EXAMINING OVERWINTER COLD-HARDINESS IN

INSECTS

Liz Manley EBIO 4120 Spring 2008Winter Ecology – Mountain Research Station, University of Colorado, Boulder

Problems during winter conditions

Insects are little bags of waterExoskeleton and hemolymphEctothermsHow do insects survive overwintering?

Why do we care?

Freeze tolerance strategy

Allows ice formation between cells Supercooling Antifreeze proteins (AFPs) Ice Nucleating Agents (INAs)

(Danks, 2004; Halfpenny and Ozanne, 1989)

Freeze avoidance strategy

Does not allow formation of ice within the body

Lowers supercooling point by 20˚C Synthesizes polyols and sugars

Main biological components of freeze tolerance and freeze avoidance strategies. (Bale, 2002)

Comparison of strategies

More than two categories…

SCP is below winter temperatures Especially under

snowpack

SCP in many studies is measured in isolation

Freezing is not the biggest threat to freeze avoidance insects

(Bale, 1996; Bale 2002)

New Categories

(Bale, 2002)

Aggregate in very large numbers during the winter; Chill tolerant

Contrast is the most important feature for overwinter habitat choice

Harmonia axyridis (Asian lady beetle)

(Nalepa et al., 2005)

Dendroctonus ponderosae

(Régnière and Bentz, 2007)

Using the model to predict SCP

Changing dynamics of SCP in pine beetle population based on daily and seasonal temperatures at different sites

(Régnière and Bentz, 2007)

Conclusions

Insects have several adaptation strategies for surviving the winter

Lady beetles use visual contrast to find overwintering sites

Mountain pine beetle populations have dynamic SCPs based on location and season.

Literature cited Bale, J.S. 2002. Insects and low temperatures: from molecular biology to distributions and

abundance. Philosophical Transactions of the Royal Society of London Series B – Biological Science 357:849-861.

Bale, J.S. 1996. Insect cold hardiness: A matter of life and death. European Journal of Entomology 93:369-382.

  Danks, H.V. 2004. Seasonal adaptations in Arctic insects. Integrative and Comparative Biology

44:85-94.

Halfpenny, J. C. and R. D. Ozanne. 1989. Winter: An Ecological Handbook. Johnson Publishing Company. Boulder, CO.

Nalepa, C. A., G. G. Kennedy, and C. Brownie. 2005. Role of visual contrast in the alighting behavior of Harmonia axyridis (Coleoptera: Coccinellidae) at overwintering sites. Environmental Entomology 34:425-431.

Régnière, J. and B. Bentz. 2007. Modeling cold tolerance in the Mountain Pine Beetle, Dendroctonus ponderosae. Journal of Insect Physiology 53:559-572.