Growth rate and the cost of calling activity in male carpenter frogs,Rana virgatipes

Summary Energy stress during the breeding season and relationships between calling activity and growth were investigated in male carpenter frogs, Rana virgatipes. This species has a prolonged breeding season of up to three months in Southern New Jersey. Monthly collections made in 1985 revealed that both dry mass and percent body lipid decreased throughout the breeding season but sharply increased at the end of the breeding season. Observations of free-living males showed that small males were more likely to gain mass than large males during the breeding season. All males gained mass at higher rates after the breeding season. A simultaneous record of calling activity and mass change was obtained for 42 males. Males called on 95% of nights, indicating that they rarely ceased their reproductive activities. Small males tended to have low calling efforts and high growth rates. When the effect of initial mass was removed, growth rate was negatively correlated with calling effort among small males. This is the first demonstration of a direct tradeoff between a reproductive activity and growth in an anuran.     

The role of synchronized calling,ambient light,and ambient noise,in anti-bat-predator behavior of a treefrog

Summary Male treefrogs, Smilisca sila (Hylidae), produce calls of varying complexity and demonstrate a remarkable ability to synchronize their calls with those of neighbors. The bat Trachops cirrhosus eats frogs and uses the frogs' advertisement calls as locational cues. The bats are less likely to respond to synchronous calls than to asynchronous calls, and when given a choice prefer complex calls to simple calls.Experiments with bat models indicate that, like other frogs, S. sila probably uses visual cues to detect hunting bats. In response to bat models the frogs decreased both the number and the complexity of their calls. The calling behavior of the frogs was sampled in the field during periods with and without artificial illumination. The frogs produced fewer and less complex calls, and they tended to call from more concealed sites, during the period without illumination, when presumably it would have been more difficult for the frogs to detect hunting bats. S. sila tended to call from sites with higher ambient noise level, the noise primarily originating from waterfalls. The frequencies of the dominant energies in the waterfall sounds completely overlapped the frequency range of the S. sila call; thus waterfalls might mask the frog calls. When given a choice between calls produced near and away from waterfall sounds, bats preferred the latter.     

Cover Caption

Cover: Radar imagery can be used to map the locations from which migratory birds depart and to highlight important stopover sites. Shown are movements of long-distance migrants, such as the Blackburnian Warbler ( Dendroica fusca ), detected during spring migration near Buffalo, New York. Warbler photo by Charles Eiseman. See pages 440–448.     

Silica nanoparticles synthesis and applications in agriculture for plant fertilization and protection: a review

Environmental Chemistry Letters - The rapidly rising population is calling for the production of more food, yet biotic and abiotic stresses caused by pests and climate change...     

Integrated model projections of climate change impacts on a North American lake

Climate change is likely to impact terrestrial and aquatic ecosystems via numerous physical and biological mechanisms. This study outlines a framework for projecting potential impacts of climate change on lakes using linked environmental models. Impacts of climate drivers on catchment hydrology and thermal balance in Onondaga Lake (New York State) are simulated using mechanistic models HSPF and UFILS4. Outputs from these models are fed into a lake ecosystem model, developed in AQUATOX. Watershed simulations project increases in the magnitude of peak flows and consequent increases in catchment nutrient export as the magnitude of extreme precipitation events increases. This occurs concurrently with a decrease in annual stream discharge as a result of increased evapotranspiration. Simulated lake water temperatures increase by as much as 5 °C during the 2040-2069 time period, accompanied by a prolonging of the duration of summer stratification. Projected changes include shifts in the timing of nutrient cycling between lake sediments and water column. Plankton taxa projected to thrive under climate change include green algae and Bosmina longirostris. Responses for species at higher trophic levels are mixed. Benthic macroinvertebrates may either prosper (zebra mussels) or decline (chironomids), while fish (e.g., gizzard shad) exhibit high seasonal variability without any clear trend.     

