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A Study of the Genus Chrotogonus (Orthoptera). VIII. Patterns of Variation in External Morphology

Robert E. Blackith and D. Keith McE. Kevan
Evolution
Vol. 21, No. 1 (Mar., 1967), pp. 76-84
DOI: 10.2307/2406741
Stable URL: http://www.jstor.org/stable/2406741
Page Count: 9
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A Study of the Genus Chrotogonus (Orthoptera). VIII. Patterns of Variation in External Morphology
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Abstract

1) Over 1000 grasshoppers of the genus Chrotogonus were measured in respect of seven characters. The underlying patterns of growth were discovered by a canonical analysis of the matrices of the interrelationships between these characters. 2) Two contrasts of form accounted for over 98 per cent of the total variation; one reflected the sexual dimorphism and the other alary polymorphism. These two contrasts of form include almost all the specific and subspecific variation in the genus, which are inextricably confounded with the two major contrasts of form. 3) In some species the range of shapes is so great that individuals can be found of the form characteristic of any other species within the genus. This situation accounts for much of the confusion which has existed in the taxonomy of Chrotogonus. 4) Although some seasonal variation in size can be established, ecological variation is, in general, also confounded with the two major contrasts of form already noted. 5) The known relationship between long wings and a narrow mesosternal interspace is shown to be part of a genetically determined pattern of growth and is not phenotypically determined by differential muscular stresses during development.

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