Elevational Shifts Research Articles

Effects of climate change and land cover on the distributions of a critical tree family in the Philippines

Southeast Asian forests are dominated by the tree family Dipterocarpaceae, whose abundance and diversity are key to maintaining the structure and function of tropical forests. Like most biodiversity, dipterocarps are threatened by deforestation and climate change, so it is crucial to understand the potential impacts of these threats on current and future dipterocarp distributions. We developed species distribution models (SDMs) for 19 species of dipterocarps in the Philippines, which were projected onto current and two 2070 representative concentration pathway (RCP) climate scenarios, RCP 4.5 and 8.5. Current land cover was incorporated as a post-hoc correction to restrict projections onto intact habitats. Land cover correction alone reduced current species distributions by a median 67%, and within protected areas by 37%. After land cover correction, climate change reduced distributions by a median 16% (RCP 4.5) and 27% (RCP 8.5) at the national level, with similar losses in protected areas. There was a detectable upward elevation shift of species distributions, consisting of suitable habitat losses below 300 m and gains above 600 m. Species-rich stable areas of continued habitat suitability (i.e., climate macrorefugia) fell largely outside current delineations of protected areas, indicating a need to improve protected area planning. This study highlights how SDMs can provide projections that can inform protected area planning in the tropics.

Surface Tradeoffs and Elevational Shifts at the Largest Italian Glacier: A Thirty-Years Time Series of Remotely-Sensed Images

Biodiversity loss occurring in mountain ecosystems calls for integrative approaches to improve monitoring processes in the face of human-induced changes. With a combination of vegetation and remotely-sensed time series data, we quantitatively identify the responses of land-cover types and their associated vegetation between 1987 and 2016. Fuzzy clustering of 11 Landsat images was used to identify main land-cover types. Vegetation belts corresponding to such land-cover types were identified by using species indicator analysis performed on 80 vegetation plots. A post-classification evaluation of trends, magnitude, and elevational shifts was done using fuzzy membership values as a proxy of the occupied surfaces by land-cover types. Our findings show that forests and scrublands expanded upward as much as the glacier retreated, i.e., by 24% and 23% since 1987, respectively. While lower alpine grassland shifted upward, the upper alpine grassland lost 10% of its originally occupied surface showing no elevational shift. Moreover, an increase of suitable sites for the expansion of the subnival vegetation belt has been observed, due to the increasing availability of new ice-free areas. The consistent findings suggest a general expansion of forest and scrubland to the detriment of alpine grasslands, which in turn are shifting upwards or declining in area. In conclusion, alpine grasslands need urgent and appropriate monitoring processes ranging from the species to the landscape level that integrates remotely-sensed and field data.

Upward elevational shift by breeding Whinchat Saxicola rubetra in response to cessation of grazing in upland grassland

ABSTRACT Capsule The distribution of breeding Whinchats Saxicola rubetra shifted uphill following the cessation of grazing, potentially compromising their breeding success through additional squeezing of suitable habitat and environmental niches. Aims To assess whether breeding territories occupied by a conservation-priority grassland bird followed changes in sward structure associated with environmental exposure following cessation of grazing. Methods Whinchat territories and breeding success were monitored at upland study sites in Scotland during a period of habitat transformation from livestock-grazed grassland to young woodland with herbivores excluded. Results After grazing was excluded, there was generally an upwards elevational shift of breeding attempts by Whinchats (by 43 m in 7 years at one site). While the study sites were grazed, breeding attempts were more successful at lower elevations. After grazing ceased, there was lower breeding success at lower elevations where the resulting taller, denser vegetation likely restricted available foraging habitat. Despite that, lower areas continued to be occupied by territorial Whinchats. Conclusions The conservation of grassland birds within afforestation schemes could be supported by the maintenance of some open habitats at suitable elevations. However wider conservation of grassland birds, including within forested and pastoral high nature value farmed landscapes would benefit from a better understanding of the mechanisms operating on breeding success and habitat choice within these dynamically changing habitats.

