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1. Nonlinear drought plasticity reveals intraspecific diversity in a dominant grass species

   https://doi.org/10.1111/1365-2435.13713  

   Hoffman, Ava M. ; Smith, Melinda D. ; Yahdjian, ed., Laura ( December 2020 , Functional Ecology)

   Intraspecific diversity of dominant species in native plant communities can modulate ecosystem function under both optimal and stressful conditions. Yet, few genotype by environment interaction studies quantify differences in the shape of plasticity functions or phenotypic breakpoints across genotypes in natural populations.

   Using three genotypes with a history of drought selection, we performed a greenhouse study on the dominant tallgrass prairie speciesAndropogon gerardii. We investigated phenotypic plasticity and recovery differences among genotypes across a water availability gradient, measuring growth‐related, instantaneous and cumulative phenotypes. To further understand genotype by environment effects, we quantified plasticity functions and breakpoints among genotypes.

   Like other studies, we found strong evidence for phenotypic and plasticity differences among genotypes. However, we also found nonlinear plasticity functions and breakpoints were common across phenotypes, especially relative growth rates, biomass allocation and root architecture. Drought selected genotypes were also more likely to flower during recovery, but all genotypes were resilient to drought across treatments.

   We demonstrate that plasticity functions may help explain intraspecific diversity, patterns of selection and nonlinear community responses to more variable rainfall within an experimental population. In particular, plasticity functions can help disentangle drought/variability tolerance versus acquisitive strategies. A better understanding of intraspecific diversity in this grass species will provide more mechanistic insight into its ability to buffer ecosystem changes and provide resiliency in the tallgrass prairie under future droughts.

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

    

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2. Phylogeography and population genetics reveal ring species patterns in a highly polymorphic California lily

   https://doi.org/10.1111/jbi.14313  

   Hernández, Adriana I. ; Landis, Jacob B. ; Specht, Chelsea D. ( January 2022 , Journal of Biogeography)

   Natural selection typically results in the homogenization of reproductive traits, reducing natural variation within populations; thus, highly polymorphic species present unresolved questions regarding the mechanisms that shape and maintain gene flow given a diversity of phenotypes. We used an integrative framework to characterize phenotypic diversity and assess how evolutionary history and population genetics affect the highly polymorphic nature of a California endemic lily.

   California, United States.

   Butterfly mariposa lily,Calochortus venustus(Liliaceae).

   We summarized phenotypic diversity at both metapopulation and subpopulation scales to explore spatial phenotypic distributions. We sampled 174 individuals across the species range representing multiple samples for each population and each phenotype. We used restriction‐site‐associated DNA sequencing (RAD‐Seq) to detect population clusters, gene flow between phenotypes and between populations, infer haplotype networks, and reconstruct ancestral range evolution to infer historical migration and range expansion.

   Polymorphic floral traits within the species such as petal pigmentation and distal spots are geographically structured, and inferred evolutionary history is consistent with a ring species pattern involving a complex of populations having experienced sequential change in genetic and phenotypic variation from the founding population. Populations remain interconnected yet have differentiated from each other along a bifurcating south‐to‐north range expansion, consequently indicating parallel evolution towards the white morphotype in the northern range. Thus, our phylogeographical analyses reveal morphological convergence with population genetic cohesion irrespective of phenotypic diversity.

   Phenotypic variation in the highly polymorphicCalochortus venustusis not due to genetic differentiation between phenotypes; rather there is genetic cohesion within six geographically defined populations, some of which maintain a high level of within‐population phenotypic diversity. Our results demonstrate that analyses of polymorphic taxa greatly benefit from disentangling phenotype from genotype at various spatial scales. We discuss results in light of ring species concepts and the need to determine the adaptive significance of the patterns we report.

    

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3. No local adaptation in leaf or stem xylem vulnerability to embolism, but consistent vulnerability segmentation in a North American oak

   https://doi.org/10.1111/nph.15886  

   Skelton, Robert P. ; Anderegg, Leander D. L. ; Papper, Prahlad ; Reich, Emma ; Dawson, Todd E. ; Kling, Matthew ; Thompson, Sally E. ; Diaz, Jessica ; Ackerly, David D. ( June 2019 , New Phytologist)

   Vulnerability to embolism varies between con‐generic species distributed along aridity gradients, yet little is known about intraspecific variation and its drivers. Even less is known about intraspecific variation in tissues other than stems, despite results suggesting that roots, stems and leaves can differ in vulnerability. We hypothesized that intraspecific variation in vulnerability in leaves and stems is adaptive and driven by aridity.

