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Raymond D. Semlitsch - One of the best experts on this subject based on the ideXlab platform.
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Seasonal Terrestrial Microhabitat Use by Gray Treefrogs (Hyla versicolor) in Missouri Oak-hickory Forests
Herpetologica, 2008Co-Authors: Jarrett R. Johnson, Rachel D. Mahan, Raymond D. SemlitschAbstract:It is important to identify and understand the critical habitat components of organisms inhabiting landscapes that are increasingly altered by human activities to adequately predict the effects of habitat alteration on natural populations. Our study identifies terrestrial habitats that are important to the gray treefrog (Hyla versicolor) during the nonbreeding season using radiotracking and mark-recapture/release of individuals captured in artificial arboreal refugia. High humidity and rainfall were associated with decreased captures in artificial refugia, while high ambient air temperatures were correlated with increases in the number of treefrog captures. Refugia placed in small trees recorded more small individuals than those in larger trees, and refugia in white oaks (Quercus alba) contained females more frequently than expected at random. We found that space-use estimates encompassing foraging and overwintering locations of gray treefrogs were relatively small and typically included only a few adjace...
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Effects of Experimental Clearcut Logging on Gray Treefrog (Hyla versicolor) Tadpole Performance
Journal of Herpetology, 2008Co-Authors: Daniel J Hocking, Raymond D. SemlitschAbstract:Abstract Clearcutting detrimentally affects the populations of many amphibian species. However, Gray Treefrogs (Hyla versicolor) have shown a preference for breeding sites located in clearcuts near forested habitat. To test the implications of this preference, we examined Gray Treefrog tadpole performance in cattle tanks along a gradient from clearcut to forest habitat. We replicated this design at three experimental clearcut sites. Tadpole performance was measured as length of the larval period, size at metamorphosis, and survival. We also examined the influence of temperature, periphyton productivity, and invertebrate predator abundances on tadpole performance. Time to metamorphosis was shorter in the clearcuts, but metamorphs tended to be smaller than metamorphs in the forest tanks. Survival was also greater in the clearcuts than in the forest treatments. Higher temperatures in the clearcuts primarily contributed to tadpole performance whereas invertebrate predators did not appear to influence performa...
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Sex and seasonal differences in the spatial terrestrial distribution of gray treefrog (Hyla versicolor) populations
Biological Conservation, 2007Co-Authors: Jarrett R. Johnson, Jason H. Knouft, Raymond D. SemlitschAbstract:Abstract Fragmentation of terrestrial landscapes has exacerbated the need to understand the spatial requirements of organisms, especially those that undergo seasonal migrations, such as pond-breeding amphibians. Pond-breeding amphibians spend much of their lives in terrestrial habitat at some distance from aquatic breeding sites. The terrestrial habitat required by a particular individual encompasses the area adjacent to a breeding pond that is used for activities such as foraging or overwintering, as well as the expanses of habitat through which it moves. To elucidate amphibian spatial habitat requirements, we monitored gray treefrog (Hyla versicolor) movements through terrestrial habitat adjacent to breeding ponds using radiotelemetry and mark–recapture along transects of artificial refugia. Results indicate that gray treefrogs frequently make migrations between foraging grounds, overwintering sites, and breeding ponds of 200 m or more, with a maximum-recorded movement distance of 330 m. Additionally, females travel farther than males for reasons independent of body size, and the distribution of males during the breeding season is biased towards breeding ponds relative to the non-breeding season. The data illustrate the importance of habitat directly adjacent to breeding sites for males, and indicate that habitat loss resulting in small patches may have a greater negative impact on females than males, and consequently may have disproportionately large effects on population persistence. These results emphasize that effective management of amphibian breeding locations via protection of both aquatic and adjacent upland terrestrial resources likely requires detailed information regarding variation in movements between the sexes and among seasonal activity periods.