Assessing a generic synapomorphy of Pseudodebis Forster, 1964 (Lepidoptera : Nymphalidae : Satyrinae) and a recent speciation with a shift in elevation between two new species in the western Andes

The field of systematics and our understanding of phylogenetic relationships have been invigorated by the use of molecular data, but analyses based on DNA sequence data are not always corroborated by diagnostic morphological characters. In particular, several taxonomic changes in butterflies (Papilionoidea) have been made solely on the basis of molecular data without identifying morphological synapomorphies that might have aided in diagnosing taxa from butterfly collections or specimens with no accessible DNA. We here focus on the butterfly genus Pseudodebis Forster, 1964 in the so-called ‘Taygetis clade’, which is one of the major clades in the diverse Neotropical nymphalid subtribe Euptychiina. We inferred the evolution of a male genitalic character using the most comprehensive molecular phylogeny for the ‘Taygetis clade’ to date. This approach allowed us to identify a synapomorphy for Pseudodebis Forster, 1964, which can be used to morphologically diagnose this genus and to distinguish it from other genera in the ‘Taygetis clade’. In addition, we describe two new species of Pseudodebis, P. nakamurai Nakahara & Willmott, sp. nov. and P. pieti Nakahara & Willmott, sp. nov., recovered as sister species based on molecular data, with an estimated time of divergence of 0.3 Ma (Bayesian confidence interval 0.03–1.61 Ma). Despite the low genetic divergence between these two Pseudodebis species, they can be readily distinguished by wing morphology. Pseudodebis nakamurai, sp. nov. and P. pieti, sp. nov. occur in partial sympatry across an elevational gradient along the western Andes, and the inferred recent speciation event might be related to a shift in elevation and possibly a change in larval hostplant preference. urn:lsid:zoobank.org:pub:38B4AF76-79E9-4D4D-BF16-FCD8F53A7277

FLOOD EVENTS AS GEOMORPHIC THRESHOLDS FOR CHANNEL BED LEVEL CHANGE

Channel bed levels are highly dynamic in time and across space, constantly adjusting under the influence of natural and anthropogenic controls. The aim of this study was to assess the role of flood events recorded between 1994 and 2018 in the bed elevation changes documented on the major tributaries of Trotuș River (Eastern Carpathians). To this purpose, the data from fifteen gauging stations was used, based on which the evolution trends of channel bed levels were determined for the investigated channel reaches. The role of geomorphic threshold was assigned to stream power. The daily maximum and total values of this parameter were used to explain the bed elevation shifts. The average channel bed deepening rate was 2.2 cm/yr. Depending on the variation trend of channel bed levels, three evolution patterns could be distinguished in relation to the reference year: (i) a category where channel degradation was nearly continuous; (ii) another one where initial aggradation of the channel bed occurred, ensued by continuous degradation, without reverting to the initial state, and (iii) a group with oscillating aggradation-degradation evolution resulting in the eventual recovery of the initial state. The recovery time for changes triggered by major flood events ranged between one and nearly 10 years, whereas in the case of shifts generated by high frequency, low magnitude events, the recovery time was maximum one year. Over short term flood events drive the direction and intensity of channel bed elevation adjustments.

Elevational shifts in phylogenetic diversity of angiosperm trees across the subtropical Brazilian Atlantic Forest

