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MORPHOLOGICAL AND GENETIC DIFFERENTIATION IN APHIDS (APHIDIDAE)

Published online by Cambridge University Press:  31 May 2012

S. M. Singh
Affiliation:
Department of Zoology, University of Western Ontario, London, Ontario N6A 5B7
T. K. Cunningham
Affiliation:
Department of Zoology, University of Western Ontario, London, Ontario N6A 5B7

Abstract

Six species of aphids belonging to four genera were measured for 12 morphological features at five developmental stages. It was concluded that reliable identification of species based on morphological features is possible only at adult stages. Samples were also analyzed for seven enzymes by gel electrophoresis. There were no enzyme pattern differences among developmental stages in any species. Three enzymes, malic dehydrogenase, malic enzyme and tetrazolium oxidase, showed the same band pattern in all species. The other four, acid phosphatase, alkaline phosphatase, esterase and leucine-alanine peptidase, showed “diagnostic” patterns specific to a given species. All species are easily identifiable by their esterase pattern which could be confirmed by acid phosphatase, alkaline phosphatase, and leucine-alanine peptidase patterns. The enzyme pattern differences were used to establish a dendrogram of genetic relationship among species which was compared with a dendrogram of morphological similarities. The close genetic similarity among species suggests that significant adaptive differentiation leading to speciation may have occurred within the context of relatively few genie changes. This is compatible with speciation in aphids being due primarily to their obligate parthenogenetic reproduction, frequent bottlenecks (drastic reduction in number), and host plant specificity.

Résumé

Douze caractères morphologiques ont été mesurés à cinq stades du développement chez six espèces d’aphides appartenant à quatre genres. Il est apparu que seuls les adultes peuvent être séparés à l’espèce avec certitude sur la base de caractères morphologiques. Des échantillons ont aussi été analysés pour la présence de sept enzymes par électrophorèse sur gel d’acrylamide. Aucune espèce n’a montré de différences entre le profile enzymatique des différents stades. Trois enzymes, la déshydrogénase malique, l’enzyme malique et la tétrazolium oxidase ont montré un profile de bandes identique pour toutes les espèces. Les quatre autres soient la phosphatase acide, la phosphatase alcaline, l’estérase et la peptidase leucine-alanine, ont révélé des profiles “diagnostiques” spécifiques à l’espèce. Toutes les espèces sont aisément identifiables à leur profile d’estérase, confirmation pouvant être obtenue à l’aide des profiles de phosphatase acide, de phosphatase alcaline, et de peptidase leucine-alanine. Les différences au niveau du profile enzymatique ont été utilisées pour obtenir un dendogramme des relations génétiques entre les espèces, lequel fût comparé avec le dendogramme des ressemblances morphologiques. La grande similarité génétique entre les espèces indique qu’une différenciation adaptative appréciable menant à la spéciation a pu se produite avec relativement peu de changements génétiques. Ceci serait compatible avec un type de spéciation résultant chez les aphides de la reproduction parthénogénétique obligatoire, de fréquentes réductions drastiques d’abondance, et de la spécificité vis-à-vis la plante-hôte.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1981

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