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Interspecific variation in Drosophila wing vein patterns
Kim van der Linde &
David Houle
Abstract
Understanding the relationship between variation at the population level and variation at the species level requires understanding the pattern of variation among species. Here, we present a comprehensive analysis of wing shape and size across the insect family Drosophilidae using geometric morphometric analysis. We collected wing-shape (landmark) data from 21,045 individuals from 111 taxa primarily in the family Drosophilidae. The data were aligned by means of the Generalized Procrustes Analysis, which removed variation in location, size, and orientation on the assumption of homogeneous uncorrelated variation in landmark position. The phenotypic space used by all species is rather limited, despite the abundant additive genetic variation for shape and size found in previous studies. Nevertheless, most individuals (~96%) were assigned to the correct taxa by linear discriminant analysis. Most variation (> 93%) contained a strong signal of phylogenetic history, underlining the conserved nature of the wings. To assess the allometric relationship in the various landmarks, we restored size to the shape data to obtain shape-size. The pattern of variation in shape-size suggested that the landmarks in the tip and base of the wing vary isometrically with size, whereas those in the mid-section of the wing are allometric. To test this hypothesis, we aligned all 12 landmarks using only the seven isometric points. The resulting graph suggests that alignment based on our hypothesis about the nature of the shape changes with size results in a better alignment than the alignment with the Generalized Procrustes Analysis. This result raises questions about how geomorphometric data should be analyzed when allometric variation in shape is important. Finally, we provide a working hypothesis about how natural selection in the form of flight performance can result in such a conserved wing shape across these species.
Related presentations:
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December 2005
Presentation: "Drosophila and their wings." E&E seminar, Florida State University, Tallahassee, Florida, U.S.A. -
June 2005
Presentation: "A comprehensive analysis of wing shape and size across the family Drosophilidae." Evolution 2005, Fairbanks, Alsaka, USA.