scholarly journals Dehydration Alters Behavioral Thermoregulation and the Geography of Climatic Vulnerability in Amazonian Lizards

2021 ◽  
Author(s):  
Agustín Camacho ◽  
Tuliana O. Brunes ◽  
Miguel Trefaut Rodrigues
Keyword(s):  
Amazon Basin ◽  
Tree Cover ◽  
Behavioral Thermoregulation ◽  
Heating Rates ◽  
Lizard Species ◽  
Climatic Risk ◽  
Simple Mapping ◽  
Thermal Risk ◽  
Start Temperature ◽  
Modelling Approaches

Abstract Since high temperatures and low water availability often strike organisms in parallel, observing how they behaviorally thermohydroregulate may help us to better understand their climatic vulnerability. This understanding is especially important for tropical lizards, purportedly under greater climatic risk. We observed the influence of hydration level on the Voluntary Thermal Maximum (VTM) of two small amazonian lizard species: Loxopholis ferreirai (semiaquatic and scansorial) and Loxopholis percarinatum (leaf litter parthenogenetic dweller), accounting for several sources of variation (turn, body weight, start temperature and heating rate). Then, we used two modelling approaches (simple mapping of thermal margins and NicheMapR), to examine the effects of dehydration, decrease in rainfall, ability to burrow, and tree cover availability, on the geography of climatic vulnerability. Dehydration decreased the VTM in both species, which also reacted to start temperature and heating rates. Our two modelling approaches show that dehydration, changes the intensity, extent and duration of thermal risk across the Amazon basin. Based on our results and previous studies, we identify new evidence needed to better understand thermohydroregulation and model the geography of climatic risk, more realistically.

scholarly journals Vulnerability to climate change of a microendemic lizard species from the central Andes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Laspiur ◽  
J. C. Santos ◽  
S. M. Medina ◽  
J. E. Pizarro ◽  
E. A. Sanabria ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Distribution Models ◽  
Activity Patterns ◽  
Geographic Range ◽  
Behavioral Thermoregulation ◽  
Rapid Loss ◽  
Distribution Models ◽  
Lizard Species ◽  
Vulnerability To Climate Change

AbstractGiven the rapid loss of biodiversity as consequence of climate change, greater knowledge of ecophysiological and natural history traits are crucial to determine which environmental factors induce stress and drive the decline of threatened species. Liolaemus montanezi (Liolaemidae), a xeric-adapted lizard occurring only in a small geographic range in west-central Argentina, constitutes an excellent model for studies on the threats of climate change on such microendemic species. We describe field data on activity patterns, use of microhabitat, behavioral thermoregulation, and physiology to produce species distribution models (SDMs) based on climate and ecophysiological data. Liolaemus montanezi inhabits a thermally harsh environment which remarkably impacts their activity and thermoregulation. The species shows a daily bimodal pattern of activity and mostly occupies shaded microenvironments. Although the individuals thermoregulate at body temperatures below their thermal preference they avoid high-temperature microenvironments probably to avoid overheating. The population currently persists because of the important role of the habitat physiognomy and not because of niche tracking, seemingly prevented by major rivers that form boundaries of their geographic range. We found evidence of habitat opportunities in the current range and adjacent areas that will likely remain suitable to the year 2070, reinforcing the relevance of the river floodplain for the species’ avoidance of extinction.

scholarly journals Different environmental gradients affect different measures of snake β-diversity in the Amazon rainforests

2018 ◽  
Author(s):  
Rafael de Fraga ◽  
Miquéias Ferrão ◽  
Adam J Stow ◽  
William E Magnusson ◽  
Albertina P Lima
Keyword(s):  
Amazon Basin ◽  
Prey Availability ◽  
Environmental Gradients ◽  
Geographic Distance ◽  
Clay Content ◽  
Tree Cover ◽  
Β Diversity ◽  
Temperature And Precipitation ◽  
Nesting Sites ◽  
Conservation Actions

Mechanisms generating and maintaining biodiversity at regional scales may be evaluated by quantifying β-diversity along environmental gradients. Differences in assemblages result in biotic complementarities and redundancies among sites, which may be quantified through multi-dimensional approaches incorporating taxonomic β-diversity (TBD), functional β-diversity (FBD) and phylogenetic β-diversity (PBD). Here we test the hypothesis that snake TBD, FBD and PBD are influenced by environmental gradients, independently of geographic distance. The gradients tested are expected to affect snake assemblages indirectly, such as clay content in the soil determining primary production and Height Above the Nearest Drainage (HAND) determining prey availability, or directly, such as percentage of tree cover determining availability of resting and nesting sites, and climate (temperature and precipitation) causing physiological filtering. We sampled snakes in 21 sampling plots, each covering 5 km2, distributed over 880 km in the central-southern Amazon Basin. We used dissimilarities between sampling sites to quantify TBD, FBD and PBD, which were response variables in multiple-linear-regression and RDA models. We show that patterns of snake community composition based on TBD, FBD and PBD are associated with environmental heterogeneity in the Amazon. Despite positive correlations between all β-diversity measures, TBD responded to different environmental gradients compared to FBD and PBD. Our findings suggest that multi-dimensional approaches are more informative for ecological studies and conservation actions compared to a single diversity measure.

