The Smiley Lab uses multi-disciplinary approaches to investigate evolutionary and ecological responses to landscape change. Our research focuses on integrating information from the modern, historical, and fossil records with geologic and climate history to understand the processes that generate and maintain patterns of multi-dimensional diversity today and in the past.
Given the myriad threats to biodiversity today, our lab is also guided by the principles of conservation paleobiology, using fossils as ecological baselines to gain new information from an old record. To better predict how species and their ecosystems will respond to future environmental change, we must deepen our understanding of how climate and landscape change have shaped communities in the past. The fossil record offers that long-term window, enabling scientists to look at how ecological processes have unfolded over a vast range of temporal and spatial scales prior to human influence. We use several tools to illuminate this history and gain insight into how and why human-caused environmental change and ecological response today differs from any time in the past.
The general themes of our research are:
Ecological dynamics & paleoenvironmental change
The rich fossil record of mammalian faunas during the Cenozoic presents the opportunity to test hypotheses for species- and community-level response to climate and environmental change over a range of temporal and spatial scales. Our research integrates field work and specimen-based approaches with a variety of laboratory and analytical analyses to investigate ecological dynamics during past intervals of warming and landscape change in western North America. Over the past decade, our work has taken place in the Mojave region of southern CA, the John Day region in eastern OR, and across multiple museum collections. At SBU, we are excited to work with the fantastic team at the Turkana Basin Institute to develop new projects in the East African Rift Zone of Kenya.
Paleoecology of small mammals
Rodents and other small mammals represent over half of extant biodiversity and much of the fossil record. In our research, we employ three primary methods for assessing species dietary ecology and morphological adaptations: stable isotope analysis, 2D-geometric-morphometric dental shape analysis, and 3D-ecometric trait analysis. Recent developments in these methods (e.g., in situ laser ablation for isotopic sampling of very small teeth) allow us to investigate small mammals, opening up a valuable, yet underutilized, part of the fossil record.
While global trends provide important information about broad-scale climate and environmental changes, assessing local ecosystem conditions is key to understanding the relevant drivers of community response. Therefore, I employ multi-proxy approaches to reconstruct past vegetation, moisture conditions, and habitat heterogeneity at the basin scale and in relation to local faunal assemblages.
Miocene Barstow Formation, Mud Hills, CA.
In situ laser ablation sampling for isotopic composition of small-mammal fossils spanning the Miocene Climate Optimum in the Crowder and Cajon Valley formations in southern CA.
Schematic of stable isotopic approaches to assessing species dietary ecology and habitat preferences, as well as isotopic niche dynamics and ecological interactions through time.
Mountains as Biodiversity Hotspots through time
Modern mammal diversity across North America follows a striking geographic gradient: areas of high elevation, topographic complexity, and habitat heterogeneity have greater species richness, ecological and phylogenetic diversity than adjacent lowlands. This topographic diversity gradient is also found in plants, birds, and large mammals across the continents today. Our research explores the influences of tectonic activity and climate change on North American faunas over the last 20 million years in order to elucidate the processes underpinning the group's diversification history. Specifically, we assess diversity patterns and macro-evolutionary processes across spatial scales and in relation to preservation effects.
A central aim of this research is to establish a general framework for assessing the origination and maintenance of diversity gradients over deep time. Merging evidence from the modern-day and fossil records, we aim to answer such questions as: What are the relative roles and rates of speciation, extinction and immigration in generat-ing topographic diversity gradients? How does the evolution of ecological and functional diversity relate to species diversity in dynamic, complex landscapes?
The research is conducted in collaboration with a diverse group of researchers, including geophysicists, landscape and climate modelers, phylogeographers, and landscape geneticists, stemming from a National Evolutionary Synthesis Center (NESCent) catalysis meeting. Our research is supported by a NSF Research Coordination Grant led by Catherine Badgley, and a NSF Collaborative Grant with SBU researchers William Holt and Troy Rasbury.
Present-day diversity for rodents, based on species ranges from IUCN and compiled at a resolution of 0.1 deg, in relation to elevation. Species richness is highest in the topographically complex and tectonically active western region.
Figure from Smiley et al. 2020.
Species richness of fossil mammals (black) from the western United States in relation to the global climate trend (oxygen-isotopic record in purple from Zachos et al., 2008) and Basin and Range tectonic extension (strain rate in green from Bahadori et al., 2018). Richness is quantified from fossil localities in mountainous and tectonically active regions (dots in yellow, red and blue regions in inset map).
Mice-oscapes: Small-mammal isotope ecology in relation to modern environmental gradients & historical land-use change
Today, species' diets, habitat preferences, and ecological interactions can vary in relation to broad-scale climate and environmental gradients. Likewise, climate, vegetation, and land-use change have had a dramatic impact on the environment and ecological dynamics across the United States over the past 100 years. The stable isotopic composition of small mammals from modern trapping efforts and historical museum specimens offer a window into changing species ecology over space and time.
In collaboration with Jennifer Cotton and Rebecca Terry, I integrate stable isotopic approaches with statistical geospatial modeling to determine the climatic and ecological controls on small-mammal diets. Currently, we are evaluating the stable isotopic composition of biological and environmental samples from the broad array of National Ecological Observatory Network (NEON) sites to
1) assess the interacting effects of climate and landscape change on ecosystems and communities at a continental scale, and 2) generate isotope landscape models – or ‘mice-oscapes’ – to make predictions about how small-mammal dietary ecology has been impacted by four types of land-use change (urbanization, agricultural expansion, deforestation, and grazing intensification). This work is supported by a NSF Macrosystems Biology Grant.
While much of this work is motivated by questions related to conserving both current biodiversity and importantly, ecosystem function, in a time of pervasive, human-mediated landscape and climate change, the implications for paleoecological research are also significant.
(a) Geographic variation in the carbon isotopic composition (isoscape) of Dipodomys ordii and Perognathus parvus diets across their combined geographic range. Diet values are predicted based on a conditional forest model. (b) Percent C4-grass abundance within the grass flora derived from the modeled isoscape.
Figure from Smiley et al. 2015.
Dipodomys ordii and Perognathus parvus specimens in the University of Utah Natural History Mammal Collections.
Isotopic approaches to study movement ecology & climate change resilience
Image credit: Isoscape Map – Bowen G. J., Wassenaar L. I., Hobson K. A. at www.waterisotopes.org; Junco image – The Cornell Lab of Ornithology, Macaulay Library, Scott Martin
Stable isotopes have become a widely-used and powerful tool for tracking the diets and seasonal migration of birds, mammals, and several other groups.
As a research fellow for Indiana University's Environmental Resilience Institute, I explored stable isotopic applications to understanding the movement ecology of different avian species in relation to the drivers of and shifts in the seasonal timing of migration, disease trans-mission, and the species resilience in the face of climate and anthropogenic changes. This research is conducted in collaboration with a wide range of researchers, including Ellen Ketterson, David Polly, Daniel Becker, Devraj Singh, Adam Fudickar, and Alex Jahn. Our collective goals are to assess 1) whether are birds shifting their timing and geography of migration because of climate and habitat change, and 2) if we as scientists can forecast how resilient or vulnerable species and ecosystems will be under future environmental scenarios.
Our work is conducted at the Stable Isotope Research Facility at IU's Department of Earth and Atmospheric Sciences and would not be possible without Peter Sauer and Katey Evans. Generous funding is provided by the Environmental Resilience Institute, funded by Indiana University’s Prepared for Environmental Change Grand Challenge initiative.