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1. Setting ecological expectations for adaptive management of marine protected areas

   https://doi.org/10.1111/1365-2664.13463  

   Nickols, Kerry J. ; White, J. Wilson ; Malone, Dan ; Carr, Mark H. ; Starr, Richard M. ; Baskett, Marissa L. ; Hastings, Alan ; Botsford, Louis W. ( July 2019 , Journal of Applied Ecology)

   Marine Protected Areas (MPAs) are being implemented worldwide, yet there are few cases where managers make specific predictions of the response of previously harvested populations to MPA implementation.

   Such predictions are needed to evaluate whether MPAs are working as expected, and if not, why. This evaluation is necessary to perform adaptive management, identifying whether and when adjustments to management might be necessary to achieve MPA goals.

   Using monitoring data and population models, we quantified expected responses of targeted species to MPA implementation and compared them to monitoring data.

   The model required two factors to explain observed responses in MPAs: (a) pre‐MPA harvest rates, which can vary at local spatial scales, and (b) recruitment variability before and after MPA establishment. Low recruitment years before MPA establishment in our study system drove deviations from expected equilibrium population size distributions and introduced an additional time lag to response detectability.

   Synthesis and applications. We combined monitoring data and population models to show how (a) harvest rates prior to Marine Protected Area (MPA) implementation, (b) variability in recruitment, and (c) initial population size structure determine whether a response to MPA establishment is detectable. Pre‐MPA harvest rates across MPAs plays a large role in MPA response detectability, demonstrating the importance of measuring this poorly known parameter. While an intuitive expectation is for response detectability to depend on recruitment variability and stochasticity in population trajectories after MPA establishment, we address the overlooked role of recruitment variability before MPA establishment, which alters the size structure at the time of MPA establishment. These factors provide MPA practitioners with reasons whether or not MPAs may lead to responses of targeted species. Our overall approach provides a framework for a critical step of adaptive management.

    

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2. Putative resistance and tolerance mechanisms have little impact on disease progression for an emerging salamander pathogen

   https://doi.org/10.1111/1365-2435.13754  

   Wilber, Mark Q. ; Carter, Edward Davis ; Gray, Matthew J. ; Briggs, Cheryl J. ; Pedersen, ed., Amy ( January 2021 , Functional Ecology)

   Resistance and tolerance are unique host defence strategies that can limit the impacts of a pathogen on a host. However, for most wildlife–pathogen systems, there are still fundamental uncertainties regarding (a) how changes in resistance and tolerance can affect disease outcomes and (b) the mechanisms underlying resistance and tolerance in host populations.

   Here, we first compared observed patterns of resistance and tolerance and their effects on disease outcomes among salamander species that are susceptible to infection and mortality from the emerging fungal pathogenBatrachochytrium salamandrivorans(Bsal). We then tested whether two putative mechanisms that contribute to host resistance and tolerance, skin sloughing and skin lesion reduction, predicted reducedBsalgrowth rate or increased host survival during infection, respectively.

   We performed multi‐doseBsalchallenge experiments on four species of Salamandridae found throughout North America. We combined the laboratory experiments with dynamic models and sensitivity analysis to examine how changes in load‐dependent resistance and tolerance functions affectedBsal‐induced mortality risk. Finally, we used our disease model to test whether skin sloughing and lesion reduction predicted variability in infection outcomes not described byBsalinfection intensity.

   We found that resistance and tolerance differed significantly among salamander species, with the most susceptible species being both less resistance and less tolerant ofBsalinfection. Our dynamic model showed that the relative influence of resistance versus tolerance on host survival was species‐dependent—increasing resistance was only more influential than increasing tolerance for the least tolerant species where changes in pathogen load had a threshold‐like effect on host survival. Testing two candidate mechanisms of resistance and tolerance, skin sloughing and lesion reduction, respectively, we found limited support that either of these processes were strong mechanisms of host defence.

   Our study contributes to a broader understanding of resistance and tolerance in host–pathogen systems by showing that differences in host tolerance can significantly affect whether changes in resistance or tolerance have larger effects on disease outcomes, highlighting the need for species and even population‐specific management approaches that target host defence strategies.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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3. Improving predictions of tropical tree survival and growth by incorporating measurements of whole leaf allocation

   https://doi.org/10.1111/1365-2745.13560  

   Rubio, Vanessa E. ; Zambrano, Jenny ; Iida, Yoshiko ; Umaña, María Natalia ; Swenson, Nathan G. ; Rosell, ed., Julieta ( November 2020 , Journal of Ecology)

   Individual‐level demographic outcomes should be predictable upon the basis of traits. However, linking traits to tree performance has proven challenging likely due to a failure to consider physiological traits (i.e. hard‐traits) and the failure to integrate organ‐level and whole plant‐level trait information.

   Here, we modelled the survival rate and relative growth rate of trees while considering crown allocation, hard‐traits and local‐scale biotic interactions, and compared these models to more traditional trait‐based models of tree performance.

