An amphibian's life history includes patterns such as growth, development, and reproduction. These life history traits are essential to the fundamental understanding of population dynamics. Despite the importance of life history traits, key knowledge gaps still exist, hindering key information on birth/death rates, age/size at sexual maturity, size at metamorphosis, and clutch sizes for amphibians. Moreover, these life patterns can vary due to environmental conditions such as temperature and food availability, further emphasizing the importance of knowledge of species demographics. In this study, I aimed to investigate the growth of young-of-the-year and juvenile plethodontid salamanders with different life cycles, Plethodon cinereus (direct development) and Eurycea cirrigera (metamorphosis). Specifically, I was interested in examining the response of growth trajectories to different temperatures and food availability. I hypothesized that salamanders in the high-temperature treatment will grow faster initially but will be smaller at the conclusion of the experiment, while salamanders in the low-temperature treatment will grow slower initially but will be larger at the end of the experiment. To investigate the interaction between body size and environmental conditions, I exposed both species of salamanders to a factorial design, with two food treatments crossed with two temperature treatments. To analyze the data, I used a generalized additive mixed model (GAMM). The study revealed distinct growth patterns for both species of salamanders. P. cinereus experienced linear growth throughout the duration of the study, whereas E. cirrigera displayed non-linear growth (Throughout the experiment, salamander experienced a decrease in total length and mass). The results of the GAMM did not support my hypothesis for P. cinereus. However, the GAMM results did provide support for my hypothesis in the case of E. cirrigera under high food availability treatment. Furthermore, salamanders with limited food availability in both experiments grew at a slower rate. Forecasting the impacts of climate change on salamander populations is complex and will require the understanding of habitat quality and climate factors. / Master of Science / With the threats of climate change, habitat fragmentation, and disease looming, it's crucial we begin to understand amphibian life history traits, which includes the patterns of growth, development, and reproduction. These life history traits can vary due to environmental conditions and are essential to the fundamental understanding of population size and structure. Despite the importance of life history traits, information on amphibian birth/death rates, age/size at sexual maturity, size at metamorphosis, and clutch sizes are unknown, further emphasizing the importance of understanding species demographics. In this study, I investigated the growth of young-of-the-year and juvenile individuals of two plethodontid salamander species: eastern red-backed salamander and the southern two-lined salamander. These species exhibit two different life strategies. The eastern red-backed salamander is a fully terrestrial direct developing salamander without a distinct metamorphic stage, experiencing gradual growth without major morphological changes. However, the southern two-lined salamander semi aquatic salamander that goes through metamorphosis (Undergoes an aquatic larval stage but transitions to a terrestrial salamander), experiencing major morphological and physiological changes. I investigated the growth response of these two species of salamanders when exposed to different temperatures and when food availability varied from high to low. I hypothesized that salamanders in the high-temperature treatment will grow faster but be smaller at the conclusion of the experiment. While salamanders in the low-temperature treatment would grow slower but be larger at the end of the experiment. To understand the interaction between body size and environmental conditions, I exposed both species of salamanders to a 2x2 factorial experiment design that consisted of 2 food treatments and 2 temperature treatments. To analyze the results, I used a generalized additive mixed model. The results of the study indicated that both species of salamander differed in growth. The eastern red-backed salamander demonstrated linear growth throughout the experiment, while the southern two-lined salamander exhibited non-linear growth (During the experiment, salamanders experienced a decrease in total length and mass). However, the results of the eastern red-backed salamander did not support my hypothesis. Conversely, when food availability was high enough, the results supported my hypothesis for the southern two-lined salamander. Moreover, salamanders exposed to limited food availability in both experiments experienced a decrease in growth rates. Forecasting the impacts of climate change on salamander populations is complex and will require comprehension and insight to habitat quality and climate variables.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/116305 |
| Date | 19 September 2023 |
| Creators | Holguin, Charlie |
| Contributors | Fish and Wildlife Conservation, Kindsvater, Holly, Haas, Carola A., Caruso, Nicholas Michael |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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