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Synopsis Urbanization promotes the formation of heat islands. For ectothermic animals in cities, the urban heat island effect can increase developmental rate and result in smaller adult body size (i.e., the temperature-size rule). A smaller adult body size could be consequential for invasive urban ectotherms due to potential effects of body size on thermal tolerance, dispersal distance, and fecundity. Here, we explored the effect of urbanization on body size in the spotted lanternfly (Lycorma delicatula), an invasive planthopper (Hemiptera: Fulgoridae) that is rapidly spreading across urban and non-urban settings in the United States. We then evaluated the consequences of spotted lanternfly body size for heat tolerance, a trait with importance for ectotherm survival in urban heat islands. Contrary to our expectations, we found that both male (P = 0.011) and female (P < 0.001) spotted lanternflies were larger in more urbanized areas and that females displayed a positive effect of body size on resistance to hot temperatures (P = 0.018). These results reject plasticity in developmental rate due to the urban heat island effect as an explanation for spotted lanternfly body size and instead lend necessary (but insufficient) support to an adaptive explanation stemming from advantages of larger body size in cities. This study demonstrates a positive effect of urbanization on spotted lanternfly body size, with potential implications for dispersal distance, fecundity, and thermal tolerance in urban areas.
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The Hydrological Urban Heat Island: Determinants of Acute and Chronic Heat Stress in Urban Streams
Research Impact Statement: Urbanization increases baseflow stream temperature and exacerbates stream temperature surges, creating a hydrological urban heat island. ABSTRACT: During and after rainfall events, the interaction of precipitation with hot urban pavements leads to hot runoff, and its merger with urban streams can result in an abrupt change in water temperature that can harm aquatic ecosystems. To understand this phenomenon and its relation to land cover and hydrometeorological parameters, we analyzed data spanning two years from 100 sites in the eastern United States. To identify surges, we first isolated temperature jumps of at least 0.5°C over 15 min occurring simultaneously with water flow increase. Surge magnitude was defined as the difference between peak stream temperature and baseflow temperature right before the jump. At least 10 surges were observed in 53 of the studied streams, with some surges exceeding 10°C. Our results demonstrate that the watershed developed area and vegetation fraction are the best descriptors of surge frequency (Spearman correlation of 0.76 and 0.77, respectively). On the other hand, for surge magnitude and peak temperature, the primary drivers are stream discharge and stream temperature immediately before the surge. In general, the more urbanized streams were found to be already warmer than their more “vegetated” counterparts during baseflow conditions, and were also the most affected by temperature surges. Together, these findings suggest the existence of a hydrological urban heat island, here defined as the increase in stream temperature (chronic and/or acute), caused by increased urbanization.
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- Award ID(s):
- 1855277
- PAR ID:
- 10301773
- Date Published:
- Journal Name:
- Journal of the American Water Resources Association
- ISSN:
- 1093-474X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/1752-1688.12963
