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1. Behavioral variation, adaptation, and evolution

   https://doi.org/doi:10.1037/0000011-011  

   Shelton, D. S.; Martins, E. P. (January 2017, APA)

   Individual animals behave differently from each other for myriad interrelated intrinsic and extrinsic reasons, and this behavioral variation is the raw substrate for evolutionary change. Behavioral varia- tion can both enhance and constrain long-term evolution (Foster, 2013), and it provides the basic materials on which natural and sexual selection can act. A rich body of historical experimental and conceptual foundations precedes many of the topics discussed. This classic literature is vast and impor- tant, and we encourage the reader to examine it in detail (e.g., Lehrman, 1953; Lorenz, 1971; Schnei- rla, 1966; Waddington, 1959) because we discuss more recent literature. For example, the study of the mechanisms that underlie behavioral variation has a divisive history, which involves carving out the relative contributions of genes and environment to a particular phenotype. Developmental systems and reaction-norm views challenged the issue of gene or environment by arguing that the interplay between genetic substrates and environmental inputs defined adaptive phenotypes across multiple contexts (Fos- ter, 2013; Gottlieb, 1991a, 1991b; Jablonka & Lamb, 2014). Identifying the interactional relationship between components permits researchers to under- stand how behavior becomes organized (Gottlieb, 1991a, 1991b) and can reveal links between indi- vidual variation and population-level persistence, species diversification (or stasis), and community dynamics (reviewed in Dingemanse & Wolf, 2013). Similarly, the study of individual differences has a rich history situated in the areas of behavioral genet- ics, sociobiology, behavioral ecology, developmen- tal psychology, personality theory, and studies of learning and cognition. Each area has its own goals, associated techniques, and levels of explanation. The study of behavioral variation during early develop- ment, for instance, has been documented primarily by psychologists studying proximate mechanisms in laboratory animal models, whereas the study of dif- ferent adult morphs using the adaptationist perspec- tive has been dominated by behavioral ecologists examining natural populations (Foster, 1995). A more complete description of individual differences requires an integrative study of the mechanisms (e.g., developmental, physiological) that guide intra- individual flexibility and the associated adaptive fine tuning of behavioral types. It is through this integra- tion that researchers can make predictions about the response of different individual phenotypes, groups, populations, and species to novel situations (e.g., captive and urban environments). 

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2. Soil microenvironmental variation drives below‐ground trait variation and interacts with macroclimate to structure above‐ground trait variation of arctic shrubs

   https://doi.org/10.1111/1365-2745.14278  

   Fraterrigo, Jennifer M; Chen, Weile; Loyal, Joshua; Euskirchen, Eugénie S (April 2024, Journal of Ecology)

   Henn, J (Ed.)

   Abstract Intraspecific trait variation can influence plant performance in different environments and may thereby determine the ability of individual plants to respond to climate change. However, our understanding of its patterns and environmental drivers across different spatial scales is incomplete, especially in understudied regions like the Arctic.To fill this knowledge gap, we examined above‐ground and below‐ground traits from three shrub taxa expanding across the tundra biome and evaluated their relationships with multiple microenvironmental and macroclimatic factors. The traits reflected plant size and structure (plant height, leaf area and root to shoot ratio), leaf economics (specific leaf area, nitrogen content), and root economics and collaboration with mycorrhizal fungi (specific root length, root tissue density, nitrogen content, and ectomycorrhizal colonisation intensity). We also measured leaf and root δ¹⁵N and leaf δ¹³C to characterise nitrogen source and acquisition pathways and plant water stress. Traits were measured in replicated plots (N = 135) varying in soil microclimate, thaw depth and organic layer thickness established across five sites spanning a macroclimate gradient in northern Alaska. This hierarchical design allowed us to disentangle the independent and combined effects of fine‐scale and broad‐scale factors on intraspecific trait variation.We found substantial intraspecific variation at fine spatial scales for most traits and less variation along the macroclimate gradient and between shrub taxa. Consistent with these patterns, microenvironmental factors, mainly soil moisture and thaw depth, interacted with macroclimate, mainly climatic water deficit, to structure size‐structural and leaf trait variation. In contrast, most root traits responded additively to thaw depth and macroclimate.Synthesis. Our results demonstrate that above‐ground and below‐ground tundra shrub traits respond differently to microenvironmental and macroclimatic variation. These differing responses contribute to substantial trait variation at fine spatial scales and may decouple above‐ground and below‐ground trait responses to climate change. 

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3. Selection on size variation: more variation in bumble bee workers and in the wild

   https://doi.org/10.1007/s00040-022-00850-y  

   Kelemen, E. P.; Skyrm, K.; Dornhaus, A. (February 2022, Insectes Sociaux)
4. Genetic variation, environment and demography intersect to shape Arabidopsis defense metabolite variation across Europe

   Katz, E.; Li jj; Jaegle, B.; Ashkenazy, H.; Abrahams SR.; Bagaza C.; Holden S.; Pires CJ.; Angelovici R.; Kliebenstein DJ. (May 2021, eLife)
5. Variation in body size drives spatial and temporal variation in lobster–urchin interaction strength

   https://doi.org/10.1111/1365-2656.13918  

   DiFiore, Bartholomew P.; Stier, Adrian C. (April 2023, Journal of Animal Ecology)

   Abstract How strongly predators and prey interact is both notoriously context dependent and difficult to measure. Yet across taxa, interaction strength is strongly related to predator size, prey size and prey density, suggesting that general cross‐taxonomic relationships could be used to predict how strongly individual species interact.Here, we ask how accurately do general size‐scaling relationships predict variation in interaction strength between specific species that vary in size and density across space and time?To address this question, we quantified the size and density dependence of the functional response of the California spiny lobsterPanulirus interruptus, foraging on a key ecosystem engineer, the purple sea urchinStrongylocentrotus purpuratus, in experimental mesocosms. Based on these results, we then estimated variation in lobster–urchin interaction strength across five sites and 9 years of observational data. Finally, we compared our experimental estimates to predictions based on general size‐scaling relationships from the literature.Our results reveal that predator and prey body size has the greatest effect on interaction strength when prey abundance is high. Due to consistently high urchin densities in the field, our simulations suggest that body size—relative to density—accounted for up to 87% of the spatio‐temporal variation in interaction strength. However, general size‐scaling relationships failed to predict the magnitude of interactions between lobster and urchin; even the best prediction from the literature was, on average, an order of magnitude (+18.7×) different than our experimental predictions.Harvest and climate change are driving reductions in the average body size of many marine species. Anticipating how reductions in body size will alter species interactions is critical to managing marine systems in an ecosystem context. Our results highlight the extent to which differences in size‐frequency distributions can drive dramatic variation in the strength of interactions across narrow spatial and temporal scales. Furthermore, our work suggests that species‐specific estimates for the scaling of interaction strength with body size, rather than general size‐scaling relationships, are necessary to quantitatively predict how reductions in body size will alter interaction strengths. 

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