AbstractElevation gradients are drivers of species diversity, and, recently, studies have considered the evolutionary process in shaping community assembly patterns. Patterns of plant species richness across elevational gradients have been studied in different parts of the Atlantic Forest; however, little is known about plant phylogenetic diversity patterns. Thus, we aimed to analyse the phylogenetic diversity of angiosperm trees along an elevation gradient in southern Brazilian Plateau, in the subtropical portion of the Atlantic Forest. We expected a decrease in phylogenetic diversity along the elevation gradient, from lowlands towards to highlands, where species may be evolutionary closely related as many tropical lineages are not capable to inhabit colder conditions. We also investigated the distribution of phylogenetic clades along the elevation gradient through principal coordinates of phylogenetic structure. Data were obtained from 28 phytosociological surveys distributed across different elevation levels, ranging from 40 to 975 m. We found a negative association between phylogenetic diversity and the elevation gradient. The representativeness of families Myrtaceae and Lauraceae increased with elevation, while most of the families decreased in species richness and are replaced by temperate families such as Winteraceae (Drimys) in higher elevations. The decrease in phylogenetic diversity with increasing elevation may be linked to niche conservatism of tropical lineages that retain their historical climatic niches and thus many species are not capable to inhabit colder environments. Most tropical clades are restricted to lower elevations; however, Myrtaceae and Lauraceae probably evolved tolerance to colder temperatures during glacial cycles. Furthermore, the probably long‐term climate stability in lowlands than highland areas may have promoted the co‐occurrence of distantly related species, resulting in higher phylogenetic diversity. Finally, we observed how historical imprints and current environmental conditions shape the phylogenetic diversity of angiosperm tree species in subtropical Atlantic Forest.

Elevational gradients in constitutive and induced oak defences based on individual traits and their correlated expression patterns

Elevational gradients are useful ecological settings for revealing the biotic and abiotic drivers of plant trait variation and plant–insect interactions. However, most work focusing on plant defences has looked at individual traits and few studies have assessed multiple traits simultaneously, their correlated expression patterns, and abiotic factors associated with such patterns across elevations. To address this knowledge gap, we studied elevational variation in direct (phenolic compounds) and indirect (volatile organic compounds) constitutive defences and their inducibility after feeding by a specialist beetle Altica quercetorum in saplings of 18 wild populations of Quercus pyrenaica. We tested for: 1) clines in each defensive trait individually, 2) their patterns of correlated expression and 3) associations between any such clines and climatic factors. We found that constitutive direct defences (lignins and hydrolysable tannins) decreased with increasing elevation. We observed no elevational gradient for constitutive indirect defences (volatile organic compounds) or the inducibility of direct or indirect defensive traits when looking at groups of compounds. However, at individual tree‐level, increased induction of two monoterpenes (α‐fenchene and camphene) at higher elevation was shown. Furthermore, we show a significant pattern of co‐expression of constitutive and induced phenolics across populations, which weakened with increasing elevation. Finally, we found no evidence that climatic factors were associated with either individual or correlated trait expression patterns across elevations. Overall, these findings call for moving beyond elevational clines in individual plant defences, and argue that assessing elevational shifts in trait correlated expression patterns and their underlying mechanisms can increase our understanding of plant defence evolution and plant–herbivore interactions along environmental gradients.

Legacy effects of fish but not elevation influence lake ecosystem response to environmental change.

How communities reorganize during climate change depends on the distribution of diversity within ecosystems and across landscapes. Understanding how environmental and evolutionary history constrain community resilience is critical to predicting shifts in future ecosystem function. The goal of our study was to understand how communities with different histories respond to environmental change with regard to shifts in elevation (temperature, nutrients) and introduced predators. We hypothesized that community responses to the environment would differ in ways consistent with local adaptation and initial trait structure. We transplanted plankton communities from lakes at different elevations with and without fish in the Sierra Nevada Mountains in California to mesocosms at different elevations with and without fish. We examined the relative importance of the historical and experimental environment on functional (size structure, effects on lower trophic levels), community (zooplankton composition, abundance and biomass) and population (individual species abundance and biomass) responses. Communities originating from different elevations produced similar biomass at each elevation despite differences in species composition; that is, the experimental elevation, but not the elevation of origin, had a strong effect on biomass. Conversely, we detected a legacy effect of predators on plankton in the fishless environment. Daphnia pulicaria that historically coexisted with fish reached greater biomass under fishless conditions than those from fishless lakes, resulting in greater zooplankton community biomass and larger average size. Therefore, trait variation among lake populations determined the top-down effects of fish predators. In contrast, phenotypic plasticity and local diversity were sufficient to maintain food web structure in response to changing environmental conditions associated with elevation.

