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Thermal ecology of montane Atelopus (Anura: Bufonidae): A study of intrageneric diversity
... Estos resultados, son similares a los observados en el trabajo de Sanabria et al. (2003), donde las variables temperatura ambiental, radiación solar y la velocidad del viento, mostraron un efecto significativo sobre la temperatura corporal. En contraste, los trabajos de Navas et al. (2013) y Rueda-Solano et al. (2016) encontraron una asocia-ción entre la temperatura corporal y el gradiente de altura. ...
... Estos resultados, son similares a los observados en el trabajo de Sanabria et al. (2003), donde las variables temperatura ambiental, radiación solar y la velocidad del viento, mostraron un efecto significativo sobre la temperatura corporal. En contraste, los trabajos de Navas et al. (2013) y Rueda-Solano et al. (2016) encontraron una asocia-ción entre la temperatura corporal y el gradiente de altura. ...
La alta permeabilidad de la piel representa una restricción fisiológica en anfibios, debido a un mayor riesgo de deshidratación por evapotranspiración en ambientes con menor disponibilidad de agua y mayor temperatura. Dendropsophus molitor es una especie semiacuática con comportamiento de tomar el sol, mecanismo termorregulatorio, necesario para llevar a cabo sus procesos vitales. El objetivo de este trabajo fue evaluar el efecto de las variables ambientales, tipo de microhábitat y color, sobre la temperatura corporal y pérdida de agua en D. molitor. Para esto, se usaron modelos de agar de dos colores, ubicados en dos tipos de microhábitat (húmedo vs. seco), cada uno en dos condiciones de exposición (sol vs. sombra), midiendo el porcentaje de cambio de peso y temperatura corporal. Se realizaron análisis estadísticos como correlación, modelos de efectos lineares mixtos, y el método del factor de inflación de la varianza. Los resultados del estudio mostraron que el punto de rocío, la humedad relativa, la radiación solar, la temperatura del sustrato y el microhábitat, pero no el color de los modelos de agar, tuvieron un efecto significativo sobre el porcentaje de cambio de peso y la temperatura corporal. Ambas variables incrementaron en la condición microhábitat seco y sol, así como en seco y sombra, entre las 12:00 y 16:00 horas. La evapotranspiración está íntimamente relacionada con la radiación y el déficit de presión de vapor, siendo importante para la temperatura corporal del anfibio, debido a que éste se enfría mediante la evapotranspiración del agua a través de su piel. Por último, se sugiere que las variables a nivel del microhábitat son vitales para estas especies, y deberían ser incorporadas en este tipo de estudios.
... A disjunct group of species occupies the eastern Amazonian Basin and the Guiana Shield (Lötters et al., 2011). Atelopus are found at elevations ranging from 0 to 4800m (La and occupy a variety of habitats, including Chocó-Darién moist forests (Veselý and Batista, 2021), treeless high-altitude páramo (Rueda Solano et al., 2016), and lowland Amazonian rainforest (Jorge et al., 2020a). Harlequin toads live in riparian areas, with males often staying close to streams and females ranging further into the surrounding areas (Mcdiarmid, 1971). ...
Toads of the genus Atelopus are chemically defended by a unique combination of endogenously synthesizedcardiotoxins (bufadienolides) and neurotoxins which may be sequestered (guanidinium alkaloids). Investigationinto Atelopus small-molecule chemical defenses has been primarily concerned with identifying and characterizingvarious forms of these toxins while largely overlooking their ecological roles and evolutionary implications. Inaddition to describing the extent of knowledge about Atelopus toxin structures, pharmacology, and biologicalsources, we review the detection, identification, and quantification methods used in studies of Atelopus toxins todate and conclude that many known toxin profiles are unlikely to be comprehensive because of methodologicaland sampling limitations. Patterns in existing data suggest that both environmental (toxin availability) andgenetic (capacity to synthesize or sequester toxins) factors influence toxin profiles. From an ecological andevolutionary perspective, we summarize the possible selective pressures acting on Atelopus toxicity and toxinprofiles, including predation, intraspecies communication, disease, and reproductive status. Ultimately, weintend to provide a basis for future ecological, evolutionary, and biochemical research on Atelopus.
... In addition, some works on phylogenetic relationships and biogeography have included this genus (Lötters, 1996;Pramuk et al., 2008;Lötters et al., 2011). In Colombia, the issues addressed in the genus Atelopus have focused on ecological aspects such as foraging behavior (Rueda-Solano & Warkentin, 2016), substrate use (Granda-Rodríguez & Del Portillo-Mozo, 2007), thermal ecology (Rueda-Solano et al., 2016a), coloration type (Rueda-Solano, 2008;Rueda-Solano, 2012), tadpole morphology (Rueda-Solano et al., 2015;Pérez-González et al., 2020), monitoring (Gómez-Hoyos et al., 2014), and diseases caused by the chytrid fungus (Rueda-Solano et al., 2016b;Flechas et al., 2017). Several authors have studied important aspects of reproductive biology associated mainly with the breeding season, reproductive effort, and the interspecific amplexus (Pérez-González et al., 2017;Rocha-Usuga et al., 2017). ...
Introduction: Testicular histology constitutes one of the least explored aspects in frogs of the genus Atelopus. This taxonomic group shows an alarming population decline; therefore, its reproductive biology is one of the greatest topics of interest for its conservation. Objective: To describe the testicular morphology and the spermatogenetic lineage cells in adult males of Atelopus laetissimus, Atelopus nahumae, and Atelopus carrikeri in the Sierra Nevada de Santa Marta, Colombia. Methods: During June – July 2017 and 2018, sampling was conducted in the localities of San Lorenzo and Páramo Cebolletas, Sierra Nevada de Santa Marta (SNSM), to collect 15 adult males, 5 per species. Testes samples were fixed in Bouin to be processed by the standard paraffin-embedding technique. Histological sections (3 μm) were stained with Hematoxylin-eosin and Mallory-Heidenhain-Azan-Gomori’s. For the description and photographic register of the germ cells, the photonic microscopy technique was used with the differential interference contrast system. Results: The testes are oval organs, compact, light yellow color, and with little vascularization. Externally, they are surrounded by a thin albuginea tunic constituted by regular dense connective tissue. Inside this layer, they are composed of numerous seminiferous tubules of hexagonal contour, in which germ cell cysts are distinguished at different stages of spermatogenesis (spermatogonia I and II, spermatocyte I and II, and early and late spermatids) and spermiogenesis (spermatozoa in fascicles and free spermatozoa). Separating the seminiferous structures is the interstitial tissue in which Leydig cells and blood vessels stand out. Additionally, in the cranial part of the testis, the Bidder’s organ was found, formed by two distinguishable regions, the cortex and the medulla. In the cortex, there are previtellogénic oocytes of different sizes surrounded by a monolayer of flat follicular cells. For its part, the medullary region is the connective tissue that nourishes the oocytes and is constituted by blood capillaries. Conclusions: The gonads of the three species analyzed present a cystic cellular organization similar to other anurans, where all stages of spermatogenesis and spermiogenesis were identified, possibly indicating a continuous reproductive activity. Likewise, the Bidder’s organ is reported for the first time in the three Atelopus species, which allows suggesting a possible sexual reversion in case of a population decrease of females as a reproductive strategy.
... In addition, some works on phylogenetic relationships and biogeography have included this genus (Lötters, 1996;Pramuk et al., 2008;Lötters et al., 2011). In Colombia, the issues addressed in the genus Atelopus have focused on ecological aspects such as foraging behavior (Rueda-Solano & Warkentin, 2016), substrate use (Granda-Rodríguez & Del Portillo-Mozo, 2007), thermal ecology (Rueda-Solano et al., 2016a), coloration type (Rueda-Solano, 2008;Rueda-Solano, 2012), tadpole morphology (Rueda-Solano et al., 2015;Pérez-González et al., 2020), monitoring (Gómez-Hoyos et al., 2014), and diseases caused by the chytrid fungus (Rueda-Solano et al., 2016b;Flechas et al., 2017). Several authors have studied important aspects of reproductive biology associated mainly with the breeding season, reproductive effort, and the interspecific amplexus (Pérez-González et al., 2017;Rocha-Usuga et al., 2017). ...