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effects of timber harvest on breeding site selection by gray treefrogs Hyla versicolor
Biological Conservation, 2007Co-Authors: Daniel J Hocking, Raymond D. SemlitschAbstract:Abstract Despite numerous studies showing reduced amphibian abundance and diversity following habitat modification, little is known about the mechanisms causing these observed patterns. We examined the effects of four experimental forest management treatments on breeding-site selection by gray treefrogs (Hyla versicolor) in Missouri. Our study of four management treatments included a clearcut with high amounts of coarse woody debris (CWD), a clearcut with lower amounts of CWD, a partial timber cut, and an uncut control. We placed five plastic wading pools in each treatment replicated at three sites and found that gray treefrogs laid significantly more eggs in the clearcuts (low-CWD 77,185 eggs; high-CWD 51,990 eggs) than in either the partial (13,553 eggs) or the control (14,068 eggs) treatments. We further examined the importance of distance between breeding sites and mature forest habitat by placing cattle tanks 50 m into clearcuts, 10 m into clearcuts, 10 m into forests, and 50 m into forests. Gray treefrogs oviposited eggs more frequently in the clearcut-edge tanks (17 occasions) than in the clearcut (7), forest (8), or forest-edge (3) tanks, but eggs were not counted. Despite the preference for open canopy breeding sites, oviposition was less in sites located farther from forest edges. Male captures at the tanks indicated that males also preferred clearcut treatments but were not inhibited by the 50 m distance from the forest edge. Although reduced canopy cover over breeding ponds may benefit tadpoles, logging operations should avoid excessively isolating aquatic habitat from forested uplands.
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Defining core habitat of local populations of the gray treefrog (Hyla versicolor) based on choice of oviposition site
Oecologia, 2003Co-Authors: Jarrett R. Johnson, Raymond D. SemlitschAbstract:Concern over amphibian population declines and loss of terrestrial and aquatic habitat have emphasized the need to define habitat requirements for each stage in a species' life history. The realization that pond-breeding amphibians spend most of their lives in the terrestrial environment suggests the need to protect terrestrial as well as aquatic habitat. Many studies on amphibian populations have focused on emigration from breeding sites to define habitat use; however these studies do not typically elucidate terrestrial activities of adults within the breeding season. We measured colonization rates of artificial pools by gray treefrogs ( Hyla versicolor ) at multiple distances from natural breeding ponds. We found a non-random distribution of egg deposition among distances, with 95% of eggs deposited within 15 m of the breeding pond. Additionally, we found that the time to first colonization of artificial pools increased with respect to distance. Our results indicate that adult gray treefrogs may travel up to 200 m within a breeding season, and that multiple breeding ponds may be considered part of a single population. We suggest that a minimum core terrestrial habitat of 60 m surrounding breeding sites is appropriate for protection of local populations of gray treefrogs.
H. Carl Gerhardt - One of the best experts on this subject based on the ideXlab platform.
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A multivariate analysis of genetic variation in the advertisement call of the gray treefrog, Hyla versicolor.
Evolution, 2014Co-Authors: Allison M. Welch, Michael J. Smith, H. Carl GerhardtAbstract:Genetic variation in sexual displays is crucial for an evolutionary response to sexual selection, but can be eroded by strong selection. Identifying the magnitude and sources of additive genetic variance underlying sexually selected traits is thus an important issue in evolutionary biology. We conducted a quantitative genetics experiment with gray treefrogs (Hyla versicolor) to investigate genetic variances and covariances among features of the male advertisement call. Two energetically expensive traits showed significant genetic variation: call duration, expressed as number of pulses per call, and call rate, represented by its inverse, call period. These two properties also showed significant genetic covariance, consistent with an energetic constraint to call production. Combining the genetic variance-covariance matrix with previous estimates of directional sexual selection imposed by female preferences predicts a limited increase in call duration but no change in call rate despite significant selection on both traits. In addition to constraints imposed by the genetic covariance structure, an evolutionary response to sexual selection may also be limited by high energetic costs of long-duration calls and by preferences that act most strongly against very short-duration calls. Meanwhile, the persistence of these preferences could be explained by costs of mating with males with especially unattractive calls.
