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1. Novel biogeographic patterns across latitudinal and elevational gradients: A case study with tropical montane epiphytes lends insights to conservation

   https://doi.org/10.1111/jbi.14059  

   Hollenbeck, Emily C. ; Sax, Dov F. ( February 2021 , Journal of Biogeography)

   While latitudinal and elevational gradients of range size have been thoroughly studied, the ways these gradients might interact with each other to shape species distributions in complex montane environments are not well understood. We examined how elevational and latitudinal gradients interact to structure individual species’ distributions and larger geographic range size patterns.

   Neotropics.

   Two epiphytic plant genera:PeperomiaandElaphoglossum.

   We compiled 35,382 GBIF records for 505 species, calculated species’ latitudinal and elevational range extents, and examined gradients in richness and range size. For individual species, we analysed the relationship between elevational and latitudinal occurrences.

   Approximately 50% of species demonstrate a significant, negative relationship between their elevational and latitudinal occurrences; most of these species occupy a non‐random, relatively narrow range of mean annual temperatures across their latitudinal distribution. Across species there is a positive relationship between latitudinal and elevational extent, a phenomenon we hereafter refer to as ‘Stevens’ pattern’. Average latitudinal extent of species’ ranges increased at higher latitudes, in support of Rapoport's rule. Average elevational extent increased with elevation in the global dataset (consistent with Rapoport's elevational rule), but most subsets of the data demonstrated a peak in average extent size at mid‐elevations.

   The prevalence of species with negative elevation‐by‐latitude relationships, along with their non‐random tracking of temperature, suggests that many tropical species with broad geographic distributions are more temperature sensitive than their broad ranges might otherwise suggest. Consequently, even tropical species that occur across a wide range of latitudes and elevations might be threatened by climate change. These wide‐ranging species drive the occurrence of two biogeographic patterns: Rapoport's elevational rule and Stevens’ pattern. Finally, while Rapoport's rule and its elevational corollary were supported in part, the unexpected occurrence of many species restricted to high elevations near the equator suggests a possible focus for conservation effort.

    

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2. Demography across latitudinal and elevational gradients for range-expanding whelks

   https://doi.org/10.3354/meps14349  

   Waite, HR ; Beshai, RA ; Sorte, CJB ( February 2024 , Marine Ecology Progress Series)

   Marine species worldwide are responding to ocean warming by shifting their ranges to new latitudes and, for intertidal species, elevations. Demographic traits can vary across populations spanning latitudinal and elevational ranges, with impacts on population growth. Understanding how demography varies across gradients from range center to edge could help us predict future shifts, species assemblages, and extinction risks. We investigated demographic traits for 2 range-expanding whelk species:Acanthinucella spirataandMexacanthina lugubris.We measured reproductive output across environmental (latitudinal and shore elevation) gradients along the coast of California, USA. We also conducted intensive measurements of offspring condition (survival and thermal tolerance) across shore elevation forM. lugubrisat one site. We found no difference in reproductive output, body size, or larval survival across shore heights forM. lugubris,suggesting that egg-laying behavior buffers developing stages from the relatively high level of thermal variation experienced due to daily tidal emersion. However, across latitudes, reproductive output increased toward the leading range edge forA. spirata, and body size increased for both species. Increased vital rates at the leading range edge could increase whelk population growth and expansion, allowing species to persist under climate change even if contractions occur at trailing edges.

    

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3. Elevational range sizes of woody plants increase with climate variability in the Tropical Andes

   https://doi.org/10.1111/jbi.14783  

   Montaño‐Centellas, Flavia ; Fuentes, Alfredo F. ; Cayola, Leslie ; Macía, Manuel J. ; Arellano, Gabriel ; Loza, M. Isabel ; Nieto‐Ariza, Beatriz ; Tello, J. Sebastián ( December 2023 , Journal of Biogeography)

   The climate variability hypothesis proposes that species subjected to wide variation in climatic conditions will evolve wider niches, resulting in larger distributions. We test this hypothesis in tropical plants across a broad elevational gradient; specifically, we use a species‐level approach to evaluate whether elevational range sizes are explained by the levels of thermal variability experienced by species.

   Central Andes.

   Present day.

   Woody plants.