scholarly journals Experiments on the effect of tropical Atlantic heating anomalies upon GCM rain forecasts over the Americas

1990 ◽  
Vol 13 ◽  
pp. 57-67
Author(s):  
Julio Buchmann ◽  
Lawrence E. Buja ◽  
Jan Paegle ◽  
Robert E. Dickinson
Keyword(s):  
General Circulation ◽  
Amazon Basin ◽  
Circulation Model ◽  
Real Data ◽  
Forecast Model ◽  
South American ◽  
Tropical Atlantic ◽  
Heating Rates ◽  
The Pacific ◽  
Dominant Influence

A series of real data experiments is performed with a general circulation model in order to ascertain the sensitivity of extended range rain forecasts over the Americas to the structure and magnitude of tropical heating anomalies. The emphasis is upon heat inputs over the tropical Atlantic which have shown particularly significant drying influences over North America in our prior simulations. The heating imposed in the prior experiments is compared to the condensation heating rates that naturally occur in the forecast model, and shown to be excessive by approximately a factor of two. Present experiments reduce the imposed anomaly by a factor of three, and also incorporate sea-surface temperature decreases over the eastern tropical Pacific Ocean. The new experimental results are in many ways consistent with our prior results. The dry North American response is statistically more significant than the South American response, and occurs at least as frequently in the different members of the experimental ensembles as in our prior experiments. The drying effect is accentuated by the presence of East Pacific cooling, but this does not appear to be the dominant influence. Over tropical South America, the Pacific and Atlantic modifications produce compensating influences, with the former dominating dominant, and allowing increased rainfall over the Amazon Basin.

Influence of tree cover and urban area on streamflow in the United States using multiple statistical attribution techniques

2021 ◽  
Author(s):  
Bailey Anderson ◽  
Louise Slater ◽  
Simon Dadson ◽  
Annalise Blum
Keyword(s):  
Land Cover ◽  
Urban Area ◽  
Regression Models ◽  
The United States ◽  
Additive Models ◽  
Tree Cover ◽  
Panel Regression ◽  
Distributional Regression ◽  
Panel Regression Models ◽  
Modelling Approaches

<p>There is still limited quantitative understanding of the effects of tree cover and urbanisation on streamflow at large scales, making it difficult to generalize these relationships. We use the globally consistent European Space Agency (ESA) Climate Change Initiative (CCI) Global Land Cover dataset to estimate the relationships between streamflow, calculated as high (Q0.99), median (Q0.50), and low (Q0.01) flow quantiles, and urbanization or tree cover changes in 2865 catchments between the years 1992 through 2018. We apply three statistical modelling approaches and examine the consistencies and inconsistencies between them. First, we use distributional regression models -- generalized additive models for location, scale, and shape (GAMLSS) -- at each site and assess goodness-of-fit. Model fits suggested a strong association between land cover, especially urban area, and low and median flows at sites with statistically significant trends in streamflow. We then examine the sign of the distributional regression model coefficients to determine whether the inclusion of a land cover variable in the regression models results in a relative increase or decrease in flow, regardless of the overall direction of trends in streamflow. Finally, we use fixed effects panel regression models to estimate the average effect across all sites. Panel regression results suggested that a 1% increase in urban area corresponds to between a < 1% and 2.1% increase in streamflow for all quantiles. Results for the tree cover panel regression models were not significant. We highlight the value of statistical approaches for large-sample attribution of hydrological change, while cautioning that considerable variability exists across catchments and modelling approaches.</p>

Thermoregulation comparisons between a threatened native and an invasive lizard species

2021 ◽  
pp. 70-76
Author(s):  
Yole Caruso
Keyword(s):  
Thermal Gradient ◽  
Southern Italy ◽  
Thermal Conditions ◽  
Selective Advantage ◽  
Behavioural Plasticity ◽  
Thermal Ecology ◽  
Heating Rates ◽  
Lizard Species ◽  
Successful Invader ◽  
Aeolian Archipelago

Lizard thermoregulation is costly and is largely behavioural. Podarcis raffonei, endemic of few islets of the Aeolian archipelago (southern Italy), is one of the most threatened lizards in Europe, its survival being under threat also due to the presence of the congeneric P. siculus, a successful invader characterised by behavioural plasticity and effectiveness and precision at regulating body temperature (Tb). We tested whether thermoregulation behaviour diverges between the two species by analysing (i) the heating rates under a standard thermal condition, and (ii) the temperature at which lizards ended basking (Tfinal) along a thermal gradient. Overall, we found behavioural differences between the two lizards (i.e. P. siculus exhibited lower Tfinal), although both species had comparable heating rates and thermoregulated in the same thermal conditions. The invasive P. siculus had lower Tfinal and, since heating rates were similar between species, it expended less time basking than native P. raffonei. We speculate that the observed thermal ecology differences could provide a selective advantage to P. siculus in the harsh island environment.

