Comparing Scales of Environmental Effects from Gasoline and Ethanol Production

Understanding the environmental effects of alternative fuel production is critical to characterizing the sustainability of energy resources to inform policy and regulatory decisions. The magnitudes of these environmental effects vary according to the intensity and scale of fuel production along each step of the supply chain. We compare the spatial extent and temporal duration of ethanol and gasoline production processes and environmental effects based on a literature review and then synthesize the scale differences on space–time diagrams. Comprehensive assessment of any fuel-production system is a moving target, and our analysis shows that decisions regarding the selection of spatial and temporal boundaries of analysis have tremendous influences on the comparisons. Effects that strongly differentiate gasoline and ethanol-supply chains in terms of scale are associated with when and where energy resources are formed and how they are extracted. Although both gasoline and ethanol production may result in negative environmental effects, this study indicates that ethanol production traced through a supply chain may impact less area and result in more easily reversed effects of a shorter duration than gasoline production.     

Low queen mating frequency in the seed-harvester ant Pogonomyrmex (Ephebomyrmex) pima: implications for the evolution of polyandry

The evolution of polyandry is a central problem in the study of insect mating systems, and both material and genetic benefits have been proposed to offset the presumed costs of multiple mating. Although most eusocial Hymenoptera queens mate with just one or occasionally two males, high levels of polyandry are exhibited by several taxa, including seed-harvester ants of the genus Pogonomyrmex. Previous studies of queen mating frequency in Pogonomyrmex have focused on monogynous (one queen per colony) species in the subgenus Pogonomyrmex. We performed a genetic mother–offspring analysis of mating frequency in Pogonomyrmex (Ephebomyrmex) pima, a queen-dimorphic species with dealate and intermorph queens that differ in colony structure (intermorph colonies contain multiple queens). Our results demonstrate that both dealate and intermorph queens of P. (E.) pima are typically single maters, unlike their congeners analyzed thus far. Polyandry appears to be a derived trait in Pogonomyrmex, but comparative tests between P. (E.) pima queen morphs and across the genus provide no evidence that it evolved as an adaptation to increase genetic diversity within colonies or to obtain more sperm, respectively.