To understand the selective pressures that have influenced the evolution and maintenance of paren... more To understand the selective pressures that have influenced the evolution and maintenance of parental care, it is necessary to assess the consequences and function(s) of specific behaviors. We used field and laboratory experiments to investigate possible fitness benefits and proximate functions of female nest attendance in marbled salamanders (Ambystoma opacum). In the first field experiment, nests at which females remained until flooding had higher hatching success than those without attendant females, but results were somewhat equivocal. In the second field experiment we used unattended eggs in artificial clutches randomly assigned to one of four treatment groups: eggs physically agitated to possibly reduce developmental malformations and/or fungal growth, eggs protected from predators, eggs moistened by addition of water and eggs in an unmanipulated control group. Clutches that were protected from predators had significantly higher hatching success than control, agitation and supplemental water groups. In the laboratory experiment, nests in which fungal infection was controlled had higher hatching success than those without sterilized substrates. Also, physical agitation and increased moisture did not confer higher hatching success when fungi were eliminated in the laboratory. Predation and fungal infections appear to decrease hatching success in this species, and female nest attendance may reduce these risks.
Despite the continuing loss of wetland habitats and associated declines in amphibian populations,... more Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog [Rana sphenocephala]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the longterm persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation. Amphibian Biomass and Abundance Gibbons et al. Biomasa y Abundancia de Anfibios Extraordinaria en un Humedal Aislado: Implicaciones para la Conservación de Humedales Resumen: A pesar de la pérdida de hábitats de humedales y las declinaciones asociadas de poblaciones de anfibios, se han realizado pocos intentos para traducir las pérdidas de humedales en pérdidas mensurables en los ecosistemas. Estimamos la productividad potencial de la comunidad de anfibios que se afectaría por la pérdida de un humedal aislado que ha estado protegido de los impactos industriales, agrícolas y urbanos durante losúltimos 54 años. Utilizamos un cerco de desvío en la Bahía Ellentonn, un humedal dulceacuícola de 10 ha en el Río Savannah, cerca de Aiken, Carolina del Sur (E.U.A.), para muestrear todos los anfibios durante 1 año después de una sequía prolongada. A pesar del intensivo uso agrícola del suelo alrededor de la Bahía Ellenton antes de 1951, documentamos 24 especies y números y biomasa de anfibios juveniles notablemente altos (>360,000 individuos; >1,400 kg) en una temporada reproductiva. Los anuros (17 especies) fueron más abundantes que las salamandras (7 especies), y comprendieron 96.4% de las capturas individuales. La mayor parte (95.9%) de la biomasa provino de 232095 individuos de una sola especie de anuro (Rana sphenocephala). Nuestros resultados revelaron que la resiliencia de la comunidad de anfibios a los estresantes naturales y a la alteración histórica del hábitat y la magnitud potencial de la transferencia de biomasa y energía desde los humedales aislados hacia el hábitat terrestre circundante. Atribuimos eléxito post-sequía de los anfibios a una combinación de longevidad de adultos (a menudo > 5 años), la reducción de la abundancia de depredadores y la abundancia de recursos alimenticios para las larvas. Asimismo, el incremento de la cobertura forestal alrededor de la Bahía Ellerton de < 20% en 1951 a > 60% en 2001 probablemente contribuyó a la persistencia de los anfibios a largo plazo en este sitio. Nuestros hallazgos proporcionan un contrapunto optimista al tema de la declinación global de la diversidad biológica al demostrar que los esfuerzos de conservación pueden mitigar a la degradación histórica del hábitat.
We present primers and amplification conditions for 15 microsatellite loci developed for the Cope... more We present primers and amplification conditions for 15 microsatellite loci developed for the Cope's giant salamander (Dicamptodon copei), 14 of which are tetranucleotide repeats. Cross-species amplification revealed 10 of these loci to also be polymorphic in the Pacific giant salamander (Dicamptodon tenebrosus). Several loci produced nonoverlapping allelic ranges between the two species and may be useful in species identification. These polymorphic microsatellite loci are potentially useful for future studies of population genetics in dicamptodontid salamanders.
