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Deploying Community Scientists to Conduct Nondestructive Genetic Sampling of Rare Butterfly Populations
Published on: October 28, 2022
Field studies reveal strong postmating isolation between ecologically divergent butterfly populations
Carolyn S McBride1, Michael C Singer
1Center for Population Biology, University of California Davis, Davis, California, USA. lmcbride@rockefeller.edu
Plos Biology
|November 5, 2010
Summary
Extrinsic postzygotic isolation (EPI) restricts gene flow when hybrid butterflies exhibit maladaptive intermediate traits. This ecological selection against hybrids creates a barrier to speciation, even without genetic differentiation.
Area of Science:
- Evolutionary Biology
- Speciation Research
- Ecological Genetics
Background:
- Gene flow between diverging populations can be limited by hybrids inheriting maladaptive traits, a process known as extrinsic postzygotic isolation (EPI).
- EPI is hypothesized to be crucial in early speciation stages, but its natural prevalence and the specific traits involved remain poorly understood.
- Butterflies (Euphydryas editha) specializing on different host plants provide a model for studying early speciation and potential EPI.
Purpose of the Study:
- To investigate the strength and impact of extrinsic postzygotic isolation in allopatric butterfly populations adapting to different host plants.
- To identify specific intermediate phenotypes in hybrids that may be maladaptive and contribute to reproductive isolation.
- To assess the fitness consequences of these intermediate traits in natural field conditions.
Main Methods:
- Compared traits of hybrids between populations using different hosts (different-host hybrids) with parental populations and hybrids using the same host (same-host hybrids).
- Conducted field experiments to quantify the fitness (growth, survival) of different-host hybrids.
- Constructed a fitness surface to visualize the adaptive landscape for hybrids.
Main Results:
- Strong evidence of extrinsic postzygotic isolation was found under field conditions.
- Different-host hybrids displayed significantly maladaptive intermediate traits, including behaviors like foraging height, and life-history traits such as oviposition preference and clutch size.
- Intermediate traits severely reduced hybrid larvae growth and survival, positioning them in an 'adaptive valley' between parental populations.
Conclusions:
- Ecological selection against hybrids with intermediate phenotypes creates a potent barrier to gene flow during early adaptive divergence.
- Extrinsic postzygotic isolation, driven by maladaptive intermediate traits, plays a significant role in the initial stages of speciation.
- The study highlights the importance of specific ecological traits in driving reproductive isolation and speciation.
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