The upward elevational shifts of pond breeding amphibians following climate warming

While poorly dispersing taxa such as amphibians may have limited scope to track recent and rapid climate change by means of large range shifts, they may follow their climate envelope with short elevational shifts in mountain areas. Such elevational shifts are poorly documented by empirical data for amphibians. In this study, we analysed a 15-year data series on the distribution of three amphibian species (Bufo bufo, Triturus carnifex and Rana temporaria) inhabiting a mountain pond network in the southern Italian Alps, where temperatures have increased significantly over the last decades. By using multi-season occupancy models, we estimated the occupancy trend of each species over the study period and tested the occurrence of an actual elevational shift after accounting for the probability of false absence. The upper elevational limit of the two eurythermal species (B. bufo and T. carnifex) underwent a significant and progressive upward shift of ca. 200 m. Our results provide evidence of the ability of amphibians to perform rapid elevational shifts, great enough to track predicted rates of climate warming. Preserving and improving habitat connectivity between lowlands and highlands could safeguard the opportunity for such elevational migrations, but mountain aquatic habitats must be preserved in order to provide a safe refuge for amphibians escaping climate warming.

Bumblebees moving up: shifts in elevation ranges in the Pyrenees over 115 years.

In a warming climate, species are expected to shift their geographical ranges to higher elevations and latitudes, and if interacting species shift at different rates, networks may be disrupted. To quantify the effects of ongoing climate change, repeating historical biodiversity surveys is necessary. In this study, we compare the distribution of a plant–pollinator community between two surveys 115 years apart (1889 and 2005–06), reporting distribution patterns and changes observed for bumblebee species and bumblebee-visited plants in the Gavarnie-Gèdre commune in the Pyrenees, located in southwest Europe at the French–Spanish border. The region has warmed significantly over this period, alongside shifts in agricultural land use and forest. The composition of the bumblebee community shows relative stability, but we observed clear shifts to higher elevations for bumblebees (averaging 129 m) and plants (229 m) and provide preliminary evidence that some bumblebee species shift with the plants they visit. We also observe that some species have been able to occupy the same climate range in both periods by shifting elevation range. The results suggest the need for long-term monitoring to determine the role and impact of the different drivers of global change, especially in montane habitats where the impacts of climate changes are anticipated to be more extreme.

Resident vegetation modifies climate-driven elevational shift of a mountain sedge

Mountain plant species are changing their ranges in response to global warming. However, these shifts vary tremendously in rate, extent and direction. The reasons for this variation are yet poorly understood. A process potentially important for mountain plant re-distribution is a competition between colonizing species and the resident vegetation. Here, we focus on the impact of this process using the recent elevational shift of the sedge Carex humilis in the northern Italian Alps as a model system. We repeated and extended historical sampling (conducted in 1976) of the species in the study region. We used the historical distribution data and historical climatic maps to parameterize a species distribution model (SDM) and projected the potential distribution of the species under current conditions. We compared the historical and the current re-survey for the species in terms of the cover of important potential competitor species as well as in terms of the productivity of the resident vegetation indicated by the Normalized Difference Vegetation Index (NDVI). We found that Carex humilis has shifted its leading range margin upward rapidly (51.2 m per decade) but left many sites that have become climatically suitable since 1976 according to the SDM uncolonized. These suitable but uncolonized sites show significantly higher coverage of all dwarf shrub species and higher NDVI than the sites occupied by the sedge. These results suggest that resistance of the resident vegetation against colonization of migrating species can indeed play an important role in controlling the re-distribution of mountain plants under climate change.