Projected vegetation changes for the American Southwest: combined dynamic modeling and bioclimatic-envelope approach

This study focuses on potential impacts of 21st century climate change on vegetation in the Southwest United States, based on debiased and interpolated climate projections from 17 global climate models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Among these models a warming trend is universal, but projected changes in precipitation vary in sign and magnitude. Two independent methods are applied: a dynamic global vegetation model to assess changes in plant functional types and bioclimatic envelope modeling to assess changes in individual tree and shrub species and biodiversity. The former approach investigates broad responses of plant functional types to climate change, while considering competition, disturbances, and carbon fertilization, while the latter approach focuses on the response of individual plant species, and net biodiversity, to climate change. The dynamic model simulates a region-wide reduction in vegetation cover during the 21st century, with a partial replacement of evergreen trees with grasses in the mountains of Colorado and Utah, except at the highest elevations, where tree cover increases. Across southern Arizona, central New Mexico, and eastern Colorado, grass cover declines, in some cases abruptly. Due to the prevalent warming trend among all 17 climate models, vegetation cover declines in the 21st century, with the greatest vegetation losses associated with models that project a drying trend. The inclusion of the carbon fertilization effect largely ameliorates the projected vegetation loss. Based on bioclimatic envelope modeling for the 21st century, the number of tree and shrub species that are expected to experience robust declines in range likely outweighs the number of species that are expected to expand in range. Dramatic shifts in plant species richness are projected, with declines in the high-elevation evergreen forests, increases in the eastern New Mexico prairies, and a northward shift of the Sonoran Desert biodiversity maximum.     

Utilization of energy substrates during calling activity in tropical frogs

Calling activity in frogs is energetically demanding to males because they usually perform at or near their physiological capacities. Metabolic fuel for muscle contractions during bouts of aerobic calling activity comes from carbohydrates and lipids that are stored in the trunk muscles. I monitored nightly calling performance in males of seven tropical frog species from two families, Hylidae and Leptodactylidae, and compared levels of glycogen and lipid in the trunk muscles from males collected before and after a three-hour period of calling activity. Trunk muscles from late-evening males in five species had up to 63% less glycogen than the trunk muscles from early-evening males; relatively little depletion was observed in two other species. Overall, glycogen reserves and rates of depletion were highest in species with very high calling rates. It was not possible to measure changes in the relatively large stores of lipid in the trunk muscles after only 3 h of calling. Nevertheless, intramuscular lipid stores probably provide a greater percentage of the energy needed for sound production than glycogen stores, and are largest in species with high calling rates. Received: 7 January 1997 / Accepted after revision: 20 July 1997     

Valuation of expectations: A hedonic study of shale gas development and New York’s moratorium

This paper examines the local impacts of shale gas development (SGD). We use a hedonic framework and exploit a discrete change in expectations about SGD caused by the New York State moratorium on hydraulic fracturing. Our research design combines difference-in-differences and border discontinuity, as well as underlying shale geology, on properties in Pennsylvania and New York. Results suggest that New York properties that were most likely to experience both the financial benefits and environmental consequences of SGD dropped in value 23% as a result of the moratorium, which under certain assumptions indicates a large and positive net valuation of SGD.     

A new method for broad-scale modeling and projection of plant assemblages under climatic,biotic, and environmental cofiltering

There is increasing interestin broad-scale analysis, modeling, and prediction of the distribution and composition of plant species assemblages under climatic, environmental, and biotic change, particularly for conservation purposes. We devised a method to reliably predict the impact of climate change on large assemblages of plant communities, while also considering competing biotic and environmental factors. To this purpose, we first used multilabel algorithms in order to convert the task of explaining a large assemblage of plant communities into a classification framework able to capture with high cross-validated accuracy the pattern of species distributions under a composite set of biotic and abiotic factors. We applied our model to a large set of plant communities in the Swiss Alps. Our model explained presences and absences of 175 plant species in 608 plots with >87% cross-validated accuracy, predicted decreases in α, β, and γ diversity by 2040 under both moderate and extreme climate scenarios, and identified likely advantaged and disadvantaged plant species under climate change. Multilabel variable selection revealed the overriding importance of topography, soils, and temperature extremes (rather than averages) in determining the distribution of plant species in the study area and their response to climate change. Our method addressed a number of challenging research problems, such as scaling to large numbers of species, considering species relationships and rarity, and addressing an overwhelming proportion of absences in presence–absence matrices. By handling hundreds to thousands of plants and plots simultaneously over large areas, our method can inform broad-scale conservation of plant species under climate change because it allows species that require urgent conservation action (assisted migration, seed conservation, and ex situ conservation) to be detected and prioritized. Our method also increases the practicality of assisted colonization of plant species by helping to prevent ill-advised introduction of plant species with limited future survival probability.     