   Combining data from 479 forest plots, we determined the elevational distributions of nearly 2300 species along an elevational gradient (~209–3800 m). For each species, we calculated the maximum annual variation in temperature experienced across its elevational distribution. We used phylogenetic generalized least square models to evaluate the effect of thermal variability on range size. Our models included additional covariates that might affect range size: body size, local abundance, mean temperature and total precipitation. We also considered interactions between thermal variability and mean temperature or precipitation. To account for geometric constraints, we repeated our analyses with a standardized measure of range size, calculated by comparing observed range sizes with values obtained from a null model.

   Our results supported the main prediction of the climate variability hypothesis. Thermal variability had a strong positive effect on the range size, with species exposed to higher thermal variability having broader elevational distributions. Body size and local abundance also had positive, yet weak effects, on elevational range size. Furthermore, there was a strong positive interaction between thermal variability and mean annual temperature.

   Thermal variability had an overriding importance in driving elevational range sizes of woody plants in the Central Andes. Moreover, the relationship between thermal variability and range size might be even stronger in warmer regions, underlining the potential vulnerability of tropical montane floras to the effects of global warming.

    

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4. Factors affecting the nesting success of Swainson's Thrush ( Catharus ustulatus ) along an elevational gradient

   https://doi.org/10.1002/ece3.10738  

   Deckel, Sarah_C ; DeLuca, William_V ; Gerson, Alexander_R ; King, David_I ( January 2024 , Ecology and Evolution)

   Montane birds experience a range of challenges that may limit their breeding success, including nest predation and severe climactic conditions. The continuing effects of climate change are causing shifts in biotic and abiotic factors that may compound these threats to montane bird species. In northeastern montane forests, many bird species are shifting downslope, potentially as the result of increased precipitation and temperature at higher elevations. Although lower elevations might be more favorable in terms of climactic conditions, nest predation is higher at lower elevations. Thus, montane birds might be faced with the opposing pressures of adverse climactic conditions at higher elevations and increased predation at lower elevations. We monitored nests of Swainson's Thrush (Catharus ustulatus) along an elevation gradient in the White Mountain National Forest in New Hampshire in 2016, 2018, 2019, and 2021 to examine the effect of biotic and abiotic factors on daily nest survival rate (DSR). Linear time explained the most variation of DSR in AICc model comparison, indicating that DSR decreases across the breeding season. Rain intensity (mm/h) had a weak negative effect on DSR, indicating that heavier rain per hour decreases Swainson's Thrush DSR. Moreover, we found some support for a negative interaction effect of elevation in conjunction with minimum daily temperature: DSR of Swainson's Thrush nests at low elevations (281 m) increased with increasing minimum daily temperatures and decreased at high elevations with increasing minimum daily temperatures. Our results suggest nesting survival of montane breeding birds may be at risk as heavier precipitation events become more frequent and intense due to the changing climate and raises the possibility that other passerine species could be at risk in this system.

    

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5. Environmental variability shapes evolution, plasticity and biogeographic responses to climate change

   https://doi.org/10.1111/geb.12953  

   Buckley, Lauren B. ; Kingsolver, Joel G. ; Hampe, ed., Arndt ( June 2019 , Global Ecology and Biogeography)

   We examine how environmental variability at seasonal and interannual time‐scales influences evolutionary trajectories and the role of plasticity in response to recent and future climate change at biogeographic scales. We investigate the interplay of selection pressures at chronic (performance) and acute (thermal stress) time‐scales.

   Colorado, USA.

   1950–2099.

   A montane butterfly, clouded sulphur (Colias eriphyleW.H. Edwards, 1876).

   We leverage field and laboratory data to construct phenotype‐based models that predict fitness and evolutionary responses to recent and future climate change. Our focal phenotype, wing solar absorptivity, responds plastically to developmental (pupal) temperatures and determines adult fitness via its influence on body temperature.

   We project that phenology accelerates with decreasing elevation and climate change, but gradients in pupal and adult temperature with climate change are modest. Fitness of the first generation is predicted to decrease at low elevations and increase at high elevations with warming. Elevational clines in optimal wing absorptivity shift towards lower absorptivities with warming. We project that temporal shifts from selection for wing darkening (to extend flight time) to selection for wing lightening (to avoid overheating) in some cool, montane locations will ultimately impose fitness costs.

   Our analysis suggests that shifts in the balance of selection between acute and chronic responses to environmental variation will alter biogeographic responses to climate change. Evolutionary lags may ultimately confer greater sensitivity to climate change, but plasticity can reduce evolutionary lags by facilitating trait evolution.

    

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