   We found that an integrative trait, total tree‐level photosynthetic mass (estimated by multiplying specific leaf area and crown area) results in superior models of tree survival and growth. These models had a lower AIC than those including the effect of initial tree size or any other combination of the traits considered. Survival rates were positively related to higher values of crown area and photosynthetic mass, while relative growth rates were negatively related to the photosynthetic mass. Relative growth rates were negatively related to a neighbourhood crowding index. Furthermore, none of the hard‐traits used in this study provided an improvement in tree performance models.

   Synthesis. Overall, our results highlight that models of tree performance can be greatly improved by including crown area information to generate a better understanding of plant responses to their environment. Additionally, the role of the hard‐traits in improving models of tree performance is likely dependent upon the level of stress (e.g. drought stress), micro‐environmental conditions or short‐term climatic variations that a particular forest experiences.

    

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4. The relative importance of reproduction and survival for the conservation of two dolphin populations

   https://doi.org/10.1002/ece3.2130  

   Manlik, Oliver ; McDonald, Jane A. ; Mann, Janet ; Raudino, Holly C. ; Bejder, Lars ; Krützen, Michael ; Connor, Richard C. ; Heithaus, Michael R. ; Lacy, Robert C. ; Sherwin, William B. ( April 2016 , Ecology and Evolution)

   It has been proposed that in slow‐growing vertebrate populations survival generally has a greater influence on population growth than reproduction. Despite many studies cautioning against such generalizations for conservation, wildlife management for slow‐growing populations still often focuses on perturbing survival without careful evaluation as to whether those changes are likely or feasible. Here, we evaluate the relative importance of reproduction and survival for the conservation of two bottlenose dolphin (Tursiopscfaduncus) populations: a large, apparently stable population and a smaller one that is forecast to decline. We also assessed the feasibility and effectiveness of wildlife management objectives aimed at boosting either reproduction or survival. Consistent with other analytically based elasticity studies, survival had the greatest effect on population trajectories when altering vital rates by equal proportions. However, the findings of our alternative analytical approaches are in stark contrast to commonly used proportional sensitivity analyses and suggest that reproduction is considerably more important. We show that

   in the stable population reproductive output is higher, and adult survival is lower;

   the difference in viability between the two populations is due to the difference in reproduction;

   reproductive rates are variable, whereas survival rates are relatively constant over time;

   perturbations on the basis of observed, temporal variation indicate that population dynamics are much more influenced by reproduction than by adult survival;

   for the apparently declining population, raising reproductive rates would be an effective and feasible tool to reverse the forecast population decline; increasing survival would be ineffective.

   Our findings highlight the importance of reproduction – even in slow‐growing populations – and the need to assess the effect of natural variation in vital rates on population viability. We echo others in cautioning against generalizations based on life‐history traits and recommend that population modeling for conservation should also take into account the magnitude of vital rate changes that could be attained under alternative management scenarios.

    

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5. How do lianas and vines influence competitive differences and niche differences among tree species? Concepts and a case study in a tropical forest

   https://doi.org/10.1111/1365-2745.13119  

   Muller‐Landau, Helene C. ; Visser, Marco D. ; Godoy, ed., Oscar ( December 2018 , Journal of Ecology)

   Lianas and other climbing plants are structural parasites of trees, generally reducing host tree survival, growth, and reproduction, yet their influences on the outcome of competition among tree species have remained largely unexplored.

   We propose that there are three distinct components to liana–tree interactions:prevalence, defined as the proportion of infested trees;load, defined as the mean liana cover on infested trees; andtolerance, defined as the effect of a given level of infestation on tree population growth rates. We introduce a new metric that integrates these components, the lianaburden, defined as the total effect of lianas on per capita population growth rates given current prevalence, load, and tolerance. Using these metrics, we quantify variation among 33 co‐occurring tropical tree species in liana–tree interactions and its relation with shade‐tolerance.

   The focal tree species vary strongly in liana prevalence, load, tolerance, and burden. Interspecific variation in tolerance is the largest contributor to interspecific variation in burden. Species rankings of per capita population growth rates under current liana infestation levels differ somewhat from rankings under liana‐free conditions, and differ strongly from rankings under uniformly high liana infestation. Thus, lianas alter competitive hierarchies to benefit tree species that are relatively tolerant of and/or resistant to lianas. Among the focal tree species, shade‐tolerance is positively correlated with liana tolerance and prevalence, but largely unrelated to load and burden, meaning shade‐tolerance does not predict which species are competitively disadvantaged by lianas. We describe a variety of mechanisms by which lianas may potentially increase or decrease niche differences among tree species, including interactions with spatial and temporal environmental niche partitioning, and potential differences among tree species in relative vulnerability to different liana species.

   Synthesis. Lianas, like other natural enemies, can in principle alter competitive hierarchies and niche structure of co‐occurring tree species, and our analyses suggest such influences are substantial in our focal tropical tree community and likely many other tree communities as well. Quantifying these effects requires a more comprehensive approach including analyses and modelling of dynamics of liana–tree interactions and their variation with tree and liana species identities.

    

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