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1. Climate‐driven range shifts of montane species vary with elevation

   https://doi.org/10.1111/geb.13246  

   Mamantov, Margaret A. ; Gibson‐Reinemer, Daniel K. ; Linck, Ethan B. ; Sheldon, Kimberly S. ; Lenoir, ed., Jonathan ( January 2021 , Global Ecology and Biogeography)

   In response to warming, species are shifting their ranges towards higher elevations. These elevational range shifts have been documented in a variety of taxonomic groups across latitude. However, the rate and direction of species range shifts in response to warming vary, potentially as a consequence of variation in species traits across elevation. Specifically, diurnal and seasonal climates are often more variable at higher elevations, which results in high‐elevation species that have broader thermal physiologies relative to low‐elevation species. High‐elevation species that are thermal generalists might not need to move as far to track their thermal niche as low‐elevation thermal specialists. We investigated whether rates of range shifts varied systematically with increasing elevation across taxa and regions.

   Sixteen montane regions world‐wide.

   1850–2013.

   Nine hundred and eighty‐seven species of plants and animals.

   We gathered published data on elevational range shifts from 20 transect studies comparing historical and recent distributions and examined how rates of range shifts changed across elevation. Specifically, we performed a meta‐analysis to calculate the pooled effect of elevation on species range shifts.

   We found that rates of range shifts show a negative relationship with elevation such that low‐elevation species have moved upslope farther than high‐elevation species on the same transect. This finding was primarily a result of shifts in the upper range limits. We also found that 28% of species shifted downslope against predictions, but elevation did not show a relationship with downslope range shifts.

   Idiosyncratic range shifts will significantly alter montane ecological communities, which are home to some of the greatest biodiversity on Earth. Our results demonstrate that species range shifts vary with elevation and might be a consequence of differences in species traits that also vary along montane gradients.

    

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2. Why is fruit colour so variable? Phylogenetic analyses reveal relationships between fruit‐colour evolution, biogeography and diversification

   https://doi.org/10.1111/geb.12900  

   Lu, Lu ; Fritsch, Peter W. ; Matzke, Nicholas J. ; Wang, Hong ; Kron, Kathleen A. ; Li, De‐Zhu ; Wiens, John J. ; Meiri, ed., Shai ( March 2019 , Global Ecology and Biogeography)

   Are different fruit colours related to large‐scale patterns of dispersal, distribution and diversification? Here, we investigate this question for the first time, using phylogenetic approaches in the tribe Gaultherieae (Ericaceae). We test relationships between fruit colour and (a) biogeographic dispersal, (b) elevational and latitudinal species distributions and (c) rates of diversification.

   Global.

   Recent to 30 million years ago.

   The plant tribe Gaultherieae in the family Ericaceae (blueberries and relatives).

   We estimated a new time‐calibrated phylogeny for Gaultherieae. Data on fruit colours and geographic distributions for each species were compiled from published sources and field observations. Using phylogenetic methods, we estimated major dispersal events across the tree and the most likely fruit colour associated with each dispersal event, and tested whether dispersal between major biogeographic regions was equally likely for different fruit colours, and whether dispersal distances were larger for certain colours. We then tested the relationships between fruit colours and geographic variables (latitude, elevation) and diversification rates.

   Large‐scale dispersal events were significantly associated with red‐fruited lineages, even though red‐fruited species were relatively uncommon. Further, different fruit colours were associated with different elevations and latitudes (e.g. red at lower elevations, violet at lower latitudes, white at higher elevations). Violet colour was related to increased diversification rates, leading to more violet‐fruited species globally.

   Overall, we show that different fruit colours can significantly impact the large‐scale dispersal, distribution and diversification of plant clades. Furthermore, the interplay between biogeography and fruit‐colour evolution seems to generate “taxon cycles” in fruit colour that may drive variation in fruit colour over macroevolutionary time‐scales.

    

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3. Factors influencing distributional shifts and abundance at the range core of a climate‐sensitive mammal

   https://doi.org/10.1111/gcb.15793  

   Billman, Peter D. ; Beever, Erik A. ; McWethy, David B. ; Thurman, Lindsey L. ; Wilson, Kenneth C. ( July 2021 , Global Change Biology)

