Countergradient variation

Growth rate and body size have important ecological implications, such as how they impact an organism's survival, life history, and fecundity.

[2] Levins first used the term when describing patterns of body size across an altitudinal gradient in populations of Drosophila,[4] and since then many other instances of countergradient variation have been discovered.

Similar to the results of this study, most of the known instances of countergradient variation are associated with a latitudinal or altitudinal gradient having an effect on growth rate (see Examples section).

Originally this maternal investment in larger eggs was thought to support increased developmental rate.

Because of this, it is thought that countergradient variation of growth is a means to compensate for the short amount of time juveniles have to prepare for winter.

[13] With a genetic disposition to grow faster, these individuals can reach a large enough body size to survive through the winter.

[3] Additionally, when countergradient variation acts on developmental rates, embryos that develop sooner or hatch out larger will have more time to grow or require less resources, respectively.

One proposed detriment of enhanced embryonic growth is that animals use too much of their supplied nutrients or yolk during development.

[15][16] Another hypothesis is that animals that grow quickly do not expend as much energy on differentiation or cellular maintenance because they have shorter incubation times.

Some examples include rapid growth leading to bone deformities in sandhill cranes[17] and increased risk of cardiovascular problems in Atlantic salmon.

Studies of countergradient variation are being explored as a useful way to predict the evolutionary constraints animals face in differing environmental conditions.