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Amphibians are sensitive indicators of environmental conditions and show measurable responses, such …


Biology Articles » Paleobiology » Paleoecology » Temporal response of the tiger salamander (Ambystoma tigrinum) to 3,000 years of climatic variation » Results

Results
- Temporal response of the tiger salamander (Ambystoma tigrinum) to 3,000 years of climatic variation

The total number of identified Ambystoma specimens from the excavation was 2850. The total minimum number of individuals (MNI) from the excavation was determined to be 99. The abundance, represented by MNI, is relatively low in Intervals A, B, D, and E. Interval C, which corresponds to the bulk of the MWP, contains 66% of the Ambystoma fossils, while the intervals before (D and E) and after the MWP (A and B) all contain lower A. tigrinum abundance based on MNI (Table 1).

The body size index (BSI) measurements for the paedomorphs and the terrestrial adults do not show significant changes through time within an age class (two-way ANOVA, p > .10). However, the data do show variability through time that may be a measure of changes in the population, even if it is not a statistically significant deviation. To identify potentially biologically relevant trends between age class BSI's and known climatic periods, the terrestrial adult BSI was compared to the paedomorph BSI. There is a significant difference between the paedomorphic and terrestrial adults when analyzed by interval (ANOVA, p = .021). Comparisons within intervals indicate a significant difference in BSI between paedomorphic and terrestrial adults within interval C (t-test, p 2). Within interval comparisons of BSI for intervals D and E do not show significant differences between paedomorphic and terrestrial adults at the .01 level (t-test, Bonferroni corrected significance level p = .01; interval D, p = .019; interval E, p = .012). However, lack of power may be due to small sample size. To further explore the difference in BSI between paedomorphic and terrestrial adults in the time period prior to interval C, we pooled intervals D and E, and find a significant difference in BSI (t-test, p 2) We also pooled intervals A and B but did not find a significant difference in BSI (t-Test p >> .10) The percent paedomorphosis does not show significant variation through time (Figure 3; p >> .10).

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