Onward but not always upward: individualistic elevational shifts of tree species in subtropical montane forests

Ongoing global climate change is driving widespread shifts in species distributions. Trends show frequent upwards shifts of treelines, but information on changes in montane forest below the treeline and in the tropics and subtropics is limited, despite the importance of these areas for biodiversity and ecosystem function. Patterns of species shifts in tropical and subtropical regions are likely to be more complex and individualistic than global averages suggest due to high species diversity and strong influence of competition, alongside direct climatic limitations on distributions. To address the question of how subtropical montane tree species are likely to move as climate changes, we used an extensive national forest inventory to estimate distribution shifts of 75 tree species in Taiwan by comparing the optimum elevation and range edges of adults and juveniles within species. Overall there was a significant difference in optimum elevation of adults and juveniles. Life stage mismatches suggested upward shifts in 35% of species but downward shifts of over half (56%), while 8% appeared stable. Upward elevation shifts were disproportionately common in high elevation species, whilst mid to low elevation species suggested greater variation in shift direction. Whilst previous research on mountain forest range shifts has been dominated by work addressing changes in treeline position, we show that although high elevation species shift up, below the treeline species may shift individualistically, heralding widespread changes in forest communities over coming decades. The wide variation of responses indicated is likely driven by individual species responses to interacting environmental factors such as competition, topography and anthropogenic influences across the broad range of forest types investigated. As global environmental changes continue, more detailed understanding of tree range shifts across a wide spectrum of forests will allow us to prepare for the implications of such changes for biodiversity, ecosystem function and dependent human populations.

A disconnect between upslope shifts and climate change in an Afrotropical bird community

AbstractClimate change threatens to push species to higher elevations and eventual extinction. Birds, in particular, are shown to be shifting upslope in the Neotropics and Southeast Asia. Yet previous studies have lacked the temporal resolution to investigate distributional dynamics over time in relation to climatic fluctuations, especially in the understudied Afrotropics. Here, we used 15 years of point‐count data from across an elevational gradient (1,767–2,940 m) in Rwanda, to assess elevational shift rates and dynamics in a community of Afrotropical birds. In general, species shifted their elevations upslope by 1.9 m/year, especially at their lower elevational limits which shifted by 4.4 m/year. Importantly, these shifts occurred despite the fact that local temperature and precipitation showed little trend over the study period. Moreover, the interannual distributions of few species were associated with temperature, suggesting that temperature played little direct role in determining elevational distributions of birds. Instead, upslope shifts may be more related to incremental shifts in habitat and resources which lag behind decades of increased temperature in the region. Precipitation appeared to have more of an effect than temperature in determining interannual elevational changes, allowing species to expand their ranges in years of higher rainfall. Our results highlight the need to understand the mechanisms driving upslope shifts as they occur throughout the tropics. It will be critical for montane regions of the tropics to preserve contiguous blocks of forest across elevational gradients to allow wildlife to shift unimpeded.

Shifting aspect or elevation? The climate change response of ectotherms in a complex mountain topography

AbstractAimClimate change is expected to cause mountain species to shift their ranges to higher elevations. Due to the decreasing amounts of habitats with increasing elevation, such shifts are likely to increase their extinction risk. Heterogeneous mountain topography, however, may reduce this risk by providing microclimatic conditions that can buffer macroclimatic warming or provide nearby refugia. As aspect strongly influences the local microclimate, we here assess whether shifts from warm south‐exposed aspects to cool north‐exposed aspects in response to climate change can compensate for an upward shift into cooler elevations.LocationSwitzerland, Swiss Alps.MethodsWe built ensemble distribution models using high‐resolution climate data for two mountain‐dwelling viviparous ectotherms, the Alpine salamander and the Common lizard, and projected them into various future scenarios to gain insights into distributional changes. We further compared elevation and aspect (northness) of current and predicted future locations to analyse preferences and future shifts.ResultsFuture ranges were consistently decreasing for the lizard, but for the salamander they were highly variable, depending on the climate scenario and threshold rule. Aspect preferences were elevation‐dependent: warmer, south‐exposed microclimates were clearly preferred at higher compared to lower elevations. In terms of presence and future locations, we observed both elevational upward shifts and northward shifts in aspect. Under future conditions, the shift to cooler north‐exposed aspects was particularly pronounced at already warmer lower elevations.Main conclusionsFor our study species, shifts in aspect and elevation are complementary strategies to mitigate climatic warming in the complex mountain topography. This complements the long‐standing view of elevational upward shift being their only option to move into areas with suitable future climate. High‐resolution climate data are critical in heterogeneous environments to identify microrefugia and thereby improving future impact assessments of climate change.

