Climate change and harvesting can affect the ecosystems' functioning by altering the population dynamics and interactions among species. Knowing how species interact is essential for better ...understanding potentially unintended consequences of harvest on multiple species in ecosystems. I analyzed how stage‐specific interactions between two harvested competitors, the haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua), living in the Barents Sea affect the outcome of changes in the harvest of the two species. Using state‐space models that account for observation errors and stochasticity in the population dynamics, I run different harvesting scenarios and track population‐level responses of both species. The increasing temperature elevated the number of larvae of haddock but did not significantly influence the older age‐classes. The nature of the interactions between both species shifted from predator‐prey to competition around age‐2 to ‐3. Increased cod fishing mortality, which led to decreasing abundance of cod, was associated with an increasing overall abundance of haddock, which suggests compensatory dynamics of both species. From a stage‐specific approach, I show that a change in the abundance in one species may propagate to other species, threatening the exploited species' recovery. Thus, this study demonstrates that considering interactions among life history stages of harvested species is essential to enhance species' co‐existence in harvested ecosystems. The approach developed in this study steps forward the analyses of effects of harvest and climate in multi‐species systems by considering the comprehension of complex ecological processes to facilitate the sustainable use of natural resources.
I analyzed how stage‐specific interactions between two harvested competitors, the haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua), living in the Barents Sea affect the outcome of changes in the harvest of the two species. From a stage‐specific approach, I show that a change in the abundance in one species may propagate to other species, threatening the exploited species' recovery.
Species spatial distributions are the result of population demography, behavioral traits, and species interactions in spatially heterogeneous environmental conditions. Hence the composition of ...species assemblages is an integrative response variable, and its variability can be explained by the complex interplay among several structuring factors. The thorough analysis of spatial variation in species assemblages may help infer processes shaping ecological communities. We suggest that ecological studies would benefit from the combined use of the classical statistical models of community composition data, such as constrained or unconstrained multivariate analyses of site-by-species abundance tables, with rapidly emerging and diversifying methods of spatial pattern analysis. Doing so allows one to deal with spatially explicit ecological models of beta diversity in a biogeographic context through the multiscale analysis of spatial patterns in original species data tables, including spatial characterization of fitted or residual variation from environmental models. We summarize here the recent progress for specifying spatial features through spatial weighting matrices and spatial eigenfunctions in order to define spatially constrained or scale-explicit multivariate analyses. Through a worked example on tropical tree communities, we also show the potential of the overall approach to identify significant residual spatial patterns that could arise from the omission of important unmeasured explanatory variables or processes.
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•The tectonic regime changes from transpression within Kopeh Dagh to transtension in eastern Alborz.•The changeover of the tectonic regime occurs at the Tazereh syntax.•The Tazareh ...Syntax is a pinpoint in which the vergence of the thrust faults changes from southward in Kopeh Dagh to the northward in eastern Alborz.•A hypothetical lever arm model in which Tazareh Syntax plays the fulcrum and Kope Dagh, and eastern Alborz are load and resistance arms, respectively. Loading of collision in Kopeh Dagh by the fulcrum of the Tazareh pushes the eastern Alborz to the north in the wake up of the South Caspian Sea, which is subducting beneath Northern Caspian Sea along the Apsheron-Balkhan sill.
By fault kinematic approach, this article addresses the clockwise rotation of the South Caspian Basin (SCB) and northeastern Alborz because of Arabian plate collision with Eurasia. The collision is accommodated by the thrust and left-lateral strike-slip faults. One of the essential features of the eastern Alborz is that the active strike-slip faults change from transpressional in the east of Tazareh Syntax to the transtensional in the west of this tectonic node. Therefore, we introduce the Tazareh syntax as the location of this changeover where the two relatively rigid crusts of SCB and Central Iran pinch the Alborz out and make a narrow escape on the way of crustal transformation from east to the west. Indeed, the interaction between Central Iran and SCB acts as an indenter leading to the clockwise rotation of the eastern Alborz. Accordingly, the general transpressional regime in Alborz, Binalud, and Kopeh Dagh that dominated since > 5 Ma switched to the transtensional tectonic regime over the eastern Alborz in Quaternary while it has remained on the mode of transpression in western Alborz, Kopeh Dagh and Binalud. Therefore, the Tazareh transitional zone represents how a part of the fold and thrust belt resumes different deformational patterns concerning the other component (s) in its evolutionary history. In a brief comparison, if the Zagros fold and thrust belt could be compare to the initial stage of the Himalayan fold and thrust belt, the Iranian plateau (including eastern Alborz) looks like a prototype of the Tibetan plateau.
How interspecific interactions change across scales is poorly known. Such knowledge might help us understand how species interact within communities and highlight scale-dependent ecological processes ...in play among species. Here, I propose to analyze the inter-annual variation of a species assemblage at different ecological levels. For this, I joined a two-stage modeling approach and a spatially explicit multivariate model to analyze the interspecies relationships among six species of pelagic seabirds from 2004 to 2015 in the Barents Sea. The large-scale (~400 km) pattern of interactions revealed by the analyses suggests a change in the composition of the seabird community along the climatic gradient from south to north. At medium-scale (~300 km), the community was split into two areas (i.e., Arctic and sub-Arctic areas) suggesting niche differentiation of Arctic and sub-Arctic species driven by resource partitioning and interference competition. At a small-scale (~40 km), species with different body sizes were positively associated suggesting facilitation for accessing food although the species with the smallest body size was negatively associated with the species involved in the facilitation process suggesting interspecific interference competition. Over the years, the large-scale patterns were persistent, suggesting niche establishment, while small-scale patterns were highly variable suggesting only ephemeral interactions among species. My study demonstrates that interspecific relationships are scale-dependent and play major roles in structuring community. Untangling how species are associated with different ecological levels over time is indispensable to better understand how community structure contributes to ecological system dynamics.
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