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A cytotaxonomic study of the most common larval Chironomidae in a series of saline waters in the southern interior of British Columbia Bassett, Michael Conway


A preliminary cytotaxonomic study of the common Chironomidae in a series of saline waters in the southern interior of British Columbia has been undertaken. The banding pattern of the salivary gland chromosomes, once it had been described, was used as a taxonomic criterion and as an indicator of the relationships between the groups involved. In order to obtain associated stages in the life cycle, the larvae were reared in individual vials. The polytene chromosome analysis revealed seven well defined larval species. The subsequent morphological analysis showed that five of these larval species could usually be separated by their external morphology. However, two cytologically distinct species are morphologically indistinguishable. Recent work on sibling species in Drosophila and Chironomus (Diptera) has shown that sibling species have salivary gland chromosomes with an identical banding pattern but, differ from one another in the frequency of inversions. The present study suggests that the morphologically identical larvae mentioned above are sibling species in larval morphology but are clearly separable by chromosome analysis. The fact that they occur together in the same lake tends to eliminate the view that they are distinct populations of a single species. That there may be more than one species involved in those here considered to be a single taxa, should however not be forgotten.

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