I study long-term diversity dynamics in order to understand the range of “normal” ecological fluctuation. Detailed historic and paleoecological records can be used to characterize these past long-term ecological dynamics, and to predict how species will respond to future change.
Abrupt Change in Ecological Systems:
How, when, and why do abrupt changes and ecological regime shifts occur? Using the extensive North American pollen record, I am applying and developing techniques to identify abrupt change in vegetation. Specific projects include:
- Intrinsic drivers of mid-Holocene hemlock decline
- Early warning signals of critical transitions in paleoecological time series
- Abrupt (or not) turnover in dominant conifer species in Northern Rockies forests.
- How common are abrupt changes in the Quaternary fossil record, on a community level? Are they geographically coordinated and/or temporally synchronous?
Conservation in a rapidly changing world:
We know from the fossil record that ecosystems are constantly in flux. However, rates of global change today are unprecedented and, among many negative outcomes, we face the likely possibility of major extinction. Paleontology can help to provide context and insight for today’s conservation challenges.
- Need for a new conservation paradigm?: Generalizable conservation insights from the fossil record: Read the Conservation Paleobiology working group publication in Science here.
Paleo biogeography in western North America:
My paleo research on the Colorado Plateau is designed to 1) expand our knowledge of the Quaternary small vertebrates, a group under-studied in this region; 2) uncover paleo macroecological patterns and relate those to modern systems; 3) develop new techniques for identifying Quaternary small mammals (e.g., Perognathine TRL from Mescal Cave; or geometric morphometrics of Neotoma jaws, a genus with notoriously high interspecific, but extraordinarily low intraspecific morphological variability); and 4) reveal how small mammals have responded to previous episodes of environmental change.
- Mescal Cave, Mojave Desert(Stegner 2015, Quaternary Research)
- Small mammals of southeastern Utah over the last 5ka; new excavations (Stegner 2016, The Holocene)
- Ecometrics: Mammalian functional group diversity dynamics (Stegner and Holmes 2013, Paleo3)
- Bears Ears National Monument: this region is an unparalleled resource for studying the history of life on earth since the Permian. I conduct fossil surveys, excavations, and small mammal surveys in the Bears Ears. I am also an active advocate for resource protection in the Bears Ears. Read more on my Teaching and Outreach page.
Colorado Plateau modern & historical biogeography:
How are species distributed across the landscape? Does abundance relate to environmental factors, intrinsic factors, or both? How do local diversity and abundance relate to regional patterns? And how does the modern compare to the fossil? I am using a combination of mark-recapture surveys and data mining to understand modern mammal diversity patterns on local and regional scales.
- Modern vs. historical biogeography of Colorado Plateau National Parks (Stegner et al 2017)
- Lemmiscus curtatus was extirpated from the Colorado Plateau during the Holocene, and their teeth are present in theEast Canyon Rims 2 locality—why is this species missing from the Colorado Plateau, when so much seemingly appropriate habitat is available?
- My modern surveys have documented Perognathus mollipilosus east of the Colorado River, where it has never been reported before. Is it’s range expanding, or have we failed to recognize it’s presence here until now?
- Notiosorex crawfordi has been preserved in Holocene deposits across southeastern Utah, including my excavations at Butler Wash Cave. This cryptic species is extralimital—has it been here all along? Has it’s range contracted? A combination of more extensive trapping efforts and radiocarbon data sheds light on this question.