Associations of Small Mammals Occurring in a Pluvial Lake Basin, Ruby Lake, Nevada

Ruby Lake is a highly mesic and vegetationally diverse pluvial lake basin of east central Nevada. Small mammal associations were examined in six plant communities at Ruby Lake using transects of live traps. Small mammal activity was recorded for these six habitats plus an additional three other specialized habitats. A total of 11 species of small mammals were trapped from the six habitat types; from the entire study area 26 species were trapped or observed. Two greasewood shrub habitats and a shadscale-spiny hopsage habitat held the highest number of trapped species, 6, 5, and 7, respectively. The mesic haymeadow and spring habitats, as well as the big sagebrush-antelope bitterbrush habitat held 4 trapped species each. Peromyscus maniculatus and Perognathus parvus made up 76% of the total captures and were found in all habitat types except marshlands. Eutamius minimus was found in four of the six habitat types, while Dipodomys ordii , Dipodomys microps , Perognathus parvus , and Microtus montanus were limited to specialized habitats. Mesic adapted, wetland species such as Mustela vison , Ondatra zibethicus , and Sorex vagrans possibly dispersed into Ruby Valley from the northeastern drainages and valleys during the late Pleistocene or Holocene.     

The directionality of distinctively mathematical explanations

In “What Makes a Scientific Explanation Distinctively Mathematical?” (2013b), Lange uses several compelling examples to argue that certain explanations for natural phenomena appeal primarily to mathematical, rather than natural, facts. In such explanations, the core explanatory facts are modally stronger than facts about causation, regularity, and other natural relations. We show that Lange's account of distinctively mathematical explanation is flawed in that it fails to account for the implicit directionality in each of his examples. This inadequacy is remediable in each case by appeal to ontic facts that account for why the explanation is acceptable in one direction and unacceptable in the other direction. The mathematics involved in these examples cannot play this crucial normative role. While Lange's examples fail to demonstrate the existence of distinctively mathematical explanations, they help to emphasize that many superficially natural scientific explanations rely for their explanatory force on relations of stronger-than-natural necessity. These are not opposing kinds of scientific explanations; they are different aspects of scientific explanation.