Browsing by Subject "SELECTION"
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Item Open Access Boom and Bust: The Effect of Entrepreneurial Inertia on Organizational Populations(Advances in Strategic Management, 2006) Ruef, MAlthough recent public attention has focused on boom-and-bust cycles in industries and financial markets, organizational theorists have made only limited contributions to our understanding of this issue. In this chapter, I argue that a distinctive strategic insight into the mechanisms generating boom-and-bust cycles arises from a focus on entrepreneurial inertia - the lag time exhibited by organizational founders or investors entering a market niche. While popular perceptions of boom-and-bust cycles emphasize the deleterious effect of hasty entrants or overvaluation, I suggest instead that slow, methodical entries into an organizational population or market may pose far greater threats to niche stability. This proposition is explored analytically, considering the development of U.S. medical schools since the mid-18th century. © 2006 Elsevier Ltd. All rights reserved.Item Open Access Forest elephant movement and habitat use in a tropical forest-grassland mosaic in Gabon.(PloS one, 2018-01) Mills, Emily C; Poulsen, John R; Fay, J Michael; Morkel, Peter; Clark, Connie J; Meier, Amelia; Beirne, Christopher; White, Lee JTPoaching of forest elephants (Loxodonta cyclotis) for ivory has decimated their populations in Central Africa. Studying elephant movement can provide insight into habitat and resource use to reveal where, when, and why they move and guide conservation efforts. We fitted 17 forest elephants with global positioning system (GPS) collars in 2015 and 2016 in the tropical forest-grassland mosaic of the Wonga Wongué Presidential Reserve (WW), Gabon. Using the location data, we quantified movement distances, home ranges, and habitat use to examine the environmental drivers of elephant movements and predict where elephants occur spatially and temporally. Forest elephants, on average, traveled 2,840 km annually and had home ranges of 713 km2, with males covering significantly larger home ranges than females. Forest elephants demonstrated both daily and seasonal movement patterns. Daily, they moved between forest and grassland at dawn and dusk. Seasonally, they spent proportionally more time in grassland than forest during the short-wet season when grasses recruit. Forest elephants also traveled faster during the short-wet season when fruit availability was greatest, likely reflecting long, direct movements to preferred fruiting tree species. Forest elephants tended to select areas with high tree and shrub density that afford cover and browse. When villages occurred in their home ranges elephants spent a disproportionate amount of time near them, particularly in the dry season, probably for access to agricultural crops and preferred habitat. Given the importance of the grassland habitat for elephants, maintenance of the forest-grassland matrix is a conservation priority in WW. Law enforcement, outreach, and education should focus on areas of potential human-elephant conflict near villages along the borders of the reserve. GPS-tracking should be extended into multi-use areas in the peripheries of protected areas to evaluate the effects of human disturbance on elephant movements and to maintain connectivity among elephant populations in Gabon.Item Open Access Free-ranging livestock threaten the long-term survival of giant pandas(Biological Conservation, 2017-12-01) Li, Binbin V; Pimm, Stuart L; Li, Sheng; Zhao, Lianjun; Luo, Chunping© 2017 Elsevier Ltd China has implemented forest policies and expanded protected areas to halt deforestation and protect giant panda habitats. These policies simultaneously encouraged local communities to raise livestock that then freely range in forests. This grazing had unintended consequences. As an alternative livelihood, it has become the most prevalent human disturbance across the panda's range. How do free-ranging livestock impact giant panda habitats and what are the implications for future conservation and policy on a larger scale? We use Wanglang National Nature Reserve as a case study. It has seen a nine-fold livestock increase during past 15 years. We combined bamboo survey plots, GPS collar tracking, long-term monitoring, and species distribution modelling incorporating species interaction to understand the impacts across spatial and temporal scales. Our results showed that livestock, especially horses, lead to a significant reduction of bamboo biomass and regeneration. The most intensively used areas by livestock are in the valleys, which are also the areas that pandas prefer. Adding livestock presence to predictive models of the giant panda's distribution yielded a higher accuracy and suggested livestock reduce panda habitat by 34%. Pandas were driven out of the areas intensively used by livestock. We recommend the nature reserve carefully implement a livestock ban and prioritise removing horses because they cause the greater harm. To give up livestock, local communities prefer long-term subsidies or jobs to a one-time payment. Thus, we recommend the government provide payments for ecosystem services that create jobs in forest stewardship or tourism while reducing the number of domestic animals.Item Open Access Maidenhair ferns, adiantum, are indeed monophyletic and sister to shoestring ferns, vittarioids (Pteridaceae)(Systematic Botany, 2016-01-01) Pryer, KM; Huiet, L; Li, F; Rothfels, CJ; Schuettpelz, E© 2016 by the American Society of Plant Taxonomists. Across the tree of life, molecular phylogenetic studies often reveal surprising relationships between taxa with radically different morphologies that have long obscured their close affiliations. A spectacular botanical example is Rafflesia, a holoparasite that produces the largest flowers in the world, but that evolved from tiny-flowered ancestors within the Euphorbiaceae. Outside of parasitic lineages, such abrupt transformations are rarely seen. One exception involves the "maidenhair ferns" (Adiantum), which are quintessential ferns: beautifully dissected, terrestrial, and shade loving. The closely related "shoestring ferns" (vittarioids), in contrast, have an extremely simplified morphology, are canopy-dwelling epiphytes, and exhibit greatly accelerated rates of molecular evolution. While Adiantum and the vittarioids together have been shown to form a robust monophyletic group (adiantoids), there remain unanswered questions regarding the monophyly of Adiantum and the evolutionary history of the vittarioids. Here we review recent phylogenetic evidence suggesting support for the monophyly of Adiantum, and analyze new plastid data to confirm this result. We find that Adiantum is monophyletic and sister to the vittarioids. With this robust phylogenetic framework established for the broadest relationships in the adiantoid clade, we can now focus on understanding the evolutionary processes associated with the extreme morphological, ecological, and genetic transitions that took place within this lineage.