Parental effects influence life history traits and covary with an environmental cline in common frog populations

What are the contributions of maternal and paternal traits to fecundity and offspring development? A case study in an amphibian species, the spined toad Bufo spinosus

Assessing the determinants of reproductive success is critical but often complicated because of complex interactions between parental traits and environmental conditions occurring during several stages of a reproductive event. Here, we used a simplified ecological situation-an amphibian species lacking post-oviposition parental care-and a laboratory approach to investigate the relationships between parental (both maternal and paternal) phenotypes (body size and condition) and reproductive success (fecundity, egg size, embryonic and larval duration, larval and metamorphic morphology). We found significant effects of maternal phenotype on fecundity, hatching success, and tadpole size, as well as on the duration of larval development. Interestingly, and more surprisingly, we also found a potential contribution of the paternal phenotype occurring during early (embryonic development duration) offspring development. Although our study focused on life-history traits such as body size and development duration, additional mechanisms involving physiological costs of development may well mediate the relationships between parental phenotypes and offspring development. Future studies are required to decipher the mechanisms underlying our findings in order to clarify the mechanistic basis of the links between parental phenotypes and offspring development.

Carryover effects from environmental change in early life: An overlooked driver of the amphibian extinction crisis?

Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of individual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life-history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short-term studies limited to single life-history stages. Herein, we review evidence for the physiological carryover effects induced by elevated ultraviolet radiation (UVR; 280-400 nm) as a potential contributor to recent amphibian population declines. UVR exposure causes a suite of molecular, cellular and physiological consequences known to underpin carryover effects in other taxa, but there is a lack of research linking embryonic and larval UVR exposures to fitness consequences post-metamorphosis in amphibians. We propose that the key impacts of UVR on disease-related amphibian declines are facilitated through carryover effects that bridge embryonic and larval UVR exposure with potential increased disease susceptibility post-metamorphosis. We conclude by identifying a practical direction for the study of ecological carryover effects in amphibians that could guide future ecological research in the broader field of conservation physiology. Only by addressing carryover effects can many of the mechanistic links between environmental change and population declines be elucidated.

Grow fast but don't die young: Maternal effects mediate life-history trade-offs of lizards under climate warming

As postulated by life-history theory, not all life-history traits can be maximized simultaneously. In ectothermic animals, climate warming is predicted to increase growth rates, but at a cost to overall life span. Maternal effects are expected to mediate this life-history trade-off, but such effects have not yet been explicitly elucidated. To understand maternal effects on the life-history responses to climate warming in lizard offspring, we conducted a manipulative field experiment on a desert-dwelling viviparous lacertid lizard Eremias multiocellata, using open-top chambers in a factorial design (maternal warm climate and maternal present climate treatments × offspring warm climate and offspring present climate treatments). We found that the maternal warm climate treatment had little impact on the physiological and life-history traits of adult females (i.e. metabolic rate, reproductive output, growth and survival). However, the offspring warm climate treatment significantly affected offspring growth, and both maternal and offspring warm climate treatments interacted to affect offspring survival. Offspring from the warm climate treatment grew faster than those from the present climate treatment. However, the offspring warm climate treatment significantly decreased the survival rate of offspring from maternal present climate treatment, but not for those from the maternal warm climate treatment. Our study demonstrates that maternal effects mediate the trade-off between growth and survival of offspring lizards, allowing them to grow fast without a concurrent cost of low survival rate (short life span). These findings stress the importance of adaptive maternal effects in buffering the impact of climate warming on organisms, which may help us to accurately predict the vulnerability of populations and species to future warming climates.