Venue and outcome in ecological experiments: manipulations of larval anurans

Authors

  • David K. Skelly,

    1. School of Forestry and Environmental Studies and Dept of Ecology and Evolutionary Biology, Yale Univ., 370 Prospect Street, New Haven, CT 06520, USA (david.skelly@yale.edu) (present address of JMK: Dept of Biology, Mueller Lab, Pennsylvania State Univ., University Park, PA 16802, USA).
    Search for more papers by this author
  • Joseph M. Kiesecker

    1. School of Forestry and Environmental Studies and Dept of Ecology and Evolutionary Biology, Yale Univ., 370 Prospect Street, New Haven, CT 06520, USA (david.skelly@yale.edu) (present address of JMK: Dept of Biology, Mueller Lab, Pennsylvania State Univ., University Park, PA 16802, USA).
    Search for more papers by this author

Abstract

The choice of venue is believed to be a critical decision for ecologists conducting experiments, yet the existence of tradeoffs in design and the impact of venue on outcome have not been quantitatively evaluated. To these ends we reviewed a set of 227 comparisons from 52 studies designed to quantify the effect of density on the growth performance of larval anurans. We predicted that both design and outcome would be related to experimental venue (laboratory, mesocosm, and field). We found that, in contrast to our predictions, laboratory experiments did not include more factors or yield more precise estimates of responses compared with mesocosm and field manipulations. In partial support of our prediction, we found that laboratory experiments did utilize somewhat larger numbers of replicates and included more levels per factor compared to the alternative venues. In addition we found that, as predicted, raising tadpoles at higher densities of conspecifics, or in the presence of heterospecifics tended to decrease growth. This effect, consistent with competition, was strongly dependent on experimental venue. In particular, we found that interspecific effects were much stronger in mesocosm versus field manipulations. This result is particularly relevant because conceptions of amphibian assemblages have included interspecific competition as integral to natural patterns of amphibian distribution. We conclude that hypothesized tradeoffs among experimental venues have not acted in a particularly strong way in shaping the design of tadpole density manipulations. However, venue may mediate strong effects on the outcome of such experiments. Quantification of such methodology based biases will help ecologists more effectively match the goals of their experiments with decisions regarding venue.

Ancillary