Size-dependent heating rates determine the spatial and temporal distribution of small-bodied lizards

2007 ◽  
Vol 28 (3) ◽  
pp. 347-356 ◽  
Author(s):  
János Török ◽  
Gábor Herczeg ◽  
Zoltán Korsós
Keyword(s):  
Body Size ◽  
Heating Rate ◽  
Time Budget ◽  
Activity Patterns ◽  
Temporal Distribution ◽  
Spatial And Temporal Distribution ◽  
Seasonal Activity ◽  
Heating Rates ◽  
Lizard Species ◽  
Joint Effects

AbstractThe rate of heat exchange with the environment is of obvious importance in determining the time budget of behavioural thermoregulation in ectotherms. In small reptiles, heating rate depends mainly on their physical characteristics. We analysed the effect of body size, and the possible joint effects originating from shape and colour differences on heating rate in three small-bodied (0.15-20 g) sympatric lizard species. Heating rate was strongly influenced by body size, while no joint effects with the two other factors were detected. We found that the increase in heating rate with decreasing body size accelerated dramatically below a body weight of 2-3 g. We also analysed associations between body size, seasonal activity patterns and thermal characteristics of the sites where lizards were encountered in the field. Differently sized lizards occurred in thermally different sites and differed in their seasonal activity patterns, both within and among species. Smaller (<2-3 g) lizards occurred in cooler sites and exhibited very low activity during summer. Our results suggest that body size has a considerable influence on the spatial and temporal distribution of extremely small lizards in environments subject to a danger of overheating.

scholarly journals Integrative Responses of Leaf-Cutting Ants to Temperature Rises

2020 ◽  
Author(s):  
Cleverson de Sousa Lima ◽  
André Frazão Helene ◽  
Agustín Camacho
Keyword(s):  
Body Size ◽  
Relative Humidity ◽  
Thermal Tolerance ◽  
Heating Rates ◽  
Atta Sexdens ◽  
Physiological Tolerance ◽  
Labor Division ◽  
Leaf Cutting ◽  
Summary Statement ◽  
Start Temperature

AbstractThermal variation has complex effects on organisms and they deal with it by combining behavioral and physiological thermal tolerance. However, we still do not understand well how these two types of traits relate to body condition (e.g. size, hydration) and environmental variables (e.g. relative humidity), some of which are typical aspects of thermal tolerance experiments (warming rates, start temperature). We explored these interactions using a set of experiments that sequentially measure behavioral (Voluntary Thermal Maxima) and physiological thermal tolerance (Critical Thermal Maxima) for individuals of Atta sexdens rubropilosa (Forel, 1908). We found non-linear effects of body size on behavioral thermal tolerance and refuted the traditional hypothesis that body size increases ant’s physiological thermal tolerance. Hydration state and humidity had complex effects on behavioral and physiological tolerance. However, both tolerance measures increased with heating rates and start temperature. Our work helps understanding how an ectotherm integrates stimuli affecting its thermal tolerance to decide which temperatures to avoid. We discuss implications for the ecology of ants, their labor division, and for their susceptibility to climate warming and drought.Summary StatementHere we show how internal (body size, hydration level) and external factors (heating rate, relative humidity) affect leaf-cutting ants behavioral and physiological responses to temperature rises.

scholarly journals Floodplains as an Achilles’ heel of Amazonian forest resilience

2017 ◽  
Vol 114 (17) ◽  
pp. 4442-4446 ◽  
Author(s):  
Bernardo M. Flores ◽  
Milena Holmgren ◽  
Chi Xu ◽  
Egbert H. van Nes ◽  
Catarina C. Jakovac ◽  
...  
Keyword(s):  
Forest Structure ◽  
Large Scale ◽  
Amazon Basin ◽  
Climatic Variation ◽  
Tree Cover ◽  
Cascading Effects ◽  
Forest Resilience ◽  
Central Amazonia ◽  
Lowland Forests ◽  
The Impact

