Blog Post Module 9: Reflection Prompt

The objective of this reflection is to pick a trait or an organism that has always fascinated you. What adaptations does it have? How have scientists tested adaptive hypotheses?

Lithobates sylvaticus (Wood frogs) have always fascinated me. These frogs have adapted to cold climates by freezing over the winter. When temperatures begin to drop, wood frogs store urea and convert glycogen to glucose. This produces a special antifreeze substance that prevents ice from freezing within their cells. These molecules help prevent the frogs cells from dehydrating while its body tissues freeze. During this time, they stop breathing, their hearts stop beating, and their blood stops flowing. They can endure freezing temperatures for months. Not only is this completely wild, but these frogs have always reminded me of that episode from Avatar: The Last Airbender (when Aang had to find frozen frogs for his friends who were sick). The only cure for their illness were these frozen frogs.

Fine spatial scale phenotypic divergence in wood frogs (Lithobates sylvaticus)

In this scientific journal, scientists tested a trait known as the local divergence in growth within Lithobates sylvaticus. What's interesting about this trait is that it appears to be both phenotypically plastic and heritable among wood frog tadpoles present within four ponds surrounded by a continuous woodland. Using a mark-recapture method, scientists discovered low levels of migration among ponds. Frequent garden experiments were also performed at two temperatures. The results showed consistent patterns of phenotypic divergence in tadpole growth performance among the four pond populations of wood frog tadpoles. The divergence in growth was maintained when controlling for parental effects regarding the half-sibling experiments. Scientists also performed a cross-transplant experiment which showed how the divergence in tadpole growth reflected either genetic drift or adaptation to local pond conditions. All results propose that divergence in growth among the wood frog tadpoles from the four ponds may be due of selection or genetic drift reinforced by low levels of gene flow within pond populations.