Extending the climatological concept of ‘Detection and Attribution’ to global change ecology in the Anthropocene

Abstract Research into global change ecology is motivated by the need to understand the role of humans in changing biotic systems. Mechanistic understanding of ecological responses requires the separation of different climatic parameters and processes that often operate on diverse spatiotemporal scales. Yet most environmental studies do not distinguish the effects of internal climate variability from those caused by external, natural (e.g. volcanic, solar, orbital) or anthropogenic (e.g. greenhouse gases, ozone, aerosols, land‐use) forcing factors. We suggest extending the climatological concept of ‘Detection and Attribution’ (DA) to unravel abiotic drivers of ecological dynamics in the Anthropocene. We therefore apply DA to quantify the relative roles of natural versus industrial temperature change on elevational shifts in the outbreak epicentres of the larch budmoth (LBM; Zeiraphera diniana or griseana Gn.); the classic example of a cyclic forest defoliating insect. Our case study shows that anthropogenic warming shifts the epicentre of travelling LBM waves upward, which disrupts the intensity of population outbreaks that occurred regularly over the past millennium in the European Alps. Our findings demonstrate the ability of DA to detect ecological responses beyond internal system variability, to attribute them to specific external climate forcing factors and to identify climate‐induced ecological tipping points. In order to implement the climatological concept of ‘Detection and Attribution’ successfully into modern global change ecology, future studies should combine high‐resolution paleoenvironmental reconstructions and state‐of‐the‐art climate model simulations to inform inference‐based ecosystem models. A free Plain Language Summary can be found within the Supporting Information of this article.

Climate change influences on the potential distribution of Dianthus polylepis Bien. ex Boiss. (Caryophyllaceae), an endemic species in the Irano-Turanian region.

Endemic and restricted-range species are considered to be particularly vulnerable to the effects of environmental change, which makes assessing likely climate change effects on geographic distributions of such species important to the development of integrated conservation strategies. Here, we determined distributional patterns for an endemic species of Dianthus (Dianthus polylepis) in the Irano-Turanian region using a maximum-entropy algorithm. In total, 70 occurrence points and 19 climatic variables were used to estimate the potential distributional area under current conditions and two future representative concentration pathway (RCP2.6 and RCP8.5) scenarios under seven general circulation models for 2050. Mean diurnal range, iso-thermality, minimum temperature of coldest quarter, and annual precipitation were major factors that appeared to structure the distribution of the species. Most current potential suitable areas were located in montane regions. Model transfers to future-climate scenarios displayed upward shifts in elevation and northward shifts geographically for the species. Our results can be used to define high-priority areas in the Irano-Turanian region for conservation management plans for this species and can offer a template for analyses of other endangered and threatened species in the region.

Direct and Indirect Analysis of the Elevational Shift of Larch Budmoth Outbreaks Along an Elevation Gradient

Larch budmoth (LBM) periodically defoliates alpine stands of European larch during vast outbreaks occurring generally at 8-10 year intervals. LBM outbreaks recently declined and the ongoing global warming has been pointed out as a possible cause of this decline. We reconstructed the recent history of LBM outbreaks at different elevations along a larch altitudinal gradient in the French Alps using direct and indirect observations based on tree-ring width and density analysis, and compared it with local climatic data. We found that LBM outbreaks time-series were better reconstructed with latewood density than with ring width. We also found that there was a recent but limited altitudinal shift of LBM outbreaks from medium towards higher elevations. We suggest that this altitudinal shift is a consequence of the variable effect of the global warming at the different elevations. Winter warming is expected to affect differently the timing of LBM egg hatch as well as that of larch bud flush, larvae being at present susceptible to emerge whereas no needles are available as food at the former optimal altitude. A better synchronization between larch and LBM may exist at higher elevations.

