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

   https://doi.org/10.1002/ece3.6851  

   Sasaki, Matthew C. ; Dam, Hans G. ( October 2020 , Ecology and Evolution)

   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 ofAcartiacopepods (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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3. High‐resolution thermal imagery reveals how interactions between crown structure and genetics shape plant temperature

   https://doi.org/10.1002/rse2.359  

   Olsoy, Peter J. ; Zaiats, Andrii ; Delparte, Donna M. ; Germino, Matthew J. ; Richardson, Bryce A. ; Roop, Spencer ; Roser, Anna V. ; Forbey, Jennifer S. ; Cattau, Megan E. ; Buerki, Sven ; et al ( July 2023 , Remote Sensing in Ecology and Conservation)

   Understanding interactions between environmental stress and genetic variation is crucial to predict the adaptive capacity of species to climate change. Leaf temperature is both a driver and a responsive indicator of plant physiological response to thermal stress, and methods to monitor it are needed. Foliar temperatures vary across leaf to canopy scales and are influenced by genetic factors, challenging efforts to map and model this critical variable. Thermal imagery collected using unoccupied aerial systems (UAS) offers an innovative way to measure thermal variation in plants across landscapes at leaf‐level resolutions. We used a UAS equipped with a thermal camera to assess temperature variation among genetically distinct populations of big sagebrush (Artemisia tridentata), a keystone plant species that is the focus of intensive restoration efforts throughout much of western North America. We completed flights across a growing season in a sagebrush common garden to map leaf temperature relative to subspecies and cytotype, physiological phenotypes of plants, and summer heat stress. Our objectives were to (1) determine whether leaf‐level stomatal conductance corresponds with changes in crown temperature; (2) quantify genetic (i.e., subspecies and cytotype) contributions to variation in leaf and crown temperatures; and (3) identify how crown structure, solar radiation, and subspecies‐cytotype relate to leaf‐level temperature. When considered across the whole season, stomatal conductance was negatively, non‐linearly correlated with crown‐level temperature derived from UAS. Subspecies identity best explained crown‐level temperature with no difference observed between cytotypes. However, structural phenotypes and microclimate best explained leaf‐level temperature. These results show how fine‐scale thermal mapping can decouple the contribution of genetic, phenotypic, and microclimate factors on leaf temperature dynamics. As climate‐change‐induced heat stress becomes prevalent, thermal UAS represents a promising way to track plant phenotypes that emerge from gene‐by‐environment interactions.

    

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4. Genetic differences in thermal tolerance among colonies of threatened coral Acropora cervicornis: potential for adaptation to increasing temperature

   https://doi.org/10.3354/meps13407  

   Yetsko, K ; Ross, M ; Bellantuono, A ; Merselis, D ; Rodriquez-Lanetty, M ; Gilg, MR ( July 2020 , Marine Ecology Progress Series)

   null (Ed.)

   Climate change is resulting in warmer temperatures that are negatively impacting corals. Understanding how much individuals within a population vary in their thermal tolerance and whether this variation is heritable is important in determining whether a species can adapt to climate change. To address this, Acropora cervicornis fragments from 20 genetically distinct colonies collected from the Coral Restoration Foundation Tavernier nursery (Florida, USA) were kept at either ambient (28 ± 1°C) or elevated (32 ± 1°C) temperatures, and mortality was monitored for 26 d. Both broad-sense ( H 2 ) and narrow-sense ( h 2 ) heritability of thermal tolerance were estimated to determine the amount of genetic variation underlying survival to elevated temperature. To understand the physiological basis of thermal tolerance, tissue from both treatments was taken 12 h after the start of the experiment to investigate gene expression at the mRNA and protein level between tolerant and susceptible colonies. Results revealed that this population has considerable total genetic variation in thermal tolerance ( H 2 = 0.528), but low variance in relatedness among colonies prevented us from making any conclusions regarding h 2 . Despite high transcriptomic variability among and within colonies, 40 genes were consistently and significantly different between tolerant and susceptible colonies, and could be potential biomarkers for thermal tolerance should they be verified in a larger sample. Overall, the results suggest that this population has substantial genetic variation for traits that directly impact thermal tolerance; however, their response to projected increases in temperature will depend on more precise estimates of the additive components of this variation ( h 2 ). 

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5. Negative relationship between thermal tolerance and plasticity in tolerance emerges during experimental evolution in a widespread marine invertebrate

   https://doi.org/10.1111/eva.13270  

   Sasaki, Matthew C. ; Dam, Hans G. ( July 2021 , Evolutionary Applications)

   Whether populations can adapt to predicted climate change conditions, and how rapidly, are critical questions for the management of natural systems. Experimental evolution has become an important tool to answer these questions. In order to provide useful, realistic insights into the adaptive response of populations to climate change, there needs to be careful consideration of how genetic differentiation and phenotypic plasticity interact to generate observed phenotypic changes. We exposed three populations of the widespread copepodAcartia tonsa(Crustacea) to chronic, sublethal temperature selection for 15 generations. We generated thermal survivorship curves at regular intervals both during and after this period of selection to track the evolution of thermal tolerance. Using reciprocal transplants between ambient and warming conditions, we also tracked changes in the strength of phenotypic plasticity in thermal tolerance. We observed significant increases in thermal tolerance in the Warming lineages, while plasticity in thermal tolerance was strongly reduced. We suggest these changes are driven by a negative relationship between thermal tolerance and plasticity in thermal tolerance. Our results indicate that adaptation to warming through an increase in thermal tolerance might not reduce vulnerability to climate change if the increase comes at the expense of tolerance plasticity. These results illustrate the importance of considering changes in both a trait of interest and the trait plasticity during experimental evolution.

    

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