemots are projected to have localized regions with increased overlap with sandeels. Most joint predator–prey models showed large changes in centroid location, however the direction of change in centroids was not simply northwards, but mostly ranged from northwest to northeast. This approach can be very useful in informing the design of spatial management policies under climate change by using the potential differences in ecological costs to weigh up the trade‐offs in decisions involving issues of large‐scale spatial use of our oceans, such as marine protected areas, commercial fishing, and large‐scale marine renewable developments.

• Sadykova, Dinara; Scott, Beth E; Dominicis, Michela De; Wakelin, Sarah L.; Sadykov, Alexander & Wolf, Judith (2017). Bayesian joint models with INLA exploring marine mobile predator-prey and competitor species habitat overlap. Ecology and Evolution. 7(14), s. 5212–5226. doi: 10.1002/ece3.3081. Fulltekst i vitenarkiv
• Sadykov, Alexander (2013). About a modification of Rogers model of parasite-host system dynamics. Proceedings of the International Academy of Ecology and Environmental Sciences. ISSN 2220-8860. 2, s. 41–49. Fulltekst i vitenarkiv
• Nedorezov, L. V.; Sadykov, Alexander & Sadykova, Dinara (2010). Dynamics of a green oak moth population: application of discrete-continuous models with a nonmonotone density-dependent birth rate. Zurnal obsej biologii. ISSN 0044-4596. 71(1), s. 41–51. Fulltekst i vitenarkiv Vis sammendrag

  Considered is a mathematical model for dynamics of an isolated population with non-overlapping generations. The individuals’ birth process (emergence of new-generation individuals) is assumed to have a discrete nature (there exist some fixed time moments at which the new generations emerge), while the death process is assumed to be continuous. In addition, the birth rate is assumed to be a function of the number of individuals survived till the moment of reproduction, the function being non-monotone: there exists an optimal value of the population size at which the birth rate reaches its maximum (Alley principle). Analysis of the discrete-continuous models has revealed that each of the new models has a rich set of dynamical regimes. New models are compared with a number of well-known discrete ones (like Skellam, Moran – Ricker, Hassell, Maynard Smith – Slatkin models, and others) when approximating an empirical time series on fluctuations of a green oak moth population (Korzukhin, Semevsky, 1992). Neither of the models can provide for a satisfactory description of the green oak moth dynamics. It is also shown that usage of the discrete-continuous models for approximation of real datasets enables one to find several important population parameters, which can hardly (or cannot) be found by means of traditional discrete models.

