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1. Life history and chemical defense interact to drive patterns of adaptation in an annual monkeyflower

   https://doi.org/10.1093/evolut/qpac048  

   Scharnagl, Anna; Genung, Mark A.; Holeski, Liza M.; Kooyers, Nicholas J. (December 2022, Evolution)

   Abstract Although chemical defenses and herbivore pressure are widely established as key targets and agents of selection, their roles in local adaptation and determining potential evolutionary responses to changing climates are often neglected. Here, we explore fitness differences between 11 rangewide M. guttatus populations in a field common garden experiment and assess the agents and targets of selection driving relative fitness patterns. We use piecewise structural equation models to disentangle associations between chemical defenses, (phenylpropanoid glycosides; PPGs), and life history traits with herbivory and fitness. While the historical environment of populations is not predictive of fitness differences between populations, >90% of variation in fitness can be predicted by the flowering time and foliar PPG defense arsenal of a population. Piecewise structural equation models indicate that life history traits, particularly earlier flowering time, are strongly and directly linked to fitness. However, herbivory, particularly fruit predation, is also an important agent of selection that creates indirect links between fitness and both chemical defenses and life history traits. Our results emphasize the multivariate nature of the agents and targets of selections in producing adaptation and suggest that future responses to selection must navigate a complex fitness landscape. 

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2. Evolution and seed dormancy shape plant genotypic structure through a successional cycle

   https://doi.org/10.1073/pnas.2026212118  

   Agrawal, Anurag A.; Hastings, Amy P.; Maron, John L. (August 2021, Proceedings of the National Academy of Sciences)

   Dormancy has repeatedly evolved in plants, animals, and microbes and is hypothesized to facilitate persistence in the face of environmental change. Yet previous experiments have not tracked demography and trait evolution spanning a full successional cycle to ask whether early bouts of natural selection are later reinforced or erased during periods of population dormancy. In addition, it is unclear how well short-term measures of fitness predict long-term genotypic success for species with dormancy. Here, we address these issues using experimental field populations of the plantOenothera biennis, which evolved over five generations in plots exposed to or protected from insect herbivory. While populations existed above ground, there was rapid evolution of defensive and life-history traits, but populations lost genetic diversity and crashed as succession proceeded. After >5 y of seed dormancy, we triggered germination from the seedbank and genotyped >3,000 colonizers. Resurrected populations showed restored genetic diversity that reduced earlier responses to selection and pushed population phenotypes toward the starting conditions of a decade earlier. Nonetheless, four defense and life-history traits remained differentiated in populations with insect suppression compared with controls. These findings capture key missing elements of evolution during ecological cycles and demonstrate the impact of dormancy on future evolutionary responses to environmental change. 

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3. Heritable plant phenotypes track light and herbivory levels at fine spatial scales

   Humphrey, P Gloss (January 2018, Oecologia)

   Organismal phenotypes often co-vary with environmental variables across broad geographic ranges. Less is known about the extent to which phenotypes match local conditions when multiple biotic and abiotic stressors vary at fine spatial scales. Bittercress (Brassicaceae: Cardamine cordifolia), a perennial forb, grows across a microgeographic mosaic of two contrasting herbivory regimes: high herbivory in meadows (sun habitats) and low herbivory in deeply shaded forest understories (shade habitats). We tested for local phenotypic differentiation in plant size, leaf morphology, and anti-herbivore defense (realized resistance and defensive chemicals, i.e., glucosinolates) across this habitat mosaic through reciprocal transplant–common garden experiments with clonally propagated rhizomes. We found habitat-specific divergence in morphological and defensive phenotypes that manifested as contrasting responses to growth in shade common gardens: weak petiole elongation and attenuated defenses in populations from shade habitats, and strong petiole elongation and elevated defenses in populations from sun habitats. These divergent phenotypes are generally consistent with reciprocal local adaptation: plants from shade habitats that naturally experience low herbivory show reduced investment in defense and an attenuated shade avoidance response, owing to its ineffectiveness within forest understories. By contrast, plants from sun habitats with high herbivory show shade-induced elongation, but no evidence of attenuated defenses canonically associated with elongation in shade-intolerant plant species. Finally, we observed differences in flowering phenology between habitat types that could potentially contribute to inter-habitat divergence by reducing gene flow. This study illuminates how clonally heritable plant phenotypes track a fine-grained mosaic of herbivore pressure and light availability in a native plant. 

