Spatial structure and habitat variation in a grasshopper hybrid zone

Bridle, J. R., Baird, S. J. E. and Butlin, R. K. (2001) Spatial structure and habitat variation in a grasshopper hybrid zone. Evolution, 55 9: 1832-1843. doi:10.1554/0014-3820(2001)055[1832:SSAHVI]2.0.CO;2

Author Bridle, J. R.
Baird, S. J. E.
Butlin, R. K.
Title Spatial structure and habitat variation in a grasshopper hybrid zone
Journal name Evolution   Check publisher's open access policy
ISSN 0014-3820
Publication date 2001
Sub-type Article (original research)
DOI 10.1554/0014-3820(2001)055[1832:SSAHVI]2.0.CO;2
Volume 55
Issue 9
Start page 1832
End page 1843
Total pages 12
Place of publication Lancaster, Pa., U.S.A.
Publisher Society for the Study of Evolution
Collection year 2002
Language eng
Subject C1
270504 Invertebrate Biology
770703 Living resources (flora and fauna)
0603 Evolutionary Biology
Abstract A hybrid zone between the grasshoppers Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) in northern Spain has been analyzed for variation in morphology and ecology. These species are readily distinguished by the number of stridulatory pegs on the hind femur. Both sexes are fully winged and inhabit disturbed habitats throughout the study area. We develop a maximum-likelihood approach to fitting a two-dimensional cline to geographical variation in quantitative traits and for estimating associations of population mean with local habitat. This method reveals a cline in peg number approximately 30 km south of the Picos de Europa Mountains that shows substantial deviations in population mean compared with the expectations of simple tension zone models. The inclusion of variation in local vegetation in the model explains a significant proportion of the residual variation in peg number, indicating that habitat-genotype associations contribute to the observed spatial pattern. However, this association is weak, and a number of populations continue to show strong deviations in mean even after habitat is included in the final model. These outliers may be the result of long-distance colonization of sites distant from the cline center or may be due to a patchy pattern of initial contact during postglacial expansion. As well as contrasting with the smooth hybrid zones described for Chorthippus parallelus, this situation also contrasts with the mosaic hybrid zones observed in Gryllus crickets and in parts of the hybrid zone between Bombina toad species, where habitat-genotype associations account for substantial amounts of among-site variation.
Keyword Ecology
Evolutionary Biology
Genetics & Heredity
Hybrid Zone
Long-distance Dispersal
Genetic Consequences
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
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Created: Tue, 14 Aug 2007, 17:36:06 EST