Introduction: Testicular histology constitutes one of the least explored aspects in frogs of the genus Atelopus. This taxonomic group shows an alarming population decline; therefore, its reproductive biology is one of the greatest topics of interest for its conservation. Objective: To describe the testicular morphology and the spermatogenetic lineage cells in adult males of Atelopus laetissimus, Atelopus nahumae, and Atelopus carrikeri in the Sierra Nevada de Santa Marta, Colombia. Methods: During June-July 2017 and 2018, sampling was conducted in the localities of San Lorenzo and Páramo Cebolletas, Sierra Nevada de Santa Marta (SNSM), to collect 15 adult males, 5 per species. Testes samples were fixed in Bouin to be processed by the standard paraffin-embedding technique. Histological sections (3 μm) were stained with Hematoxylin-eosin and Mallory-Heidenhain-Azan-Gomori's. For the description and photographic register of the germ cells, the photonic microscopy technique was used with the differential interference contrast system. Results: The testes are oval organs, compact, light yellow color, and with little vascularization. Externally, they are surrounded by a thin albuginea tunic constituted by regular dense connective tissue. Inside this layer, they are composed of numerous seminiferous tubules of hexagonal contour, in which germ cell cysts are distinguished at different stages of spermatogenesis (spermatogonia I and II, spermatocyte I and II, and early and late spermatids) and spermiogenesis (spermatozoa in fascicles and free spermatozoa). Separating the seminiferous structures is the interstitial tissue in which Leydig cells and blood vessels stand out. Additionally, in the cranial part of the testis, the Bidder's organ was found, formed by two distinguishable regions, the cortex and the medulla. In the cortex, there are previtellogénic oocytes of different sizes surrounded by a monolayer of flat follicular cells. For its part, the medullary region is the connective tissue that nourishes the oocytes and is constituted by blood capillaries. Conclusions: The gonads of the three species analyzed present a cystic cellular organization similar to other anurans, where all stages of spermatogenesis and spermiogenesis were identified, possibly indicating a continuous reproductive activity. Likewise, the Bidder's organ is reported for the first time in the three Atelopus species, which allows suggesting a possible sexual reversion in case of a population decrease of females as a reproductive strategy.
... In addition, some works on phylogenetic relationships and biogeography have included this genus (Lötters, 1996;Pramuk et al., 2008;Lötters et al., 2011). In Colombia, the issues addressed in the genus Atelopus have focused on ecological aspects such as foraging behavior (Rueda-Solano & Warkentin, 2016), substrate use (Granda-Rodríguez & Del Portillo-Mozo, 2007), thermal ecology (Rueda-Solano et al., 2016a), coloration type (Rueda-Solano, 2008;Rueda-Solano, 2012), tadpole morphology (Rueda-Solano et al., 2015;Pérez-González et al., 2020), monitoring (Gómez-Hoyos et al., 2014), and diseases caused by the chytrid fungus (Rueda-Solano et al., 2016b;Flechas et al., 2017). Several authors have studied important aspects of reproductive biology associated mainly with the breeding season, reproductive effort, and the interspecific amplexus (Pérez-González et al., 2017;Rocha-Usuga et al., 2017). ...
Introduction:
Testicular histology constitutes one of the least explored aspects in frogs of the genus Atelopus. This taxonomic group shows an alarming population decline; therefore, its reproductive biology is one of the greatest topics of interest for its conservation.
Objective:
To describe the testicular morphology and the spermatogenetic lineage cells in adult males of Atelopus laetissimus, Atelopus nahumae, and Atelopus carrikeri in the Sierra Nevada de Santa Marta, Colombia.
Methods:
During June - July 2017 and 2018, sampling was conducted in the localities of San Lorenzo and Páramo Cebolletas, Sierra Nevada de Santa Marta (SNSM), to collect 15 adult males, 5 per species. Testes samples were fixed in Bouin to be processed by the standard paraffin-embedding technique. Histological sections (3 μm) were stained with Hematoxylin-eosin and Mallory-Heidenhain-Azan-Gomori’s. For the description and photographic register of the germ cells, the photonic microscopy technique was used with the differential interference contrast system.
Results:
The testes are oval organs, compact, light yellow color, and with little vascularization. Externally, they are surrounded by a thin albuginea tunic constituted by regular dense connective tissue. Inside this layer, they are composed of numerous seminiferous tubules of hexagonal contour, in which germ cell cysts are distinguished at different stages of spermatogenesis (spermatogonia I and II, spermatocyte I and II, and early and late spermatids) and spermiogenesis (spermatozoa in fascicles and free spermatozoa). Separating the seminiferous structures is the interstitial tissue in which Leydig cells and blood vessels stand out. Additionally, in the cranial part of the testis, the Bidder’s organ was found, formed by two distinguishable regions, the cortex and the medulla. In the cortex, there are previtellogénic oocytes of different sizes surrounded by a monolayer of flat follicular cells. For its part, the medullary region is the connective tissue that nourishes the oocytes and is constituted by blood capillaries.
Conclusions:
The gonads of the three species analyzed present a cystic cellular organization similar to other anurans, where all stages of spermatogenesis and spermiogenesis were identified, possibly indicating a continuous reproductive activity. Likewise, the Bidder’s organ is reported for the first time in the three Atelopus species, which allows suggesting a possible sexual reversion in case of a population decrease of females as a reproductive strategy.
... These high rates may be explained (at least in part) by the stronger climate-physiology relationships in amphibians relative to other groups (Qu and Wiens 2020). Amphibians may also show greater variability in their temperatures (and higher rates of evolution) because most species are thought to have relatively limited or no thermoregulation, especially salamanders (Brattstrom 1979;Olalla-Tárraga and Rodríguez 2007;Solano et al. 2016). Furthermore, amphibians have mean body temperatures that are much lower than other tetrapods, especially in salamanders (Fig. 2). ...
Body temperature is a crucial variable in animals that affects nearly every aspect of their lives. Here we analyze for the first time largescale patterns in the evolution of body temperatures across terrestrial vertebrates (tetrapods: including amphibians, mammals, birds and other reptiles). Despite the traditional view that endotherms (birds and mammals) have higher body temperatures than ectotherms, we find they are not significantly different. However, rates of body-temperature evolution are significantly different, with lower rates in endotherms than ectotherms, and the highest rates in amphibians. We find that body temperatures show strong phylogenetic signal and conservatism over 350 million years of evolutionary history in tetrapods, and some lineages appear to have retained similar body temperatures over time for hundreds of millions of years. Although body temperatures are often unrelated to climate in tetrapods, we find that body temperatures are significantly related to day-night activity patterns. Specifically, body temperatures are generally higher in diurnal species than nocturnal species, both across ectotherms and, surprisingly, across endotherms also. Overall, our results suggest that body temperatures are significantly linked to phylogeny and diel-activity patterns within and among tetrapod groups, rather than just climate and the endotherm-ectotherm divide.
... This area is located at 1560m and has its central point placed at 11°10" N, 74°10´45". The locality is characterised by a tropical montane cloud forest with average annual rainfall of 2446 mm and steep slopes of primary and secondary forest in advanced state of regeneration, with temperatures from 14 to 24°C (Hernández-Camacho and Sánchez-Páez 1992; Rueda-Solano et al. 2016). There is a high diversity of microhabitats in the sector, including rocky areas, sand and leaf litter on the banks of the stream. ...