ABSTRACT Animals that are susceptible to predation sometimes engage in crypsis to conceal themsel... more ABSTRACT Animals that are susceptible to predation sometimes engage in crypsis to conceal themselves from predators. Such behavior often consists of background color matching via substrate choice. Intraspecific color variation may result in differential substrate preference among color morphs. I investigated this idea using juvenile Northern Leopard Frogs (Rana pipiens), which exhibit either green or brown background color. Both color morphs spent more time on dark, concealing substrates than light, revealing ones and hopped less frequently when located on dark, concealing substrates. Frogs did not respond differently to green and brown fabric substrates, and they preferred brown natural substrates over green ones. Because green and brown frogs did not behave differently in any experiment, this study suggests that juvenile Northern Leopard Frogs exhibit a generalized cryptic behavior pattern independent of background body color.
The prevalence of female multiple mating in natural populations is important for many questions i... more The prevalence of female multiple mating in natural populations is important for many questions in mating system evolution. Several statistical techniques use genetic data to estimate the number of fathers that contribute gametes to broods, but they have not been widely compared to assess the magnitude of differences in their performance. With a combination of new data and reanalysis of previously published data, we compared five analytical approaches: (1) allele-counting, (2) parental reconstruction in GERUD, (3) a Bayesian probability model to estimate the frequency of multiple mating (FMM), (4) computer simulations based on population allele frequencies in HAPLOTYPES and (5) Bayesian parental reconstruction in PARENTAGE. The results show that choice of analysis technique can significantly affect estimates of sire number. Estimates from GERUD conformed exactly to results obtained from strict exclusion of potential sires in an experimental context. However, estimates yielded by HAPLOTYPES and PARENTAGE sometimes exceeded the numbers from GERUD by as much as 120 and 55%, respectively. We recommend GERUD over these other approaches for most purposes because of its accuracy and consistency in this analysis. Our novel genetic data set allowed us to investigate the extent and frequency of multiple paternity in a marbled salamander (Ambystoma opacum) population in South Carolina, USA. A. opacum contrasted with other salamander species by having relatively low levels of multiple paternity (only 31-54% compared with 71-96%). Although A. opacum had the lowest level of multiple paternity under all analytical approaches used here, the magnitude of differences among species varied.
Nest site selection is an important part of adult reproductive behavior because growth and surviv... more Nest site selection is an important part of adult reproductive behavior because growth and survival of young are often affected by the local environment. In terrestrially nesting marbled salamanders, nest elevation is likely important to reproductive success because it is directly related to the time of hatching. We tested the hypothesis that females choose nest sites based on elevation and its correlates by controlling the availability of nesting cover, a potentially important factor in nest site selection which often covaries with elevation. Breeding adults were confined to field enclosures in which natural nesting cover had been removed and replaced with equal proportions of artificial cover in each of three elevation zones. In four enclosures that spanned from lowest to highest areas of a wetland breeding site, females used artificial nesting cover most frequently at low elevations. These results contrast with other studies in which intermediate elevations had highest nest densities, but are consistent with a conceptual model in which opposing selective forces result in locally adapted nest site selection.
We describe polymerase chain reaction (PCR) primers and amplification conditions for seven micros... more We describe polymerase chain reaction (PCR) primers and amplification conditions for seven microsatellite DNA loci isolated from the red-spotted newt ( Notophthalmus viridescens ). Primers were tested on 16 individuals from two populations on the Savannah River Site in Aiken County, South Carolina. We detected six to 10 alleles per locus and an overall observed heterozygosity range of 0.31-0.81. Despite low heterozygosity at two of the seven loci, the high polymorphic information contents (from 0.54 to 0.85) of these markers render them useful for future studies of the behavioural and population ecology of this common salamander.
... microsatellite primers in the first chapter and did much of the genotyping for chapter two. M... more ... microsatellite primers in the first chapter and did much of the genotyping for chapter two. Mandy Schable did the digests, enrichments, and cloning for chapter one. ... becoming extinct, endangered, or threatened (Pechmann and Wake 1997; Alford and Richards 1999). ...
