Contrasting effects of environmental factors during larval stage on morphological plasticity in post-metamorphic frogs

Abstract

In organisms with complex life cycles, environmentally induced plasticity across sequential stages can have important consequences on morphology and life history traits such as developmental and growth rates. However, previous research in amphibians and other ectothermic vertebrates suggests that some morphological traits are generally insensitive to environmental inductions. We conducted a literature survey to examine the allometric responses in relative hind leg length and head shape of post-metamorphic anuran amphibians to induced environmental (temperature, resource level, predation and desiccation risk) variation operating during the larval phase in 44 studies using 19 species. To estimate and compare plastic responses across studies, we employed both an index of plasticity and effect sizes from a meta-analysis. We found contrasting trait responses to different environmental cues. Higher temperatures increased development more than growth rate and induced smaller heads but not overall shifts in hind leg length. In contrast, an increment in resource availability increased growth more than development, with a parallel increase in hind leg length but no change in head shape. Increases in predation risk decreased both development and growth rates and slightly reduced relative hind leg length, but there was no change in head shape. Pond desiccation induced quick development and low growth rates, with no changes in morphology. Across environments, both hind leg and head shape plasticity were positively correlated with growth rate plasticity. However, plasticity of developmental rate was only correlated with head shape plasticity. Overall, these results suggest that environmental trends predicted by global warming projections, such as increasing pond temperature and accelerating pond desiccation, will significantly influence hind leg and head morphology in metamorphic frogs, which may affect performance and, ultimately, fitness.

Artificial warming increases size at metamorphosis in plateau frogs (Rana kukunoris) in the presence of predators

“…Warming increased development rate more than growth rate in the absence of predators, while it increased growth rate more than development rate in the presence of predators, such that size at metamorphosis was reduced in the absence of predators but was increased in the presence of predators. The negative effect of warming on size at metamorphosis in the absence of predators is consistent with the prediction, based on the general rule for ectotherms, that increased temperature will facilitate development more than growth (Smith-Gill and Berven 1979), and it is also consistent with many experimental studies that show a reduced size at metamorphosis under higher temperatures (Newman 1998;Alvarez and Nicieza 2002;Tejedo et al 2010). However, the positive effect of warming on size at metamorphosis in Fig.…”

“…For instance, Newman (1998) found that Scaphiopus couchii metamorphosed earlier with a smaller size at metamorphosis at higher temperatures. This tendency has been further confirmed in many latter reports (Alvarez and Nicieza 2002;Laurila et al 2008; see also review by Tejedo et al 2010). However, such a tendency may not always hold true as there are often contrasting trait responses to specific environmental cues (Tejedo et al 2010).…”

“…This tendency has been further confirmed in many latter reports (Alvarez and Nicieza 2002;Laurila et al 2008; see also review by Tejedo et al 2010). However, such a tendency may not always hold true as there are often contrasting trait responses to specific environmental cues (Tejedo et al 2010). For example, the outcome of (lethal or nonlethal) predator effects on tadpole size at metamorphosis may be positive, neutral, or negative depending on food availability, hydroperiod, and geographic range (see review by Benard 2004 andRelyea 2007).…”

Climate warming mediates negative impacts of rapid pond drying for three amphibian species

“…The effects of warming on time to metamorphosis and early growth support the hypothesis that higher water temperatures accelerate larval growth and development by increasing metabolic rate (Newman 1998) as well as resource availability. Likewise, larvae in temporary pools accelerated growth and development, likely in response to desiccation cues (Leips et al 2000, Tejedo et al 2010. The effect of warming in reducing time to metamorphosis was about three times stronger than the effect of drying, suggesting that drying rate may not have imposed as strong a constraint on development.…”

Adaptive phenotypic plasticity and resilience of vertebrates to increasing climatic unpredictability

“…For both approaches, the key steps are the characterization of environmental predictability (as discussed by Cavieres & Sabat 2008 to explain unexpected results), the choice of the metrics of phenotypic plasticity to be used (e.g. Ghalambor et al 2007, Tejedo et al 2010 and the phenotypic traits to be measured.…”