Paramos are high-elevation tropical Andean ecosystems above the tree line that display variable temperature and frequent freezing spells. Because a significant anuran community lives in this environment, physiological protection against freezing must characterise individuals in this community. Antifreeze protection has been studied in amphibians from other communities, and it is likely that Paramo anurans rely on the same underlying molecules that convey such protection to Nearctic species. However, given the pervasive presence of freezing spells in the Paramos year-round, the processes of activating protection mechanisms may differ from that of seasonal counterparts. Accordingly, this study investigated cryoprotection strategies in high-elevation tropical frogs, using as a model the terrestrial and nocturnal genus Pristimantis , specifically P. bogotensis , P. elegans and P. nervicus from Paramos, and the warm ecosystem counterparts P. insignitus , P. megalops and P. sanctaemartae . We focused on freeze tolerance and its relationship with glucose accumulation and ice formation. Under field conditions, the highest elevation P. nervicus exhibited higher glucose concentration at dawn compared to noon (1.7 ± 0.6 mmol/L versus 3.5 ± 1.32 mmol/L). Under experimental thermal freeze exposure for 2 hours between −2 and −4 ºC, the glucose concentration of the three Paramo species increased but physiological diversity was evident ( P. nervicus 126%; P. bogotensis 100%; and P. elegans 55%). During this test, body ice formation was assessed calorimetrically. The species with the highest body ice formation was P. bogotensis (17% ± 5.37; maximum value: 63%; n = 8), followed by P. nervicus (5% ± 3.27; maximum value: 11%; n = 5) and P. elegans (0.34% ± 0.09; maximum value: 1%; n = 4). The study shows physiological diversity both within a genus and across the amphibian community around the freezing contour. Overall, Paramo species differ in freezing physiology from their low-elevation counterparts. Thus, climate shifts increasing freezing spells may affect the structure of communities in this zone.
... The climate variability hypothesis (CVH; Janzen, 1967;Stevens, 1989) predicts that organisms should have wide thermal tolerance breadths in environments with wide temperature ranges, such as in tropical mountain areas. As a result, tropical high elevation amphibian species appear to have greater warming tolerance and wider thermal tolerance breadths than amphibians living in environments with relatively narrow temperature ranges (Catenazzi et al., 2014;Navas, 1996aNavas, , 1996bNavas et al., 2013;Rueda-Solano et al., 2016;von May et al., 2017). Compared to lower-elevation species in closed-canopy habitats, high elevation ectotherms appear to be more buffered from climatic warming, as their upper critical thermal limits (i.e., CT max ) are farther away from the maximum temperatures that they regularly experience in the environment (Catenazzi et al., 2014;von May et al., 2017). ...
en Temperature plays a key role in the biology of ectotherms, including anurans, which are found at higher elevations in the tropics than anywhere in the temperate zone. High elevation tropical environments are characterized by extreme daily thermal fluctuation including high daily maxima and nightly freezing. Our study investigated the contrasting operative temperatures of the anurans Telmatobius marmoratus and Pleurodema marmoratum in different environmental contexts at the same elevation and biome above 5,200 m. Telmatobius marmoratus avoids extremes of daily temperature fluctuation by utilizing thermally buffered aquatic habitat at all life stages, with minimal operative temperature variation (range: 4.6–8.0°C). Pleurodema marmoratum, in contrast, experienced operative temperatures from −3.5 to 44°C and has one of the widest thermal breadths reported for any tropical frog, from >32°C (critical thermal maximum) to surviving freezing periods of 1 and 6 hr down to −3.0°C. Our findings expand experimental evidence of frost tolerance in amphibians to the widespread Neotropical family Leptodactylidae, the first such evidence of frost tolerance in a tropical amphibian. Our study identifies three strategies (wide thermal tolerance breadth, use of buffered microhabitats, and behavioral thermoregulation), which allow these tropical frogs to withstand the current wide daily thermal fluctuation above 5,000 m.a.s.l. and which may help them adapt to future climatic changes.
Abstract in Spanish is available with online material
RESUMEN
es La temperatura del ambiente es clave en la biología de organismos ectotermos, incluidos los anuros, que se encuentran en elevaciones más altas en los trópicos que en cualquier parte de la zona templada. Los ambientes tropicales de alta montaña se caracterizan por una fluctuación térmica diaria extrema. Nuestro estudio investiga las temperaturas operativas contrastantes de los anuros Telmatobius marmoratus y Pleurodema marmoratum en diferentes contextos ambientales (acuática y terrestre) pero en la misma elevación y bioma, en un ambiente térmico extremo por encima de 5,200 metros sobre el nivel del mar. Telmatobius marmoratus evita extremos de temperatura diaria mediante el uso de hábitat acuático con protección térmica en todas las etapas de la vida; las temperaturas operativas a 1 m de profundidad fluctuaron entre 4.6 y 8.0°C. Por el contrario, modelos biofísicos determinaron que las temperaturas operativas de la rana terrestre oscilaban entre −3.5 y 44°C en un solo día. Pleurodema marmoratum cuenta con uno de los valores más altos de la temperatura crítica máxima (>32°C) reportados en los Andes tropicales y tolera la congelación, sobreviviendo períodos de congelación de 1 hr y 6 hr hasta −3°C. Nuestros resultados amplían la primera confirmación experimental de la tolerancia al congelación corporal en anfibios a la familia Neotropical ubicua Leptodactylidae, y además la primera evidencia experimental de tolerancia a congelación corporal en un anfibio tropical. Nuestro estudio identifica tres estrategias (amplitud de tolerancia térmica amplia, uso de microhábitats amortiguadas, y termorregulación conductual), que permiten que estes anfibios tropicales resistan la fluctuación térmica diaria amplia actual por encima de 5,000 msnm y que pueden ayudarles a adaptarse a cambios climáticos futuros.
... Habitat selection allows organisms to avoid adverse environmental conditions, like extremely low temperatures (Navas 1996). Recently, A. laetissimus has been described as a thermoconforming species, showing a direct relationship between the temperature of substrate and the activity temperature (Rueda-Solano et al. 2016b). Therefore, the differential selection of substrates could be associated with some thermoregulatory strategy. ...
Atelopus laetissimus is a bufonid toad that inhabits the mountainous areas of the Sierra Nevada de Santa Marta (SNSM), Colombia. This species is endemic and threatened, for which information about their ecology and distribution are crucial for the conservation of this toad. Here, we described the abundance, habitat use, vocalization and potential distribution in A. laetissimus from the San Lorenzo creek of the Sierra Nevada de Santa Marta. To this end, 447 individuals of A. laetissimus were analyzed during several sampling performed from 2010 to 2012. Against expectations, population density was significantly higher in the stream than riparian forest. Overall, A. laetissimus used seven different diurnal habitats with a high preference by leaf litter substrates and rocks. Rate of recaptures was decreasing lineally along the survey nights. We recorded two types of vocalization in A. latissimus. A short call characterized by a series of pulses like a buzz and another also short, but lacking pulses. According to our analysis, the areas with higher habitat suitability for A. laetissimus were located principally in the northern and northwestern region of the SNSM, which was in agreement with the findings reported in literature. Moreover, the modeling of data indicated a significant increase in habitat loss from 2013 to 2017. Our information should be considered as a starting point for the conservation of this valuable amphibian in the tropical landscapes of America.
... Habitat selection allows organisms to avoid adverse environmental conditions, like extremely low temperatures (Navas 1996). Recently, A. laetissimus has been described as a thermoconforming species, showing a direct relationship between the temperature of substrate and the activity temperature (Rueda-Solano et al. 2016b). Therefore, the differential selection of substrates could be associated with some thermoregulatory strategy. ...