To understand the selective pressures that have influenced the evolution and maintenance of paren... more To understand the selective pressures that have influenced the evolution and maintenance of parental care, it is necessary to assess the consequences and function(s) of specific behaviors. We used field and laboratory experiments to investigate possible fitness benefits and proximate functions of female nest attendance in marbled salamanders (Ambystoma opacum). In the first field experiment, nests at which females remained until flooding had higher hatching success than those without attendant females, but results were somewhat equivocal. In the second field experiment we used unattended eggs in artificial clutches randomly assigned to one of four treatment groups: eggs physically agitated to possibly reduce developmental malformations and/or fungal growth, eggs protected from predators, eggs moistened by addition of water and eggs in an unmanipulated control group. Clutches that were protected from predators had significantly higher hatching success than control, agitation and supplemental water groups. In the laboratory experiment, nests in which fungal infection was controlled had higher hatching success than those without sterilized substrates. Also, physical agitation and increased moisture did not confer higher hatching success when fungi were eliminated in the laboratory. Predation and fungal infections appear to decrease hatching success in this species, and female nest attendance may reduce these risks.
Despite the continuing loss of wetland habitats and associated declines in amphibian populations,... more Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog [Rana sphenocephala]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the longterm persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation. Amphibian Biomass and Abundance Gibbons et al. Biomasa y Abundancia de Anfibios Extraordinaria en un Humedal Aislado: Implicaciones para la Conservación de Humedales Resumen: A pesar de la pérdida de hábitats de humedales y las declinaciones asociadas de poblaciones de anfibios, se han realizado pocos intentos para traducir las pérdidas de humedales en pérdidas mensurables en los ecosistemas. Estimamos la productividad potencial de la comunidad de anfibios que se afectaría por la pérdida de un humedal aislado que ha estado protegido de los impactos industriales, agrícolas y urbanos durante losúltimos 54 años. Utilizamos un cerco de desvío en la Bahía Ellentonn, un humedal dulceacuícola de 10 ha en el Río Savannah, cerca de Aiken, Carolina del Sur (E.U.A.), para muestrear todos los anfibios durante 1 año después de una sequía prolongada. A pesar del intensivo uso agrícola del suelo alrededor de la Bahía Ellenton antes de 1951, documentamos 24 especies y números y biomasa de anfibios juveniles notablemente altos (>360,000 individuos; >1,400 kg) en una temporada reproductiva. Los anuros (17 especies) fueron más abundantes que las salamandras (7 especies), y comprendieron 96.4% de las capturas individuales. La mayor parte (95.9%) de la biomasa provino de 232095 individuos de una sola especie de anuro (Rana sphenocephala). Nuestros resultados revelaron que la resiliencia de la comunidad de anfibios a los estresantes naturales y a la alteración histórica del hábitat y la magnitud potencial de la transferencia de biomasa y energía desde los humedales aislados hacia el hábitat terrestre circundante. Atribuimos eléxito post-sequía de los anfibios a una combinación de longevidad de adultos (a menudo > 5 años), la reducción de la abundancia de depredadores y la abundancia de recursos alimenticios para las larvas. Asimismo, el incremento de la cobertura forestal alrededor de la Bahía Ellerton de < 20% en 1951 a > 60% en 2001 probablemente contribuyó a la persistencia de los anfibios a largo plazo en este sitio. Nuestros hallazgos proporcionan un contrapunto optimista al tema de la declinación global de la diversidad biológica al demostrar que los esfuerzos de conservación pueden mitigar a la degradación histórica del hábitat.
We present primers and amplification conditions for 15 microsatellite loci developed for the Cope... more We present primers and amplification conditions for 15 microsatellite loci developed for the Cope's giant salamander (Dicamptodon copei), 14 of which are tetranucleotide repeats. Cross-species amplification revealed 10 of these loci to also be polymorphic in the Pacific giant salamander (Dicamptodon tenebrosus). Several loci produced nonoverlapping allelic ranges between the two species and may be useful in species identification. These polymorphic microsatellite loci are potentially useful for future studies of population genetics in dicamptodontid salamanders.