   We quantified leaf and stem vulnerability ofQuercus douglasiiusing the optical technique. To assess contributions of genetic variation and phenotypic plasticity to within‐species variation, we quantified the vulnerability of individuals growing in a common garden, but originating from populations along an aridity gradient, as well as individuals from the same wild populations.

   Intraspecific variation in water potential at which 50% of total embolism in a tissue is observed (P₅₀) was explained mostly by differences between individuals (>66% of total variance) and tissues (16%). There was little between‐population variation in leaf/stem P₅₀in the garden, which was not related to site of origin aridity. Unexpectedly, we observed a positive relationship between wild individual stem P₅₀and aridity.

   Although there is no local adaptation and only minor phenotypic plasticity in leaf/stem vulnerability inQ. douglasii, high levels of potentially heritable variation within populations or strong environmental selection could contribute to adaptive responses under future climate change.

    

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4. Tracking the assembly of nested parasite communities: Using β ‐diversity to understand variation in parasite richness and composition over time and scale

   https://doi.org/10.1111/1365-2656.13204  

   Moss, Wynne E. ; McDevitt‐Galles, Travis ; Calhoun, Dana M. ; Johnson, Pieter T. J. ; Cattadori, ed., Isabella ( March 2020 , Journal of Animal Ecology)

   Community composition is driven by a few key assembly processes: ecological selection, drift and dispersal. Nested parasite communities represent a powerful study system for understanding the relative importance of these processes and their relationship with biological scale. Quantifyingβ‐diversity across scales and over time additionally offers mechanistic insights into the ecological processes shaping the distributions of parasites and therefore infectious disease.

   To examine factors driving parasite community composition, we quantified the parasite communities of 959 amphibian hosts representing two species (the Pacific chorus frog,Pseudacris regillaand the California newt,Taricha torosa) sampled over 3 months from 10 ponds in California. Using additive partitioning, we estimated how much of regional parasite richness (γ‐diversity) was composed of within‐host parasite richness (α‐diversity) and turnover (β‐diversity) at three biological scales: across host individuals, across species and across habitat patches (ponds). We also examined howβ‐diversity varied across time at each biological scale.

   Differences among ponds comprised the majority (40%) of regional parasite diversity, followed by differences among host species (23%) and among host individuals (12%). Host species supported parasite communities that were less similar than expected by null models, consistent with ecological selection, although these differences lessened through time, likely due to high dispersal rates of infectious stages. Host individuals within the same population supported more similar parasite communities than expected, suggesting that host heterogeneity did not strongly impact parasite community composition and that dispersal was high at the individual host-level. Despite the small population sizes of within‐host parasite communities, drift appeared to play a minimal role in structuring community composition.

   Dispersal and ecological selection appear to jointly drive parasite community assembly, particularly at larger biological scales. The dispersal ability of aquatic parasites with complex life cycles differs strongly across scales, meaning that parasite communities may predictably converge at small scales where dispersal is high, but may be more stochastic and unpredictable at larger scales. Insights into assembly mechanisms within multi‐host, multi‐parasite systems provide opportunities for understanding how to mitigate the spread of infectious diseases within human and wildlife hosts.

    

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5. LTP2 hypomorphs show genotype‐by‐environment interaction in early seedling traits in Arabidopsis thaliana

   https://doi.org/10.1111/nph.19334  

   Alexandre, Cristina M. ; Bubb, Kerry L. ; Schultz, Karla M. ; Lempe, Janne ; Cuperus, Josh T. ; Queitsch, Christine ( October 2023 , New Phytologist)

   Isogenic individuals can display seemingly stochastic phenotypic differences, limiting the accuracy of genotype‐to‐phenotype predictions. The extent of this phenotypic variation depends in part on genetic background, raising questions about the genes involved in controlling stochastic phenotypic variation.

   Focusing on early seedling traits inArabidopsis thaliana, we found that hypomorphs of the cuticle‐related geneLIPID TRANSFER PROTEIN 2(LTP2) greatly increased variation in seedling phenotypes, including hypocotyl length, gravitropism and cuticle permeability. Manyltp2hypocotyls were significantly shorter than wild‐type hypocotyls while others resembled the wild‐type.

   Differences in epidermal properties and gene expression betweenltp2seedlings with long and short hypocotyls suggest a loss of cuticle integrity as the primary determinant of the observed phenotypic variation. We identified environmental conditions that reveal or mask the increased variation inltp2hypomorphs and found that increased expression of its closest paralogLTP1is necessary forltp2phenotypes.

   Our results illustrate how decreased expression of a single gene can generate starkly increased phenotypic variation in isogenic individuals in response to an environmental challenge.

    

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