Atelopus laetissimus is a bufonid toad that inhabits the mountainous areas of the Sierra Nevada de Santa Marta (SNSM), Colombia. This species is endemic and threatened, for which information about their ecology and distribution are crucial for the conservation of this toad. Here, we described the abundance, habitat use, vocalization and potential distribution in A. laetissimus from the San Lorenzo creek of the Sierra Nevada de Santa Marta. To this end, 447 individuals of A. laetissimus were analyzed during several sampling performed from 2010 to 2012. Against expectations, population density was significantly higher in the stream than riparian forest. Overall, A. laetissimus used seven different diurnal habitats with a high preference by leaf litter substrates and rocks. Rate of recaptures was decreasing lineally along the survey nights. We recorded two types of vocalization in A. latissimus. A short call characterized by a series of pulses like a buzz and another also short, but lacking pulses. According to our analysis, the areas with higher habitat suitability for A. laetissimus were located principally in the northern and northwestern region of the SNSM, which was in agreement with the findings reported in literature. Moreover, the modeling of data indicated a significant increase in habitat loss from 2013 to 2017. Our information should be considered as a starting point for the conservation of this valuable amphibian in the tropical landscapes of America.
... Perhaps because of this complexity, fewer studies have been carried out on this topic in anurans than in other tetrapods, especially in the case of contrasting climatic models with physiological performance (Duarte et al., 2012;Gouveia et al., 2013;Gerick et al., 2014). For this reason, available information on the thermal physiology of temperate amphibians is limited, and there are few studies that estimate climatic niches in regions characterized by harsh environmental conditions (e.g., high winds, low air temperatures and snowfall in winter) (Araujo et al., 2006;Gouveia et al., 2013;Blank et al., 2014;Gerick et al., 2014;Merilä and Hendry, 2014;Rueda Solano et al., 2016). ...
Ectotherms are vulnerable to climate change, given their dependence on temperature, and amphibians are particularly interesting because of their complex life cycle. Tadpoles may regulate their body temperature by using suitable thermal microhabitats. Thus, their physiological responses are the result of adjustment to the local thermal limits experienced in their ponds. We studied three anuran tadpole species present in Argentina and Chile: Pleurodema thaul and Pleurodema bufoninum that are seasonal and have broad geographic ranges, and Batrachyla taeniata, a geographically restricted species with overwintering tadpoles. Species with restricted distribution are more susceptible to climate change than species with broader distribution that may cope with potential climatic changes in the environments in which they occur. We aim to test whether these species can buffer the potential effects of climate warming. We used ecological niche models and the outcomes of their thermal attributes (critical thermal limits, optimal temperature, and locomotor performance breadth) as empirical evidence of their capacity. We found that Pleurodema species show broader performance curves, related to their occurrence, while the geographically restricted B. taeniata shows a narrower thermal breadth, but is faster in warmer conditions. The modeled distributions and empirical physiological results suggest no severe threats for these three anurans. However, the risk level is increasing and a retraction of their distribution range might be possible for Pleurodema species, and some local population extinctions may happen, particularly for the narrowly distributed B. taeniata.
In spite of their small global area and restricted distributions, tropical montane forests (TMFs) are biodiversity hotspots and important ecosystem services providers, but are also highly vulnerable to climate change. To protect and preserve these ecosystems better, it is crucial to inform the design and implementation of conservation policies with the best available scientific evidence, and to identify knowledge gaps and future research needs. We conducted a systematic review and an appraisal of evidence quality to assess the impacts of climate change on TMFs. We identified several skews and shortcomings. Experimental study designs with controls and long-term (≥10 years) data sets provide the most reliable evidence, but were rare and gave an incomplete understanding of climate change impacts on TMFs. Most studies were based on predictive modelling approaches, short-term (<10 years) and cross-sectional study designs. Although these methods provide moderate to circumstantial evidence, they can advance our understanding on climate change effects. Current evidence suggests that increasing temperatures and rising cloud levels have caused distributional shifts (mainly upslope) of montane biota, leading to alterations in biodiversity and ecological functions. Neotropical TMFs were the best studied, thus the knowledge derived there can serve as a proxy for climate change responses in under-studied regions elsewhere. Most studies focused on vascular plants, birds, amphibians and insects, with other taxonomic groups poorly represented. Most ecological studies were conducted at species or community levels, with a marked paucity of genetic studies, limiting understanding of the adaptive capacity of TMF biota. We thus highlight the long-term need to widen the methodological, thematic and geographical scope of studies on TMFs under climate change to address these uncertainties. In the short term, however, in-depth research in well-studied regions and advances in computer modelling approaches offer the most reliable sources of information for expeditious conservation action for these threatened forests.
High‐elevation organisms are expected to evolve physiological adaptations to cope with harsh environmental conditions. Yet, evidence for such adaptive differences, especially compared to closely related lowland taxa occurring along the same elevational gradient, is rare. Revisiting an anecdotal natural history observation by O. Bangs from 1899 and based on new measurements of museum specimens, we confirmed that the high‐elevation hermit wood wren (Henicorhina anachoreta) from the Sierra Nevada de Santa Marta, Colombia, has longer, more insulative feathers on the chest and back, than its lower‐elevation counterpart the grey‐breasted wood wren (H. leucophrys). However, we did not find evidence for the same specializations in subspecies of H. leucophrys that live at high elevations on other elevational gradients in the Colombian Andes, although similar adaptive solutions have arisen in separate mountain systems like the Himalayas. Adaptations in plumage may be associated with the recurrence of elevational species replacements throughout the tropics. We show that high‐elevation H. anachoreta has more insulative feathers than low‐elevation H. leucophrys. But H. leucophrys has not evolved similar modification in regions where it has colonized high elevations.
Toads of the genus Atelopus are chemically defended by a unique combination of endogenously synthesized cardiotoxins (bufadienolides) and what are likely exogenously sequestered neurotoxins (guanidinium alkaloids). Investigation into Atelopus small-molecule chemical defenses has been primarily concerned with identifying and characterizing various forms of these toxins while largely overlooking their ecological roles and evolutionary implications. In addition to describing the extent of knowledge about Atelopus toxin structures, pharmacology, and biological sources, we review the detection, identification, and quantification methods used in studies of Atelopus toxins to date and conclude that many known toxin profiles are unlikely to be comprehensive because of methodological and sampling limitations. Patterns in existing data suggest that both environmental (toxin availability) and genetic (capacity to synthesize or sequester toxins) factors influence toxin profiles. From an ecological and evolutionary perspective, we summarize the possible selective pressures acting on Atelopus toxicity and toxin profiles, including predation, intraspecies communication, disease, and reproductive status. Ultimately, we intend to provide a basis for future ecological, evolutionary, and biochemical research on Atelopus.
El objetivo principal de este Manual es el desarrollo de un compendio de técnicas y protocolos estándares para el inventario y monitoreo de poblaciones de anfibios, actualizado con los procedimientos, herramientas y técnicas de análisis más recientes y adaptado a las condiciones y realidades nacionales. Su contenido está destinado a ayudar a superar algunas de las dificultades que se pueden enfrentar al configurar un programa de inventario y monitoreo para anfibios. Pretendemos brindar una orientación práctica sobre cómo diseñar y llevar a cabo estudios que puedan servir para múltiples aplicaciones más allá de las necesidades de un proyecto particular. En este manual compilamos las experiencias y consejos de numerosos especialistas sobre diferentes temáticas que pudieran permitir a los lectores y usuarios de este manual obtener la mayor cantidad y calidad de datos durante la realización de futuros proyectos de investigación relacionados con estas temáticas.
The temperature of anuran activity from arid regions have been poorly studied. In recent years, the emphasis was placed on predicting the impacts of global warming on the fauna of ectotherms in general. Many times future impacts are predicted based on global thermal information (macroscale) but not on an individual scale. We used literature data about body temperature in anurans that inhabit the desert region of the Northwest of Argentina to analyze the role of the elevation, eco-region and substrate temperature on the individual scale. Also, we evaluated the predictive capacity that global environmental variables obtained from WorldClim for this region, and compared them with those of local scale. Our results showed that the activity body temperature of the toads in the arid region of western Argentina strongly influenced by elevation and the substrate temperature on the individual scale. We observed that data of the global scale (WorldClim) can predict the body temperature of the studied amphibians, but with a deviation, not less than 8 °C. According to our results, it is evident that to making reliable predictions of how global warming impacts on amphibians in the region, the environmental temperature data need to be recorded at the local scale (operative temperatures).