ABSTRACT Animals that are susceptible to predation sometimes engage in crypsis to conceal themsel... more ABSTRACT Animals that are susceptible to predation sometimes engage in crypsis to conceal themselves from predators. Such behavior often consists of background color matching via substrate choice. Intraspecific color variation may result in differential substrate preference among color morphs. I investigated this idea using juvenile Northern Leopard Frogs (Rana pipiens), which exhibit either green or brown background color. Both color morphs spent more time on dark, concealing substrates than light, revealing ones and hopped less frequently when located on dark, concealing substrates. Frogs did not respond differently to green and brown fabric substrates, and they preferred brown natural substrates over green ones. Because green and brown frogs did not behave differently in any experiment, this study suggests that juvenile Northern Leopard Frogs exhibit a generalized cryptic behavior pattern independent of background body color.
The prevalence of female multiple mating in natural populations is important for many questions i... more The prevalence of female multiple mating in natural populations is important for many questions in mating system evolution. Several statistical techniques use genetic data to estimate the number of fathers that contribute gametes to broods, but they have not been widely compared to assess the magnitude of differences in their performance. With a combination of new data and reanalysis of previously published data, we compared five analytical approaches: (1) allele-counting, (2) parental reconstruction in GERUD, (3) a Bayesian probability model to estimate the frequency of multiple mating (FMM), (4) computer simulations based on population allele frequencies in HAPLOTYPES and (5) Bayesian parental reconstruction in PARENTAGE. The results show that choice of analysis technique can significantly affect estimates of sire number. Estimates from GERUD conformed exactly to results obtained from strict exclusion of potential sires in an experimental context. However, estimates yielded by HAPLOTYPES and PARENTAGE sometimes exceeded the numbers from GERUD by as much as 120 and 55%, respectively. We recommend GERUD over these other approaches for most purposes because of its accuracy and consistency in this analysis. Our novel genetic data set allowed us to investigate the extent and frequency of multiple paternity in a marbled salamander (Ambystoma opacum) population in South Carolina, USA. A. opacum contrasted with other salamander species by having relatively low levels of multiple paternity (only 31-54% compared with 71-96%). Although A. opacum had the lowest level of multiple paternity under all analytical approaches used here, the magnitude of differences among species varied.
Nest site selection is an important part of adult reproductive behavior because growth and surviv... more Nest site selection is an important part of adult reproductive behavior because growth and survival of young are often affected by the local environment. In terrestrially nesting marbled salamanders, nest elevation is likely important to reproductive success because it is directly related to the time of hatching. We tested the hypothesis that females choose nest sites based on elevation and its correlates by controlling the availability of nesting cover, a potentially important factor in nest site selection which often covaries with elevation. Breeding adults were confined to field enclosures in which natural nesting cover had been removed and replaced with equal proportions of artificial cover in each of three elevation zones. In four enclosures that spanned from lowest to highest areas of a wetland breeding site, females used artificial nesting cover most frequently at low elevations. These results contrast with other studies in which intermediate elevations had highest nest densities, but are consistent with a conceptual model in which opposing selective forces result in locally adapted nest site selection.
We describe polymerase chain reaction (PCR) primers and amplification conditions for seven micros... more We describe polymerase chain reaction (PCR) primers and amplification conditions for seven microsatellite DNA loci isolated from the red-spotted newt ( Notophthalmus viridescens ). Primers were tested on 16 individuals from two populations on the Savannah River Site in Aiken County, South Carolina. We detected six to 10 alleles per locus and an overall observed heterozygosity range of 0.31-0.81. Despite low heterozygosity at two of the seven loci, the high polymorphic information contents (from 0.54 to 0.85) of these markers render them useful for future studies of the behavioural and population ecology of this common salamander.
... microsatellite primers in the first chapter and did much of the genotyping for chapter two. M... more ... microsatellite primers in the first chapter and did much of the genotyping for chapter two. Mandy Schable did the digests, enrichments, and cloning for chapter one. ... becoming extinct, endangered, or threatened (Pechmann and Wake 1997; Alford and Richards 1999). ...
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