Natural variation in morphology of larval amphibians: Phenotypic plasticity in nature?

Abstract

Phenotypic plasticity has been studied intensively in experimental settings but infrequently in nature, and therefore the relevance of experimental findings is poorly known. This is especially true for morphological plasticity in amphibian larvae induced by predators and competitors. This paper describes a seven-year survey of head and tail shape in eight species of anuran and newt larvae in northern Switzerland, involving 6824 individual larvae and 59 ponds. I tested relationships between geometric measures of size and shape and five habitat gradients: pond permanence, cover by forest canopy and aquatic vegetation, and the densities of predators and competitors. Responses to competitors and predators were often similar to those reported in experiments. High competitor density was associated with small size and a large head in newt larvae, a long or deep head/body in anuran larvae, and a short or shallow tail in newts and some tadpoles. High predator density was correlated with a deep tail fin and tail muscle in many species. In anurans, the change in shape between low-and highpredator ponds in nature closely paralleled the plastic response to nonlethal predators in mesocosm experiments. The survey revealed many previously undescribed relationships between morphology and the other habitat features. Several species had relatively large tails in ponds that were shaded or thickly vegetated. Associations between year-to-year changes in shape and habitat within ponds implicated phenotypic plasticity rather than genetic population divergence, at least in anurans. These results inspire confidence in the relevance of experiments and highlight many new patterns that will merit further study. Abstract. Phenotypic plasticity has been studied intensively in experimental settings but infrequently in nature, and therefore the relevance of experimental findings is poorly known. This is especially true for morphological plasticity in amphibian larvae induced by predators and competitors. This paper describes a seven-year survey of head and tail shape in eight species of anuran and newt larvae in northern Switzerland, involving 6824 individual larvae and 59 ponds. I tested relationships between geometric measures of size and shape and five habitat gradients: pond permanence, cover by forest canopy and aquatic vegetation, and the densities of predators and competitors. Responses to competitors and predators were often similar to those reported in experiments. High competitor density was associated with small size and a large head in newt larvae, a long or deep head/body in anuran larvae, and a short or shallow tail in newts and some tadpoles. High predator density was correlated with a deep tail fin and tail muscle in many species. In anurans, the change in shape between low-and highpredator ponds in nature closely paralleled the plastic response to nonlethal predators in mesocosm experiments. The survey revealed many previously undescribed relationships between morphology and the other habitat features. Several species h...

Geometric morphometrics in herpetology: modern tools for enhancing the study of morphological variation in amphibians and reptiles

“…However, while general trends appear relatively uniform, allometric trajectories frequently vary among closely related species (LArSon, 2005;IvAnovIć et al, 2007IvAnovIć et al, , 2008, providing a potentially important mechanism of morphological differentiation, both in extant and extinct taxa (wITzMAnn et al, 2009). The same is true for body shape variation before and through metamorphosis in newts (vAn BUSkIrk, 2009;IvAnovIć et al, 2011), although further studies should investigate the generality of the results obtained for Triturus, since remarkable variation of allometric patterns has been observed in some cases (vAn Figure 3: yearly evolution of the number of publications using GM methods to analyse morphological variation in extant and extinct amphibians and reptiles. Data retrieved from Google Scholar and Isi web of Science.…”

“…*records concerning 2011 include studies published or in press until July 31. BUSkIrk, 2009). Finally, caution should be taken when extrapolating between groups or even populations of the same species, since allometric trajectories of amphibian shape have been found to present radical modifications in both plastic and adaptive responses to environmental variation (see below).…”

“…As is common for this group (wELLS, 2007), multiple studies support the existence of extensive phenotypic plasticity in both head and body shape. Temperature (JorGEnSEn & SHEIL, 2008), predation risk (JoHnSon et al, 2008;vAn BUSkIrk, 2009;HoSSIE et al, 2010), competition (GArrIGA & LLorEnTE, in press), as well as numerous other habitat components (vAn BUSkIrk, 2009) have been shown to produce plastic responses on larval body shape and ontogenetic shape allometry. Furthermore, body shape has been shown to Figure 5: Three-dimensional shell shape variation observed between male pseudemys turtles inhabiting fast-flowing and slow-flowing water environments, as visualised through a pcA analysis of the three-dimensional coordinates of the carapace.…”

Thrice as easy to catch! Copper and temperature modulate predator‐prey interactions in larval dragonflies and anurans

“…Predators and competitors both cause larval amphibians to alter their behavior (Relyea 2001, Van Buskirk 2009. Behavioral effects caused by multiple stressors also have the ability to alter species interactions (e.g., Preisser et al 2005).…”

Phenotypic convergence along a gradient of predation risk

“…They tend to focus on a single class of trait (e.g. morphology [7], or life history [6]; but see [8]) and the source but not the magnitude of predation risk. They thus begin to illuminate how combinations of traits function together in a plastic phenotype (a complex; cf.…”