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1. Elevated [ CO2 ] and temperature augment gas exchange and shift the fitness landscape in a montane forb

   https://doi.org/10.1111/nph.19765  

   Denney, Derek A. ; Patel, Pratik ; Anderson, Jill T. ( April 2024 , New Phytologist)

   Climate change is simultaneously increasing carbon dioxide concentrations ([CO₂]) and temperature. These factors could interact to influence plant physiology and performance. Alternatively, increased [CO₂] may offset costs associated with elevated temperatures. Furthermore, the interaction between elevated temperature and [CO₂] may differentially affect populations from along an elevational gradient and disrupt local adaptation.

   We conducted a multifactorial growth chamber experiment to examine the interactive effects of temperature and [CO₂] on fitness and ecophysiology of diverse accessions ofBoechera stricta(Brassicaceae) sourced from a broad elevational gradient in Colorado. We tested whether increased [CO₂] would enhance photosynthesis across accessions, and whether warmer conditions would depress the fitness of high‐elevation accessions owing to steep reductions in temperature with increasing elevation in this system. Elevational clines in [CO₂] are not as evident, making it challenging to predict how locally adapted ecotypes will respond to elevated [CO₂].

   This experiment revealed that elevated [CO₂] increased photosynthesis and intrinsic water use efficiency across all accessions. However, these instantaneous responses to treatments did not translate to changes in fitness. Instead, increased temperatures reduced the probability of reproduction for all accessions. Elevated [CO₂] and increased temperatures interacted to shift the adaptive landscape, favoring lower elevation accessions for the probability of survival and fecundity.

   Our results suggest that elevated temperatures and [CO₂] associated with climate change could have severe negative consequences, especially for high‐elevation populations.

    

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2. Competition-driven eco-evolutionary feedback reshapes bacteriophage lambda’s fitness landscape and enables speciation

   https://doi.org/10.1038/s41467-024-45008-5  

   Doud, Michael B. ; Gupta, Animesh ; Li, Victor ; Medina, Sarah J. ; De La Fuente, Caesar A. ; Meyer, Justin R. ( January 2024 , Nature Communications)

   A major challenge in evolutionary biology is explaining how populations navigate rugged fitness landscapes without getting trapped on local optima. One idea illustrated by adaptive dynamics theory is that as populations adapt, their newly enhanced capacities to exploit resources alter fitness payoffs and restructure the landscape in ways that promote speciation by opening new adaptive pathways. While there have been indirect tests of this theory, to our knowledge none have measured how fitness landscapes deform during adaptation, or test whether these shifts promote diversification. Here, we achieve this by studying bacteriophage$$\lambda$$$\lambda$, a virus that readily speciates into co-existing receptor specialists under controlled laboratory conditions. We use a high-throughput gene editing-phenotyping technology to measure$$\lambda$$$\lambda$’s fitness landscape in the presence of different evolved-$$\lambda$$$\lambda$competitors and find that the fitness effects of individual mutations, and their epistatic interactions, depend on the competitor. Using these empirical data, we simulate$$\lambda$$$\lambda$’s evolution on an unchanging landscape and one that recapitulates how the landscape deforms during evolution.$$\lambda$$$\lambda$heterogeneity only evolves in the shifting landscape regime. This study provides a test of adaptive dynamics, and, more broadly, shows how fitness landscapes dynamically change during adaptation, potentiating phenomena like speciation by opening new adaptive pathways.

    

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3. Movement ecology of vulnerable lowland tapirs between areas of varying human disturbance

   https://doi.org/10.1186/s40462-022-00313-w  

   Medici, E. P. ; Mezzini, S. ; Fleming, C. H. ; Calabrese, J. M. ; Noonan, M. J. ( March 2022 , Movement Ecology)

   Animal movement is a key ecological process that is tightly coupled to local environmental conditions. While agriculture, urbanisation, and transportation infrastructure are critical to human socio-economic improvement, these have spurred substantial changes in animal movement across the globe with potential impacts on fitness and survival. Notably, however, human disturbance can have differential effects across species, and responses to human activities are thus largely taxa and context specific. As human disturbance is only expected to worsen over the next decade it is critical to better understand how species respond to human disturbance in order to develop effective, case-specific conservation strategies.

   Here, we use an extensive telemetry dataset collected over 22 years to fill a critical knowledge gap in the movement ecology of lowland tapirs (Tapirus terrestris) across areas of varying human disturbance within three biomes in southern Brazil: the Pantanal, Cerrado, and Atlantic Forest.

