Carryover Aquatic Effects On Survival Of Metamorphic Frogs During Pond Emigration

Abstract

In organisms with complex life cycles, physiological stressors during early life stages may have fitness-level impacts that are delayed into later stages or habitats. We tested the hypothesis that body size and date of metamorphosis, which are highly responsive to aquatic stressors, influence post-metamorphic survival and movement patterns in the terrestrial phase of an ephemeral pond-breeding frog by examining these traits in two populations of northern red-legged frogs (Rana aurora aurora). To increase variation of body size at metamorphosis, we manipulated food availability for 314 of 1045 uniquely marked tadpoles and estimated the probability that frogs survived and emigrated using concentric rings of drift fencing surrounding ponds and Bayesian capture-recapture modeling. The odds of surviving and emigrating from the ponds to the innermost drift fences, approximately 12 m, increased by factors of 2.20 (95% credibility intervals 1.39-4.23) and 2.54 (0.94-4.91) with each millimeter increase in snout-vent length and decreased by factors of 0.91 (0.85-0.96) and 0.89 (0.80-1.00) with each day's delay in metamorphosis for the two ponds. The odds of surviving and moving to the next ring of fencing, 12 m to approximately 40 m from the ponds, increased by a factor of 1.20 (0.45-4.06) with each millimeter increase in size. Our results demonstrated that body size and timing of metamorphosis relate strongly to the performance of newly metamorphosed frogs during their initial transition into terrestrial habitat. Carryover effects of aquatic stressors that reduce size and delay metamorphosis may have population-level impacts that are not expressed until terrestrial stages. Since changes in both aquatic and terrestrial systems are implicated in many amphibian declines, quantifying both immediate and delayed effects of stressors on demographic rates is critical to sound management.

From metamorphosis to maturity in complex life cycles: equal performance of different juvenile life history pathways

“…Phenotypic variation in metamorphic phenotype was similar to the variation observed in other field March 2012 663 FROM METAMORPHOSIS TO MATURITY studies (Smith 1987, Semlitsch et al 1988). The previously described positive phenotypic correlations between metamorphic, juvenile, and adult life-history traits (Smith 1987, Semlitsch et al 1988, Berven 1990, Goater 1994, Scott 1994, Morey and Reznick 2001, Altwegg and Reyer 2003, Chelgren et al 2006 were only confirmed when we looked at one trait at a time. Yet, because disadvantages in one trait can be cancelled out by other traits (Dobzhansky 1956), more integrative fitness measures, such as the probability to reach maturity and population growth rate, are necessary (McPeek and Peckarsky 1998).…”

“…As previous studies showed, performance in the larval aquatic environment, as measured by the metamorphic phenotype, is likely to affect performance in later terrestrial stages. This relationship is not universal, however, or it may be limited to a short period of time (McPeek and Peckarsky 1998, Boone 2005, De Block and Stoks 2005, Chelgren et al 2006. In amphibians, long periods of post-metamorphic growth are the rule; maturity is often delayed and attained at different ages by individuals from the same cohort (Bell 1977, Werner 1986).…”

Syntopic frogs reveal different patterns of interaction with the landscape: A comparative landscape genetic study of Pelophylax nigromaculatus and Fejervarya limnocharis from central China

“…Land cover may subject F. limnocharis to more biological interactions, such as predation, and environmental stresses, such as desiccation. Desiccation has been noted to be prevalent in small‐bodied amphibians that try to pass through different land cover types due to erratic environmental conditions (Becker, Fonseca, Haddad, Batista, & Prado, 2007; Chelgren, Rosenberg, Heppell, & Gitelman, 2006; Tracy, Christian, & Tracy, 2010). …”

Growth and development of tadpoles (Xenopus laevis) exposed to selective serotonin reuptake inhibitors, fluoxetine and sertraline, throughout metamorphosis

“…Body size of frogs at metamorphosis is an important determinant for adult fitness, and larger body weights may enable frogs a greater ability to escape predation, seek out new territories, and mate more successfully [30,31]. A possible corollary of reduced growth in frogs to human health is low birth weight.…”