University of California

Experimental studies on hybridization and sexual isolation between some Aphytis species (Hymenoptera: Aphelinidae): I. Experimental hybridization and an interpretation of evolutionary relationships among the species


Sudha V. Rao
Paul DeBach

Authors Affiliations

Sudha V. Rao (now Mrs. Sudha Nagarkatti) was with the Commonwealth Institute of Biological Control, Indian Station, Bellary Road, Bangalore (6), India; Paul DeBach was Professor of Biological Control, College of Biological and Agricultural Sciences, and Entomologist in the Experiment Station, Riverside.

Publication Information

Hilgardia 39(19):515-553. DOI:10.3733/hilg.v39n19p515. June 1969.

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A biosystematic study was made of cultures of closely similar species of Aphytis (Hymenoptera, Chalcidoidea, Aphelinidae) from various countries. Sexual isolation was an important barrier to interspecific hybridization. Laboratory manipulations were devised to partially overcome this. Some fertile interspecific hybrids were obtained and hybrid lines established. Fecundity and sex ratio of hybrids improved in successive laboratory generations. A mathematical index was developed, based upon extent of hybrid progeny production, sex ratio, and degree of fertility of F1 hybrids, which depicts the degree of reproductive isolation between a given pair of species. It was concluded that the described species, africanus, lepidosaphes, melinus, fisheri and boloxanthus, are valid species with respect to each other and with respect to all other species studied. Aphytis coheni and “khunti,” A. lingnanensis and “2002,” and “R-65-23” and “2002” are considered to be semispecies with respect to each other. Additionally, the following are considered to be valid species with respect to each other: lingnanensis and coheni; lingnanensis and “khunti”; “2002” and coheni; “2002” and “khunti”; lingnanensis and “R-65-23”; “khunti” and “R-65-23”; and coheni and “R-65-23.”

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Rao S, DeBach P. 1969. Experimental studies on hybridization and sexual isolation between some Aphytis species (Hymenoptera: Aphelinidae): I. Experimental hybridization and an interpretation of evolutionary relationships among the species. Hilgardia 39(19):515-553. DOI:10.3733/hilg.v39n19p515
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