   From these data we found that the mean home range size across all monitored tapirs was 8.31 km²(95% CI 6.53–10.42), with no evidence that home range sizes differed between sexes nor age groups. Interestingly, although the Atlantic Forest, Cerrado, and Pantanal vary substantially in habitat composition, levels of human disturbance, and tapir population densities, we found that lowland tapir movement behaviour and space use were consistent across all three biomes. Human disturbance also had no detectable effect on lowland tapir movement. Lowland tapirs living in the most altered habitats we monitored exhibited movement behaviour that was comparable to that of tapirs living in a near pristine environment.

   Contrary to our expectations, although we observed individual variability in lowland tapir space use and movement, human impacts on the landscape also had no measurable effect on their movement. Lowland tapir movement behaviour thus appears to exhibit very little phenotypic plasticity in response to human disturbance. Crucially, the lack of any detectable response to anthropogenic disturbance suggests that human modified habitats risk being ecological traps for tapirs and this information should be factored into conservation actions and species management aimed towards protecting lowland tapir populations.

    

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4. Environmental modulation of global epistasis in a drug resistance fitness landscape

   https://doi.org/10.1038/s41467-023-43806-x  

   Diaz-Colunga, Juan ; Sanchez, Alvaro ; Ogbunugafor, C. Brandon ( December 2023 , Nature Communications)

   Interactions between mutations (epistasis) can add substantial complexity to genotype-phenotype maps, hampering our ability to predict evolution. Yet, recent studies have shown that the fitness effect of a mutation can often be predicted from the fitness of its genetic background using simple, linear relationships. This phenomenon, termedglobal epistasis, has been leveraged to reconstruct fitness landscapes and infer adaptive trajectories in a wide variety of contexts. However, little attention has been paid to how patterns of global epistasis may be affected by environmental variation, despite this variation frequently being a major driver of evolution. This is particularly relevant for the evolution of drug resistance, where antimicrobial drugs may change the environment faced by pathogens and shape their adaptive trajectories in ways that can be difficult to predict. By analyzing a fitness landscape of four mutations in a gene encoding an essential enzyme ofP. falciparum(a parasite cause of malaria), here we show that patterns of global epistasis can be strongly modulated by the concentration of a drug in the environment. Expanding on previous theoretical results, we demonstrate that this modulation can be quantitatively explained by how specific gene-by-gene interactions are modified by drug dose. Importantly, our results highlight the need to incorporate potential environmental variation into the global epistasis framework in order to predict adaptation in dynamic environments.

    

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5. Functional traits predict species responses to environmental variation in a California grassland annual plant community

   https://doi.org/10.1111/1365-2745.13845  

   Kandlikar, Gaurav S. ; Kleinhesselink, Andrew R. ; Kraft, Nathan J. B. ( February 2022 , Journal of Ecology)

   Turnover in species composition and the dominant functional strategies in plant communities across environmental gradients is a common pattern across biomes, and is often assumed to reflect shifts in trait optima. However, the extent to which community‐wide trait turnover patterns reflect changes in how plant traits affect the vital rates that ultimately determine fitness remain unclear.

   We tested whether shifts in the community‐weighted means of four key functional traits across an environmental gradient in a southern California grassland reflect variation in how these traits affect species' germination and fecundity across the landscape.

   We asked whether models that included trait–environment interactions help explain variation in two key vital rates (germination rates and fecundity), as well as an integrative measure of fitness incorporating both vital rates (the product of germination rate and fecundity). To do so, we planted seeds of 17 annual plant species at 16 sites in cleared patches with no competitors, and quantified the lifetime seed production of 1360 individuals. We also measured community composition and a variety of abiotic variables across the same sites. This allowed us to evaluate whether observed shifts in community‐weighted mean traits matched the direction of any trait–environment interactions detected in the plant performance experiment.

   We found that commonly measured plant functional traits do help explain variation in species responses to the environment—for example, high‐SLA species had a demographic advantage (higher germination rates and fecundity) in sites with high soil Ca:Mg levels, while low‐SLA species had an advantage in low Ca:Mg soils. We also found that shifts in community‐weighted mean traits often reflect the direction of these trait–environment interactions, though not all trait–environment relationships at the community level reflect changes in optimal trait values across these gradients.

   Synthesis. Our results show how shifts in trait–fitness relationships can give rise to turnover in plant phenotypes across environmental gradients, a fundamental pattern in ecology. We highlight the value of plant functional traits in predicting species responses to environmental variation, and emphasise the need for more widespread study of trait–performance relationships to improve predictions of community responses to global change.

    

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