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Gray tree frogs, Hyla versicolor, give lower-frequency aggressive calls in more escalated contests
Behavioral Ecology and Sociobiology, 2013Co-Authors: Michael S. Reichert, H. Carl GerhardtAbstract:As animal contests escalate, variation in the performance of aggressive signaling behaviors can give important insights into contest dynamics. In anuran amphibians, males of numerous species utilize distinctive aggressive vocalizations during disputes over calling spaces. Little is known, however, about the causes and consequences of variation in aggressive-call characteristics. We analyzed recordings of calls made during staged aggressive interactions between male gray tree frogs, Hyla versicolor , to determine how variation in a key aggressive-call characteristic, dominant frequency, was affected by increasing contest escalation. We found that dominant frequencies of aggressive calls were lower than those of advertisement calls used to attract females. Furthermore, we found that males lowered their aggressive-call frequencies with increases in escalation. Winners tended to have lower-frequency aggressive calls than losers. We conclude that aggressive calls in H. versicolor are similar to the graded aggressive calls that have been described in several other species. This gradation may allow males to balance the energetic costs of producing lower-frequency calls with the benefits of efficiently repelling rival males. Other processes related to motivation and the physiological effects of participating in contests may also be responsible for the observed variation in aggressive-call frequency with contest escalation. Our results demonstrate that detailed experimental studies of aggressive calling behavior in anurans, which to this point have rarely been performed, are feasible and generate important insights relating to general problems in animal contest behavior and animal communication.
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Socially mediated plasticity in call timing in the gray tree frog, Hyla versicolor
Behavioral Ecology, 2012Co-Authors: Michael S. Reichert, H. Carl GerhardtAbstract:Call timing is an important component of the behavioral repertoire of many chorusing species that compete acoustically for mates. The costs and benefits of particular call-timing patterns may vary with factors in the social environment, yet few studies have examined the possibility of socially mediated plasticity in call timing. We studied the effects of competition on advertisement-call timing in the gray tree frog, Hyla versicolor, by manipulating intermale distances in staged interactions. We measured phase angles and the proportion of calls that overlapped as interacting pairs of males were moved closer to one another, simulating an increase in acoustic competition. We observed a shift in phase angle resulting in substantially higher levels of overlap as males were moved so that they were calling at extremely close range. At close range, males often engage in intense agonistic contests over the calling space and we found that call timing may play a role in these interactions. Although there were not major differences in the call-timing behavior of winners and losers of contests, we suggest that call overlap may be a general signal of aggressive motivation. Changes in call timing with changes in intermale distance may, therefore, be related to changes in the intended audience as competition escalates.
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Trade-Offs and Upper Limits to Signal Performance during Close-Range Vocal Competition in Gray Tree Frogs Hyla versicolor
The American Naturalist, 2012Co-Authors: Michael S. Reichert, H. Carl GerhardtAbstract:Abstract Performance limitations on signal production constrain signal evolution. Variation in signaling performance may be related to signaler quality and therefore is likely to be a salient aspect of communication systems. When multiple signal components are involved in communication, there may be trade-offs between components, and performance can be measured as the degree to which signalers approach the upper limits of the trade-off function. We examined vocal performance in the gray tree frog Hyla versicolor, in which females prefer values of call duration and rate exceeding the usual range of variation within and among males. We recorded interactions between pairs of males calling on mobile platforms that allowed us to manipulate intermale distance and place males in highly competitive environments. We found that, although there was a clear upper boundary on the ability of males to maximize call duration and call rate simultaneously, call effort did not remain constant in this highly competitive situ...
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A precedence effect underlies preferences for calls with leading pulses in the grey treefrog, Hyla versicolor.