Pigeon homing: Different effects of olfactory deprivation in different countries

Summary This study compares the orientation of untreated pigeons and pigeons subjected to olfactory deprivation at two lofts near Pisa, Italy, at a loft at Ithaca, New York, USA, and at a loft at Frankfurt a.M., FRG. The experimental birds were rendered anosmic by nasal plugs until Gingicain, a local anaesthetic, was applied shortly before release. The Italian and American control pigeons appeared to orient towards home equally well, while the control pigeons in Germany frequently preferred directions that deviated significantly from the home direction. The effect of olfactory deprivation was small in the USA and in Germany; it was significantly larger in Italy, indicating that Italian pigeons depend on olfactory information to a much greater extent. These findings suggest that there are important regional differences in the strategies and cues pigeons use to navigate. The varied roles of olfactory information, and the reasons for these differences are discussed.     

Multimodal signaling in the Small Torrent Frog (Micrixalus saxicola) in a complex acoustic environment

Many animals use multimodal (both visual and acoustic) components in courtship signals. The acoustic communication of anuran amphibians can be masked by the presence of environmental background noise, and multimodal displays may enhance receiver detection in complex acoustic environments. In the present study, we measured sound pressure levels of concurrently calling males of the Small Torrent Frog (Micrixalus saxicola) and used acoustic playbacks and an inflatable balloon mimicking a vocal sac to investigate male responses to controlled unimodal (acoustic) and multimodal (acoustic and visual) dynamic stimuli in the frogs’ natural habitat. Our results suggest that abiotic noise of the stream does not constrain signal detection, but males are faced with acoustic interference and masking from conspecific chorus noise. Multimodal stimuli elicited greater response from males and triggered significantly more visual signal responses than unimodal stimuli. We suggest that the vocal sac acts as a visual cue and improves detection and discrimination of acoustic signals by making them more salient to receivers amidst complex biotic background noise.     

Mercury budget estimates for the State of New York

The development of two comprehensive modelling systems and a test application to estimate the mercury budget for the State of New York is discussed in the present study. The modelling tools developed are based on two well known meteorological modelling systems namely, RAMS and SKIRON/Eta. Both models have been modified and the developed modules describing the physico-chemical processes of mercury have been incorporated in each modelling system. Model calculations and measurements have been compared during the 14 to 26 August 1997 simulation period. Two different simulations were performed, scenario1 where all available sources of mercury were used and scenario2 where the New York State mercury sources were excluded. An attempt was made to identify and quantify critical gaps in the current understanding of regional scale transport deposition and fate of mercury in New York State, improving modelling capabilities and understanding of mercury as an air pollutant, and provide a tool for policy makers in mitigating the impacts of mercury pollution.     

Use of Land Facets to Plan for Climate Change: Conserving the Arenas,Not the Actors

Abstract: Even under the most optimistic scenarios, during the next century human‐caused climate change will threaten many wild populations and species. The most useful conservation response is to enlarge and link protected areas to support range shifts by plants and animals. To prioritize land for reserves and linkages, some scientists attempt to chain together four highly uncertain models (emission scenarios, global air–ocean circulation, regional circulation, and biotic response). This approach has high risk of error propagation and compounding and produces outputs at a coarser scale than conservation decisions. Instead, we advocate identifying land facets—recurring landscape units with uniform topographic and soil attributes—and designing reserves and linkages for diversity and interspersion of these units. This coarse‐filter approach would conserve the arenas of biological activity, rather than the temporary occupants of those arenas. Integrative, context‐sensitive variables, such as insolation and topographic wetness, are useful for defining land facets. Classification procedures such as k‐means or fuzzy clustering are a good way to define land facets because they can analyze millions of pixels and are insensitive to case order. In regions lacking useful soil maps, river systems or riparian plants can indicate important facets. Conservation planners should set higher representation targets for rare and distinctive facets. High interspersion of land facets can promote ecological processes, evolutionary interaction, and range shift. Relevant studies suggest land‐facet diversity is a good surrogate for today's biodiversity, but fails to conserve some species. To minimize such failures, a reserve design based on land facets should complement, rather than replace, other approaches. Designs based on land facets are not biased toward data‐rich areas and can be applied where no maps of land cover exist.     

