Climate change is expected to increase amphibian extinction rates; however, little is known about the physiological responses of amphibian populations to climate change projections for their region. For the Cascade Mountain Range of the U.S. Pacific Northwest, high-resolution climate models predict temperature increases during summer months. We evaluated phenotypic plasticity in larval growth and development in response to this projected increase in temperature in three co-occurring Anuran species: Cascades Frogs (Rana cascadae), Western Toads (Anaxyrus boreas), and Pacific Chorus Frogs (Pseudacris regilla). We exposed each species to two temperature regimes: the control treatment simulated the historical summer temperatures for the decade of 2001–11; the warmed treatment mirrored this seasonal trend but simulated a 4°C average increase in temperature. To quantify the magnitude of plasticity and any consequences to body size, we measured growth characteristics throughout larval development and metamorphosis. We found significant acceleration in larval developmental rates and increased larval body mass under the warmed temperature treatment for all three species. When compared across Gosner developmental stages, however, the perceived weight gain in the warmed treatment was largely because of the advancement in development triggered by warming. As a consequence of rapid development, we observed differential shifts in body size features. We further identified an optimal temperature range (22–25°C) within which all three species showed maximum weight gain and development rates and above which performance plateaued. We provide empirical evidence for species-specific thermal tolerances and the potential for individualistic responses to climate change among co-occurring amphibian species.
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Vol. 51 • No. 2