Intraguild predation leads to genetically based character shifts in the threespine stickleback

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Intraguild predation, where a species preys on a competitor, can drive population divergence.
• Character shifts in intraguild prey (IG-prey) may be environmental or evolutionary.
• Threespine stickleback populations exhibit variation in the presence of prickly sculpin, an intraguild predator (IG-predator).

Purpose of the Study:

• To investigate the genetic basis and inducibility of character shifts in threespine stickleback in response to intraguild predation.
• To determine if observed trait differences are environmentally induced or genetically based.

Main Methods:

• Common garden experiments raising stickleback from sympatric and allopatric populations with prickly sculpin.
• Laboratory experiments exposing marine and freshwater stickleback to the presence or absence of intraguild predators.
• Analysis of morphological (defensive armor, body shape) and behavioral (water column height preference) traits.

Main Results:

• Differences in armor, body shape, and behavior between freshwater stickleback populations persisted in a common garden, indicating a genetic basis.
• Marine stickleback exhibited induced trait changes in the presence of sculpin.
• Freshwater stickleback did not show induced trait changes, suggesting their differences are not environmentally plastic in response to the predator.

Conclusions:

• Behavioral and morphological trait differences in freshwater stickleback populations are genetically based.
• These genetic differences suggest an evolutionary response to intraguild predation by prickly sculpin.
• Intraguild predation acts as a selective pressure driving evolutionary divergence in prey populations.