Characteristics of Ice Age evolution and adaptations

Matt Williams

Brian Prall

Matt Lyerly

Questions

• How do populations adapt to their niche during climate changes?

• What phenotypic changes were found in animals that allowed for their population to survive and prosper in Ice age conditions?

• How did climate affect the survival of various species?

Definitions

• Refugium-a location of an isolated or relict population of a once widespread animal or plant species.

• Younger Drias- also known as “The Great Freeze” time from 12,900-11,500 years ago

• Older Drias- 1000 years prior to Younger Drias.

What causes an Ice Age?

• Milankovitch theory = proposes that the process is the orbital eccentricity of the earth around the sun (Gribbin 1989)

• Other factors such as tectonic movement and ocean currents play an effect, but it is not yet determined (Hewitt 1994)

Climax of The Ice Age

The Polar Front

Factors of the Ice Age That Enhance Evolution

• Highly selective environments

• Change in overall geographic environments– Division of existing populations by new

geographic barriers– New geographic areas/paths

• Induced founder effect on islands due to change in the sea level

Factors of the Ice Age That Enhance Evolution

Factors of the Ice Age that Inhibit Evolution

• Short-term/reversible changes in the environment may not be enough time for speciation

• Each time the environment reverts from extreme cold, selection would lower Ice Age suited individuals

• Migrations do not allow for genetic changes to accumulate

Flexible Adaptations and Examples

• Flexible adaptations = “features that allow for individuals to survive in variable or varying environments” (Lister 2004)– Can be accomplished through:

• Behavioral• Broad-use adaptations• Ecophenotypic plasticity (difference in

phenotypes that are the result of environmental characteristics instead of gene expression)

Ice Age Cod

• Ice Age Circulation Patterns

• Cod habitat range

• Genetic Analyses

Ice Age Brown Bears

Ice Age Brown Bears

• Researchers examined a series of permafrost-preserved bear bones

• Performed DNA sequencing and Phylogenetic Analysis

• Clades in East Beringian brown bears

• Climate Effects

In-detail Example: Red Deer

In-detail Example: Red Deer

• Red deer – Cervus elaphus

• Broad-use adapation:– ‘Mesodont’ teeth

• Allowed for deer to both graze for food from grasses/low plants as well as consume soft leaves from shrubs

• Behavioral adapation:– Deer will seek food only when available

• Some eat sea-weed (only consumed during low tide)

In-detail Example: Red Deer

• Red deer – Cervus elaphus• Ecophenotypic plasticity:

– Changes in the rumen (stomach) are found• Deer that eat mostly grass have an open

rumen with small papillae (typical of other grazing species)

• Deer that mostly browse on leaves will develop large, flat papillae (typical of other browsing species)

• Change develops in two to three weeks

Additional Examples:

• Domestic Swine – If raised at 5oC, the animals develop

shorter/stockier legs and a thicker coat than those swine raised at 30oC

• Mice– Mice that are raised in colder conditions

will grow shorter tails, than those in warmer conditions, to prevent heatloss and frostbite

Fitness by Distribution

• Some species increase their success by quickly expanding their range as the Ice Age progresses

• Many species also expand southward during an Ice Age and Northward during periods of warming

• This tends to create subspecies and less Genetic diversity

In-detail: Meadow Grasshopper Chorthippus parallelus

Meadow Grasshopper Chorthippus parallelus

Hewitt (1996) – Grasshopper movement based on DNA data

Chorthippus parallelus

• Durring periods of warming in the last ice age many Populations including Chorthippu Parrallalus spread through out Europe and Western Russia.

• When the temperature in these areas began to fluctuate the species was divided

• Researchers used DNA to track the varying sub-species origins.

• The two events of the last ice age that caused the greatest population decrease were the Younger Dryas 12,800 to 11,500 and Older Dryas 1000 years prior.

Expansion during cooler and warming periods

Traits allowing for continued survival

Further Research

• Exploring genetic relationship of birds– Song cannot be fossilized, nor can

coloration

• Determining relationship and survival of reptiles during the ice age

Results

• Some organisms had traits that allowed them to survive, while other were not able to

• Populations took advantage of expanding ranges, leading to new populations and eventually evolution

• Climate change lead to less diversity among certain species

References• http://www.dodo.blog.br/wp-content/uploads/2007/08/ferahgo.jpg• hepokatti.net/nurmiheinasirkka.jpg • www.quantum-conservation.org/ESB/Ursus%20arct • Bigg, G., Cunningham, C., Ottersen, G., Pogson, G., Wadley, M., Williamson,

P. 2008. Ice-age survival of Atlantic cod: agreement between palaeoecology models and genetics. Pro. R. Soc. 275; 163-173.

• Hewitt, G. 1996. Some genetic consequences of ice ages, and their role in divergence and speciation. Biol. J. Linn. Soc. Lond. 58; 247-276.

• Leonard, J., Wayne, R., Cooper, A. 2000. Population genetics of Ice Age brown bears. Evolution. 97; 1651-1654.

• Lister, A. 2004. The impact of Quaternary Ice Ages on Mammalian Evolution. Phil. Trans. R. Soc. Lond. 359; 221-241.

• O’Regan, H. 2008. The Iberian Peninsula – corridor or cul-de-sac? Mammalian faunal change and possible routes of dispersal in the last 2 million years. Quat. Sci. Rev. 27; 2136-2144

• Provan, J., Bennet, K. Phylogeographic insights into cryptic glacial refugia. Trends Ecol. Evol. 23; 565-571.