Los plecópteros son un grupo de insectos acuáticos que se caracterizan por vivirprincipalmente en aguas frías, de corrientes rápidas, oxigenadas y oligotróficas;además son sensibles a cambios en las condiciones del hábitat y la calidad delagua. Este estudio pretende conocer la distribución espacio-temporal y los hábitosalimentarios de las ninfas del orden Plecoptera en la parte alta del río Gaira. Para talefecto se realizaron colectas de ninfas de abril a septiembre de 2004 en el ParqueNacional Natural Sierra Nevada de Santa Marta-sector de San Lorenzo (11°10´2´´Norte y 74°10´41.5´´ Oeste). Las morfoespecies encontradas pertenecen al géneroAnacroneuria (Perlidae) y se nominan provisionalmente como A. spW, A. spX, A.spY y A. spZ, de las cuales la más dominante y frecuente fue A. spY. Se encontró quela gravilla en corriente rápida es el microhábitat con mayores abundancias y la piedracon las menores; en el microhábitat sedimento no se encontró ningún plecópteroasociado. La variación de las abundancias durante el estudio estuvo relacionadacon el régimen pluviométrico de la zona. El análisis de contenido estomacal de lasninfas de Anacroneuria, muestra que su dieta es principalmente carnívora y no haydiferencia aparente entre las morfoespecies estudiadas, sin embargo, entre la dieta deninfas juveniles y maduras hubo variación en los ítems consumidos
La diversidad climática de la Sierra Nevada de Santa Marta y la cuenca del río Gaira se debe principalmente a su
posición geográfica, la cercanía al mar, la variación altitudinal y la exposición a los vientos circundantes, lo que
permite que sea una zona de alta diversidad biológica y de gran interés para el estudio de su paisaje, en especial de la
zonificación climática. Se elaboraron los mapas de zonificación climática e índice hídrico para la cuenca del río Gaira,
y se adaptaron algunos rangos de clasificación propuestos por el Instituto de Hidrología, Meteorología y de Estudios
Ambientales - IDEAM.
Amphibian population declines and extinctions have occurred in conserved sites or
protected areas far from anthropogenic activities as a result of emerging infectious diseases such
as chytridiomycosis. Regular epidemiological surveillance, monitoring of key species, and the
implementation of biosecurity protocols are fundamental actions for the in-situ conservation of
amphibian fauna. Since 2008 biosecurity protocols have been implemented for all personnel that
enter the Estación Experimental de San Lorenzo, a partly mountainous protected and conserved area
of the Sierra Nevada de Santa Marta with a high diversity of endemic and endangered amphibians.
Semiannual disease screenings of amphibians were carried out, as well as an amphibian inventory
and a survey of species of the genus Atelopus. To-date no mass mortality events have been reported
and Bd has not been detected. Nevertheless, some individuals of Ikakogi tayrona and Pristimantis
megalops showed symptoms of disease, the latter of which included individuals affected with
skin tumors. Deformities in individuals of Atelopus were also observed. The implementation of
epidemiological surveillance, monitoring of key amphibian species, and biosecurity protocols
are important strategies for the conservation management of the endemic amphibians within the
protected area of the Sierra Nevada of Santa Marta.
Diverse anuran lineages have colonized a tropical high-elevation Neotropical ecosystem called páramo, which is located above the tree-line and below the snow and characterized by low and variable temperatures on a daily basis. Amphibian species apparently become exposed to the freezing temperatures in the páramo, particularly at elevations above 3500 m.a.s.l. (meters above sea level). If the body temperatures of these amphibians indeed reach freezing levels during the night, amphibian survival in the páramo would require permanent (as opposed to seasonal) physiological tolerance to freezing. However, such physiological studies would be justified only with evidence that microhabitat temperatures reach subzero temperatures for periods long enough to induce partial tissue freezing. Therefore, the purpose of this work is to investigate whether páramo amphibians are exposed to freezing. We focused on Pristimantis nervicus, an amphibian that is active at night in exposed microhabitats, making it potentially vulnerable to all aspects of the páramo climate. We recorded body temperatures and used plaster models to evaluate operational temperatures along diverse transects located at 3500 m.a.s.l. in the Eastern Andes of Central Colombia. We found that, regardless of the substrate where this species is present, individuals are at risk of freezing. The body temperatures recorded were as low as -1.05°C and the operational temperatures estimated values slightly lower than -5.0°C These data suggest the existence of cryoprotection mechanisms in this, and possibly other páramo anuran species.
To investigate whether ambient temperature constrains behavioral performance in high-elevation anurans I studied the thermal dependency of field calling rate and locomotor performance of four Colombian Andean frogs at 2900-3500 m (Atelopus sp. nov., Colostethus subpunctatus, Eleutherodactylus bogotensis, and Hyla labialis), and compared them with low-elevation (<350 m) congener species (A. varius, C. talamancae, E. diastema, and H. microcephala). Apparently low temperatures constrain only high levels of sustained performance. Body temperature explained 40% of the variance in calling rate of high-elevation frogs that call vigorously (H. labialis and C. subpunctatus), but did not affect the lower calling rates of A. sp. nov. and E. bogotensis. High-elevation frogs in the genera Eleutherodactylus, Atelopus, and Colostethus may exhibit less energetically demanding vocal behaviors than low-elevation congenerics. Both high-elevation and low-elevation frogs moved at low speeds with sporadic bursts of activity. Body temperature did not correlate with the time, speed, or distances that high-elevation frogs moved, which were similar to those of low-elevation congenerics. Reliance on glycolysis, presumably less sensitive to temperature than aerobic metabolic pathways, may partially explain the thermal independence of field locomotion patterns in high-elevation anurans.
The biodiversity of the entire planet is threatened by global warming, and among vertebrates, Amphibia is the taxon most negatively affected by this problem. Amphibians depend on an external heat source to achieve and maintain an adequate body temperature, which has a signifi cant impact on their fi tness. Therefore, an increase in the average environmental temperature will affect, probably in a negative way, the general performance of amphibians. This makes it imperative to increase our scarce knowledge of amphibian thermoregulation. The aim of this work is to contribute to the knowledge of amphibian thermoregulation by studying the winter thermal ecology of one of the most widely distributed species in Chile, Pleurodema thaul. Individuals were collected during the mid-austral winter in Península de Hualpén, which corresponds to the midpoint of the latitudinal range of distribution of P. thaul. In the fi eld and laboratory we recorded body temperature and the substrate and air temperatures. The data indicate that P. thaul is a thermoconformer, as its body temperature varies during the day, following the temperature of the substrate and the air. Pleurodema thaul does not seem to use morphological body properties to facilitate thermoregulation; body temperature was unrelated to the body size or weight of individuals. The fact that during winter P. thaul does not thermoregulate actively constitutes a clear indication that the global warming may have serious effects on this species.
1. Tropical montane amphibians have been the focus of recent and crucial conservation efforts. These initiatives require understanding on how elevation influences amphibian body temperature beyond the simplistic assumption of a monotonical decrease with elevation. This study addresses patterns and potential for inference in this context. 2. As elevation increases, mean body temperature (BT) of tropical montane amphibians decreases linearly, but intrapopulation variation (VAR) in BT increases exponentially. These relationships are influenced by biome structure, but display both local nuances and species-specific remarks. 3. Substrate temperature (ST) and BT hold a close relationship across elevation. The noise around this relationship is lowest in mid-elevation cloud forests and maximum in the paramo, a biome above the tree line. 4. The relationships between BT and ST, and between elevation and either BT or VAR, are valuable to infer general patterns of thermal ecology for amphibians and to highlight species-specific exceptional cases. 5. The BT of montane tropical amphibians can be estimated from temperature data collected at a scale compatible with the size and microhabitat of individual frogs. Estimates from eleva-tion are valid as general trends that can be enhanced if natural history is taken into account. Worldclim data allow for rough inference only and have limited predictive power. 6. A framework is proposed to study how the BT and VAR of amphibians change with eleva-tion. This framework encompasses information on biome structure and natural history.