The massive forests of central Amazonia are often considered relatively resilient against climatic variation, but this view is challenged by the wildfires invoked by recent droughts. The impact of such fires that spread from pervasive sources of ignition may reveal where forests are less likely to persist in a drier future. Here we combine field observations with remotely sensed information for the whole Amazon to show that the annually inundated lowland forests that run through the heart of the system may be trapped relatively easily into a fire-dominated savanna state. This lower forest resilience on floodplains is suggested by patterns of tree cover distribution across the basin, and supported by our field and remote sensing studies showing that floodplain fires have a stronger and longer-lasting impact on forest structure as well as soil fertility. Although floodplains cover only 14% of the Amazon basin, their fires can have substantial cascading effects because forests and peatlands may release large amounts of carbon, and wildfires can spread to adjacent uplands. Floodplains are thus an Achilles’ heel of the Amazon system when it comes to the risk of large-scale climate-driven transitions.

scholarly journals Exploring Surface Biophysical-Climate Sensitivity to Tropical Deforestation Rates Using a GCM: A Feasibility Study*

2012 ◽  
Vol 16 (4) ◽  
pp. 1-23 ◽  
Author(s):  
C. Kendra Gotangco Castillo ◽  
Kevin Robert Gurney
Keyword(s):  
Climate Sensitivity ◽  
Amazon Basin ◽  
Forest Cover ◽  
Tropical Deforestation ◽  
Tree Cover ◽  
Dynamic Global Vegetation Model ◽  
Climate System Model ◽  
Deforestation Rates ◽  
Global Vegetation

Abstract Deforestation perturbs both biophysical and carbon feedbacks on climate. However, biophysical feedbacks operate at temporally immediate and spatially focused scales and thus may be sensitive to the rate of deforestation rather than just to total forest-cover loss. Explored here is a method for simulating annual tropical deforestation in the fully coupled Community Climate System Model, version 3.0 (CCSM3) with the Dynamic Global Vegetation Model (DGVM) for testing biosphere climate sensitivity to “preservation pathways.” Two deforestation curves were simulated—a 10% deforestation curve with a 10% preservation target (DFC10-PT10) versus a 1% deforestation curve with a 10% preservation target (DFC1-PT10). During active deforestation, albedo, net radiation, latent heat flux, and climate variables were compared for time dependence and sensitivity to tropical tree cover across the tropical band and the Amazon basin, central African, and Southeast Asian regions. The results demonstrated the feasibility of modeling incremental deforestation and detecting both transient and long-term impacts, although a warm/dry bias in CCSM3–DGVM and the absence of carbon feedbacks preclude definitive conclusions on the magnitude of sensitivities. The deforestation rates produced characteristic trends in biophysical variables with DFC10-PT10 resulting in rapid increase/decrease during the initial 10–30 years before leveling off, whereas DFC1-PT10 exhibits gradual changes. The rate had little effect on biophysical and climate sensitivities when averaged over tropical land but produced significant differences at a regional level. Over the long term, the rates produced dissimilar vegetation distributions, despite having the same preservation target in both cases. Overall, these results indicate that the question of rates is one worth further analysis.

scholarly journals Species distribution modeling and conservation assessment of the black-headed night monkey (Aotus nigriceps) – A species of Least Concern that faces widespread anthropogenic threats

2020 ◽  
Author(s):  
William D. Helenbrook ◽  
Jose W. Valdez
Keyword(s):  
Protected Areas ◽  
Species Distribution ◽  
Amazon Basin ◽  
Forest Cover ◽  
Indigenous Communities ◽  
Sympatric Species ◽  
Tree Cover ◽  
Conservation Assessment ◽  
Buffer Zones ◽  
Deforestation Rates

AbstractDeforestation rates in the Brazilian Amazon have been steadily increasing since 2007. Recent government policy, projected growth of agriculture, and expansion of the cattle industry is expected to further pressure primates within the Amazon basin. In this study, we examined the anthropogenic impact on the widely distributed black-headed night monkey, Aotus nigriceps, whose distribution and population status have yet to be assessed. We 1) modeled species distribution in A. nigriceps; 2) estimated impact of habitat loss on population trends; and 3) highlight landscape-based conservation actions which maximize potential for their long-term sustainability. We found the black-headed night monkey to be restricted by several biotic and environmental factors including forest cover, elevation, isothermality, and precipitation. Over the last two decades, over 132,908 km2 of tree cover (18%) has been lost within their documented range. We found this species occupies only 49% of habitat within in their range, a loss of 19% from their estimated 2000 distribution, and just over 34% of occupied areas were in protected areas. Projected deforestation rates of A. nigriceps equates to an additional loss of 23,084 km2 of occupied habitat over the next decade. This study suggests that although classified as a species of Least Concern, A. nigriceps may have a much smaller range and is likely more at risk than previously described. The future impact of continued expansion of mono-cultured crops, cattle ranching, and wildfires is still unknown. However, expanded use of participatory REDD+, sustainable agroforestry in buffer zones, secured land tenor for indigenous communities, wildlife corridors, and the expansion of protected areas can help ensure viability for this nocturnal primate and other sympatric species throughout the Amazon Basin.

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