Understanding the impact of geological events on diversification processes is central to evolutionary ecology. The recent amalgamation between ecological niche models (ENMs) and phylogenetic analyses has been used to estimate historical ranges of modern lineages by projecting current ecological niches of organisms onto paleoclimatic reconstructions. A critical assumption underlying this approach is that niches are stable over time. Using Notophthalmus viridescens (eastern newt), in which four ecologically diverged subspecies are recognized, we introduce an analytical framework free from the niche stability assumption to examine how refugial retreat and subsequent postglacial expansion have affected intraspecific ecological divergence. We found that the current subspecies designation was not congruent with the phylogenetic lineages. Thus, we examined ecological niche overlap between the refugial and modern populations, in both subspecies and lineage, by creating ENMs independently for modern and estimated last glacial maximum (LGM) newt populations, extracting bioclimate variables by randomly generated points, and conducting principal component analyses. Our analyses consistently showed that when tested as a hypothesis, rather than used as an assumption, the niches of N. viridescens lineages have been unstable since the LGM (both subspecies and lineages). There was greater ecological niche differentiation among the subspecies than the modern phylogenetic lineages, suggesting that the subspecies, rather than the phylogenetic lineages, is the unit of the current ecological divergence. The present study found little evidence that the LGM refugial retreat caused the currently observed ecological divergence and suggests that ecological divergence has occurred during postglacial expansion to the current distribution ranges.
In 1818, John Cleves Symmes (1780-1829) circulated a flyer announcing his theory of Earth's structure and polar geography. Declaring that Earth is "hollow, and habitable within; containing a number of solid concentric spheres, one within the other, and that it is open at the poles 12 or 16 degrees," Symmes solicited "one hundred brave men" for an expedition north of the 82nd parallel in search of "a warm and rich land, stocked with thrifty vegetables and animals, if not men." So began the history of American polar exploration. Symmes's idea attracted general ridicule, but it also tapped a vein of cultural patriotism, national pride, and expansionist ambition that won him a group of loyal followers. Chief among Symmes's supporters was Jeremiah Reynolds, who played a key role in obtaining congressional funding for the Great American Exploring Expedition of 1838-1842. In this paper, I recount the story of Symmes's theory and trace its influence on the establishment of a wholly American scientific enterprise and American literature and fringe culture. [
The City of Winnipeg has been evaluating options for its new water treatment plant's (WTP's) residuals management. Several mechanical systems such as centrifugation and belt presses were reviewed. However, a cost effective and environmentally friendly solution was desired for final dewatering of the solids sludge. Due to the favourable climatic conditions, the feasibility of freeze thaw technology for the City of Winnipeg's residuals solids dewatering was evaluated. A desktop evaluation and pilot study were completed. The desktop study concluded that freeze thaw ponds have been effectively used throughout cold regions of Canada and the United States. Due to the large scale of the Winnipeg project and to obtain practical confidence in the technology, a pilot scale sludge thickening test device was constructed in order to more closely identify the anticipated sludge concentration and supernatant quality after thickening. From a ten-week pilot trial, it was noted that solids concentrations increased from approximately 0.6% by weight to as high as 8% by weight after freezing. The test results also showed that the sludge solids concentration as high as approximately 50% can be achieved with an adequate drying period. Conventional higher energy technologies do not provide such a high solids concentration. Upon review of the pilot work and desktop study, the application of the freeze thaw technology was accepted as the way forward for the City of Winnipeg solids dewatering project. Due to site constraints, operational and economic reasons, the design of the facility posed several challenges. This paper intends to highlight some of the design criteria and challenges.
An abandoned beer can in Bear Meadows, a central Pennsylvania bog and state natural area, is a convenient focus for reflecting on Bnature,^within the dualistic Western conception nature and humans, in natural history. I begin by considering the difficulty of writing the natural history of a highly humanized place, the Susquehanna watershed, then consider relationships between place, meaning, and nature from legal, environmental historical, and paleoecological perspectives on Bear Meadows and its surrounding landscapes. A more satisfying conceptualization comes from a topological model that makes it possible to map ourselves and our doings in relation to a gradient from wholly natural to highly artificial but preserves the insight that we and our artifacts are simultaneously of nature and fundamentally different from it. Bears, balsam, and beer cansIt is a fine September day at Bear Meadows, a 320-acre bog in central Pennsylvania's Seven Mountains region, a place notable for an exceptionally rich array of dragonfly, damselfly, and bird species and old-growth populations of boreal tree species-red spruce, black spruce, and balsam fir-more at home in Canada than the oak-dominated Ridge and Valley. On higher ground at the edge, vireos and warblers haunt a rhododendron thicket near a giant hemlock, and black gum leaves scream scarlet at rust-colored blueberries and red maples just starting to tinge yellow. In the bog, cottongrass puffs on nearly invisible stems float above the spongy peat, like heavy clumps of wet snow that decided last-second to wait for winter before going the rest of the way down. 1 In the middle of all this, Tony Fornataro is trying to keep his tripod and camera from sinking, and I am squatting on a pair of sedge tussocks thinking about a dead beer can on a log.From the looks of the claw marks and shredded wood, a bear had worked over the fallen trunk a few days earlier. Since then, judging by the state of the can and the debris stuck to it, somebody drained it, shot it several times, stomped it flat over by the hemlock, then carefully set the carcass in the center of the fallen trunk.That was a year ago. A few weeks afterwards, Tony delivered a stunning 7-ft-long panoramic print of the scene that now hangs across from my desk. I have spent too much time since then staring at the log in the foreground wondering why the beer can is missing.The short answer is that I pocketed it while Tony was setting up his shot. We were in a state natural area working on a natural history of the Susquehanna. The beer can was out of place so picking it up seemed a natural thing to do. The longer answer has everything to do with two words, Bnaturalâ nd Bplace,^and is a nutshell version of a bigger and longerrunning vexation about relationships between people and nature that I have happily ignored for nearly 20 years. It started bubbling up while doing fieldwork for the natural history, gathered to a foamy head when I started writing, and then boiled over into the fire. The smell is not good.
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