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1. Genetic and physiological mechanisms of freezing tolerance in locally adapted populations of a winter annual

   https://doi.org/10.1002/ajb2.1385  

   Sanderson, Brian J. ; Park, Sunchung ; Jameel, M. Inam ; Kraft, Joshua C. ; Thomashow, Michael F. ; Schemske, Douglas W. ; Oakley, Christopher G. ( November 2019 , American Journal of Botany)

   Despite myriad examples of local adaptation, the phenotypes and genetic variants underlying such adaptive differentiation are seldom known. Recent work on freezing tolerance and local adaptation in ecotypes ofArabidopsis thalianafrom Italy and Sweden provides an essential foundation for uncovering the genotype–phenotype–fitness map for an adaptive response to a key environmental stress.

   We examined the consequences of a naturally occurring loss‐of‐function (LOF) mutation in an Italian allele of the gene that encodes the transcription factorCBF2,which underlies a major freezing‐tolerance locus. We used four lines with a Swedish genetic background, each containing aLOFCBF2allele. Two lines had introgression segments containing the ItalianCBF2allele, and two contained deletions created usingCRISPR‐Cas9. We used a growth chamber experiment to quantify freezing tolerance and gene expression before and after cold acclimation.

   Freezing tolerance was lower in the Italian (11%) compared to the Swedish (72%) ecotype, and all four experimentalCBF2LOFlines had reduced freezing tolerance compared to the Swedish ecotype. Differential expression analyses identified 10 genes for which allCBF2LOFlines, and theITecotype had similar patterns of reduced cold responsive expression compared to theSWecotype.

   We identified 10 genes that are at least partially regulated byCBF2that may contribute to the differences in cold‐acclimated freezing tolerance between the Italian and Swedish ecotypes. These results provide novel insight into the molecular and physiological mechanisms connecting a naturally occurring sequence polymorphism to an adaptive response to freezing conditions.

    

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2. Physiological and regulatory underpinnings of geographic variation in reptilian cold tolerance across a latitudinal cline

   https://doi.org/10.1111/mec.14580  

   Campbell‐Staton, Shane_C ; Bare, Anna ; Losos, Jonathan_B ; Edwards, Scott_V ; Cheviron, Zachary_A ( April 2018 , Molecular Ecology)

   Understanding the mechanisms that produce variation in thermal performance is a key component to investigating climatic effects on evolution and adaptation. However, disentangling the effects of local adaptation and phenotypic plasticity in shaping patterns of geographic variation in natural populations can prove challenging. Additionally, the physiological mechanisms that cause organismal dysfunction at extreme temperatures are still largely under debate. Using the green anole,Anolis carolinensis, we integrate measures of cold tolerance (CT_min), standard metabolic rate, heart size, blood lactate concentration andRNAseq data from liver tissue to investigate geographic variation in cold tolerance and its underlying mechanisms along a latitudinal cline. We found significant effects of thermal acclimation and latitude of origin on variation in cold tolerance. Increased cold tolerance correlates with decreased rates of oxygen consumption and blood lactate concentration (a proxy for oxygen limitation), suggesting elevated performance is associated with improved oxygen economy during cold exposure. Consistent with these results, co‐expression modules associated with blood lactate concentration are enriched for functions associated with blood circulation, coagulation and clotting. Expression of these modules correlates with thermal acclimation and latitude of origin. Our findings support the oxygen and capacity‐limited thermal tolerance hypothesis as a potential contributor to variation in reptilian cold tolerance. Moreover, differences in gene expression suggest regulation of the blood coagulation cascade may play an important role in reptilian cold tolerance and may be the target of natural selection in populations inhabiting colder environments.

    

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3. Reestablishment of Protium cordatum (Burseraceae) based on integrative taxonomy

   https://doi.org/10.1002/tax.12022  

   Damasco, Gabriel ; Daly, Douglas C. ; Vicentini, Alberto ; Fine, Paul V. A. ( April 2019 , TAXON)

