The contributions of phenotype- and condition-dependent factors to juvenile amphibian movement: A high throughput assay
Dispersal is the movement of individuals from their natal population to a different breeding population. The frequency with which individuals disperse to a new population or settle near natal sites has strong consequences for individual survival and fitness, population demography and persistence; and drives gene flow and thus adaptation and speciation. A growing body of literature identifying dispersal syndromes suggests that dispersal does not involve a random sample of individuals. Rather, individuals that disperse are morphologically, physiologically, and/or behaviorally dissimilar from residents.
We tested whether movement behavior differed between juvenile pond-breeding salamanders and if an individual’s behavior was repeatable over time. We also sought to identify factors that could predict whether an individual was likely to be a disperser. Specifically, we tested if natal habitat or morphology were related to an individual’s propensity to move.
We manipulated the larval density of ringed salamanders (Ambystoma annulatum) and spotted salamanders (A. maculatum) in pond mesocosms, and quantified the movement of recently metamorphosed juveniles in the laboratory (N = 914), and measured a suite of morphological traits to identify any that correlated to movement distance. We also tested whether individuals consistently exhibited the same activity levels (i.e. repeatability) in a subset of A. annulatumover a three month period (N = 57).
We observed considerable variation in movement between individuals. Some animals did not move at all during a trial, while others moved farther than 10 m. We also found support for natal habitat affecting movement behavior: natal density was a strong predictor of movement with individuals from high density natal ponds moving less far in the laboratory than individuals from low density ponds. We tested for repeatability of movement behavior in a subset of A. annulatumover a three month period, and found that individuals were consistent in the distances they moved (Intraclass correlation coefficient: 37.1% ± 9.9; CI: 23.7, 60.9).
We found strong support for individuals varying in their movement behavior. More significantly, we identified carry-over effects of natal habitat on distance moved and very high repeatability of behavior over time. This project is a step towards identifying factors contributing to a dispersal syndrome in pond-breeding salamanders.