Comparative population ecology of Ephydra hians Say (Diptera: Ephydridae) at Mono Lake (California) and Abert Lake (Oregon)

Abstract

The population dynamics of Ephydra hians Say final instar larvae and pupae were compared over a two year period in rocky littoral habitats of two alkaline saline lakes in the western Great Basin. Relative abundance increased from 1983 to 1984 at Mono Lake (California), during dilution from ca. 90 to 80 g 1 -' TDS (total dissolved solids). In contrast, relative abundance decreased over the same period at Abert Lake (Oregon), accompanied by a dilution of salinity from ca. 30 to 20 g 1-1 and a marked increase in the number and abundance of other benthic macroinvertebrate species. These observations are consistent with a hypothesis that proposes biotic interactions limit E. hians abundance at low salinity, and physiological stress limits abundance at high salinity.Oviposition extends from early spring to early fall. Mixed instars present throughout this period indicates multivoltine population dynamics with overlapping generations. The standing stock biomass of final instars increases exponentially in late spring and peaks in late summer or early fall. Pupae increase in proportional representation and abundance from a spring minimum to a fall maximum. The body size of adults and pupae cycle seasonally from a spring maximum to a fall minimum, and may be related to either or both food limitation, or water temperature.

Benthos of a prerennially-astatic, saline, soda lake in Mexico

“…Our findings support the hypothesis proposed by Colburn (1988), Herbst (1988), and Williams et al (1990) that physical and chemical factors may exert primary control on community composition in saline waters.…”

“…E. hians and C. occidentalis were present throughout the year, while the other three species appeared only occasionally in samples. The low species richness of Tecuitlapa Norte is similar to other saline lakes worldwide within a similar salinity range (Alcocer et al, 1997;Colburn, 1988;Dejoux, 1993;Herbst, 1988;Timms, 1982Timms, , 1983Williams and Kokkinn, 1988).…”

“…A freshwater lake allows other species to establish that compete and/or predate on C. occidentalis and E. hians. Ephydrids, for example, are successful and abundant only in lakes lacking predators (Herbst, 1988(Herbst, , 1990. This explains why saline, alkaline lakes, in which predators and competitors are lacking, or greatly diminished due to salinity stress, offer an excellent habitat for ephydrids to live in and multiply in large numbers.…”

Relationships between Artemia monica life history characteristics and salinity

“…At lower salinities, however, predation and competition may exert a significant influence on Artemia populations as other species invade. Herbst (1988) proposed an 'intermediate salinity hypothesis' where productivity of individual species reaches a m~imum at sa~~ities inte~ediate between physiologically-limiting high salinities, and low salinities where competition and predation from other species limit population growth. In the Great Salt Lake, Utah significant declines in A~~rnj~ ~~~c~c~~~ Kellogg abundance and restructure of the entire ecosystem occurred foflowing a decline in salinity from 250 to SO g I-' and a co-occurring invasion of an invertebrate predator, Trichocorixa verticalis Fieber.…”

Biodiversity of the Hypersaline Urmia Lake National Park (NW Iran)

“…Eggs of the genus Ephydra are attached to an algae mat [69]. The main food sources of adults and larvae are algae, some bacteria, and protozoa [70][71][72]. Nemenz [73] had observed adults of Ephydra cinerea feeding on masses of algae washed ashore at the Great Salt Lake in Utah, USA.…”