   Species delimitation remains a challenge worldwide, but especially in biodiversity hotspots such as the Amazon. Here, we use an integrative taxonomic approach that combines data from morphology, phylogenomics, and leaf spectroscopy to clarify the species limits within theProtium heptaphyllumspecies complex, which includes subsp.cordatum, subsp.heptaphyllum, and subsp.ulei. Molecular phylogeny indicates that populations of subsp.cordatumdo not belong to theP. heptaphyllumclade, while morphology and near‐infrared spectroscopy data provide additional support for the recognition of a separate taxon.Protium cordatum(Burseraceae) is reinstated at species rank and described in detail. As circumscribed here,P. cordatumis endemic to white‐sand savannas located in the Faro and Tucuruí Districts, Pará State, Brazil, whereasP. heptaphyllumis a dominant and widespread plant lineage found in Amazonia, the Cerrado, and the Brazilian Atlantic Forest. We present an identification key toP. cordatumand closely related lineages and a detailed taxonomic description ofP. cordatum, including habitat and distribution, a list and images of diagnostic features. This study demonstrates the importance of using multiple tools to characterize and distinguish plant species in highly diverse tropical regions.

    

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4. Assessing the factors influencing natural regeneration patterns in the diverse, multi‐cohort, and managed forests of Maine, USA

   https://doi.org/10.1111/jvs.12433  

   Bose, Arun_K ; Weiskittel, Aaron ; Wagner, Robert_G ; Kuehne, Christian ; Michalet, ed., Richard ( June 2016 , Journal of Vegetation Science)

   What are the primary biotic and abiotic factors driving composition and abundance of naturally regenerated tree seedlings across forest landscapes of Maine? Do seedling species richness (SR) and density (SD) decrease with improved growing conditions (climate and soil), but increase with increased diversity of overstorey composition and structure? Does partial harvesting disproportionately favour relative dominance of shade‐intolerant hardwoods (PIHD) over shade‐tolerant softwoods (PTSD)?

   Forest landscapes across the diverse eco‐regions and forest types of Maine,USA.

   This study usedUSDAForest Service Forest Inventory Analysis permanent plots (n = 10 842), measured every 5 yr since 1999. The best models for each response variable (SR,SD,PIHDandPTSD) were developed based onAICand biological interpretability, while considering 35 potential explanatory variables incorporating climate, soil, site productivity, overstorey structure and composition, and past harvesting.

   Mean annual temperature was the most important abiotic factor, whereas overstorey tree size diversity was the most important biotic factor forSRandSD. Both mean annual temperature and overstorey tree size diversity had a curvilinear relationship withSRandSD. Average overstorey shade tolerance and percentage tolerant softwood basal area in the overstorey were the top predictor variables ofPIHDandPTSD,respectively. Partial harvesting favouredPIHDbut notPTSD.

   This is one of the first studies to comprehensively evaluate a number of factors influencing naturally established tree seedlings at a broad landscape scale in the Northern Forest region of the easternUSAand Canada. Despite limitations associated with relatively small plot size, large seedling size class and lack of direct measurements of light, water and nutrients, this study documents the influence of these factors amid high variability associated with patterns of natural regeneration. The curvilinear relationship between mean annual temperature withSRandSDsupports the argument that species richness and abundance usually have unimodal relationships with productivity indicators, whereas the curvilinear relationship between overstorey tree size diversity andSRandSDsuggest that moderate overstorey diversity incorporates multiple species as well as higher seedling individuals.

    

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5. Morphological Analysis of Size and Shape ( MASS ): An integrative software program for morphometric analyses of leaves

   https://doi.org/10.1002/aps3.11288  

   Chuanromanee, Tya S. ; Cohen, James I. ; Ryan, Gillian L. ( September 2019 , Applications in Plant Sciences)

   Morphometric analysis is a common approach for comparing and categorizing botanical samples; however, completing a suite of analyses using existing tools may require a multi‐stage, multi‐program process. To facilitate streamlined analysis within a single program, Morphological Analysis of Size and Shape (MASS) for leaves was developed. Its utility is demonstrated using exemplar leaf samples fromAcer saccharum,Malus domestica, andLithospermum.

   Exemplar samples were obtained from across a single tree (Acer saccharum), three trees in the same species (Malus domestica), and online, digitized herbarium specimens (Lithospermum).MASSwas used to complete simple geometric measurements of samples, such as length and area, as well as geometric morphological analyses including elliptical Fourier and Procrustes analyses. Principal component analysis (PCA) of data was also completed within the same program.

   MASSis capable of making desired measurements and analyzing traditional morphometric data as well as landmark and outline data.

   UsingMASS, differences were observed among leaves of the three studied taxa, but only inMalus domesticawere differences statistically significant or correlated with other morphological features. In the future,MASScould be applied for analysis of other two‐dimensional organs and structures.MASSis available for download athttps://github.com/gillianlynnryan/MASS.

    

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