Small mammal faunal stasis in Natural Trap Cave (Pleistocene-Holocene), Bighorn Mountains, Wyoming

Abstract

Paleocommunity behavior through time is a topic of fierce debate in paleoecology, one with ramifications for the general study of macroevolution. The predominant viewpoint is that communities are ephemeral objects during the Quaternary that easily fall apart, but evidence exists that suggests geography and spatial scale plays a role. Natural Trap Cave is a prime testing ground for observing how paleocommunities react to large-scale climate change. Natural Trap Cave has a continuous faunal record (100 ka-recent) that spans the last glacial cycle, large portions of which are replicated in local rockshelters, which is used here to test for local causes of stasis. The Quaternary fauna of North America is relatively well sampled and dated, so the influence of spatial scale and biogeography on local community change can also be tested for. Here I use the herbivorous and omnivorous small mammal fauna (50%). The likely cause for the local stasis in Natural Trap Cave is distance from the modern northern and southern edges of the member taxa distributions, a reflection of their broad range of adaptation. North-south oriented mountain barriers preserve the integrity of the regional fauna by allowing habitat-tracking down-elevation. These mountain barriers also limit east-west dispersal from neighboring faunal provinces.