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1. Genetic differentiation underlies seasonal variation in thermal tolerance, body size, and phenotypic plasticity in a short-lived copepod

   https://doi.org/0.1002/ece3.6851  

   Sasaki, Matthew ; Dam, Hans G ( October 2020 , Ecology and evolution)

   null (Ed.)

   Organisms experience variation in the thermal environment on several different temporal scales, with seasonality being particularly prominent in temperate regions. For organisms with short generation times, seasonal variation is experienced across, rather than within, generations. How this affects the seasonal evolution of thermal tolerance and phenotypic plasticity is understudied, but has direct implications for the thermal ecology of these organisms. Here we document intra-annual patterns of thermal tolerance in two species of Acartia copepods (Crustacea) from a highly seasonal estuary, showing strong variation across the annual temperature cycle. Common garden, split-brood experiments indicate that this seasonal variation in thermal tolerance, along with seasonal variation in body size and phenotypic plasticity, is likely affected by genetic polymorphism. Our results show that adaptation to seasonal variation is important to consider when predicting how populations may respond to ongoing climate change. 

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2. Seasonal plasticity of thermal tolerance in ants

   https://doi.org/10.1002/ecy.3051  

   Bujan, Jelena ; Roeder, Karl A. ; Yanoviak, Stephen P. ; Kaspari, Michael ( April 2020 , Ecology)

   Analyses of heat tolerance in insects often suggest that this trait is relatively invariant, leading to the use of fixed thermal maxima in models predicting future distribution of species in a warming world. Seasonal environments expose populations to a wide annual temperature variation. To evaluate the simplifying assumption of invariant thermal maxima, we quantified heat tolerance of 26 ant species across three seasons that vary two‐fold in mean temperature. Our ultimate goal was to test the hypothesis that heat tolerance tracks monthly temperature. Ant foragers tested at the end of the summer, in September, had higher average critical thermal maximum (CT_max) compared to those in March and December. Four out of five seasonal generalists, species actively foraging in all three focal months, had, on average, 6°C higher CT_maxin September. The invasive fire ant,Solenopsis invicta, was among the thermally plastic species, but the native thermal specialists still maintained higher CT_maxthanS. invicta. Our study shows that heat tolerance can be plastic, and this should be considered when examining species‐level adaptations. Moreover, the plasticity of thermal traits, while potentially costly, may also generate a competitive advantage over species with fixed traits and promote resilience to climate change.

    

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3. Local climate determines vulnerability to camouflage mismatch in snowshoe hares

   https://doi.org/10.1111/geb.13049  

   Zimova, Marketa ; Sirén, Alexej P. K. ; Nowak, Joshua J. ; Bryan, Alexander M. ; Ivan, Jacob S. ; Morelli, Toni Lyn ; Suhrer, Skyler L. ; Whittington, Jesse ; Mills, L. Scott ; Morellato, ed., Patricia ( December 2019 , Global Ecology and Biogeography)

   Phenological mismatches, when life‐events become mistimed with optimal environmental conditions, have become increasingly common under climate change. Population‐level susceptibility to mismatches depends on how phenology and phenotypic plasticity vary across a species’ distributional range. Here, we quantify the environmental drivers of colour moult phenology, phenotypic plasticity, and the extent of phenological mismatch in seasonal camouflage to assess vulnerability to mismatch in a common North American mammal.

   North America.

   2010–2017.

   Snowshoe hare (Lepus americanus).

   We used > 5,500 by‐catch photographs of snowshoe hares from 448 remote camera trap sites at three independent study areas. To quantify moult phenology and phenotypic plasticity, we used multinomial logistic regression models that incorporated geospatial and high‐resolution climate data. We estimated occurrence of camouflage mismatch between hares’ coat colour and the presence and absence of snow over 7 years of monitoring.

   Spatial and temporal variation in moult phenology depended on local climate conditions more so than on latitude. First, hares in colder, snowier areas moulted earlier in the fall and later in the spring. Next, hares exhibited phenotypic plasticity in moult phenology in response to annual variation in temperature and snow duration, especially in the spring. Finally, the occurrence of camouflage mismatch varied in space and time; white hares on dark, snowless background occurred primarily during low‐snow years in regions characterized by shallow, short‐lasting snowpack.

