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1. Thermal niche variation among individuals of the poison frog, Oophaga pumilio , in forest and converted habitats

   https://doi.org/10.1111/btp.12691  

   Rivera‐Ordonez, Juana M. ; Justin Nowakowski, A. ; Manansala, Adrian ; Thompson, Michelle E. ; Todd, Brian D. ( August 2019 , Biotropica)

   The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog,Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (T_b), preferred body temperatures (T_pref), critical thermal maxima (CT_max), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater meanT_bandT_prefthan those from forests. In contrast,CT_maxandTSMdid not differ significantly between habitats. However,CT_maxdid increase moderately with increasingT_b, suggesting that changes inCT_maxmay be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. AlthoughO. pumilioexhibited moderate divergence inT_pref,CT_maxappears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain theirT_bbelow air temperatures that reach or exceedCT_max. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming.

   Abstract in Spanish is available with online material.

    

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2. Sustained Drought, but Not Short-Term Warming, Alters the Gut Microbiomes of Wild Anolis Lizards

   https://doi.org/10.1128/aem.00530-22  

   Williams, Claire E. ; Kueneman, Jordan G. ; Nicholson, Daniel J. ; Rosso, Adam A. ; Folfas, Edita ; Casement, Brianna ; Gallegos-Koyner, Maria A. ; Neel, Lauren K. ; Curlis, John David ; McMillan, W. Owen ; et al ( October 2022 , Applied and Environmental Microbiology)

   Rudi, Knut (Ed.)

   ABSTRACT As rising temperatures threaten biodiversity across the globe, tropical ectotherms are thought to be particularly vulnerable due to their narrow thermal tolerance ranges. Nevertheless, physiology-based models highlighting the vulnerability of tropical organisms rarely consider the contributions of their gut microbiota, even though microbiomes influence numerous host traits, including thermal tolerance. We combined field and lab experiments to understand the response of the slender anole lizard ( Anolis apletophallus ) gut microbiome to climatic shifts of various magnitude and duration. First, to examine the effects of long-term climate warming in the wild, we transplanted lizards from the mainland Panama to a series of warmer islands in the Panama Canal and compared their gut microbiome compositions after three generations of divergence. Next, we mimicked the effects of a short-term “heat-wave” by using a greenhouse experiment and explored the link between gut microbiome composition and lizard thermal physiology. Finally, we examined variation in gut microbiomes in our mainland population in the years both before and after a naturally occurring drought. Our results suggest that slender anole microbiomes are surprisingly resilient to short-term warming. However, both the taxonomic and predicted functional compositions of the gut microbiome varied by sampling year across all sites, suggesting that the drought may have had a regional effect. We provide evidence that short-term heat waves may not substantially affect the gut microbiota, while more sustained climate anomalies may have effects at broad geographic scales. IMPORTANCE As climate change progresses, it is crucial to understand how animals will respond to shifts in their local environments. One component of this response involves changes in the microbial communities living in and on host organisms. These “microbiomes” can affect many processes that contribute to host health and survival, yet few studies have measured changes in the microbiomes of wild organisms experiencing novel climatic conditions. We examined the effects of shifting climates on the gut microbiome of the slender anole lizard ( Anolis apletophallus ) by using a combination of field and laboratory studies, including transplants to warm islands in the Panama Canal. We found that slender anole microbiomes remain stable in response to short-term warming but may be sensitive to sustained climate anomalies, such as droughts. We discuss the significance of these findings for a species that is considered highly vulnerable to climate change. 

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3. Interaction of hydric and thermal conditions drive geographic variation in thermoregulation in a widespread lizard

   https://doi.org/10.1002/ecm.1440  

   Rozen‐Rechels, David ; Rutschmann, Alexis ; DupouÉ, AndrÉaz ; Blaimont, Pauline ; Chauveau, Victor ; Miles, Donald B. ; Guillon, Michael ; Richard, Murielle ; Badiane, Arnaud ; Meylan, Sandrine ; et al ( January 2021 , Ecological Monographs)

