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1. Radial growth response to climate change along the latitudinal range of the world's southernmost conifer in southern South America

   https://doi.org/10.1111/jbi.13199  

   Holz, Andrés ; Hart, Sarah J. ; Williamson, Grant J. ; Veblen, Thomas T. ; Aravena, Juan C. ( March 2018 , Journal of Biogeography)

   We examined whether and how tree radial‐growth responses to climate have changed for the world's southernmost conifer species throughout its latitudinal distribution following rapid climate change in the second half of the 20th century.

   Temperate forests in southern South America.

   New and existing tree‐ring radial growth chronologies representing the entire latitudinal range ofPilgerodendron uviferumwere grouped according to latitude and then examined for differences in growth trends and non‐stationarity in growth responses to a drought severity index (scPDSI) over the 1900–1993ADperiod and also before and after significant shifts in climate in the 1950s and 1970s.

   The radial‐growth response ofP. uviferumclimate was highly variable across its full latitudinal distribution. There was a long‐term and positive association between radial growth and higher moisture at the northern and southern edges of the distribution of this species and the opposite relationship for the core of its distribution, especially following the climatic shifts of the 1950s and 1970s. In addition, non‐stationarity in moisture‐radial growth relationships was observed in all three latitudinal groups (southern and northern edges and core) for all seasons during the 20th century.

   Climate shifts in southern South America in the 1950s and 1970s resulted in different responses in the mean radial growth ofP. uviferumat the southern and northern edges and at the core of its range. Dendroclimatic analyses document that during the first half of the 20th century climate‐growth relationships were relatively similar between the southern and northern range edges but diverged after the 1950s. Our findings imply that simulated projections of climate impacts on tree growth, and by implication on forest ecosystem productivity, derived from models of past climate‐growth relationships need to carefully consider different and non‐stationarity responses along the wide latitudinal distribution of this species.

    

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2. Persistent biotic interactions of a Gondwanan conifer from Cretaceous Patagonia to modern Malesia

   https://doi.org/10.1038/s42003-020-01428-9  

   Donovan, Michael P. ; Wilf, Peter ; Iglesias, Ari ; Cúneo, N. Rubén ; Labandeira, Conrad C. ( November 2020 , Communications Biology)

   Many plant genera in the tropical West Pacific are survivors from the paleo-rainforests of Gondwana. For example, the oldest fossils of the Malesian and Australasian coniferAgathis(Araucariaceae) come from the early Paleocene and possibly latest Cretaceous of Patagonia, Argentina (West Gondwana). However, it is unknown whether dependent ecological guilds or lineages of associated insects and fungi persisted on Gondwanan host plants likeAgathisthrough time and space. We report insect-feeding and fungal damage on PatagonianAgathisfossils from four latest Cretaceous to middle Eocene floras spanning ca. 18 Myr and compare it with damage on extantAgathis. Very similar damage was found on fossil and modernAgathis, including blotch mines representing the first known Cretaceous–Paleogene boundary crossing leaf-mine association, external foliage feeding, galls, possible armored scale insect (Diaspididae) covers, and a rust fungus (Pucciniales). The similar suite of damage, unique to fossil and extantAgathis, suggests persistence of ecological guilds and possibly the component communities associated withAgathissince the late Mesozoic, implying host tracking of the genus across major plate movements that led to survival at great distances. The living associations, mostly made by still-unknown culprits, point to previously unrecognized biodiversity and evolutionary history in threatened rainforest ecosystems.

    

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3. Taxonomic decomposition of the latitudinal gradient in species diversity of North American floras

   https://doi.org/10.1111/jbi.13131  

   Weiser, Michael D. ; Swenson, Nathan G. ; Enquist, Brian J. ; Michaletz, Sean T. ; Waide, Robert B. ; Zhou, Jizhong ; Kaspari, Michael ( November 2017 , Journal of Biogeography)

   To test the latitudinal gradient in plant species diversity for self‐similarity across taxonomic scales and amongst taxa.

   North America.

   We used species richness data from 245 local vascular plant floras to quantify the slope and shape of the latitudinal gradients in species diversity (LGSD) across all plant species as well as within each family and order. We calculated the contribution of each family and order to the empiricalLGSD.

   We observed the canonicalLGSDwhen all plants were considered with floras at the lowest latitudes having, on average, 451 more species than floras at the highest latitudes. When considering slope alone, most orders and families showed the expected negative slope, but 31.7% of families and 27.7% of orders showed either no significant relationship between latitude and diversity or a reverseLGSD. Latitudinal patterns of family diversity account for at least 14% of thisLGSD. Most orders and families did not show the negative slope and concave‐down quadratic shape expected by the pattern for all plant species. A majority of families did not make a significant contribution in species to theLGSDwith 53% of plant families contributing little to nothing to the overall gradient. Ten families accounted for more than 70% of the gradient. Two families, the Asteraceae and Fabaceae, contributed a third of theLGSD.

