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1. Ecological strategies begin at germination: Traits, plasticity and survival in the first 4 days of plant life

   https://doi.org/10.1111/1365-2435.13543  

   Larson, Julie E. ; Anacker, Brian L. ; Wanous, Sara ; Funk, Jennifer L. ; Baltzer, ed., Jennifer ( March 2020 , Functional Ecology)

   We commonly use trait variation to characterize plant function within and among species and understand how vegetation responds to the environment. Seedling emergence is an especially vulnerable window affecting population and community dynamics, yet trait‐based frameworks often bypass this earliest stage of plant life. Here we assess whether traits vary in ecologically meaningful ways when seedlings are just days old. How do shared evolutionary history and environmental conditions shape trait expression, and can traits explain which seedlings endure drought?

   We measured seedling traits in the first 4 days of life for 16 annual plant species under two water treatments, exploring trait trade‐offs, species‐level plasticity and the ability of traits to predict duration of survival under drought.

   Nearly half of traits showed the imprint of evolutionary history (i.e. significant phylogenetic signal), often reflecting differences between grasses and forbs, two groups separated by a deep evolutionary split. Water availability altered trait expression in most cases, though species‐level plastic responses also reflected evolutionary history.

   On average, new seedlings exhibited substantial trait variation structured as multiple trade‐offs like those found in mature plants. Some species invested in thick roots and shoots, whereas others invested in more efficient tissues. Separately, some invested in tougher roots and others in deeper roots. We also observed trade‐offs related to growth rates (fast or slow) and biomass allocation (above‐ or below‐ground). Drought survival time was correlated most strongly with seed mass, root construction and allocation traits, and phylogeny (grasses vs. forbs).

   Synthesis.Our results show that seed and seedling trait variation among annual species is substantial, and that a few attributes could capture major dimensions of ecological strategies during emergence. With seedling survival times ranging twofold among annuals (from 7.5 to 14.5 days), these strategies could mitigate recruitment responses to more frequent or longer dry spells. Multivariate trait and plasticity strategies should be further explored in studies designed to assess trait‐fitness linkages during recruitment.

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

    

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2. Extreme environments and the origins of biodiversity: Adaptation and speciation in sulphide spring fishes

   https://doi.org/10.1111/mec.14497  

   Tobler, Michael ; Kelley, Joanna L. ; Plath, Martin ; Riesch, Rüdiger ( February 2018 , Molecular Ecology)

   Organisms adapted to physiochemical stressors provide ideal systems to study evolutionary mechanisms that drive adaptation and speciation. This review study focuses on livebearing fishes of thePoecilia mexicanaspecies complex (Poeciliidae), members of which have repeatedly colonized hydrogen sulphide (H₂S)‐rich springs. H₂S is a potent respiratory toxicant that creates extreme environmental conditions in aquatic ecosystems. There is also a rich history of research on H₂S in toxicology and biomedicine, which has facilitated the generation of a priori hypotheses about the proximate mechanisms of adaptation. Testing these hypotheses through the application of high‐throughput genomic and transcriptomic analyses has led to the identification of the physiological underpinnings mediating adaptation to H₂S‐rich environments. In addition, systematic natural history studies have provided a nuanced understanding of how the presence of a physiochemical stressor interacts with other sources of selection to drive evolutionary change in a variety of organismal traits, including physiology, morphology, behaviour and life history. Adaptation to extreme environments inP. mexicanaalso coincides with ecological speciation, and evolutionarily independent lineages span almost the full range of the speciation continuum from panmixia to complete reproductive isolation. Multiple mechanisms of reproductive isolation are involved in reducing gene flow between adjacent populations that are adapted to contrasting environmental conditions. Comparative studies among evolutionarily independent lineages within theP. mexicanaspecies complex and, more recently, other members of the family Poeciliidae that have colonized H₂S‐rich environments will provide insights into the factors facilitating or impeding convergent evolution, providing tangible links between micro‐evolutionary processes and macro‐evolutionary patterns.

    

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3. Predation risk drives long‐term shifts in migratory behaviour and demography in a large herbivore population

   https://doi.org/10.1111/1365-2656.14022  

   Williams, S. ; Hebblewhite, M. ; Martin, H. ; Meyer, C. ; Whittington, J. ; Killeen, J. ; Berg, J. ; MacAulay, K. ; Smolko, P. ; Merrill, E. H. ( November 2023 , Journal of Animal Ecology)

   Migration is an adaptive life‐history strategy across taxa that helps individuals maximise fitness by obtaining forage and avoiding predation risk. The mechanisms driving migratory changes are poorly understood, and links between migratory behaviour, space use, and demographic consequences are rare.

