Countergradient Variation in the Wood Frog
This paper has come from the independent ecology study I did as my senior thesis for the Intensive B.S. in Ecology and Evolutionary Biology at Yale.
I worked in the Skelly Lab
under Professor David Skelly of the Yale School of Forestry and Environmental Studies
The paper is available online through
Evolutionary Ecology Research as at
(Ligon and Skelly 2009).
It will be published this fall in Evolutionary Ecology Research
Do wood frog (Rana sylvatica) populations show evidence of cryptic variation, wherein inherited variation is masked by environmental effects? Have these populations diverged in larval traits across a gradient of canopy cover? How do trends in larval traits differ when observed in the field vs. in a common garden experiment?
Due to strong selection in their cooler environment, wood frogs from heavily shaded wetlands will grow and develop more slowly in the field but more quickly in a common garden experiment, when compared to their counterparts from sunnier wetlands.
We monitored growth and development of wood frog larvae from six wetlands of varying canopy cover. We studied populations in the natal wetlands and individuals raised in incubators from embryos through metamorphosis.
Observations of natural populations revealed no evidence of strong trends in phenotype. However when raised in a common environment, larvae from more shaded natal wetlands grew and developed faster, and were larger at any given stage. This is evidence for cryptic divergence wherein the lack of an observed phenotypic trend masks the underlying inherited variation.
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