• Sadykova, Dinara; Skurdal, Jostein; Sadykov, Alexander; Taugbol, Trond & Hessen, Dag Olav (2009). Modelling crayfish population dynamics using catch data: A size-structured model. Ecological Modelling. ISSN 0304-3800. 220(20), s. 2727–2733. doi: 10.1016/j.ecolmodel.2009.07.002. Fulltekst i vitenarkiv
• Sadykova, Dinara; Skurdal, Jostein; Sadykov, Alexander; Taugbøl, Trond & Hessen, Dag Olav (2009). Modelling crayfish population dynamics using catch data: A size-structured model. Ecological Modelling. ISSN 0304-3800. 220(20), s. 2727–2733. Fulltekst i vitenarkiv
• Hassanali, A.; Nedorezov, LV & Sadykov, Alexander (2008). Zooprophylactic diversion of mosquitoes from human to alternative hosts: A static simulation model. Ecological Modelling. ISSN 0304-3800. 212, s. 155–161. Fulltekst i vitenarkiv
• Nedorezov, Lev V.; Volkova, E.V. & Sadykov, Alexander (2008). On the Impact of the Winter Conditions on the Dynamics of an Isolated Population. I Deutsch, Andreas; Parra, Rafael Bravo de la; Boer, Rob J. de; Diekmann, Odo; Jagers, Peter; Kisdi, Eva; Kretzschmar, Mirjam; Lansky, Petr & Metz, Hans (Red.), Mathematical Modeling of Biological Systems, Volume II. Birkhäuser Boston. ISSN 9780817645557. s. 91–104. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Sadykov, Alexander (2013). Unified theory of population growth. Fulltekst i vitenarkiv
• Rouyer, Tristan Alexander; Sadykov, Alexander; Ohlberger, Jan & Stenseth, Nils Christian (2012). Does increasing mortality change the response of fish populations to environmental fluctuations? Ecology Letters. ISSN 1461-023X. 15(7), s. 658–665. doi: 10.1111/j.1461-0248.2012.01781.x. Fulltekst i vitenarkiv
• Sadykov, Alexander & Stenseth, N.C (2011). Can short-term climate variation be the cause of long-term persistence of epidemic infection? Fulltekst i vitenarkiv
• Sadykov, Alexander & Stenseth, N.C (2010). Epidemiology of conspecific community. Fulltekst i vitenarkiv
• Sadykov, Alexander & Stenseth, NC (2010). War and Peace (toward to microbial ecology). Fulltekst i vitenarkiv
• Sadykov, Alexander & Stenseth, Nils Christian (2008). New approach to community population modeling. Fulltekst i vitenarkiv
• Sadykov, Alexander & Stenseth, Nils Christian (2007). On the Trait Distribution-based Population model approach. Fulltekst i vitenarkiv
• Sadykov, Alexander; Stenseth, Nils Christian & Ottersen, Geir (2011). Conspecific Community Dynamics Models and their applications. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The thesis introduces a new integrated approach to ecological and evolutionary modeling, the goal of which is to create an analytical platform for applied interdisciplinary researches. This Conspecific Community Dynamics Model (CCDM) approach establishes links between the ecology of the individual, community ecology, behavioral ecology, population dynamics and natural selection. The approach related to co-selection timescale and singlespecies (conspecific) community scale. The co-selection timescale extends from several to several hundreds of generations. Presumably, at this timescale, viable mutations leading to a change in the underlying physiology of the species do not occur, but the interaction between individuals within a conspecific community can lead to a change in the frequency distribution of certain functional traits. The conspecific community scale is an organizational scale, which is intermediate between entire population and the individual. This is the scale on which an organism can be recognized not only as a representative of their own species, not only as a passive carrier of genetic material, but also as a member of the conspecific community in which its reproductive success depends on other members of this community. This is the scale on which the differences between the two conspecific communities can potentially undergo a critical transition and becomes differences between species, and thus, this scale may occur at the earliest stages of reproductive isolation. Finally, this is the scale at which apparently random differences between individuals are added to the overall mosaic of an intrinsically organized system. This approach emphasizes that the phenomenon of single-species organisms within a population organizing themselves into conspecific communities has deep natural reasons and cannot be ignored; furthermore, this fact may become a key nodal point of the synthesis of ecology and evolution. The approach also stresses that such synthesis can hardly be realized at the level of mechanical combinations of existing models, but requires a special analytical platform that would (i) include the basic postulates of population ecology, quantitative genetics and evolutionary biology, (ii) allow, despite the inherent stochasticity, the investigation of conspecific communities at the level of cause-effect relationships. Half of the thesis relates to the basic issues associated with the mathematical formalization of the approach, the other half is entirely devoted to its various applications in the fields of demography, fish population dynamics, community ecology, microbiology and community epidemiology. For each of these fields a set of CCDM models are constructed, subsequent analyses of which lead to interesting results. These results are intended to demonstrate the great potential of this approach, its ability to integrate various aspects of the population and its analytical power. It should be emphasized that this approach does not create any new entities, but is instead based on the widely-accepted (within each particular field) postulates. Nevertheless, the consideration of these postulates in combination sometimes leads to much unexpected results. However, the distinguishing feature of the approach is its analyticity, that is, any result that at first glance seems unusual, can be traced to these basic tenets.

Se alle arbeider i NVA