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1. Extreme copy number variation at a tRNA ligase gene affecting phenology and fitness in yellow monkeyflowers

   https://doi.org/10.1111/mec.14904  

   Nelson, Thomas C.; Monnahan, Patrick J.; McIntosh, Mariah K.; Anderson, Kayli; MacArthur‐Waltz, Evan; Finseth, Findley R.; Kelly, John K.; Fishman, Lila (December 2018, Molecular Ecology)

   Abstract Copy number variation (CNV) is a major part of the genetic diversity segregating within populations, but remains poorly understood relative to single nucleotide variation. Here, we report on atRNAligase gene (Migut.N02091;RLG1a) exhibiting unprecedented, and fitness‐relevant,CNVwithin an annual population of the yellow monkeyflowerMimulus guttatus.RLG1a variation was associated with multiple traits in pooled population sequencing (PoolSeq) scans of phenotypic and phenological cohorts. Resequencing of inbred lines revealed intermediate‐frequency three‐copy variants ofRLG1a (trip+;5/35 = 14%), andtrip+lines exhibited elevatedRLG1a expression under multiple conditions.trip+carriers, in addition to being over‐represented in late‐flowering and large‐flowered PoolSeq populations, flowered later under stressful conditions in a greenhouse experiment (p < 0.05). In wild population samples, we discovered an additional rareRLG1a variant (high+) that carries 250–300 copies ofRLG1a totalling ~5.7 Mb (20–40% of a chromosome). In the progeny of ahigh+carrier, Mendelian segregation of diagnostic alleles andqPCR‐based copy counts indicate thathigh+is a single tandem array unlinked to the single‐copyRLG1a locus. In the wild,high+carriers had highest fitness in two particularly dry and/or hot years (2015 and 2017; bothp < 0.01), while single‐copy individuals were twice as fecund as eitherCNVtype in a lush year (2016:p < 0.005). Our results demonstrate fluctuating selection onCNVs affecting phenological traits in a wild population, suggest that planttRNAligases mediate stress‐responsive life‐history traits, and introduce a novel system for investigating the molecular mechanisms of gene amplification. 

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2. Within‐species patterns challenge our understanding of the leaf economics spectrum

   https://doi.org/10.1111/ele.12945  

   Anderegg, Leander D. L.; Berner, Logan T.; Badgley, Grayson; Sethi, Meera L.; Law, Beverly E.; HilleRisLambers, Janneke; Penuelas, ed., Josep (March 2018, Ecology Letters)

   Abstract The utility of plant functional traits for predictive ecology relies on our ability to interpret trait variation across multiple taxonomic and ecological scales. Using extensive data sets of trait variation within species, across species and across communities, we analysed whether and at what scales leaf economics spectrum (LES) traits show predicted trait–trait covariation. We found that most variation inLEStraits is often, but not universally, at high taxonomic levels (between families or genera in a family). However, we found that trait covariation shows distinct taxonomic scale dependence, with some trait correlations showing opposite signs within vs. across species.LEStraits responded independently to environmental gradients within species, with few shared environmental responses across traits or across scales. We conclude that, at small taxonomic scales, plasticity may obscure or reverse the broad evolutionary linkages between leaf traits, meaning that variation inLEStraits cannot always be interpreted as differences in resource use strategy. 

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3. Anatomical changes with needle length are correlated with leaf structural and physiological traits across five Pinus species

   https://doi.org/10.1111/pce.13516  

   Wang, Na; Palmroth, Sari; Maier, Christopher_A; Domec, Jean‐Christophe; Oren, Ram (February 2019, Plant, Cell & Environment)

   Abstract The genusPinushas wide geographical range and includes species that are the most economically valued among forest trees worldwide. Pine needle length varies greatly among species, but the effects of needle length on anatomy, function, and coordination and trade‐offs among traits are poorly understood. We examined variation in leaf morphological, anatomical, mechanical, chemical, and physiological characteristics among five southern pine species:Pinus echinata,Pinus elliottii,Pinus palustris,Pinus taeda, andPinus virginiana. We found that increasing needle length contributed to a trade‐off between the relative fractions of support versus photosynthetic tissue (mesophyll) across species. From the shortest (7 cm) to the longest (36 cm) needles, mechanical tissue fraction increased by 50%, whereas needle dry density decreased by 21%, revealing multiple adjustments to a greater need for mechanical support in longer needles. We also found a fourfold increase in leaf hydraulic conductance over the range of needle length across species, associated with weaker upward trends in stomatal conductance and photosynthetic capacity. Our results suggest that the leaf size strongly influences their anatomical traits, which, in turn, are reflected in leaf mechanical support and physiological capacity. 

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4. Thermal niche variation among individuals of the poison frog, Oophaga pumilio , in forest and converted habitats

   https://doi.org/10.1111/btp.12691  

   Rivera‐Ordonez, Juana M.; Justin Nowakowski, A.; Manansala, Adrian; Thompson, Michelle E.; Todd, Brian D. (August 2019, Biotropica)

   Abstract The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog,Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (T_b), preferred body temperatures (T_pref), critical thermal maxima (CT_max), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater meanT_bandT_prefthan those from forests. In contrast,CT_maxandTSMdid not differ significantly between habitats. However,CT_maxdid increase moderately with increasingT_b, suggesting that changes inCT_maxmay be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. AlthoughO. pumilioexhibited moderate divergence inT_pref,CT_maxappears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain theirT_bbelow air temperatures that reach or exceedCT_max. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming. Abstract in Spanish is available with online material. 

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5. Using multirate rapid A / C _i curves as a tool to explore new questions in the photosynthetic physiology of plants

   https://doi.org/10.1111/nph.15657  

   Stinziano, Joseph R.; Adamson, Rachael K.; Hanson, David T. (January 2019, New Phytologist)

   Summary Steady‐state photosyntheticCO₂responses (A/C_icurves) are used to assess environmental responses of photosynthetic traits and to predict future vegetative carbon uptake through modeling. The recent development of rapidA/C_icurves (RACiRs) permits faster assessment of these traits by continuously changing [CO₂] around the leaf, and may reveal additional photosynthetic properties beyond what is practical or possible with steady‐state methods.Gas exchange necessarily incorporates photosynthesis and (photo)respiration. Each process was expected to respond on different timescales due to differences in metabolite compartmentation, biochemistry and diffusive pathways. We hypothesized that metabolic lags in photorespiration relative to photosynthesis/respiration andCO₂diffusional limitations can be detected by varying the rate of change in [CO₂] duringRACiR assays. We tested these hypotheses through modeling and experiments at ambient and 2% oxygen.Our data show that photorespiratory delays cause offsets in predictedCO₂compensation points that are dependent on the rate of change in [CO₂]. Diffusional limitations may reduce the rate of change in chloroplastic [CO₂], causing a reduction in apparentRACiR slopes under highCO₂ramp rates.MultirateRACiRs may prove useful in assessing diffusional limitations to gas exchange and photorespiratory rates. 

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