Se presentan registros adicionales de Atelopus nahumae y Atelopus laetissimus en la Sierra Nevada de Santa Marta (Magdalena), Colombia, y una caracterización actual de su ecosistema. Las especies son endémicas del macizo montañoso y están clasificadas en Peligro Crítico de extinción por su vulnerabilidad ecológica y por la ausencia de registros verificables desde 1992. Mediante registro visual diurno y en un transecto de 3 x 700 m se tomaron datos de densidad, actividad y datos morfométricos de las ranas presentes, además se realizó una exploración del área tomando muestras florísticas y datos ambientales. Se encontraron cuatro especies de ranas (dos de cada uno de los géneros Pristimantis y Atelopus) de las cuales 26 especímenes son de Atelopus nahumae y 12 de Atelopus laetissimus. De las especies de Atelopus se tienen registros fotográficos y audiovisuales con vocalizaciones, amplexos y organismos aparentemente sanos juveniles y adultos. El ecosistema es un bosque secundario en recuperación, de dosel cerrado y continuo con elementos arbóreos de estratos altos (25 m), siendo Licania cuspidata (Chrysobalanaceae) la especie más abundante (38 ind/0,1 ha); también se encuentran plantaciones de especies del género Pinus. Los Atelopus se encontraron exclusivamente en el bosque secundario y el sector de la quebrada, mientras Pristimantis megalops se encontró también en el bosque de pinos. Este reporte permite evidenciar la supervivencia actual de estas poblaciones.
(1) Juvenile Andean toads (Bufo spinulosus) observed at 4300 m were markedly diurnal and more active during sunny days than cloudy days. (2) On a sunny day basking toads increased Tb from near freezing to a mean maximum of 22.9°C at mid-day, 7.7°C above the ambient air temperature. (3) On a cloudy day, basking was reduced and Tb closely matched adjacent water temperature. (4) These results suggest that at extreme elevations, strictly diurnal activity and basking behavior are advantageous for both adult and juvenile anuran life stages.
We surveyed the population status of the Neotropical toad genus Atelopus, and document recent catastrophic declines that are more severe than previously reported for any amphibian genus. Of 113 species that have been described or are candidates for description, data indicate that in 42 species, population sizes have been reduced by at least half and only ten species have stable populations. The status of the remaining taxa is unknown. At least 30 species have been missing from all known localities for at least 8 yr and are feared extinct. Most of these species were last seen between 1984 and 1996. All species restricted to elevations of above 1000 m have declined and 75 percent have disappeared, while 58 percent of lowland species have declined and 38 percent have disappeared. Habitat loss was not related to declines once we controlled for the effects of elevation. In fact, 22 species that occur in protected areas have disappeared. The fungal disease Batrachochytrium dendrobatidis has been documented from nine species that have declined, and may explain declines in higher elevation species that occur in undisturbed habitats. Climate change may also play a role, but other potential factors such as environmental contamination, trade, and introduced species are unlikely to have affected more than a handful of species. Widespread declines and extinctions in Atelopus may reflect population changes in other Neotropical amphibians that are more difficult to survey, and the loss of this trophic group may have cascading effects on other species in tropical ecosystems.
The body temperature of free-ranging Andean toadsBufo spinulosus was measured either directly or radiotelemetrically during two 15-day periods at 3200 m elevation in the Mantaro Valley, Central Per. All toads attempted to maintain their diurnal sum of body temperature within a narrow range. Consequently thermoregulatory behaviour differed according to cloud cover and precipitation. If the sky was clear, toads emerged from their hiding place and exposed themselves to solar radiation during 3–5 h in the morning. Core temperature increased up to 15 C above the air temperature in shade and reached maximum values of about 32 C. At air temperatures (in sun) exceeding 29 C, toads maintained body temperatures below 32 C by evaporative cooling. Following heliothermic heating during the moring toads retreated to the shade, thereby decreasing body temperature below air temperature. Under overcast sky toads remained exposed during the whole day displaying body temperatures at or slightly above ambient levels. Quantitative models to predict the core temperature of toads under the different weather conditions demonstrated that the substrate temperature was the main energy source accounting for 64.6–77.9% of total variance whereas air temperature was of minor importance (1.5–4.4%). The unexplained variance was probably due to evaporative cooling. The volume of urine stored into the urinary bladder of toads varied diurnally; during basking in the morning hours most bladders contained large volumes of urine, whereas during the afternoon the bladders were mostly empty. The bladder contents probably serve as water reserves during basking when evaporative water loss was high. Toads preferred sites that provided shady hiding places as well as sun-exposed bare soil within a radius of 5 m. However, they frequently changed their centers of activity and moved to other sites in 20–70 m distance after periods of 2–5 days. The helio-and thigmothermic behaviour of the Andean toad permits the maintenance of high core temperature during morning which probably increases the digestion rate and accelerate growth. Evaporative cooling and preference of shady sites were employed to regulate body temperature below the morning levels in response to the constraints of water balance. Periodic changes between thigmothermic behaviour and locomotory activity during the night maintains body temperature above air temperature and prolongs the period of food uptake.
Two new species of Atelopus from Ecuador are described; both are from the highlands of the Cordillera Occidental of the Andes, one from the Chimbo Basin and the other from the Páramos del Cajas. I include osteological data of both species and the description of the gastromyzophorous tadpoles of one of the new species. Patterns of diversity and endemism of Atelopus justify the necessity of further research and conservation efforts directed toward Andean habitats. Resumen Se reconocen dos especies de Atelopus de Ecuador nuevas para la ciencia; la una de la Hoya de Chimbo, la otra de los Páramos del Cajas; ambas provienen de regiones altas en la Cordillera Occidental de los Andes. Se proveen descripciones osteológicas de ambas especies y del renacuajo de torrente de una de las especies nuevas. Los patrones de diversidad y endemismo de Atelopus justifican la necesidad de mayores investigaciones biológicas y esfuerzos de conservación dirigidos a habitats andinos.
The role of global climate change in the decline of biodiversity and the emergence of infectious diseases remains controversial, and the effect of climatic variability, in particular, has largely been ignored. For instance, it was recently revealed that the proposed link between climate change and widespread amphibian declines, putatively caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), was tenuous because it was based on a temporally confounded correlation. Here we provide temporally unconfounded evidence that global El Niño climatic events drive widespread amphibian losses in genus Atelopus via increased regional temperature variability, which can reduce amphibian defenses against pathogens. Of 26 climate variables tested, only factors associated with temperature variability could account for the spatiotemporal patterns of declines thought to be associated with Bd. Climatic predictors of declines became significant only after controlling for a pattern consistent with epidemic spread (by temporally detrending the data). This presumed spread accounted for 59% of the temporal variation in amphibian losses, whereas El Niño accounted for 59% of the remaining variation. Hence, we could account for 83% of the variation in declines with these two variables alone. Given that global climate change seems to increase temperature variability, extreme climatic events, and the strength of Central Pacific El Niño episodes, climate change might exacerbate worldwide enigmatic declines of amphibians, presumably by increasing susceptibility to disease. These results suggest that changes to temperature variability associated with climate change might be as significant to biodiversity losses and disease emergence as changes to mean temperature.
