An ecological study of some of the chironomidae inhabiting a series of saline lakes in central British Columbia with special reference to Chironomus tentans Fabricius

This thesis is concerned with a study of the Chironomidae occuring in a saline lake series in central British Columbia. It describes the ecological distribution of species, their abundance, phenology and interaction, with particular attention being paid to Chironomus tentans. Emphasis is placed on the species of Chironomus that coexist in these lakes and a further analysis is made of the chromosome inversion frequencies in C. tentans. Of the thirty-four species represented by identifiable adults in the study, eleven species have not been previously reported in British Columbia, five are new records for Canada and seven species are new to science. The chironomid fauna of the lake series is divided into dominant associations whose existence seems to depend on salinity and productivity levels. A Cricotopus albanus -Procladius bellus - Ablabesmyia peleensis association prevails in the lowest salinities (40 to 80 μmho/cm conductivity) while in conductivities between 400 and 2800 μmho/cm a Glyptotendipes barbipes - Einfeldia pagana association dominates. In the most saline lakes (conductivity 4100 to 12000 μmho/cm) a Calopsectra gracilenta - Cryptotendipes ariel association is characteristic. Analysis of physical and chemical factors influencing the life cycle of C. tentans indicates that conditions associated with high levels of organic carbon promote large numbers of larvae and greater emergence success. The results suggest that competition between C. tentans and other Chironomus species is reduced through spatial separation due to different preferences for salinity or related factors. Furthermore, temporal separation among these and other abundant species such as G. barbipes and E. pagana occurs as a result of staggered generation times. The inversion frequency in chromosome 1 of C. tentans is negatively correlated with organic carbon levels and positively correlated with dissolved oxygen and the abundance of Glyptotendipes barbipes. Since the inversion frequency is lowest in habitats where competing species are few and where C. tentans is most successful, it is suggested that the inversion governs a mechanism reducing competition. A major contribution of this work is the revision of the distribution of many of the chironomid species under consideration. In the past, little research has been done on populations of chironomids in a saline lake series. The present study, in attempting to fill this gap in entomological research, shows that a species' life history and population structure can vary radically in closely associated lakes of differing chemical and biological constitution.Science, Faculty ofZoology, Department ofGraduat