   Behavioral thermoregulation is an efficient mechanism to buffer the physiological effects of climate change. Thermal ecology studies have traditionally tested how thermal constraints shape thermoregulatory behaviors without accounting for the potential major effects of landscape structure and water availability. Thus, we lack a general understanding of the multifactorial determinants of thermoregulatory behaviors in natural populations. In this study, we quantified the relative contribution of elevation, thermal gradient, moisture gradient, and landscape structure in explaining geographic variation in thermoregulation strategies of a terrestrial ectotherm species. We measured field‐active body temperature, thermal preferences, and operative environmental temperatures to calculate thermoregulation indices, including thermal quality of the habitat and thermoregulation efficiency for a very large sample of common lizards (Zootoca vivipara) from 21 populations over 3 yr across the Massif Central mountain range in France. We used an information‐theoretic approach to compare eight a priori thermo‐hydroregulation hypotheses predicting how behavioral thermoregulation should respond to environmental conditions. Environmental characteristics exerted little influence on thermal preference with the exception that females from habitats with permanent access to water had lower thermal preferences. Field body temperatures and accuracy of thermoregulation were best predicted by the interaction between air temperature and a moisture index. In mesic environments, field body temperature and thermoregulation accuracy increased with air temperature, but they decreased in drier habitats. Thermoregulation efficiency (difference between thermoregulation inaccuracy and the thermal quality of the habitat) was maximized in cooler and more humid environments and was mostly influenced by the thermal quality of the habitat. Our study highlights complex patterns of variation in thermoregulation strategies, which are mostly explained by the interaction between temperature and water availability, independent of the elevation gradient or thermal heterogeneity. Although changes in landscape structure were expected to be the main driver of extinction rate of temperate zone ectotherms with ongoing global change, we conclude that changes in water availability coupled with rising temperatures might have a drastic impact on the population dynamics of some ectotherm species.

    

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4. Miami heat: Urban heat islands influence the thermal suitability of habitats for ectotherms

   https://doi.org/10.1111/gcb.14509  

   Battles, Andrew C. ; Kolbe, Jason J. ( November 2018 , Global Change Biology)

   The urban heat island effect, where urban areas exhibit higher temperatures than less‐developed suburban and natural habitats, occurs in cities across the globe and is well understood from a physical perspective and at broad spatial scales. However, very little is known about how thermal variation caused by urbanization influences the ability of organisms to live in cities. Ectotherms are sensitive to environmental changes that affect thermal conditions, and therefore, increased urban temperatures may pose significant challenges to thermoregulation and alter temperature‐dependent activity. To evaluate whether these changes to the thermal environment affect the persistence and dispersal of ectothermic species in urban areas, we studied two species ofAnolislizards (Anolis cristatellusandAnolis sagrei) introduced to Miami‐Dade County, FL, USA, where they occur in both urban and natural habitats. We calculated canopy openness and measured operative temperature (T_e), which estimates the distribution of body temperatures in a non‐thermoregulating population, in four urban and four natural sites. We also captured lizards throughout the day and recorded their internal body temperature (T_b). We found that urban areas had more open canopies and higherT_ecompared to natural habitats. Laboratory trials showed thatA. cristatelluspreferred lower temperatures thanA. sagrei. Urban sites currently occupied by each species appear to lower thermoregulatory costs for both species, but onlyA. sagreihad fieldT_bthat were more often within their preferred temperature range in urban habitats compared to natural areas. Furthermore, based on availableT_ewithin each species' preferred temperature range, urban sites with onlyA. sagreiappear less suitable forA. cristatellus, whereas natural sites with onlyA. cristatellusare less suitable forA. sagrei. These results highlight how the thermal properties of urban areas contribute to patterns of persistence and dispersal, particularly relevant for studying species invasions worldwide.

    

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5. Thermal traits predict the winners and losers under climate change: an example from North American ant communities

   https://doi.org/10.1002/ecs2.3645  

   Roeder, Karl A. ; Bujan, Jelena ; de Beurs, Kirsten M. ; Weiser, Michael D. ; Kaspari, Michael ( July 2021 , Ecosphere)

   Across the globe, temperatures are predicted to increase with consequences for many taxonomic groups. Arthropods are particularly at risk as temperature imposes physiological constraints on growth, survival, and reproduction. Given that arthropods may be disproportionately affected in a warmer climate—the question becomes which taxa are vulnerable and can we predict the supposed winners and losers of climate change? To address this question, we resurveyed 33 ant communities, quantifying 20‐yr differences in the incidence of 28 genera. Each North American ant community was surveyed with 30 1‐m²plots, and the incidence of each genus across the 30 plots was used to estimate change. From the original surveys in 1994–1997 to the resurveys in 2016–2017, temperature increased on average 1°C (range, −0.4°C to 2.5°C) and ~64% of ant genera increased in more than half of the sampled communities. To test Thermal Performance Theory's prediction that genera with higher average thermal limits will tend to accumulate at the expense of those with lower limits, we quantified critical thermal maxima (CT_max: the high temperatures at which they lose muscle control) and minima (CT_min: the low temperatures at which ants first become inactive) for common genera at each site. Consistent with prediction, we found a positive decelerating relationship between CT_maxand the proportion of sites in which a genus had increased. CT_min, by contrast, was not a useful predictor of change. There was a strong positive correlation (r = 0.85) between the proportion of sites where a genus was found with higher incidence after 20 yr and the average difference in number of plots occupied per site, suggesting genera with high CT_maxvalues tended to occupy more plots at more sites after 20 yr. Thermal functional traits like CT_maxhave thus proved useful in predicting patterns of long‐term community change in a dominant, diverse insect taxon.

    

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