Operative and standard operative temperatures (Tc and Tcs, respectively) are thermal indices that allow single-number representations of the complex thermal environment. They can be measured directly using various physical models of the animal of interest. These models explore the thermal environment at the same spatial scale that the animal experiences, and can be replicated relatively easily to measure conditions at multiple sites. Thus, they offer a complementary approach to elaborate computer models, and have proven valuable in integrating biophysical and population ecology
This workshop paper is primarily a summary and critical review of the uses and measurement of Tc and Tcs. I first review the principles behind Tc and Tcs. I then describe the various methods used to construct Tc and Tcs “thermometers,” and discuss their relative merits for various classes of animals and types of studies. Finally, I review typical applications. The most important is in mapping the nanoclimate experienced by small animals and in defining indices of thermal quality of home ranges based on such maps. Others include use as null models in physiological studies, and use as single-number descriptors of complex thermal environments in behavioral, physiological, and energetics studies.
We describe a research protocol for evaluating temperature regulation from data on small field-active ectothermic animals, especially lizards. The protocol requires data on body temperatures (Tb) of field-active ectotherms, on available operative temperatures (Te, "null temperatures" for nonregulating animals), and on the thermoregulatory set-point range (preferred body temperatures, Tset). These data are used to estimate several quantitative indexes that collectively summarize temperature regulation: the "precision" of body temperature (variance in Tb, or an equivalent metric), the "accuracy" of body temperature relative to the set-point range (the average difference between Tb and Tset), and the "effectiveness" of thermoregulation (the extent to which body temperatures are closer on the average to the set-point range than are operative temperatures). If additional data on the thermal dependence of performance are available, the impact of thermoregulation on performance (the extent to which performance is enhanced relative to that of nonregulating animals) can also be estimated. A sample analysis of the thermal biology of three Anolis lizards in Puerto Rico demonstrates the utility of the new protocol and its superiority to previous methods of evaluating temperature regulation. We also discuss several ways in which the research protocol can be extended and applied to other organisms.
As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with 'very high confidence' (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.
Elevated body temperatures of Hyla cinerea are best explained by the presence of reduced evaporative water loss relative to typical frogs. Reduction in water loss may have evolved in heliothermic arboreal frogs as an adaptation permitting long-term occupancy of elevated perch sites. -from Authors
Rates of cutaneous evaporative water loss were measured in seven arboreal and 11 nonarboreal anuran species under controlled environmental conditions. Areaspecific rates of cutaneous evaporative water loss of arboreal species (genera Hyla and Osteopilus) were 47% lower than those of nonarboreal species (genera Acris, Atelopus, Bufo, Gastrophryne, Rana, Scaphiopus, and Xenopus). Body and skin temperatures of arboreal species averaged 4.4 C higher than those of nonarboreal ones. Boundary layer resistance was similar in both groups of frogs and averaged 0.80 s cm⁻¹; skin resistance averaged 0.05 s cm⁻¹ in nonarboreal frogs and was 41 times higher in arboreal ones. The results of this study conflict with those of previous studies and emphasize the need for careful control of animal posture and water vapor density when measuring evaporative water loss.
Temperature pervasively impacts the phenotypes and distributions of organisms. These thermal effects generate strong selective pressures on behaviour, physiology, and life history when environmental temperatures vary over space and time. Despite this fact, progress toward a quantitative theory of thermal adaptation has lagged behind empirical descriptions of patterns and processes. This book draws on current evolutionary paradigms (optimization, quantitative genetics, and genetic algorithms) to establish a theory of thermal adaptation. It initially focuses on simple models that describe the evolution of thermosensitivity, thermoregulation, or acclimation. Later chapters focus on more complex models describing the coadaptation of traits or the coevolution of species. Throughout the book, various lines of evidence are used to question the major assumptions of these models. Furthermore, the predictions of these models are confronted with experimental and comparative data. Empirical examples represent a wide range of taxa, including bacteria, plants, fungi, and animals. The result is a synthesis of theoretical and empirical studies of thermal biology that offers insights about evolutionary processes.
Operative and standard operative temperatures are thermal indices that allow single-number representations of the complex thermal environment. They can be measured directly using various physical models of the animal of interest. These models explore the thermal environment at the same spatial scale that the animal experiences, and can be replicated relatively easily to measure conditions at multiple sites. The most important application is in mapping the nanoclimate experienced by small animals and in defining indices of thermal quality of home ranges based on such maps. Others include use as null models in physiological studies, and use as single-number descriptors of complex thermal environments in behavioral, physiological, and energetics studies. -from Author
Modelling thermal environments at high resolution becomes simpler when using operative temperature, which condenses microclimate and morphology into an index of thermal stress. Operative temperature can be mapped using large numbers of ‘operative temperature thermometers’, hollow models that duplicate external properties of the animal.As climatologists predict that air will warm by 2–4 °C by 2100, biologists must be able to distinguish climate change from systematic errors in operative temperature of the same magnitude.A systematic error in operative temperature of 2 °C or a similar amount of climate warming can change predicted surface activity and indices of habitat quality, thermoregulatory precision and predation risk by 5–12%, and in some cases more than 30%.As construction details of operative temperature thermometers can affect their accuracy by 2 °C or more, biologists should use detailed physical models calibrated against living animals over potential ranges of postures, orientations and microclimates.Water‐filled models do not measure operative temperature correctly, fail to capture thermal extremes and are an unnecessary complication as one can easily compute the body temperature of moving or stationary animals from body mass and the spatio‐temporal distribution of operative temperatures.
Climate change will increase both average temperatures and extreme summer temperatures. Analyses of the fitness consequences of climate change have generally omitted negative fitness and population declines associated with heat stress.Here, we examine how seasonal and interannual temperature variability will impact fitness shifts of ectotherms from the past (1961–1990) to future (2071–2100), by modelling thermal performance curves (TPCs) for insect species across latitudes.In temperate regions, climate change increased the length of the growing season (increasing fitness) and increased the frequency of heat stress (decreasing fitness). Consequently, species at mid-latitudes (20–40°) showed pronounced but heterogeneous responses to climate change. Fitness decreases for these species were accompanied by greater interannual variation in fitness. An alternative TPC model and a larger data set gave qualitatively similar results.How close maximum summer temperatures are to the critical thermal maximum of a species – the thermal buffer – is a good predictor of the change in mean fitness expected under climate change. Thermal buffers will decrease to near or below zero by 2100 for many tropical and mid-latitude species.Our forecasts suggest that mid-latitude species will be particularly susceptible to heat stress associated with climate change due to temperature variation.
Past studies of ecogeographic character variations have failed to provide a quantitative relationship between the character being measured and the environmental parameter which impinges upon that character. We offer an example in amphibians directly relating a character variation, the range of temperature tolerance, and the critical environmental parameter for that character, the environmental temperature variation. In this example, the range of temperature tolerance is closely related to the environmental temperature variations. Where the environmental temperature variation increases so does the range of temperature tolerance. In addition, where environmental temperatures decrease, the capacity to tolerate such temperatures is lost. These data are consistent with the thesis that congeneric and conspecific populations in different habitats have partially independent evolutionary pathways and that where populations have been displaced from a less to a more uniform environment, characters which are no longe...