   The empiricalLGSDwe describe here is a consequence of a gradient in the number of families and diversification within relative few plant families. Macroecological studies typically aim to generate models that are general across taxa with the implicit assumption that the models are general within taxa. Our results strongly suggest that models of the latitudinal gradient in plant species richness that rely on environmental covariates (e.g. temperature, energy) are likely not general across plant taxa.

    

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4. Analysis of condensed tannins in Populus spp. using reversed phase UPLC‐PDA‐(−)esi‐MS following thiolytic depolymerisation

   https://doi.org/10.1002/pca.2810  

   Rubert‐Nason, Kennedy F. ; Lindroth, Richard L. ( December 2018 , Phytochemical Analysis)

   Condensed tannins (CTs) are proanthocyanidin heteropolymers that are widely distributed among plants. Their biochemical properties are determined by molecular structure (e.g. polymer size, hydroxylation, stereochemistry). InPopulus, genetically and environmentally‐determined CT concentrations have been related to ecological effects, while the potential role of CT molecular structure has received little attention.

   Evaluate CT polymerisation, major constituent monomers, stereochemistry and overall content inPopulus tremuloidesfoliage using ultra‐high‐performance liquid chromatography with photodiode array and mass spectrometry (UPLC‐PDA‐(−)esi‐MS) detection following thiolytic depolymerisation of the CTs.

   CTs were extracted from dried foliage of sixP. tremuloidesgenotypes into methanol and thiolytically depolymerised into constituent monomers. Calibration standards were prepared by thiolysis of CT mixtures isolated fromP. tremuloidesfoliage on Sephadex LH‐20, followed by preparative high‐performance liquid chromatography (HPLC).

   Populus tremuloidesCTs contained predominantly repeating subunits of three putative stereoisomers each of catechin and gallocatechin. Linear calibrations for standards of these subunits and their thioethers (purities 44–87%, UPLC‐(−)esi‐MS) were generally stable over the course of 10 months. CT polymer size, hydroxylation, stereochemistry and concentrations differed among genotypes.

   This thiolysis‐UPLC‐PDA‐(−)esiMS method was optimised for analysis of CT polymer size, hydroxylation, stereochemistry, and total concentration inPopulusfoliage. It revealed significant variation in each of these properties amongP. tremuloidesgenotypes, and will facilitate evaluation of how environmental factors affect CT molecular structures.

    

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5. Refining stratigraphy and tectonic history using detrital zircon maximum depositional age: an example from the Cerro Fortaleza Formation, Austral Basin, southern Patagonia

   https://doi.org/10.1111/bre.12272  

   Sickmann, Zachary T. ; Schwartz, Theresa M. ; Graham, Stephan A. ( January 2018 , Basin Research)

   The north–south trending, Late Cretaceous to modern Magallanes–Austral foreland basin of southernmost Patagonia lacks a unified, radiometric, age‐controlled stratigraphic framework. By simplifying the sedimentary fill of the basin to deep‐marine, shallow‐marine and terrestrial deposits, and combining 13 new U‐Pb detrital zircon maximum depositional ages (DZ MDAs) with publishedDZ MDAs and U‐Pb ash ages, we provide the first attempt at a unified, longitudinal stratigraphic framework constrained by radiometric age controls. We divide the foreland basin history into two phases, including (1) an initial Late Cretaceous shoaling upward phase and (2) a Cenozoic phase that overlies a Palaeogene unconformity. NewDZsamples from the shallow‐marine La Anita Formation, the terrestrial Cerro Fortaleza Formation and several previously unrecognized Cenozoic units provide necessary radiometric age controls for the end of the Late Cretaceous foreland phase and the magnitude of the Palaeogene unconformity in the Austral sector of the basin. These samples show that the La Anita and Cerro Fortaleza Formations have CampanianDZ MDAs, and that overlying Cenozoic strata have Eocene to MioceneDZ MDAs. By filling this data gap, we are able to provide a first attempt at constructing a basinwide, age‐controlled stratigraphic framework for the Magallanes–Austral foreland basin. Results show southward progradation of shallow marine and terrestrial environments from the Santonian through the Maastrichtian, as well as a northward increase in the magnitude of the Palaeogene unconformity. Furthermore, our new age data significantly impact the chronology of fossil flora and dinosaur faunas in Patagonia.

    

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