ISSN:
1573-5117
Schlagwort(e):
saline lakes
;
ecology
;
physiology
;
Hemiptera
;
Corixidae
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Abstract Two closely related species of Cenocorixa inhabit saline lakes in British Columbia. C. bifida lives in lakes with a conductivity of 20 to 20 000 µS cm-1, while C. expleta occurs in lakes with a conductivity ranging from 5 000 to 30 000 µS cm-1. The factors limiting the differential distribution of these species in higher salinities, and those governing the exclusion of C. expleta in low salinities have been studied. Mortality experiments, and an investigation of osmotic and ionic balance, indicate that the two species differ in their ability to tolerate high salinity: these data correlate with the limits computed from field data and suggest that the differential distribution in the high saline lakes is because of physiological differences. However, these same data indicate that both species have a similar ability to live in low salinity lakes. Although C. expleta does not occur in such lakes, it is physiologically capable of doing so and has been reared in freshwater. It is proposed that ecological rather than physiological factors exclude C. expleta from low salinity waters. Competitive exclusion by C. bifida might be suggested, but available data do not support this. A study of life cycle phenology, fundamental food niche and realized feeding niche of the two species shows that these are not significantly different. No interactive segregation is evident in sympatry, and so competitive exclusion of C. expleta in freshwater is unlikely. Hence, other biological factors in fresh and low salinity water have been investigated. A marked difference in susceptibility to mite parasitism of the species has been discovered. Although both C. bifida and C. expleta are parasitized by larval Eylais and Hydrachna, C. expleta appears unable to survive such parasitism. It is suggested that this is the biological factor that excludes C. expleta in the fresh and low salinity lakes where water mites are abundant.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00025184
