Amphibian breeding phenology influences offspring size and response to a common wetland contaminant

Abstract

Background Increases in temperature variability associated with climate change have critical implications for the phenology of wildlife across the globe. For example, warmer winter temperatures can induce forward shifts in breeding phenology across taxa (“false springs”), which can put organisms at risk of freezing conditions during reproduction or vulnerable early life stages. As human activities continue to encroach on natural ecosystems, it is also important to consider how breeding phenology interacts with other anthropogenic stressors (e.g., pollutants). Using 14 populations of a widespread amphibian (wood frog; Rana sylvatica), we compared 1) growth; 2) tolerance to a common wetland contaminant (NaCl); and 3) the ability of tadpoles to acclimate to lethal NaCl exposure following sublethal exposure earlier in life. We evaluated these metrics across two breeding seasons (2018 and 2019) and across populations of tadpoles whose parents differed in breeding phenology (earlier- versus later-breeding cohorts). In both years, the earlier-breeding cohorts completed breeding activity prior to a winter storm and later-breeding cohorts completed breeding activities after a winter storm. The freezing conditions that later-breeding cohorts were exposed to in 2018 were more severe in both magnitude and duration than those in 2019. Results In 2018, offspring of the later-breeding cohort were larger but less tolerant of NaCl compared to offspring of the earlier-breeding cohort. The offspring of the earlier-breeding cohort additionally were able to acclimate to a lethal concentration of NaCl following sublethal exposure earlier in life, while the later-breeding cohort became less tolerant of NaCl following acclimation. Interestingly, in 2019, the warmer of the two breeding seasons, we did not detect the negative effects of later breeding phenology on responses to NaCl. Conclusions These results suggest that phenological shifts that expose breeding amphibians to freezing conditions can have cascading consequences on offspring mass and ability to tolerate future stressors but likely depends on the severity of the freeze event.

Spring temperature and land use change are associated withRana temporariareproductive success and phenology

“…In common toads Bufo bufo in the United Kingdom, warmer than average temperatures correlated with decreased body condition and survival (Reading 2007). Recent work on wood frogs showed that phenological shiZs can expose individuals to colder temperatures and resulted in lower tolerance of offspring to pollutants like NaCl (Buss et al 2021). Collectively these data suggest that in some species, warming can induce cryptic cost of breeding plasticity in multiple life stages that are not immediately apparent if looking at phenological variables alone (see Blaustein et al 2010).…”

“…Increased winter precipitation resulting from climate change can benefit some amphibians (Benard 2015), but extreme weather events and advanced phenologies are likely to negatively impact others (Blaustein et al . 2010; Buss et al 2021). In a review of the impacts of increased droughts and extreme precipitation, Walls et al .…”

Random Frogs: Using future climate and land-use scenarios to predict amphibian distribution change in the Upper Missouri River Basin

“…The effects of climate change on amphibians are threatening the survival of numerous species by altering phenological cues for spring emergence (Buss et al 2021) and shifting available temperature ranges surrounding biological processes (Fontaine et al 2018), forcing species to rapidly adapt or migrate to remain within thermal optima (Enriquez-Urzelai et al 2019). For example, amphibians have a bi-phasic (aquatic and terrestrial) lifestyle and many of their biological and reproductive processes rely on narrow environmental temperature and moisture ranges, and so amphibians are especially sensitive among vertebrates to climate induced stressors and abrupt changes in land use (Zellmer et al 2020).…”

Shifts in competitive structures can drive variation in species' phenology

“…Among the known responses to climate change, shifts in phenology or the timing of key life-history events of organisms are the most well documented (Cohen et al, 2018;Roslin et al, 2021;Visser & Both, 2005;Walther et al, 2002). Often, the timing of important phenological events (e.g., reproduction) matches periods of high resource availability to support high fitness and survival costs (Bradshaw & Holzapfel, 2007;Buss et al, 2021;Forchhammer et al, 1998;Helm et al, 2013;Reed et al, 2013;Walther et al, 2002). Fitness costs of reproduction are often attributed to the increased energetic demands of maintaining and developing reproductive organs and behaviors (Audzijonyte & Richards, 2018), and survival costs are incurred from increased predation risk (Kelt et al, 1995).…”