Animal Behaviour, 2010Co-Authors: Vincent T. Marshall, H. Carl GerhardtAbstract:The temporal relationship between signals often has strong and repeatable influences on receiver behaviour. While several studies have shown that receivers prefer temporally leading signals, we show that the relative timing of signal elements within overlapping signals can also have repeatable influences on receiver responses. Female grey treefrogs, Hyla versicolor, preferred overlapping conspecific advertisement call alternatives in which pulses were in the leading position relative to pulses in an alternative. The preference was maintained even when the first pulse of the stimulus with leading pulses began after that of the call with following pulses. To rule out the possibility of masking interference of the pulse pattern, we used a split-pulse design in which the playback of two nonoverlapping pulse elements were synchronized from spatially separated speakers. Females were attracted to the source of the short (6 ms) leading pulse element, which did not attract females in isolation, even though its amplitude was 24 dB lower than the long (24 ms) following element, which did attract females in isolation. Taken together, our results fall within a range of phenomena that have been classified as precedence effects. However, to our knowledge, showing localization based on successive leading pulses rather than the very first-arriving pulse is a novel discovery for nonhuman animals.
Michael S. Reichert - One of the best experts on this subject based on the ideXlab platform.
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Frequency channel-dependent selectivity for temporal call characteristics in gray treefrogs, Hyla versicolor.
The Journal of experimental biology, 2017Co-Authors: Michael S. Reichert, Gerlinde HöbelAbstract:Sensory receptors transmit information on multiple stimulus dimensions. Much remains to be understood about how the processing of different signal characteristics is partitioned and integrated in different areas of the nervous system. Amphibian hearing involves two morphologically distinct inner-ear organs that process different components of the frequency spectrum. Many anuran signals contain two frequency peaks, each one matching the sensitivity of one of these two organs. We hypothesized that the processing of temporal characteristics of acoustic signals would differ in these two frequency channels, perhaps because of differences in the response properties of the two inner-ear organs. We tested this hypothesis in the gray treefrog, Hyla versicolor; male advertisement calls of this species contain a bimodal frequency spectrum. We generated synthetic male advertisement calls in which we independently manipulated the pattern of amplitude modulation in the low-frequency peak or the high-frequency peak and measured the attractiveness of these stimuli to females in single-speaker and two-speaker phonotaxis tests. We obtained multiple lines of evidence that females were more selective for fine-temporal characteristics in the high-frequency peak. We discuss the potential implications of frequency channel-dependent temporal processing for signal evolution and suggest that additional neurophysiological investigations of the anuran auditory periphery will give important insights into how the nervous system partitions the encoding of multiple characteristics of complex signals.
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Female gray treefrogs, Hyla versicolor, are responsive to visual stimuli but unselective of stimulus characteristics.
The Journal of experimental biology, 2014Co-Authors: Michael S. Reichert, Holland Galante, Gerlinde HöbelAbstract:The visual ecology of nocturnal anurans is poorly understood, but there is growing evidence that vision plays a role in important behaviors such as mate choice. While several recent studies have demonstrated that females are responsive to visual cues when selecting mates, the forces responsible for these preferences are unknown. We investigated the responsiveness of female gray treefrogs, Hyla versicolor, to video playbacks of calling conspecific males in which we varied attributes of the vocal sac, a conspicuous visual characteristic of calling males and a target of female choice in other species. Females responded surprisingly strongly to the video playbacks, but did so indiscriminately with respect to variation in vocal sac characteristics. We followed up on these results with a series of additional tests that examined female responses to abstract stimuli. Females continued to respond to such stimuli, leading us to conclude that their behavior was related to a generalized phototactic response. Because of this, we were unable to make conclusions regarding female preferences for vocal sac characteristics. Nonetheless, our results are significant in two respects. First, we illustrate that despite much effort into improving video playback methodologies, challenges remain, and we offer our experimental design as a method to ensure that appropriate conclusions can be drawn from such studies. Second, we argue that the female phototactic response has potentially significant behavioral implications and in general the consequences of anuran visual preferences deserve further investigation.
