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A coevolutionary arms race causes ecological speciation in crossbills
Julie W Smith1, Craig W Benkman
1Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003, USA. smith@plu.edu
The American Naturalist
|February 3, 2007
Summary
Ecological speciation is occurring in South Hills crossbills due to coevolution with lodgepole pine. This involves habitat isolation, immigrant infecundity, and strong behavioral isolation between crossbill call types.
Area of Science:
- Ecology
- Evolutionary Biology
- Speciation
Background:
- Coevolutionary interactions can drive ecological speciation.
- Premating reproductive isolation mechanisms are key to understanding speciation.
- Crossbills (Loxia curvirostra complex) and lodgepole pine (Pinus contorta latifolia) exhibit a classic predator-prey system.
Purpose of the Study:
- To investigate ecological factors causing premating reproductive isolation in South Hills crossbills.
- To determine if divergent selection from coevolution with lodgepole pine promotes ecological speciation.
Main Methods:
- Examined three ecological factors: habitat isolation, immigrant infecundity, and behavioral isolation.
- Quantified reproductive isolation between South Hills crossbills and other call types using a scale of 0 to 1.
Main Results:
- Habitat isolation resulted from enhanced lodgepole pine seed defenses.
- Immigrant infecundity occurred due to late-season arrival and poor feeding conditions.
- Strongly assortative pairing by call type demonstrated behavioral isolation.
- Total reproductive isolation reached extremely high levels (0.9975 and 0.9998).
Conclusions:
- Divergent selection from coevolutionary arms race is driving speciation in South Hills crossbills.
- Ecological factors contribute significantly to reproductive isolation and speciation.
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