   Here, we use a nearly 20‐year record of individual‐based monitoring of a large herbivore, elk (Cervus canadensis) to test hypotheses for changing patterns of migration in and adjacent to a large protected area in Banff National Park (BNP), Canada.

   We test whether bottom‐up (forage quality) or top‐down (predation risk) factors explained trends in (i) the proportion of individuals using 5 different migratory tactics, (ii) differences in survival rates of migratory tactics during migration and whilst on summer ranges, (iii) cause‐specific mortality by wolves and grizzly bears, and (iv) population abundance.

   We found dramatic shifts in migration consistent with behavioural plasticity in individual choice of annual migratory routes. Shifts were inconsistent with exposure to the bottom‐up benefits of migration. Instead, exposure to landscape gradients in predation risk caused by exploitation outside the protected area drove migratory shifts. Carnivore exploitation outside the protected area led to higher survival rates for female elk remaining resident or migrating outside the protected area.

   Cause‐specific mortality aligned with exposure to predation risk along migratory routes and summer ranges. Wolf predation risk was higher on migratory routes than summer ranges of montane‐migrant tactics, but wolf predation risk traded‐off with heightened risk from grizzly bears on summer ranges. A novel eastern migrant tactic emerged following a large forest fire that enhanced forage in an area with lower predation risk outside of the protected area.

   The changes in migratory behaviour translated to population abundance, where abundance of the montane‐migratory tactics declined over time. The presence of diverse migratory life histories maintained a higher total population abundance than would have been the case with only one migratory tactic in the population.

   Our study demonstrates the complex ways in which migratory populations change over time through behavioural plasticity and associated demographic consequences because of individuals balancing predation risk and forage trade‐offs.

    

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4. Positive genetic associations among fitness traits support evolvability of a reef‐building coral under multiple stressors

   https://doi.org/10.1111/gcb.14764  

   Wright, Rachel M. ; Mera, Hanaka ; Kenkel, Carly D. ; Nayfa, Maria ; Bay, Line K. ; Matz, Mikhail V. ( August 2019 , Global Change Biology)

   Climate change threatens organisms in a variety of interactive ways that requires simultaneous adaptation of multiple traits. Predicting evolutionary responses requires an understanding of the potential for interactions among stressors and the genetic variance and covariance among fitness‐related traits that may reinforce or constrain an adaptive response. Here we investigate the capacity ofAcropora millepora, a reef‐building coral, to adapt to multiple environmental stressors: rising sea surface temperature, ocean acidification, and increased prevalence of infectious diseases. We measured growth rates (weight gain), coral color (a proxy for Symbiodiniaceae density), and survival, in addition to nine physiological indicators of coral and algal health in 40 coral genets exposed to each of these three stressors singly and combined. Individual stressors resulted in predicted responses (e.g., corals developed lesions after bacterial challenge and bleached under thermal stress). However, corals did not suffer substantially more when all three stressors were combined. Nor were trade‐offs observed between tolerances to different stressors; instead, individuals performing well under one stressor also tended to perform well under every other stressor. An analysis of genetic correlations between traits revealed positive covariances, suggesting that selection to multiple stressors will reinforce rather than constrain the simultaneous evolution of traits related to holobiont health (e.g., weight gain and algal density). These findings support the potential for rapid coral adaptation under climate change and emphasize the importance of accounting for corals’ adaptive capacity when predicting the future of coral reefs.

    

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5. Disentangling sex allocation in a viviparous reptile with temperature‐dependent sex determination: a multifactorial approach

   https://doi.org/10.1111/jeb.13219  

   Gruber, J. ; Cunningham, G. D. ; While, G. M. ; Wapstra, E. ( December 2017 , Journal of Evolutionary Biology)

   Females are predicted to alter sex allocation when ecological, physiological and behavioural variables have different consequences on the fitness of male and female offspring. Traditionally, tests of sex allocation have examined single causative factors, often ignoring possible interactions between multiple factors. Here, we used a multifactorial approach to examine sex allocation in the viviparous skink,Niveoscincus ocellatus. We integrated a 16‐year observational field study with a manipulative laboratory experiment to explore whether the effects of the maternal thermal environment interact with the resources available to females for reproduction to affect sex allocation decisions. We found strong effects of temperature on sex allocation in the field, with females born in warm conditions and males in cold conditions; however, this was not replicated in the laboratory. In contrast, we found no effect of female resource availability on sex allocation, either independently, or in interaction with temperature. These results corresponded with an overall lack of an effect of resource availability on any of the life history traits that we predicted would mediate the benefits of differential sex allocation in this system, suggesting that selection for sex allocation in response to resource availability may be relatively weak. Combined, these results suggest that temperature may be the predominant factor driving sex allocation in this system.

    

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