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A selection of recent scholarship on coevolutionary arms races:

Natural selection drives the fine-scale divergence of a coevolutionary arms race involving a long-mouthed weevil and its obligate host plant.

Hirokazu Toju, BMC Evolutionary Biology 9:273. 2009.

Co-evolutionary arms race between brood parasites and their hosts at the nestling stage.

Manuel Soler, Journal of Avian Biology,3:237-240. 2009.

Intersexual Arms Race? Genital Coevolution in Nephilid Spiders (Araneae, Nephilidae).

Who will win the game?

Australian crab spiders and honeybees are in a coevolutionary arms race . But which is ahead? And how will this dynamic be shifted in the future?

To understand what’s coming next, it is helpful to understand the underlying principals of this “arms race.” This term is used in describing genes that are co-evolving, such as an Australian crab spiders ability to anticipate a honeybee’s preference in flowers and a honeybees ability to identify crab spiders and avoid landing on the flowers they occupy. As these two species develop adaptations, they must then develop counter-adaptations as a result of the other species’ advances. This positive feedback resembles a military arms race. There are numerous examples of these arms races in evolution, and while many have asymmetrical selective pressures, like those acting on the Australian crab spiders and the honeybees, there are symmetrical selection processes as well.

Even though Australian crab spiders are masters of prey deception, making the flowers they sit upon look even more enticing to a bee than less dangerous pollinating sites, scientists hypothesize that they have relinquished the upper hand in the arms race (Heiling and Herberstein, 2004). As more honeybees are able to recognize and combat the Australian crab spiders’ trickery, they will be forced to try new tactics. One anticipated evolutionary response is that the Australian crab spiders will become increasingly less conspicuous to honeybees, which may occur even without becoming less conspicuous to the human eye. There is an increasing body of literature that explain how animals reinvent the common notion of camouflage, that is the their bodies match the colors or patterns of their backgrounds, to a newer definition that includes non-pattern matching body designs that creative disruptive coloration patterns that trick their prey in the same way. Therefore, concealment can occur even if the background is not matched (Stevens et. al, 2006). Or conversely, perhaps the Australian crab spiders might change the way they are ambushing their hymenopteran prey. Instead of pouncing from the petals of a flower, they could hide below the surface, waiting to ambush from their sheltered location. The Australian crab spiders have countless evolutionary paths that they could take, although they must expect the honeybees to be simultaneously fighting back, looking to preserve and advance themselves at the same time and only time will tell how the Australian crab spider responds to these evolutionary pressures.

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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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