Thermal Physiology,Disease, and Amphibian Declines on the Eastern Slopes of the Andes

Rising temperatures, a widespread consequence of climate change, have been implicated in enigmatic amphibian declines from habitats with little apparent human impact. The pathogenic fungus Batrachochytrium dendrobatidis (Bd), now widespread in Neotropical mountains, may act in synergy with climate change causing collapse in thermally stressed hosts. We measured the thermal tolerance of frogs along a wide elevational gradient in the Tropical Andes, where frog populations have collapsed. We used the difference between critical thermal maximum and the temperature a frog experiences in nature as a measure of tolerance to high temperatures. Temperature tolerance increased as elevation increased, suggesting that frogs at higher elevations may be less sensitive to rising temperatures. We tested the alternative pathogen optimal growth hypothesis that prevalence of the pathogen should decrease as temperatures fall outside the optimal range of pathogen growth. Our infection‐prevalence data supported the pathogen optimal growth hypothesis because we found that prevalence of Bd increased when host temperatures matched its optimal growth range. These findings suggest that rising temperatures may not be the driver of amphibian declines in the eastern slopes of the Andes. Zoonotic outbreaks of Bd are the most parsimonious hypothesis to explain the collapse of montane amphibian faunas; but our results also reveal that lowland tropical amphibians, despite being shielded from Bd by higher temperatures, are vulnerable to climate‐warming stress. Fisiología Termal, Enfermedades y Disminuciones de Anfibios en las Laderas Orientales de los Andes     

Temperature ecotypes near the southern boundary of the kelp Laminaria saccharina

Effects of temperature on survival, growth, and photosynthesis were compared for two USA populations of Laminaria saccharina Lamour. One population was located in New York State, near the southern latitudinal boundary of the species in the western North Atlantic. This southern boundary population was exposed to ambient temperatures 20°C for about 6 wk each summer. The second population was located in Maine, toward the center of the latitudinal range of the species, and was rarely exposed to temperatures>17°C. sporophytes from the New York (NY) population exhibited greater tolerance of high temperature than plants from the Maine (ME) site. Juvenile sporophytes from the two sites had similar rates of survivorship and growth at temperatures below 20°C, but showed different responses at 20°C in laboratory experiments. NY plants survived and grew for 6 wk at 20°C. ME plants showed negative growth during wk 2 and 100% mortality during wk 3. NY and ME plants held in situ at the NY site during June to September, 1985, also exhibited differential survivorship when ambient temperatures exceeded 20°C. Results of photosynthesis and dark respiration measurements on NY and ME plants grown at various temperatures suggested that the high-temperature tolerance of NY plants was attributable to their ability to maintain positive daily net C-fixation at 20°C. The high-temperature tolerance of the NY plants appeared to be due to genetic adaptation and is probably crucial to the persistence of the species near its southern boundary.     

The theory behind,and the challenges of,conserving nature's stage in a time of rapid change

Most conservation planning to date has focused on protecting today's biodiversity with the assumption that it will be tomorrow's biodiversity. However, modern climate change has already resulted in distributional shifts of some species and is projected to result in many more shifts in the coming decades. As species redistribute and biotic communities reorganize, conservation plans based on current patterns of biodiversity may fail to adequately protect species in the future. One approach for addressing this issue is to focus on conserving a range of abiotic conditions in the conservation‐planning process. By doing so, it may be possible to conserve an abiotically diverse “stage” upon which evolution will play out and support many actors (biodiversity). We reviewed the fundamental underpinnings of the concept of conserving the abiotic stage, starting with the early observations of von Humboldt, who mapped the concordance of abiotic conditions and vegetation, and progressing to the concept of the ecological niche. We discuss challenges posed by issues of spatial and temporal scale, the role of biotic drivers of species distributions, and latitudinal and topographic variation in relationships between climate and landform. For example, abiotic conditions are not static, but change through time—albeit at different and often relatively slow rates. In some places, biotic interactions play a substantial role in structuring patterns of biodiversity, meaning that patterns of biodiversity may be less tightly linked to the abiotic stage. Furthermore, abiotic drivers of biodiversity can change with latitude and topographic position, meaning that the abiotic stage may need to be defined differently in different places. We conclude that protecting a diversity of abiotic conditions will likely best conserve biodiversity into the future in places where abiotic drivers of species distributions are strong relative to biotic drivers, where the diversity of abiotic settings will be conserved through time, and where connectivity allows for movement among areas providing different abiotic conditions.     

