Thermoregulatory opportunity and competition act independently on life‐history traits in aquatic ectotherms

Abstract

1. Many ectothermic species use behavioural thermoregulation to reduce their exposure to climate change. The buffering effect of behavioural thermoregulation will depend on the time available for an ectotherm to attain a body temperature within the target range, that is, the 'opportunity for thermoregulation'.Behavioural thermoregulation can be further altered by the presence of competitors. Spatiotemporal dynamics in opportunity for thermoregulation and competition intensity should affect variation in ectotherm life history and fitness; however, experimental support for their joint influence is missing.2. I tested this prediction in a mesocosm experiment using larvae of two sympatric amphibians, the alpine newt Ichthyosaura alpestris and the common newt Lissotriton vulgaris. Thermoregulatory opportunities and competition intensities were manipulated by exposing larvae to warmer temperatures and altering densities of con-and heterospecifics. Life-history traits were monitored until metamorphic emergence from the water.3. Thermoregulatory opportunity accelerated differentiation rate and time to metamorphic emergence, while both intra-and interspecific competition affected growth rate and mass at emergence. The impact of competition on survival and injury rates varied between taxa. 4. Thermoregulatory opportunity and competition impacted larval life-history traits in an additive fashion. Suitable conditions for thermoregulation allowed larvae to shorten their developmental period, and thus escape from the aquatic environment earlier than in thermoregulatory challenging environment.Competition was a primary determinant of mass at emergence, which is an important fitness correlate in amphibians. Species-specific survival under competition may contribute to variation in habitat requirements between sympatric taxa. 5. To sum up, predictions on the impact of climate change on ectotherm life histories require information not only about environmental temperatures, but also about species thermoregulatory opportunities and competitive abilities. Thermoregulatory opportunity is an ecologically relevant habitat property not only for basking ectotherms but also for taxa using less conspicuous | 2521

Sensitivity of amphibian embryos to timing and magnitude of present and future thermal extremes

“…Moreover, it reduces the risk of desiccation during periods of high water volume fluctuations in temporary pools (Williams, 2006). Larger size decreases vulnerability to predation (Gvoždík & Smolinský, 2015) and increases competitive ability in newt larvae (Gvoždík, 2022). Consequently, the effects of thermal extremes on embryonic traits are likely to be beneficial, yet highly context‐dependent in our study system.…”

“…The increased exploratory activity in larvae can have both beneficial and detrimental effects on fitness. More active larvae have a higher chance of locating suitable food or temperature patches, which accelerate their development (Gvoždík, 2022). However, heightened locomotor activity may also increase the risk of predation from visually oriented predators such as dragonfly larvae.…”

Standard methods for marking caudate amphibians do not impair animal welfare over the short term: An experimental approach

“…Despite this, the majority of assessments of marking techniques have focused on anurans (but see Ott & Scott 1999 ; Davis & Ovaska 2001 ; Kinkead et al 2006 ). Here, we examined the behavioural impacts of two invasive marking techniques on the European alpine newt ( Ichthyosaura alpestris ), a caudate species that is often the subject of numerous demographic and behavioural studies (for recent examples, see Diego-Rasilla & Phillips 2021 ; Gvoždík 2022 ; Bernabò et al 2023 ). The overriding aim of the study was to systematically evaluate the short-term effects of handling versus toe clipping and VIE marking on newt behaviour.…”

Standard methods for marking caudate amphibians do not impair animal welfare over the short term: an experimental approach

“…Despite this, the majority of assessments of marking techniques have focussed on anurans (but see Ott & Scott 1999; Davis & Ovaska 2001; Kinkead et al 2006; McCarthy et al 2009). Here, we examined the impacts of two invasive marking techniques on the European alpine newt ( ichthyosaura alpestris ), a caudate species that is often the subject of numerous demographic and behavioural studies (recent examples: Bernabo et al 2023; Gvoždík 2022; Diego-Rasilla & Phillips 2021). The overriding aim of the study was to systematically evaluate the short-term effects of handling versus toe-clipping and VIE marking on newt behaviour.…”