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Gray tree frogs, Hyla versicolor, give lower-frequency aggressive calls in more escalated contests
Behavioral Ecology and Sociobiology, 2013Co-Authors: Michael S. Reichert, H. Carl GerhardtAbstract:As animal contests escalate, variation in the performance of aggressive signaling behaviors can give important insights into contest dynamics. In anuran amphibians, males of numerous species utilize distinctive aggressive vocalizations during disputes over calling spaces. Little is known, however, about the causes and consequences of variation in aggressive-call characteristics. We analyzed recordings of calls made during staged aggressive interactions between male gray tree frogs, Hyla versicolor , to determine how variation in a key aggressive-call characteristic, dominant frequency, was affected by increasing contest escalation. We found that dominant frequencies of aggressive calls were lower than those of advertisement calls used to attract females. Furthermore, we found that males lowered their aggressive-call frequencies with increases in escalation. Winners tended to have lower-frequency aggressive calls than losers. We conclude that aggressive calls in H. versicolor are similar to the graded aggressive calls that have been described in several other species. This gradation may allow males to balance the energetic costs of producing lower-frequency calls with the benefits of efficiently repelling rival males. Other processes related to motivation and the physiological effects of participating in contests may also be responsible for the observed variation in aggressive-call frequency with contest escalation. Our results demonstrate that detailed experimental studies of aggressive calling behavior in anurans, which to this point have rarely been performed, are feasible and generate important insights relating to general problems in animal contest behavior and animal communication.
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Sources of variability in advertisement and aggressive calling in competitive interactions in the grey treefrog, Hyla versicolor
Bioacoustics, 2013Co-Authors: Michael S. ReichertAbstract:Understanding the sources and magnitudes of variation in signal traits is an important first step towards understanding the forces that may act on signal evolution. In anuran amphibians, acoustic communication plays a major role in the processes of mate attraction and aggression. The significance of variation in characteristics of the mate-attracting advertisement calls is relatively well understood, whereas another call type, the aggressive call, has received much less attention. I recorded both advertisement and aggressive calls given by male grey treefrogs, Hyla versicolor, in staged competitive interactions. From these recordings, I assessed the effects of physical and abiotic influences on signal production by measuring the correlations between the call characteristics of both call types and variables associated with size, body condition and body temperature. I also estimated within- and between-male variation in call characteristics. Temperature affected diverse characteristics of both call types, w...
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Socially mediated plasticity in call timing in the gray tree frog, Hyla versicolor
Behavioral Ecology, 2012Co-Authors: Michael S. Reichert, H. Carl GerhardtAbstract:Call timing is an important component of the behavioral repertoire of many chorusing species that compete acoustically for mates. The costs and benefits of particular call-timing patterns may vary with factors in the social environment, yet few studies have examined the possibility of socially mediated plasticity in call timing. We studied the effects of competition on advertisement-call timing in the gray tree frog, Hyla versicolor, by manipulating intermale distances in staged interactions. We measured phase angles and the proportion of calls that overlapped as interacting pairs of males were moved closer to one another, simulating an increase in acoustic competition. We observed a shift in phase angle resulting in substantially higher levels of overlap as males were moved so that they were calling at extremely close range. At close range, males often engage in intense agonistic contests over the calling space and we found that call timing may play a role in these interactions. Although there were not major differences in the call-timing behavior of winners and losers of contests, we suggest that call overlap may be a general signal of aggressive motivation. Changes in call timing with changes in intermale distance may, therefore, be related to changes in the intended audience as competition escalates.
A.m. Welch - One of the best experts on this subject based on the ideXlab platform.
