PS 18-165
Effect of time since fire on larval performance and recruitment in Oak Toads (Anaxyrus quercicus)
Relatively little is known about how varying fire regimes affect amphibians, especially during the larval stage. This is particularly true for species found in habitats highly adapted to frequent fire, such as Florida scrub, which naturally burns every 5-30 years. We investigated how time since fire (TSF) of seasonal ponds embedded in a matrix of Florida scrub affected larval Oak Toad (Anaxyrus quercicus) development, growth and survival. We selected 12 ponds in scrub habitat at Archbold Biological Station (ABS): four burned in the last 4 months, four burned in the last 3-4 years and four burned 11 years ago. We hatched eggs and reared larvae from three amplexed pairs of Oak Toads collected from a pond at ABS on 9/21/2012. At two weeks post-hatching, we sorted larvae into groups of 24, each having equal representation of individuals from the three clutches. Groups were randomly assigned to 0.22 m3 field enclosures in each pond (N = 2 or 3 enclosures per pond). We measured a variety of environmental variables across the ponds (e.g., specific conductance, pH, temperature, ammonium, total P, ortho-P.) and enclosures (e.g., water volume, specific conductance, pH, temperature, vegetation cover, periphyton growth).
After 15 days survival was significantly higher in the most recently burned ponds (excluding 9 enclosures that were colonized by invertebrate predators; F2,11 = 4.956, p = 0.046). The mean number of survivors was 15.38±4.80 in ponds burned in the last 4 months, 8.71±4.93 in ponds burned 3-4 years ago and 4.75±3.45 in ponds burned 11 years ago. TSF did not have a significant effect on mean Gosner (developmental) stage (F2,4.1 = 2.041, p = 0.243) or mean tadpole length (F2,4.1 = 0.035, p = 0.966), although there was a trend towards faster development in the most recently burned ponds. The mean final Gosner stage was 40.54±0.44 in ponds burned in the past 4 months, 39.42±0.57 in ponds burned 3-4 years ago and 39.39±0.47 in ponds burned 11 years ago. Of the environmental variables measured, only pH was found to vary significantly (declining) with TSF (univariate ANOVA: F2,9 = 4.177, p = 0.052). Insignificant differences in other parameters may be due to low power. Overall our results suggest that performance and recruitment of larval Oak Toads are higher in recently burned ponds.
1990 M Street, NW Suite 700, Washington, DC 20036
phone 202-833-8773
fax 202-833-8775
email esahq@esa.org
. All rights reserved.