CRYPTIC SPECIATION IN THE VERNALIS GROUP OF CYCLOPIDAE

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Abstract
Breeding experiments performed on the descendants of 30 separate populations of Cyclops vernalis Fischer show a pattern of positive and negative results indicating the existence of seven reproductive isolates. Most of these isolates vary morphologically, but they differ in the nature and degree of this variation. They are, for the most part, not easily indentifiable but the one which varies the least is shown to be referable to C. brevispinosus Herrick, a species which had been placed in the synonymy of C. vernalis. No attempt is made to name the six other isolates.In addition to their experimentally demonstrated reproductive isolation and differences in morphological variability, the isolates are regarded as species on the basis of differences in their ability to serve as first intermediate hosts for the tapeworm Triaenophorus crassus Forel.