PS 6-52
Holocene arthropod remains from woodrat (Neotoma spp.) middens used to aid the study of prehistoric climate in the Great Basin
Middens composed of the fossilized urine of woodrats (Neotoma spp.) can be found in rock crevices throughout the Great Basin. Carbon-dating and taxonomic identification of plant remains preserved in such middens have revealed strata providing a continual record of local flora, and by extension prevailing climate, stretching back nearly 30,000 years. Such studies can be complemented and potentially refined by incorporating additional proxy data, e.g. arthropod remains from the same middens, information regarding their host plants, and other associated flora and fauna. Insect parts (e.g. leg segments, head capsules, mouthparts) recovered from 10 strata dated from 370 +/- 40 YBP to 10,320 +/- 170 YBP of a fossil midden located in War Canyon, within the Clan Alpine Mountains of central Nevada, were compared to contemporary specimens and photographs in order to identify them to the lowest taxonomic level possible. Analysis was focused on identified arthropods known to have novel/restricted habitat requirements, allowing inferences to be made about the environment at the time of their occurrence.
Results/Conclusions
Fossil remains of over 80 taxa of arthropods in at least 31 families were recovered from the War Canyon midden. This assemblage is dominated by Coleoptera, particularly Carabidae, Curculionidae, Scarabaeidae, and Tenebrionidae; as well as Hymenoptera, specifically Formicidae; and various Orthoptera. This study does not attempt to relate abundance of an insect in a sample to abundance in the environment at the time, restricting analysis to presence/absence within strata. The scattered presence of certain species such as the Western conifer seed bug, Leptoglossus occidentalis (Hemiptera: Coreidae), a species that breeds on conifers and feeds on conifer seeds, supports previous findings on past environmental conditions as indicated from plant remains. The absence of otherwise ubiquitous taxa from certain strata, e.g. Diplotaxis sp. (Coleoptera: Scarabaeidae) and Stenopelmatus sp. (Orthoptera: Stenopelmatidae) may reflect climatic extremes, indicating the temporary unsuitability of the local habitat for those species. These preliminary findings indicate that further study of arthropod specimens from the War Canyon and other middens is warranted to improve our understanding of Late Pleistocene and Holocene Great Basin flora and fauna and the climatic changes that shaped them.