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1. The compounding consequences of wildfire and climate change for a high‐elevation wildflower ( Saxifraga austromontana )

   https://doi.org/10.1111/jbi.13441  

   Bloom, Trevor D. S. ; Flower, Aquila ; Medler, Michael ; DeChaine, Eric G. ( October 2018 , Journal of Biogeography)

   High‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.

   Rocky Mountain Floristic Region, western North America.

   Saxifraga austromontana(Saxifragaceae), a wildflower endemic to high elevations of the Rocky Mountain Floristic Region.

   Our approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.

   Our results indicate wildfire has significantly reduced the abundance and increased the likelihood of extirpation forS. austromontana. Increased fire frequency compounded with direct climatic changes will likely reduce the range of the species by approximately 43% by 2050 compared to 38% due to climate alone, under a moderateCO₂emissions scenario. The influence of wildfire varies regionally. For instance, the Middle Rockies will likely lose 74% of its suitable habitat of which 16% may be lost due to fire, while other regions, such as the northern range, will be less negatively affected by direct and indirect effects.

   Our evidence that increased wildfire frequency will compound the impacts of climate change on alpine taxa in North America led to the development of a new, general hypothesis on the fundamental interaction between direct and indirect effects of climate change on species range reductions.

    

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2. SNP discovery in candidate adaptive genes using exon capture in a free‐ranging alpine ungulate

   https://doi.org/10.1111/1755-0998.12560  

   Roffler, Gretchen H. ; Amish, Stephen J. ; Smith, Seth ; Cosart, Ted ; Kardos, Marty ; Schwartz, Michael K. ; Luikart, Gordon ( July 2016 , Molecular Ecology Resources)

   Identification of genes underlying genomic signatures of natural selection is key to understanding adaptation to local conditions. We used targeted resequencing to identifySNPmarkers in 5321 candidate adaptive genes associated with known immunological, metabolic and growth functions in ovids and other ungulates. We selectively targeted 8161 exons in protein‐coding and nearby 5′ and 3′ untranslated regions of chosen candidate genes. Targeted sequences were taken from bighorn sheep (Ovis canadensis) exon capture data and directly from the domestic sheep genome (Ovis ariesv. 3; oviAri3). The bighorn sheep sequences used in the Dall's sheep (Ovis dalli dalli) exon capture aligned to 2350 genes on the oviAri3 genome with an average of 2 exons each. We developed a microfluidic qPCR‐basedSNPchip to genotype 476 Dall's sheep from locations across their range and test for patterns of selection. Using multiple corroborating approaches (lositanandbayescan), we detected 28SNPloci potentially under selection. We additionally identified candidate loci significantly associated with latitude, longitude, precipitation and temperature, suggesting local environmental adaptation. The three methods demonstrated consistent support for natural selection on nine genes with immune and disease‐regulating functions (e.g. Ovar‐DRA,APC,BATF2,MAGEB18), cell regulation signalling pathways (e.g.KRIT1,PI3K,ORRC3), and respiratory health (CYSLTR1). Characterizing adaptive allele distributions from novel genetic techniques will facilitate investigation of the influence of environmental variation on local adaptation of a northern alpine ungulate throughout its range. This research demonstrated the utility of exon capture for gene‐targetedSNPdiscovery and subsequentSNPchip genotyping using low‐quality samples in a nonmodel species.

    

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3. Increasing phylogenetic stochasticity at high elevations on summits across a remote North American wilderness

   https://doi.org/10.1002/ajb2.1328  

   Marx, Hannah E. ; Richards, Melissa ; Johnson, Grahm M. ; Tank, David C. ( July 2019 , American Journal of Botany)

   At the intersection of ecology and evolutionary biology, community phylogenetics can provide insights into overarching biodiversity patterns, particularly in remote and understudied ecosystems. To understand community assembly of the high alpine flora in the Sawtooth National Forest,USA, we analyzed phylogenetic structure within and between nine summit communities.

   We used high‐throughput sequencing to supplement existing data and infer a nearly completely sampled community phylogeny of the alpine vascular flora. We calculated mean nearest taxon distance (MNTD) and mean pairwise distance (MPD) to quantify phylogenetic divergence within summits, and assessed whether maximum elevation explains phylogenetic structure. To evaluate similarities between summits, we quantified phylogenetic turnover, taking into consideration microhabitats (talus vs. meadows).

   We found different patterns of community phylogenetic structure within the six most species‐rich orders, but across all vascular plants phylogenetic structure was largely not different from random. There was a significant negative correlation between elevation and tree‐wide phylogenetic diversity (MPD) within summits: overdispersion degraded as elevation increased. Between summits, we found high phylogenetic turnover driven by greater niche heterogeneity on summits with alpine meadows.

   Our results provide further evidence that stochastic processes may also play an important role in the assembly of vascular plant communities in high alpine habitats at regional scales. However, order‐specific patterns suggest that adaptations are still important for assembly of specific sectors of the plant tree of life. Further studies quantifying functional diversity will be important in disentangling the interplay of eco‐evolutionary processes that likely shape broad community phylogenetic patterns in extreme environments.

    

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4. Plant community response to Artemisia rothrockii (sagebrush) encroachment and removal along an arid elevational gradient

   https://doi.org/10.1111/jvs.12669  

   Kopp, Christopher W. ; Cleland, Elsa E. ; Kikvidze, ed., Zaal ( August 2018 , Journal of Vegetation Science)

   Shrub expansion into alpine ecosystems worldwide raises important questions regarding the influence of shrub encroachment on alpine species diversity. The stress gradient hypothesis (SGH) predicts interactions will be competitive when resources are plentiful and the environment is benign, but that facilitative interactions will dominate when conditions are stressful. We asked howArtemisia rothrockii(sagebrush) encroachment in an arid mountain range is affecting alpine plant species there and how the plant community responds to the experimental removal of sagebrush at three sites along an elevational gradient.

   The White Mountains, California,USA(37°30′N, 118°10′W).

   A shrub removal experiment was established at three elevations (2,900, 3,100 and 3,750 m) to evaluate how sagebrush interacts with alpine and sub‐alpine plant communities.

   The study sites experienced a strong drought over the 4 yrs of the experiment and plant cover declined overall. However, in the sagebrush removal treatment, cover of co‐occurring species increased at both the high‐elevation and low‐elevation sites, with no differences observed at the mid‐elevation site.

   We observed the greatest inhibitory effects of sagebrush at high and low elevations, where plants experience the largest temperature and moisture stress, respectively, and no evidence of facilitation anywhere along the elevational gradient. These results demonstrate that while sagebrush has important influences on herbaceous species composition in the White Mountains, they are inconsistent with the classic predictions of theSGH.

    

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5. 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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