Hydrologic Influences on Insect Emergence Production from Central Platte River Wetlands

Abstract

The physical template of freshwater ecosystems has a pervasive influence on biological communities and processes. To examine the influence of hydrology on wetland insect communities, we quantified insect emergence from five riparian sloughs in the central Platte River valley. Annual hydroperiods of the wetlands ranged from 94 to 365 d/yr, and frequency and magnitude of drying events were inversely proportional to hydroperiod length. Three emergence traps were placed in each wetland from April through November 1997. Most insects collected in traps were identified to genus, and individual dry mass (DM) also was determined. Abundance of emerging insects (24 124 individuals/m 2 ) and emergence production (5.1 g DM·m Ϫ2 ·yr Ϫ1 ) were highest from the site with an intermediate hydroperiod of 296 d. Sites with longer and shorter hydroperiods had lower emergence abundance and production. Emergence production from the perennial site, which contained fish year-round, was only 0.26 g DM·m Ϫ2 ·yr Ϫ1 . Diptera generally dominated emergence trap catches. Chironomidae, Culicidae, and Ceratopogonidae were among the dominant contributors to abundance, whereas Sciomyzidae and Muscidae were important contributors to biomass at most sites.Quadratic equations best described relationships between taxa richness and annual hydroperiod (r 2 ϭ 0.78, P Ͻ 0.05) or number of drying events/yr (r 2 ϭ 0.81, P Ͻ 0.05), reflecting a peak in richness at intermediate levels of both. These relationships followed predictions of the intermediate disturbance hypothesis, but specific mechanisms underlying patterns were difficult to discern. Like emergence production, taxa richness was also highest at intermediate hydroperiods. Hence, insect diversity (measured as richness) and emergence production were positively correlated (r 2 ϭ 0.85, P Ͻ 0.05). Results indicate that the hydrology of central Platte River wetlands exerts a strong influence on insect species richness and emergence production, and that intermittent sites harbor the highest insect diversity and produce more emergent insect biomass. However, trends in seasonal emergence patterns and taxonomic shifts across the hydrologic gradient in this study suggest that a landscape containing a mosaic of hydrologically distinct wetlands will maximize aquatic insect diversity and productivity at larger spatial and temporal scales.

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

“…Our estimates of emergent biomass for individual taxa were equal to, or exceeded, estimates for some aquatic insect communities in stream (Fisher and Likens 1973), wetland (Whiles and Goldowitz 2001), and pond systems (Naiman et al 1986). Our estimates for salamander assemblages were equal to emergent biomass of midges from open-water habitats of an Alabama wetland (0.5 g DM m À2 year À1 ; Stagliano et al 1998) and exceeded exports of final instar caddisflies migrating from a Nebraska wetland (0.3 g AFDM m À2 year À1 ; Whiles et al 1999).…”

“…We calculated total surface area as the product of transect interval length and the sum of transect wetted lengths; the lengths of transects where water was ‡0.3 m deep were summed to estimate surface area for deep-water habitats, and the difference between these values was littoral surface area (Masser and Jensen 1991). Surface areas of temporary ponds changed seasonally, so we constructed linear and quadratic regression models to predict surface area and the proportion of each habitat type from staff gauges installed in these ponds (Whiles and Goldowitz 2001). We used seasonal maximum perimeter (P) and surface area (A) to calculate P:A ratios for all ponds.…”

Factors affecting Sciomyzidae (Diptera) across a transect at Skealoghan Turlough (Co. Mayo, Ireland)

“…Vaňhara (1986), in describing the effect of water management (drainage) on brachyceran composition at a wet-woodland in Moravia has noted, ''Of Sciomyzidae only 42% of species and 14.9 % of individuals remained, but a fundamental change took place in favour of species feeding on land snails'' (Vaňhara 1986). Also, a study of Diptera at temporarily flooded sloughs in North America indicated that sites with an intermediate hydroperiod (296 days = 81% of the year) were most species-rich and abundant, but that Sciomyzidae were prominent (in terms of abundance and production) at sloughs with hydroperiods between 96 (=26% of the year) and 158 (=43% of the year) days (Whiles and Goldowitz 2001). The results of the present study are consistent with these findings, indicating that similarity in hydrological regime is central to similarity in the composition of a zone's sciomyzid fauna.…”

Effects of Habitat Size, Vegetation Cover, and Surrounding Land Use on Diptera Diversity in Temperate Nearctic Bogs

“…This idea can be related to this study since all bog sites were completely surrounded by forested land before undergoing extreme anthropogenic transformations in the surrounding matrix. The IDH has explained diversity patterns for multiple wetland arthropod taxa (Ward and Stanford 1983;Townsend et al 1997;Whiles and Goldowitz 2001) and provides a possible explanation for the high diversity of assemblages from LAN and JON.…”