   Species are frequently responding to contemporary climate change by shifting to higher elevations and poleward to track suitable climate space. However, depending on local conditions and species’ sensitivity, the nature of these shifts can be highly variable and difficult to predict. Here, we examine how the American pika (Ochotona princeps), a philopatric, montane lagomorph, responds to climatic gradients at three spatial scales. Using mixed‐effects modeling in an information‐theoretic approach, we evaluated a priori model suites regarding predictors of site occupancy, relative abundance, and elevational‐range retraction across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains of North America, during 2017–2020. The top environmental predictors differed across these response metrics. Warmer temperatures in summer and winter were associated with lower occupancy, lower relative abundances, and greater elevational retraction across watersheds. Occupancy was also strongly influenced by habitat patch size, but only when combined with climate metrics such as actual evapotranspiration. Using a second analytical approach, acute heat stress and summer precipitation best explained retraction residuals (i.e., the relative extent of retraction given the original elevational range of occupancy). Despite the study domain occurring near the species’ geographic‐range center, where populations might have higher abundances and be at lower risk of climate‐related stress, 33.9% of patches showed evidence of recent extirpations. Pika‐extirpated sites averaged 1.44℃ warmer in summer than did occupied sites. Additionally, the minimum elevation of pika occupancy has retracted upslope in 69% of watersheds (mean: 281 m). Our results emphasize the nuance associated with evaluating species’ range dynamics in response to climate gradients, variability, and temperature exceedances, especially in regions where species occupy gradients of conditions that may constitute multiple range edges. Furthermore, this study highlights the importance of evaluating diverse drivers across response metrics to improve the predictive accuracy of widely used, correlative models.

    

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4. Machine learning and phylogenetic models identify predictors of genetic variation in Neotropical amphibians

   https://doi.org/10.1111/jbi.14795  

   Amador, Luis ; Arroyo‐Torres, Irvin ; Barrow, Lisa N. ( January 2024 , Journal of Biogeography)

   Intraspecific genetic variation is key for adaptation and survival in changing environments and is known to be influenced by many factors, including population size, dispersal and life‐history traits. We investigated genetic variation within Neotropical amphibian species to provide insights into how natural history traits, phylogenetic relatedness, climatic and geographic characteristics can explain intraspecific genetic diversity.

   Neotropics.

   Amphibians.

   We assembled data sets using open‐access databases for natural history traits, genetic sequences, phylogenetic trees, climatic and geographic data. For each species, we calculated overall nucleotide diversity (π) and tested for isolation by distance (IBD) and isolation by environment (IBE). We then identified predictors ofπ, IBD and IBE using random forest (RF) regression or RF classification. We also fitted phylogenetic generalized linear mixed models (PGLMMs) to predictπ, IBD and IBE.

   We compiled 4052 mitochondrial DNA sequences from 256 amphibian species (230 frogs and 26 salamanders), georeferencing 2477 sequences from 176 species that were not linked to occurrence data. RF regressions and PGLMMs were congruent in identifying range size and precipitation (σ) as the most important predictors ofπ, influencing it positively. RF classification and PGLMMs identified minimum elevation as an important predictor of IBD; most species without IBD tended to occur at higher elevations. Maximum latitude and precipitation (σ) were the best predictors of IBE, and most species without IBE occur at lower latitudes and in areas with more variable precipitation.

   This study identified predictors of genetic variation in Neotropical amphibians using both machine learning and phylogenetic methods. This approach was valuable to determine which predictors were congruent between methods. We found that species with small ranges or living in zones with less variable precipitation tended to have low genetic diversity. We also showed that Western Mesoamerica, Andes and Atlantic Forest biogeographic units harbour high diversity across many species that should be prioritized for protection. These results could play a key role in the development of conservation strategies for Neotropical amphibians.

    

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5. Human trampling disturbance exerts different ecological effects at contrasting elevational range limits

   https://doi.org/10.1111/1365-2664.13384  

   Chardon, Nathalie Isabelle ; Rixen, Christian ; Wipf, Sonja ; Doak, Daniel Forest ; Pauchard, ed., Anibal ( April 2019 , Journal of Applied Ecology)

   Shifts in species geographic distributions in response to climate change have spurred numerous studies to determine which abiotic (e.g. climatic) and, less commonly, biotic (e.g. competitive) processes determine range limits. However, the impact of disturbances on range limits and their interactions with climatic and biotic effects is not well understood, despite their potential to alter competitive relationships between species or override climatic effects. Disturbance might have differential effects at contrasting range limits, based on Darwin's theory that biotic interactions set abiotically benign range limits and abiotic factors set abiotically stressful range limits.

   We predicted that plants at lower elevation (abiotically benign) range limits experience a net positive effect of disturbance, whereas those at higher elevation (abiotically stressful) range limits experience a net neutral effect. We examined plant populations along elevational gradients in the Colorado Rocky Mountains, in order to quantify the effects of human trampling disturbance at lower and upper elevational range limits of the common alpine cushion plantsSilene acaulisandMinuartia obtusiloba.

   Our results are consistent with Darwin's theory. A disturbance‐mediated reduction of competitive effects increases the performance of cushion plants at lower elevations, suggesting a range limit set by biotic factors. At higher elevations, where biotic interactions are minimal, disturbance has neutral or negative effects on cushion plants.

   Synthesis and applications. Human trampling disturbance exerts differential effects on alpine cushion plant populations at contrasting range limits, emphasizing the need to account for the effects of climate change into the management and conservation of disturbed areas. Disturbance can diminish plant–plant competitive interactions at lower elevational range limits, and thus possibly stabilize alpine species populations susceptible to climate change‐mediated encroachment by lower elevation species. Conservation and management approaches should therefore particularly account for the differential effects of disturbance across climatic gradients.

    

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