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Spatial structure and habitat variation in a grasshopper hybrid zone
J R Bridle1, S J Baird, R K Butlin
1Centre for Biodiversity and Conservation, School of Biology, University of Leeds, United Kingdom. j.bridle@ucl.ac.uk
Evolution; International Journal of Organic Evolution
|October 30, 2001
Summary
This study analyzed grasshopper hybrid zones in Spain, revealing complex patterns of genetic variation. Habitat influences are present but weak, suggesting other factors like colonization shape these zones.
Area of Science:
- Evolutionary Biology
- Genetics
- Ecology
Background:
- Hybrid zones offer insights into speciation and genetic exchange.
- Chorthippus brunneus and C. jacobsi form a hybrid zone in northern Spain.
- Morphological traits, like stridulatory peg number, distinguish these species.
Purpose of the Study:
- To analyze variation in morphology and ecology within a Chorthippus grasshopper hybrid zone.
- To investigate geographical patterns of genetic variation and their association with local habitat.
- To model spatial variation using a maximum-likelihood approach.
Main Methods:
- Collected morphological and ecological data from grasshopper populations.
- Developed a maximum-likelihood method to fit a two-dimensional cline.
- Incorporated local vegetation data to explain variation in quantitative traits.
Main Results:
- Identified a cline in stridulatory peg number south of the Picos de Europa Mountains.
- Observed significant deviations from simple tension zone models.
- Found that local vegetation explains some, but not all, variation in peg number.
Conclusions:
- Habitat-genotype associations play a role but are weak in this hybrid zone.
- Outlier populations suggest colonization or patchy postglacial expansion.
- This hybrid zone contrasts with smoother or mosaic patterns seen in other species.