This is a small synopsis of the current threat with extinction of an entire species-rich genus of neotropical toad. Nowadays, 62 of 77 described species in the genus Atelopus are allocated to the IUCN Red List category Critically Endangered. Three are extinct while a total of 30 species is considered as possibly extinct. Extinctions in Atelopus are ‘enigmatic’, happening over short time and generally for unknown reasons including remote areas. There is strong evidence that most extinctions undergo due to a combination of chytridiomycosis (an apparently emerging infectious disease caused through an epizootic fungus) and global warming. A synchronous multi-disciplinary approach – i.e. basically taxonomic, disease and other research plus monitoring, captive breeding and habitat protection – is suggested to amend survival chances of Atelopus species. Such an approach needs novel law, policy and conservation frameworks, as pointed out in the IUCN ‘Amphibian Conservation Action Plan’. The latter is still not entirely put into practice. The future will show if it will help to prevent at least some harlequin toads from extinction. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The Brazilian tree-frog Corythomantis greeningi inhabits the Caatinga, a semi-arid habitat. This species exhibits putative adaptations to a dry environment, including a flat head, co-ossification of the cranial skin, and phragmotic behaviour (retreat to crevices using the head to seal the entrance). Real frogs were compared with agar models to study water balance under simulated Caatinga conditions and to investigate the ability of C. greeningi to find small water sources. The benefits of skin co-ossification were also studied by comparing agar models with and without nail polish on the head. Tree-frogs repeatedly preferred a humid test tube out of 10 possible choices, and adopted phragmotic behaviour inside it. In both agar models and tree-frogs, total water evaporation increased with body size, but relative water loss was higher in smaller individuals. The presence of nail polish on agar models barely reduced water loss, suggesting that cranial skin co-ossification has a small role in water economy. Although both models and tree-frogs evaporated about 90% more water when exposed than when phragmotic, tree-frogs evaporated about 50% less water than agar models at any test condition. We conclude that reduced skin permeability, phragmotic behaviour and a keen capacity to identify humid crevices, explain the success of this species in a semi-arid habitat.
This paper focuses on whether microhabitat selection reduces exposure to cold temperatures in highelevation tropical amphibians. I studied the microhabitat associations and thermal ecology of four anurans (Colostethus subpunctatus, Atelopus sp. nov., Eleutherodactylus bogotensis, and Hyla labialis) that live in the Andes of central Colombia. I compared two populations (3500 m and 2900 m) to evaluate the impact of a change in elevation on microhabitat thermal regimes and frog behavior. Ambient temperatures of frequently used microhabitats (soil surface, retreat sites, bogs, and ponds) were significantly lower at 3500 m. However, for each species the microhabitat associations and general patterns of activity were similar at both elevations. Body temperatures of active frogs were mainly determined by the interaction between microhabitat selection and time of the day, therefore frogs at 3500 m had lower activity temperatures than conspecifics at 2900 m. Terrestrial and diurnal anurans (Atelopus sp. nov.) experienced highly variable activity temperatures. Frogs associated with water bodies (C. subpunctatus, and H. labialis) experienced more moderate and less variable temperatures. Terrestrial, nocturnal frogs (E. bogotensis) exhibited the lowest activity temperatures, and their thermal ecology was strongly affected by increase in altitude. The physical nature of high tropical elevations limits the opportunities for behavioral thermoregulation in amphibians, and increases the importance of physiological adjustments to tolerate a wide thermal range. This may partially explain why only a small number of amphibian species, representing genera that are much more diverse at lower elevations, have been able to exploit these environments.
1.1. Some anurans live in the tropical Andes above 3000 m, a cold and variable environment.2.2. Coping with high-elevation climate includes shifts in activity patterns, avoidance of extreme temperatures, and thermoregulation by heliothermy and thigmothermy.3.3. Behavior alone does not allow for full compensation of low environmental temperatures.4.4. Modifications of metabolic physiology allow high-elevation frogs to be active at low temperatures. However at warm temperatures their thermal physiology is similar to that of low-elevation forms.
During the last quarter of a century, the evolution of the thermal sensitivity of performance in ectotherms has become a major focus of research programs in evolutionary physiology. Graphical and mathematical models describe how the relationship between body temperature and performance, termed the performance function, should evolve in response to the thermal environment. Interspecific comparisons of the thermal sensitivity of locomotor performance have revealed that the performance function is evolutionarily labile in some taxa but is more conservative in others. A lack of heritable variation or weak selection on performance may explain the conservation of thermal physiology in certain groups, but evolutionary trade-offs do not appear to have been important constraints. Other aspects of thermal physiology, such as the thermal sensitivity of growth rate, have evolved rapidly in ectotherms. Despite the apparent lability of thermal physiology in some taxa, there is limited evidence that thermoregulatory behavior and thermal physiology are coadapted. Future studies should broaden taxonomic and phenotypic foci, while paying close attention to the assumptions of current theories.
Among ectothermic tetrapods, amphibians are by far the most diverse group at high elevations in the tropical Andes. This article asks whether this pattern reflects intrinsic aspects of amphibian natural history. An interdisciplinary analysis suggests that amphibians have a long evolutionary history at moderate Andean elevations and that adaptation for activity at low temperature occurred frequently and independently in different taxa. One conclusion is that temperature is unlikely to be the only or the main factor constraining some unrepresented anuran taxa that do not reach high elevations. Other physical variables (e.g. the effects of ultraviolet radiation on egg development) could better explain anuran diversity along tropical altitudinal gradients. In contrast, heliothermic taxa, such as lizards, might indeed be constrained by the low and variable temperatures that characterize high tropical elevations. Ecological gradients, therefore, might not affect ectothermic tetrapods in a similar manner, and differential susceptibility to biotic and abiotic factors that change with elevation might help to explain current patterns of distribution and diversity.
Studies on thermoregulation in the laboratory and field have come a long way from the early work done between 1940 and 1960. While some physiological studies on amphibians have progressed at the same rate as those on reptiles, field studies have been far behind. Laboratory studies have largely delt with thermal acclimation, evaporative water loss, and thermal and moisture gradient behavior. Field studies, following early summaries of body temperatures of field animals, have stressed behavioral thermoregulation; yet, detailed studies on behavioral thermoregulation in amphibians have been completed for only a handful of species. A few studies have placed behavioral and physiological thermoregulation into an ecological or energetic framework; these studies are reviewed, and suggestions are made for future work.
http://deepblue.lib.umich.edu/bitstream/2027.42/56469/1/OP030.pdf
http://deepblue.lib.umich.edu/bitstream/2027.42/56467/1/OP028.pdf
Inanimate objects may exhibit distributions of temperature similar to those of reptiles in the field. The uncontrolled field methods of collecting body temperatures of reptiles have resulted in the accumulation of much inconclusive data. A return to more comprehensive study is called for.
Thermal and water balance are coupled in anurans, and species with particularly permeable skin avoid overheating more effectively than minimizing variance of body temperature. In turn, temperature affects muscle performance in several ways, so documenting the mean and variance of body temperature of active frogs can help explain variation in behavioral performance. The two types of activities studied in most detail, jumping and calling, differ markedly in duration and intensity, and there are distinct differences in the metabolic profile and fiber type of the supporting muscles. Characteristics of jumping and calling also vary significantly among species, and these differences have a number of implications that we discuss in some detail throughout this paper. One question that emerges from this topic is whether anuran species exhibit activity temperatures that match the temperature range over which they perform best. Although this seems the case, thermal preferences are variable and may not necessarily reflect typical activity temperatures. The performance versus temperature curves and the thermal limits for anuran activity reflect the thermal ecology of species more than their systematic position. Anuran thermal physiology, therefore, seems to be phenotypically plastic and susceptible to adaptive evolution. Although generalizations regarding the mechanistic basis of such adjustments are not yet possible, recent attempts have been made to reveal the mechanistic basis of acclimation and acclimatization.
Atelopus nahumae IUCN Red List of Threatened Species
- M P Ramírez-Pinilla
- M Osorno-Muñoz
- J V Rueda
- A Amézquita
- M C Ardila-Robayo
Ramírez-Pinilla, M.P., Osorno-Muñoz, M., Rueda, J.V., Amézquita, A., Ardila-Robayo,
M. C., 2004a. Atelopus nahumae. In: IUCN 2015. IUCN Red List of Threatened
Species. 〈http://www.iucnredlist.org〉. Version 2015-3. (Accessed 14.10.15).
Activity temperature of Atelopus carrikeri, A. laetissimus y A. nahumae in function to substrate and air temperature. Regression Analysis (Solid line), Isotherma (Dotted line) Registers (N)
- Fig
Fig. 7. Activity temperature of Atelopus carrikeri, A. laetissimus y A. nahumae in function to substrate and air temperature. Regression Analysis (Solid line), Isotherma (Dotted
line). Registers (N).