The timing of calling,movement, and mating in the field crickets Gryllus veletis,G. pennsylvanicus,and G. integer

Summary The temporal relationships between mating, calling, and movement were studied in natural habitats at different densities in the field crickets, Gryllus veletis, G. pennsylvanicus and G. integer. There was variation between and within species, but males generally showed increased calling at dawn followed by a decline during the day. Matings were also more frequent at sunrise in most observations, and male and female movement declined near dawn. Female movement and sexual receptivity are closely related to levels of male calling and movement.     

The effect of perceived intruder proximity and resident body size on the aggressive responses of male green frogs, Rana clamitans (Anura: Ranidae)

We examined variation in aggressive responses within and among individuals in the green frog, Rana clamitans. We tested the hypothesis that resident males respond in a graded fashion to changes in perceived intruder proximity (stimulus intensity). We also investigated how response level varied with responder body size. We found that green frogs differentially alter aggressive responses (increasing movement and calling rates while decreasing the duration and dominant frequency of their calls) with an increase in stimulus intensity. Body size did not appear to be a significant influence on most response levels. We suggest that aggressive responses are graded, and advertisement and aggressive calls represent opposite ends of a continuum. Green frogs do not exhibit clearly defined thresholds for responses like those reported for some other frogs. By using graded responses rather than discrete all-or-nothing responses, males may reduce the potential costs of aggressive encounters.     

Northward shifts of the distributions of Spanish reptiles in association with climate change

It is predicted that climate change will drive extinctions of some reptiles and that the number of these extinctions will depend on whether reptiles are able to change their distribution. Whether the latitudinal distribution of reptiles may change in response to increases in temperature is unknown. We used data on reptile distributions collected during the 20th century to analyze whether changes in the distributions of reptiles in Spain are associated with increases in temperature. We controlled for biases in sampling effort and found a mean, statistically significant, northward shift of the northern extent of reptile distributions of about 15.2 km from 1940-1975 to 1991-2005. The southern extent of the distributions did not change significantly. Thus, our results suggest that the latitudinal distributions of reptiles may be changing in response to climate change.     

Early holocene openlands in southern New England

The pre-historical vegetation structure in temperate forest regions is much debated among European and North American ecologists and conservationists. Frans Vera's recent hypothesis that large mammals created mosaics of forest and openland vegetation in both regions throughout the Holocene has been particularly controversial and has provoked new approaches to conservation management. Thirty years earlier, American paleoecologists Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake, Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen from Midwestern prairies. Using new pollen records from Harvard Forest and the North American Pollen Database, we address this question and offer insights to the openland discussion. Ragweed and other forbs exceed 3.5% at five sites in a restricted area of southern New England between 10,100 and 7700 yr BP. Strong evidence suggests this pollen originated from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages do not increase with longitude from New England to the Midwest. Ragweed pollen percentages are also unrelated to basin size and therefore unrelated to the proportion of extraregional pollen in New England. High forbs values were associated with increases in oak, decreases in white pine, and relatively high charcoal values. Modern pollen records with similar forb and tree percentages occur along the Prairie Peninsula region of the Upper Midwest. However, the closest analogue to the southern New England early Holocene assemblages comes from Massachusetts' Walden Pond in the early 18th century. These results and the affiliation of ragweed for open, disturbed habitats suggest that oak-pine forests with large openings persisted for over 2000 years due to dry conditions and perhaps increased fire frequency. This conclusion is corroborated by independent lake level and climate reconstructions. Because these early Holocene openlands have no detectable analogue in New England for the past 7000 years before European settlement, we suggest that all important openlands today are almost exclusively a legacy of Colonial agriculture and should be managed accordingly. Nonetheless, our results may have implications for forest dynamics accompanying projected climate change to more arid conditions in New England over the next century.