Invasive fountain grass (Pennisetum setaceum (Forssk.) Chiov.) increases its potential area of distribution in Tenerife island under future climatic scenarios

Mapping the distribution of invasive species under current and future climate conditions is crucial to implement sustainable and effective conservation strategies. Several studies showed how invasive species may benefit from climate change fostering their invasion rate and, consequently, affecting the native species community. In the Canary Islands and on Tenerife in particular, previous research mostly focused on climate change impacts on the native communities, whereas less attention has been paid on alien species distribution under climate change scenarios. In this study, we modelled the habitat distribution of Pennisetum setaceum, one of the most invasive alien species on Tenerife. In addition, we described the species’ potential distribution shift in the light of two climate change scenarios (RCP2.6, RCP8.5), highlighting the areas that should be prioritized during management and eradication programs. P. setaceum’s suitable areas are located in the coastal area, with higher habitat suitability near cities and below 800 m asl. In both future climate change scenarios, the geographic distribution of P. setaceum suitable areas is characterized by an elevational shift, which is more pronounced in the RCP8.5 scenario. Despite being drought resistant, water supply is crucial for the species’ seed germination, thus supporting future species’ shift to higher elevation and in the north–north–west part of the island, where it could benefit from the combined effect of orographic precipitations and humidity carried by trade winds.

Responding to increased aridity: Evidence for range shifts in lizards across a 50-year time span in Joshua Tree National Park

North American deserts are warming and becoming more arid at rates that exceed global averages. Desert lizard populations are typically dependent on plant and arthropod food resources catalyzed by variations in aridity. Shifts in those lizard distributions coincident with increasing aridity therefore present an opportunity to document responses to modern climate change as it is happening. Here, we analyzed observation frequencies across an elevation gradient for seven lizard species, comparing a historical dataset (1958–1972) to recent observations (2014–2018) within Joshua Tree National Park, a landscape straddling the Mojave and Colorado Deserts in southern California. Phrynosoma platyrhinos, Aspidoscelis tigris, and Callisaurus draconoides, now appear to occupy new, higher elevation habitats compared to the historical baseline. Except for Sceloporus occidentalis, observation records for each species indicated shifts toward the upper elevations of their ranges. Observations for Uta stansburiana, C. draconoides and A. tigris each shifted their mean elevation upslope ≥10%. Phrynosoma platyrhinos and A. tigris shifted their maximum elevations by ≥15%. To assess whether those elevation shifts could then be corroborated with independent data, we compared the historic-recent observation data with plot-based surveys where we measured lizard densities varying with elevation and rainfall levels from 2014 to 2019. Those historical-recent shifts paralleled changes in lizard densities over the same elevation gradient, with statistical support for the upslope shifts identified for U. stansburiana, A. tigris and, S. magister. Additionally, despite increases in warming and aridity, we found species-specific elevations where local conditions are supporting higher population densities and that may represent climate refugia.

Hydrogeology and Landform Morphology Affect Plant Communities in a Great Lakes Ridge-and-Swale Wetland Complex

Trajectories of vegetative change in wetlands can be influenced strongly by shifts in water-table elevation driven by evapotranspiration and spatial-temporal variability in groundwater. The specific dynamics of such interactions are difficult to quantify because of spatial complexities associated with local climate, geomorphology, and underlying geology. Nonetheless, a better understanding of the effects of groundwater and landform pattern on plant communities in wetlands can help with future predictions of change. Over two successive growing seasons, we investigated water-balance dynamics in 15 wetlands in a forested Great Lakes coastal wetland complex consisting of relict beach ridges and intervening swales. Our goal was to explore how variation in hydrogeology and landform morphology affected plant community composition. Water-balance analyses from water-level fluctuation methods, along with interpretation of underlying stratigraphy and slope, were used to explain plant-community ordination results. Our findings showed that phreatophytic plant communities developed in locations where hydrogeology or greater slopes allowed for supplemental groundwater flow to the swales. Conversely, shallow water-table slopes maintained standing water in swales, leading to obligate wetland plant communities. This study provides a clearer representation of hydrogeologic and ecohydrologic interactions to help inform our understanding of the relationship between groundwater hydrology and plant communities in wetlands.