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Genetic variation and a fitness tradeoff in the tolerance of gray treefrog (Hyla versicolor) tadpoles to the insecticide carbaryl
Oecologia, 2000Co-Authors: R.d. Semlitsch, C.m. Bridges, A.m. WelchAbstract:One of the major unanswered questions in the study of global amphibian declines is why only some species or populations suffer declines. A possible explanation is that species and populations vary in the genetic basis of their tolerance to environmental stress such as chemical contamination. The presence of genetic variation in tolerance to chemicals and in fitness traits of amphibians is essential for persistence of species populations through survival and successful reproduction in contaminated environments. We tested for the presence of genetic variation in the tolerance of amphibian larvae to the insecticide carbaryl using gray treefrog tadpoles ( Hyla versicolor ). We also assessed whether tolerance of tadpoles is negatively associated with larval performance traits directly related to adult fitness, thereby providing a test of the "cost of tolerance" hypothesis. Our results demonstrate significant variation in tolerance of tadpoles to the insecticide carbaryl within a single population of the gray treefrog, Hyla versicolor . Our half-sibship design indicates that variation among sires explains a significant amount of the variation in chemical tolerance thereby suggesting a heritability genetic basis. Our results also indicate the presence of a fitness tradeoff with tolerance to the chemical carbaryl being negatively correlated, or traded off, with survival of tadpoles reared in the field in the absence of the chemical. Knowledge of genetic tradeoffs with chemical tolerance under realistic environmental conditions will be important for predicting the rate of adaptation and potential for persistence of species. Finally, the partitioning of environmental and genetic variation in tolerance to chemicals is critical to identifying which species are most susceptible, the amount of genetic variance present, the potential for adaptation to contaminants, and the presence of fitness tradeoffs. Such information is necessary to clearly understand the persistence of populations, and ultimately, the processes leading to species declines.
Rick A. Relyea - One of the best experts on this subject based on the ideXlab platform.
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Critical thermal maximum (CTmax), sample size (N) and body mass (Mass) of Hyla versicolor tadpoles, in four treatments.
2014Co-Authors: Marco Katzenberger, John Hammond, Helder Duarte, Miguel Tejedo, Cecilia Calabuig, Rick A. RelyeaAbstract:Critical thermal maximum (CTmax), sample size (N) and body mass (Mass) of Hyla versicolor tadpoles, in four treatments.
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ANOVA using burst speed as dependent variable, and temperature, mesocosm, predator cues and Roundup as categorical predictors, with mesocosm nested within the interaction of predator cues and Roundup, for Hyla versicolor.
2014Co-Authors: Marco Katzenberger, John Hammond, Helder Duarte, Miguel Tejedo, Cecilia Calabuig, Rick A. RelyeaAbstract:ANOVA using burst speed as dependent variable, and temperature, mesocosm, predator cues and Roundup as categorical predictors, with mesocosm nested within the interaction of predator cues and Roundup, for Hyla versicolor.
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Parameters of thermal performance curves for maximum swimming speed in four treatments, for Hyla versicolor, estimated with TMV method (Izem and Kingsolver, 2005) and nlinfit/nlparci functions in Matlab (Mathworks, 2009).
2014Co-Authors: Marco Katzenberger, John Hammond, Helder Duarte, Miguel Tejedo, Cecilia Calabuig, Rick A. RelyeaAbstract:Parameters of thermal performance curves for maximum swimming speed in four treatments, for Hyla versicolor, estimated with TMV method (Izem and Kingsolver, 2005) and nlinfit/nlparci functions in Matlab (Mathworks, 2009).
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ANOVA using CTmax as dependent variable, predator cues and Roundup as categorical factors (including the interaction of these factors) and, mesocosm nested within the interaction of predator cues and Roundup, for Hyla versicolor.
2014Co-Authors: Marco Katzenberger, John Hammond, Helder Duarte, Miguel Tejedo, Cecilia Calabuig, Rick A. RelyeaAbstract:ANOVA using CTmax as dependent variable, predator cues and Roundup as categorical factors (including the interaction of these factors) and, mesocosm nested within the interaction of predator cues and Roundup, for Hyla versicolor.
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Interspecific distribution-abundance relationship for thirteen species of ESGR amphibians.
2014Co-Authors: Earl E. Werner, Rick A. Relyea, Christopher J. Davis, David K. Skelly, Michael F. Benard, Shannon J. MccauleyAbstract:Data fit to the relationship, y = a(1−bx), R2 = 0.73, F1,11 = 30.4, p = 0.0002. Species represented are: Hyla versicolor (Hve), Pseudacris crucifer (Pcr), P. triseriata (Ptr), Rana catesbeiana (Rca), R. clamitans (Rcl), R. pipiens (Rpi), R. sylvatica (Rsy), Ambystoma laterale (Ala), A. maculatum (Ama), A. tigrinum (Ati), and Notophthalmus viridescens (Nvi).