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Abstract Phenotypic differences between urban and rural populations are well‐documented, but the evolutionary processes driving trait variation along urbanization gradients are often unclear. We combined spatial data on abundance, trait variation, and measurements of fitness to understand cline structure and test for natural selection on heritable coat color morphs (melanic, gray) of eastern gray squirrels (Sciurus carolinensis) along an urbanization gradient. Population surveys using remote cameras and visual counts at 76 sites along the urbanization gradient revealed a significant cline in melanism, decreasing from 48% in the city center to <5% in rural woodlands. Among 76 squirrels translocated to test for phenotypic selection, survival was lower for the melanic than gray morph in rural woodlands, whereas there was no difference in survival between color morphs in the city. These results suggest the urban–rural cline in melanism is explained by natural selection favoring the gray morph in rural woodlands combined with relaxed selection in the city. Our study illustrates how trait variation between urban and rural populations can emerge from selection primarily in rural populations rather than adaptation to novel features of the urban environment.
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Functional Frogs
Evolution by natural selection and adaptation are core concepts in biology that students must see and correctly understand their meaning. However, using these concepts in evidence-based learning strategies in the classroom is a difficult task. Here, we present a 5E lesson plan to address the Next Generation Science Standards performance expectation HS-LS4-4, to “construct an explanation based on evidence for how natural selection leads to adaptation of populations.” The Functional Frogs lesson provides multiple hands-on activities to engage students in the development of hypotheses, collection and analysis of empirical data on frog swimming, presentation of results, and construction of explanations supported by evidence for the results. The lesson’s central idea is for students to understand the trait values that provide an advantage in the aquatic environment, increasing a frog’s survival. The link between morphological changes and survival is used to explain how natural selection acts on populations, leading to adaptive evolution.
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- Award ID(s):
- 2430681
- PAR ID:
- 10529669
- Publisher / Repository:
- American Biology Teacher
- Date Published:
- Journal Name:
- The American Biology Teacher
- Volume:
- 85
- Issue:
- 8
- ISSN:
- 0002-7685
- Page Range / eLocation ID:
- 448 to 453
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1525/abt.2023.85.8.448