   Long‐term climate and annual variation in snow and temperature determine coat colour moult phenology in snowshoe hares. In most areas, climate change leads to shorter snow seasons, but the occurrence of camouflage mismatch varies across the species’ range. Our results underscore the population‐specific susceptibility to climate change‐induced stressors and the necessity to understand this variation to prioritize the populations most vulnerable under global environmental change.

    

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4. Vertebrate Phenological Plasticity: From Molecular Mechanisms to Ecological and Evolutionary Implications

   https://doi.org/10.1093/icb/icac121  

   Aubry, Lise M. ; Williams, Cory T. ( July 2022 , Integrative and Comparative Biology)

   Seasonal variation in the availability of essential resources is one of the most important drivers of natural selection on the phasing and duration of annually recurring life-cycle events. Shifts in seasonal timing are among the most commonly reported responses to climate change and the capacity of organisms to adjust their timing, either through phenotypic plasticity or evolution, is a critical component of resilience. Despite growing interest in documenting and forecasting the impacts of climate change on phenology, our ability to predict how individuals, populations, and species might alter their seasonal timing in response to their changing environments is constrained by limited knowledge regarding the cues animals use to adjust timing, the endogenous genetic and molecular mechanisms that transduce cues into neural and endocrine signals, and the inherent capacity of animals to alter their timing and phasing within annual cycles. Further, the fitness consequences of phenological responses are often due to biotic interactions within and across trophic levels, rather than being simple outcomes of responses to changes in the abiotic environment. Here, we review the current state of knowledge regarding the mechanisms that control seasonal timing in vertebrates, as well as the ecological and evolutionary consequences of individual, population, and species-level variation in phenological responsiveness. Understanding the causes and consequences of climate-driven phenological shifts requires combining ecological, evolutionary, and mechanistic approaches at individual, populational, and community scales. Thus, to make progress in forecasting phenological responses and demographic consequences, we need to further develop interdisciplinary networks focused on climate change science.

    

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5. Spatial and temporal variation in phenotypes and fitness in response to developmental thermal environments

   https://doi.org/10.1111/1365-2435.13910  

   Pruett, Jenna E. ; Warner, Daniel A. ( October 2021 , Functional Ecology)

   Phenotypic variation within populations is influenced by the environment via plasticity and natural selection. How phenotypes respond to the environment can vary among traits, populations and life stages in ways that can influence fitness.

   Plastic responses during early development are particularly important because they can affect components of fitness throughout an individual's life. Consequently, how natural selection shapes developmental plasticity could be influenced by fitness consequences across different life stages. Moreover, spatial variation in selection pressures could generate differences in plastic responses among populations.

   To gain insight into sources of variation in phenotypes and survival, we used a laboratory egg incubation experiment using brown anole lizardsAnolis sagreifrom mainland (ancestral) and island (descendent) populations, combined with a mark–release–recapture experiment in the field. Our study was designed to (a) quantify the effects developmental temperature on embryo development and offspring morphology, (b) assess how developmental temperature influences offspring survival across different life stages and (c) quantify how thermal reaction norms vary among ancestral and descendant populations.

   Developmental temperature influenced offspring morphology, but thermal reaction norms of embryos showed little variation among populations. Developmental temperature influenced offspring survival, but the patterns differed between embryo and hatchling stages; the optimal temperature for embryos was about 5℃ lower than that for hatchlings. High temperatures were thermally stressful to embryos, but they reduced incubation duration and led to early hatching. In turn, earlier hatching increased the probability of survival to adulthood. Moreover, the effect of developmental temperature on hatchling survival was most pronounced for offspring that hatched late in the season.

   The difference in optimal developmental temperatures between life stages may be driven by physiological tolerance for embryos and by ecological factors for hatchlings. Moreover, the fitness consequences of the developmental environment depend on the phenology of hatching. Overall, these results highlight how the developmental environment can differentially affect fitness across life stages and show that temporal thermal heterogeneity can influence survival of embryos, but the consequences on post‐hatching stages may vary at different times of the season.

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

    

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