SREL Reprint #3714

Droughts reduce growth rates and increase vulnerability to increasingly frequent and severe drying events in an aquatic ectotherm

Thomas M. Luhring1,2, Lyndsie S. Wszola3, Grant M. Connette4,5, and Christopher M. Schalk6

1Biological Sciences, Wichita State University, Wichita, Kansas, USA 67260
2Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA 29802
3Biological Sciences, University of Nebraska, Lincoln, Nebraska, USA, 68588
4Working Land and Seascapes, Conservation Commons, Smithsonian Institution,
Washington DC, USA, 20013
5Conservation Ecology Center, Smithsonian Conservation Biology Institute,
Front Royal, Virginia, USA, 22630
6Arthur Temple College of Forestry and Agriculture, Stephen F. Austin University,
Nacogdoches, Texas, USA, 75962

Abstract: Many aquatic organisms are experiencing increasingly severe and frequent droughts and drying events. Simultaneously, drought effects are carrying over to nondrought years as ecosystems remain in incomplete states of recovery. Aquatic organisms are thus faced with fewer sequential years under degraded environmental conditions to prepare for increasingly severe droughts and potential drying events. We assessed the effect of droughts and sex on the growth, mass, and mass-dependent estivation potential of long-lived aquatic salamanders (Greater Sirens, Siren lacertina) that estivate during drying events brought on by severe droughts. We calculated growth rates of S. lacertina based on mark–recapture data spanning 11 yr of a severe drought local minimum (of past 50 yr) in the southeastern United States. Sirens showed a distinct seasonal gain in body length and mass from March through September and little growth for the rest of the year. Gains during the growth season were strongly reduced by drought conditions. Although male and female sirens were predicted to reach a similar maximum body size, females grew much slower. Recruitment into drying event ‘‘size refugia’’ is constrained by drying event severity (determines minimum size required), frequency (determines available time between events to grow), and environmental conditions between drying events (determines the rate of growth). Thus, increases in drying event severity and frequency will require faster growth to a larger body size for successful recruitment into a size class that is resistant to drying events. The slower growth of females and reduction of growth during suboptimal years (mild to moderate droughts) suggest that the life history strategy of Greater Sirens for persisting through drying events potentially increases their demographic susceptibility to the predicted effects of climate change.

SREL Reprint #3714

Luhring, T. M., L. S. Wszola, G. M. Connette, and C. M. Schalk. 2022. Droughts reduce growth rates and increase vulnerability to increasingly frequent and severe drying events in an aquatic ectotherm. Journal of Herpetology 56(4): 521-527.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).