Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950-2010) and prospective (2011-2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish assemblages associated with groundwater pumping from the United States High Plains Aquifer. We modeled the relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes. Scaling down to subwatersheds revealed consistent transformations in fish assemblage structure among western subwatersheds with increasing depths to groundwater. Although transformations occurred in the absence of barriers, barriers along mainstem rivers isolate depauperate western fish assemblages from relatively intact eastern fish assemblages. Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater. Our work illustrates the shrinking of streams and homogenization of Great Plains stream fish assemblages related to groundwater pumping, and we predict similar transformations worldwide where local and regional aquifer depletions occur.
Emerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision-analytic model that combines empirical knowledge of host-pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad (Anaxyrus boreas boreas) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape-level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.
AN OVERVIEWThis paper presents some results of a study of speech variation and social structure in a North Carolina Piedmont community. Only one linguistic variable is considered here: the pronunciation of postvocalic r.The major results to be discussed are the following. The rates at which r was pronounced are not normally distributed about a single central value but tend to be bimodal. Moreover, such bimodality-suggesting the possibility of two r-pronunciation norms-is most pronounced among the higher status residents of the community. That there are two r-norms is further reflected by the tendency for younger and newer residents to pronounce 7 and for older ones and those with long tenure in the community to refrain from making the sound. As attention becomes more focused on pronunciation the general tendency is to increase, rather than decrease, the use of the r-sound.Word pronunciations were elicited in two ways: in sentences and in a word list; both methods show these results. Moreover, differences in pronunciation between the two eliciting situations are related to these social and demographic factors; however, overriding differences between the situations also appear.Just as people differ in their r-pronunciation habits, so also do words vary in the extent to which they elicit r-pronunciations in postvocalic position. When words are ranked in this respect we find linguistic factors which affect r-pronunciation; these factors are independent of the eliciting situation.Finally, a study of transcriber reliability shows that perception of r in postvocalic position, in at least one sense of the term "perception," is influenced by the speech habits of transcribers as well as syllable structure.
Some populations of Mountain Whitefish Prosopium williamsoni, a widely distributed native Rocky Mountain salmonid, have experienced catastrophic declines while other populations remain robust. To assess the possibility that the declines have arisen from climate‐related factors, several experiments were conducted to determine the upper thermal tolerances of embryos and fry and the effects of temperature on growth. Hatching of eggs was measured at 5.7, 6.4, 8.4, and 10.4°C (three replicates each). Survival and growth of fry were measured for 33 d at 5.7, 8.2, 11.8, 16.5, 19.1, 22.2, and 25.2°C (three replicates each). Mean hatching success was 96.7% (SD, 2.9) at 5.7°C, 98.3% (2.9) at 6.4°C, 90.0% (8.7) at 8.4°C and 38.3% (10.4) at 10.4°C. The ultimate upper incipient lethal temperature for fry was 23.6°C (95% CI, 23.5–23.7°C) after 7 d, which decreased with time to 22.6°C (22.1–23.0°C) after 33 d. The critical thermal maximum was 26.7°C (SD, 0.8) for fry acclimated to 13.4°C. The temperature for maximum growth was 13.8°C (95% CI, 10.8–16.8°C). Growth rates above and below the temperature for maximum growth decreased sharply to about 40% of the maximum at 5.7°C and 22.2°C. Based on these experimental data, the criteria for the protection of Mountain Whitefish fry are 21.6°C for acute water temperature and 16.8°C for chronic water temperature. The acute criterion for reproduction—based on the maximum temperature for successful incubation—is 8.4°C. The low upper thermal tolerance of Mountain Whitefish relative to those of other salmonids suggests that they will be very vulnerable to the increasing stream temperatures resulting from climate change.
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