PARENT SESSION
Oral Session #4: Animal Population Ecology.
Presiding: L. Mitchell
Monday, August 5. 8:00 AM to 11:30 AM. Gila Meeting Room, TCC.

Effect of oviposition site choice on anuran performance.

Freidenburg, Kealoha^*,1, ¹ University of Connecticut, Storrs, CT

ABSTRACT- Oviposition site choice is a potentially important mechanism underlying amphibian distributional patterns. However, the consequences of oviposition site have not been well studied. Within ponds, fine-scale variation of abiotic variables could affect the performance of embryos and hatchlings, and adults may use these variables as oviposition cues. I investigated the effect of oviposition site choice on both embryos and hatchlings of the wood frog, Rana sylvatica . I focused on how gradients of light and temperature affected embryonic and larval performance. Egg masses in four ponds were moved; in each pond 25 masses were left at the original site and 25 masses were moved to an alternate site. Developmental rates, mortality, and time to hatching were recorded. Once hatched, the larvae were placed in field enclosures and spent two weeks at four sites within each pond. Embryos placed at the alternate site tended to develop slower and to hatch later than embryos at the original site. Effects of the embryonic environment were detectable two weeks after hatching: larvae from the original site survived better and grew faster than larvae from the alternate site. These results suggest that light and thermal gradients within ponds may have large effects on embryonic performance. Additionally, placement of embryos appears to have persistent effects on larval performance; there was little suggestion that early larval environment could overcome the impact of poor embryonic conditions.

KEY WORDS: oviposition, environmental effects, offspring performance, Rana