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4. Adaptation to warm environments with a fast pace of life in a marine predatory snail

   https://doi.org/10.1101/2025.06.20.660751  

   Dwane, Christopher; Komoroske, Lisa M; Rugila, Allison L; Bentley, Blair P; Rawson, Emma; Clark, Elizabeth; Nichols, Gillian; Newbrey, Mikayla; Bucari, Emily; Yan, Chance; et al (June 2025, bioRxiv)

   Understanding how latitudinal temperature variation shapes local adaptation of life history strategies is crucial for predicting future responses to warming. Contrasting predictive frameworks explain how growth and other life history traits may respond to differing selective pressures across latitude. However, these frameworks have rarely been explored within the context of fluctuating environmental temperatures across longer (i.e., seasonal) time scales experienced in nature. Furthermore, consequences of growth differences for other aspects of fitness, including reproductive output, remain unclear. Here, we conducted a long-term (17-month) simulated reciprocal transplant experiment to examine local adaptation in two populations of the predatory marine snail Urosalpinx cinerea separated by 8.6 degrees latitude (1000 km). We reared F1 offspring under two seasonally fluctuating temperature regimes (warm and cold, simulating field thermal conditions experienced by low and high latitude populations, respectively), quantifying temporal patterns in growth, maturation, and reproductive output. We identified striking divergence in life-history strategies between populations in the warm regime, with offspring from the low latitude population achieving greater growth in their first year, and high reproductive output coupled with reduced growth in their second year. In contrast, the high latitude population grew slower in their first year, but eventually attained larger sizes in their second year, at the expense of reduced reproductive output. Responses were consistent with this in the cold regime, although growth and reproductive output was reduced in both populations. Our data provides support for adaptive divergence across latitude consistent with the Pace-of-Life hypothesis, with the low latitude population selected for a fast-paced life characterized by rapid development and early reproduction. In contrast, the high latitude population exhibited slower growth and delayed maturation. Our results highlight the potential limitations of short-term comparisons of growth without considering processes over longer time scales that may exhibit seasonal temperature variation and ontogenetic shifts in energy allocation and imply a radical reshaping of physiological performance and life history traits across populations under climate change. 

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5. Herbivory and water availability interact to shape the adaptive landscape in the perennial forb, Boechera stricta

   https://doi.org/10.1093/evolut/qpae186  

   Jameel, M_Inam; Duncan, Lisa; Mooney, Kailen; Anderson, Jill_T; Friedman, ed., Jannice; Wolf, ed., Jason (December 2024, Evolution)

   Abstract Abiotic and biotic factors interact to influence phenotypic evolution; however, identifying the causal agents of selection that drive the evolution and expression of traits remains challenging. In a field common garden, we manipulated water availability and herbivore abundance across 3 years, and evaluated clinal variation in functional traits and phenology, phenotypic plasticity, local adaptation, and selection using diverse accessions of the perennial forb, Boechera stricta. Consistent with expectations, drought stress exacerbated damage from herbivores. We found significant plasticity and genetic clines in foliar and phenological traits. Water availability and herbivory interacted to exert selection, even on traits like flowering duration, which showed no clinal variation. Furthermore, the direction of selection on specific leaf area in response to water availability mirrored the genetic cline and plasticity, suggesting that variation in water levels across the landscape influences the evolution of this trait. Finally, both herbivory and water availability likely contribute to local adaptation. This work emphasizes the additive and synergistic roles of abiotic and biotic factors in shaping phenotypic variation across environmental gradients. 

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