Catchment‐scale determinants of nonindigenous minnow richness in the eastern United States

Understanding the drivers of biological invasions is critical for preserving aquatic biodiversity. Stream fishes make excellent model taxa for examining mechanisms driving species introduction success because their distributions are naturally limited by catchment boundaries. In this study, we compared the relative importance of catchment‐scale abiotic and biotic predictors of native and nonindigenous minnow (Cyprinidae) richness in 170 catchments throughout the eastern United States. We compared historic and contemporary cyprinid distributional data to determine catchment‐wise native/nonindigenous status for 152 species. Catchment‐scale model predictor variables described natural (elevation, precipitation, flow accumulation) and anthropogenic (developed land cover, number of dams) abiotic features, as well as native congener richness. Native congener richness may represent either biotic resistance via interspecific competition, or trait preadaptation according to Darwin's naturalisation hypothesis. We used generalised linear mixed models to examine evidence supporting the relative roles of abiotic and biotic predictors of cyprinid introduction success. Native congener richness was positively correlated with nonindigenous cyprinid richness and was the most important variable predicting nonindigenous cyprinid richness. Mean elevation had a weak positive effect, and effects of other abiotic factors were insignificant and less important. Our results suggest that at this spatial scale, trait preadaptation may be more important than intrageneric competition for determining richness of nonindigenous fishes.     

Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient

Production of biomass is central to the ecology and sustainability of fish assemblages. The goal of this study was to empirically estimate and compare fish assemblage production, production‐to‐biomass (P/B) ratios and species composition for 25 second‐ to third‐order streams spanning the Appalachian Mountains (from Vermont to North Carolina) that vary in their temperature regimes. Fish assemblage production estimates ranged from 0.15 to 6.79 g m^?2 year^?1, and P/B ratios ranged from 0.20 to 1.07. There were no significant differences in mean assemblage production across northern cold‐water, southern cold‐water and southern cool‐water streams (p = .35). Two warm‐water streams, not included in these comparisons, had the highest mean production and biomass values. Mean assemblage P/B was significantly higher in northern cold‐water streams relative to southern cold‐water and cool‐water streams (p = .01). Species evenness in production declined with stream temperature and differed significantly across the lower latitude cold‐water, cool‐water and warm‐water streams and the higher latitude (i.e. more northern) cold‐water streams. Our fish assemblage production estimates and P/B ratios were both lower and higher compared to previously published estimates for similar stream habitats. This study provides empirical fish assemblage production estimates to inform future research on southern Appalachian streams and on the potential impacts of varying temperature regimes on cold‐water, cool‐water and warm‐water fish production in the coming decades as climate change continues to threaten fish assemblages.     

Suppression of green peach aphid (Myzus persicae) (Sulz.), citrus mealybug (Planococcus citri) (Risso), and two spotted spider mite (Tetranychus urticae) (Koch.) attacks on tomatoes and cucumbers by aqueous extracts from vermicomposts

Vermicomposts are produced through interactions between earthworms and microorganisms in the breakdown of organic wastes. Aqueous extracts were prepared in commercial brewing equipment (Growing Solutions Inc.) from vermicomposts processed from pre-consumer food waste. The ratio of vermicompost to water was 1 to 5 v:v to produce a 20% aqueous solution. The effects of soil drenches at dilutions of 20%, 10%, and 5% vermicompost extracts, were compared with those of deionized water, in the suppression of green peach aphids, mealybugs, and two spotted spider mites attacking tomatoes and cucumbers, in greenhouse cage experiments.     

Ridge to reef modelling for use within land–sea planning under data‐limited conditions

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Mechanical comparison of two suture constructs for extra-capsular stifle stabilization

Objective: Mechanical evaluation of 2 suture constructs for extracapsular stifle stabilization. Study Design: In vitro study. Sample Population: Crimped interlocking loop constructs (ILC) of 45 kg nylon leader line (NLL) and Orthofiber^® (OF). Methods: ILC were tightened to 100 N, then crimp secured. Ramp to failure (n=10/group)—Data were derived from force/displacement plots. Stress–relaxation testing (n=10/group)—ILC's were nondestructively loaded and held at resultant displacement as force data were recorded. Incremental, cyclic loading (n=10/group)—ILC's were loaded (5 cycles/set) starting at 100 N and incrementally increased by 50 N (1 and 3 Hz protocols). Loop tension and elongation were recorded after each set. Results: Ramp to failure—initial loop tension was similar (NLL 75.5 ± 9.5 N; OF 68.7 ± 10.4 N, P=.140). Tested OF constructs were stiffer (NLL 125.7 ± 4.0; OF 234.6 ± 25.0 N/mm, P≤.001), had lower yield load (NLL 193.6 ± 13.8; OF 137.3 ± 94.3 N, P≤.001), lower peak load (NLL 873.7 ± 68.6; OF 653.6 ± 80.2 N, P≤.001), and lower elongation at failure (NLL 19.1 ± 1.4; OF 5.2 ± 1.0 mm, P≤.001) and at yield (NLL 1.52 ± 0.2; OF 0.3 ± 0.6 mm, P=.003) than NLL constructs. Yield in NLL ILC's was variable knot tightening/crimp slippage, but only crimp‐suture slippage in OF. Stress–relaxation testing—OF demonstrated greater relaxation. Incremental, cyclic loading—induced ILC elongation and tension loss in both groups, independent of loading frequency. NLL lost tension at lower rate, but elongated more than OF. Conclusions: NLL construct is mechanically superior to OF construct.