Naturally occurring variation in tadpole morphology and performance linked to predator regime

Abstract

Divergent natural selection drives a considerable amount of the phenotypic and genetic variation observed in natural populations. For example, variation in the predator community can generate conflicting selection on behavioral, life-history, morphological, and performance traits. Differences in predator regime can subsequently increase phenotypic and genetic variations in the population and result in the evolution of reproductive barriers (ecological speciation) or phenotypic plasticity. We evaluated morphology and swimming performance in field collected Bronze Frog larvae (Lithobates clamitans) in ponds dominated by predatory fish and those dominated by invertebrate predators. Based on previous experimental findings, we hypothesized that tadpoles from fish-dominated ponds would have small bodies, long tails, and large tail muscles and that these features would facilitate fast-start speed. We also expected to see increased tail fin depth (i.e., the tail-lure morphology) in tadpoles from invertebrate-dominated ponds. Our results support our expectations with respect to morphology in affecting swimming performance of tadpoles in fish-dominated ponds. Furthermore, it is likely that divergent natural selection is playing a role in the diversification on morphology and locomotor performance in this system.

Unraveling the relative contribution of inter‐ and intrapopulation functional variability in wild populations of a tadpole species

“…Therefore, individuals could display larger and rounded mouth, more propulsion and/or maneuverability but lower endurance (dorso-ventral flexion) along the increasing of PC1 values. PC2 was principally driven by functional traits related to locomotion, indicated that with increased PC2 values, individuals were more compact and rounded, but less propulsion and/or maneuverability (i.e., lower movement precision; Wassersug, 1989;Hoff & Wassersug, 2000;Van Buskirk & McCollum, 2000;Larson & Reilly, 2003;Mcnamara et al, 2009;Aguayo et al, 2009;Johnson, Saenz, Adams, & Hibbitts, 2015).…”

Effect of hydric stress on locomotion and morphology of tadpoles from temporary ponds

“…The tail of tadpoles may show significant polyphenism, being able to change shape or color quickly in response to environmental modifications (Hoff & Wassersug, 2000). Such phenotypic plasticity allows the tail length to increase in response to stressful factors such as predators (Johnson, Saenz, Adams, & Hibbitts, 2015;McCollum & Leimberger, 1997;Van Buskirk & McCollum, 2000). The hydric stress applied in the present study, however, caused an inverse effect, reducing the tail length in tadpoles of both L. fuscus and P. nattereri, when compared with tadpoles that had not suffered any hydric stress ( Table 2).…”

Egg‐laying environment modulates offspring responses to predation risk in an amphibian

“…short periods of rapid movements), mean distance covered during bursts, maximum duration of bursts, maximum distance covered during bursts and maximum velocity (in mm/frame; Table S2). Because none of the measured traits were a priori expected to be of special relevance (for instance, aeshnid predators do not induce higher maximum velocity in amphibian larvae; Van Buskirk & McCollum, ; Gvoždík & Smolinský, ; Johnson et al ., ), we used a principal component analysis (PCA) on all seven positively correlated variables (pairwise correlations [ r s ] ranged from 0.37 to 0.91) to calculate overall locomotor activity of the larvae. Prior to PCA, the first six measures, characterized by right‐skewed distributions, were log‐transformed to reduce the influence of extreme values and to ensure that variables are linearly, or at least monotonically, related to one another (Quinn & Keough, ).…”