Graduate Thesis Or Dissertation

 

Comparative studies of the population ecology and life history patterns of an alkaline salt lake insect : Ephydra (Hydropyrus) hians Say (Diptera:Ephydridae) Public Deposited

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  • Seasonal abundance and life history traits were compared between populations of the brine fly Ephydra (Hydrokyrus) hians Say (Diptera:Ephydridae), from two western Great Basin alkaline salt lakes. Abert Lake, Oregon, has a relatively low salinity (20-30 g/1 total dissolved solids) and more co-inhabitant benthic species than the higher salinity Mono Lake, California (75-90 g/l). During a period of declining salinities at both lakes, the abundance of this osmoregulating insect decreased at Abert Lake, and increased at Mono Lake. This suggests that abundance may be maximized at intermediate salinities due to biotic limitations imposed by competing and predatory species at dilute salinities, and physiological limitations imposed by osmotic stress at high salinities. Experimental rearing of larvae at high salinities, or reduced algal food supply levels, produced low survival, prolonged development, and smaller size at maturity. When food is not limiting, Mono Lake larvae exhibit greater independence of the inhibitory effects of increased salt concentration compared to larvae from less saline Abert Lake. Selection for enhanced salt tolerance may thus have occurred at Mono Lake, but appears to be limited above 150 g/1 because survival of first instars, and maturation of final instars are impaired at 200 g/l. Besides direct physiological effects, increased salinity also reduces algal growth and may thereby limit food availability to E. hians. Heritable differences in body size exist between populations in addition to environmentally induced changes in growth and size. Abert flies are inherently larger than Mono flies, and develop more rapidly at comparable salinity. Reduction in pupal size severely curtails emergence, and any small-bodied adults that do emerge possess only slight lipid stores, and have a low resistance to starvation. Improvements in algal food supplied to adults increases the proportion of flies reproducing, fecundity, and egg production rates. Reproductive effort has a negative impact on survival only when food is limiting. These results suggest that direct and indirect effects of changing salinity may play an important role in shaping life history patterns and regulating population dynamics of the alkali fly.
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  • 1986
  • description.provenance : Made available in DSpace on 2013-07-22T19:01:23Z (GMT). No. of bitstreams: 1 HerbstDavidB1986.pdf: 1453734 bytes, checksum: d921f83fd26fa31fc8ecbb5f0093327e (MD5) Previous issue date: 1986-03-06

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