10. July 2017 · Categories: Publications

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Our lab’s first official foray into the world of stable isotopes will be coming out in Functional Ecology, with OSU Honors undergraduate Megan Guerre and grad student David Taylor as co-authors.  Check it out! (Photo by Susan Anderson).

Terry, R.C., M.E. Guerre and D.S. Taylor (2017) How specialized is a diet specialist? Niche flexibility and local persistence through time of the Chisel-toothed kangaroo rat. Functional Ecology.

Abstract: Rapid environmental changes are putting many species at risk, particularly niche specialists. In response, species can shift their ranges or remain in place by taking advantage of new resources. The potential for specialists to undergo in situ niche shifts is not well understood yet can buffer species from the effects of long-term environmental change over centuries and millennia.  In the Great Basin of western North America, the Chisel-toothed kangaroo rat, Dipodomys microps, is a folivore thought to be an obligate specialist on the desert shrub Atriplex confertifolia. Because of its association with A. confertifolia, D. microps is presumed to have tracked the shrub as it moved south during the last glacial maximum. However, recent phylogeographic evidence indicates that D. microps did not shift or contract its range into a southern refugium.

Here we evaluate the role that niche flexibility may have played in allowing this presumed dietary specialist to cope with a changing environment and resource base. We do so using carbon and nitrogen isotopes measured in D. microps bone collagen from modern and fossil specimens spanning the last 8000 years at Two Ledges Chamber (TLC) in northwestern Nevada. δ13C values indicate that, contrary to expectation, the population of D. microps at TLC consumes a variety of plants other than A. confertifolia, an isotopically distinct C4 shrub, and has done so for millennia. Mixing models suggest that the proportion of C4 in the diet was highest (∼35%) in the middle Holocene, and has declined towards the recent, especially over the last 30 years. δ15N values are consistently elevated through time, suggesting that D. microps at TLC are potentially also consuming a high proportion of insects. Our results indicate that this population of dietary specialists has greater niche flexibility than previously assumed. This implies that, at the species level, even presumed niche specialists may be capable of undergoing niche shifts over centennial to millennial time-scales in response to changing environmental conditions, and highlights the unique role that historical and paleontological data can play in establishing resource-use baselines of the past.

The first paper from our newly funded NARLEE (North American Rodents Landscapes Ecology & Evolution) Research Coordination Network is out in Trends in Ecology & Evolution (and it’s even on the cover!).TREE

Topographically complex regions on land and in the oceans feature hotspots of biodiversity that reflect geological influences on ecological and evolutionary processes. Over geologic time, topographic diversity gradients wax and wane over millions of years, tracking tectonic or climatic history. Topographic diversity gradients from the present day and the past can result from the generation of species by vicariance or from the accumulation of species from dispersal into a region with strong environmental gradients. Biological and geological approaches must be integrated to test alternative models of diversification along topographic gradients. Reciprocal illumination among phylogenetic, phylogeographic, ecological, paleontological, tectonic, and climatic perspectives is an emerging frontier of biogeographic research.

Badgley, C., T. M. Smiley, R. Terry, E. B. Davis, L. R. G. DeSantis, D. L. Fox, S. S. B. Hopkins, T. Jezkova, M. D. Matocq, N. Matzke, J. L. McGuire, A. Mulch, B. R. Riddle, V. L. Roth, J. X. Samuels, C. A. E. Strömberg, and B. J. Yanites. Biodiversity and Topographic Complexity: Modern and Geohistorical Perspectives. Trends in Ecology & Evolution 32:211-226.

Look for Tara’s summary talk of the paper at the Evolution meetings later this year!

 

Our new postdoc Tara Smiley and I have just published an update to the “Paleoecology: Methods” review I first wrote for the Encyclopedia of Life Science several years ago.  Check it out!

Smiley, T. M., and R. C. Terry. 2017. Palaeoecology: Methods. eLS. John Wiley & Sons, Ltd.

Here’s the abstract:

Paleoecology investigates the ecology of extinct organisms in relation to their environments and community assemblages. Major aims of paleoecology include the documentation of taxonomic occurrences and abundances across time and space and the reconstruction of species- to community-level ecological traits. Although methodologically similar to the techniques of neontological ecologists, the discipline is distinct for its deeper temporal perspective capturing long-term processes that shape Earth’s ecological patterns. The foundational components of paleoecological research are the study of taphonomy, or the processes by which organic remains become incorporated into the fossil record, and methods that standardise the sampling and counting of individuals and species. The development and integration of a diverse array of paleoecological methods and data have broadened the scope of paleoecology to gain insight into the processes shaping both ancient and modern communities and inform conservation strategies for ecosystems undergoing rapid anthropogenic-driven changes today.

Understanding how ecological communities are organized and how they change through time is critical to predicting the effects of climate change. Recent work documenting the co-occurrence structure of modern communities found that most significant species pairs co-occur less frequently than would be expected by chance. However, little is known about how co-occurrence structure changes through time.

In a new paper now published in Nature from our Evolution of Terrestrial Ecosystems working group (supported by the Smithsonian and an NSF Research Coordination Network), we evaluated changes in plant and animal community organization over geological time by quantifying the co-occurrence structure of 359,896 unique taxon pairs in 80 assemblages spanning the past 300 million years. Co-occurrences of most taxon pairs were statistically random, but a significant fraction were spatially aggregated or segregated. Aggregated pairs dominated from the Carboniferous period (307 million years ago) to the early Holocene epoch (11,700 years before present), when there was a pronounced shift to more segregated pairs, a trend that continues in modern assemblages. The organization of modern and late Holocene plant and animal assemblages thus fundamentally differs from that of assemblages over the past 300 million years, suggesting that perhaps the rules governing the assembly of communities have recently been changed by human activity.

Kathleen Lyons, S., K. L. Amatangelo, A. K. Behrensmeyer, A. Bercovici, J. L. Blois, M. Davis, W. A. DiMichele, A. Du, J. T. Eronen, J. Tyler Faith, G. R. Graves, N. Jud, C. Labandeira, C. V. Looy, B. McGill, J. H. Miller, D. Patterson, S. Pineda-Munoz, R. Potts, B. Riddle, R. Terry, A. Tóth, W. Ulrich, A. Villaseñor, S. Wing, H. Anderson, J. Anderson, D. Waller, and N. J. Gotelli. 2016. Holocene shifts in the assembly of plant and animal communities implicate human impacts. Nature 529:80-83.

Also see the corrigendum and the following commentaries and response:

Telford, R. J., J. D. Chipperfield, H. H. Birks, and H. J. B. Birks. 2016. How foreign is the past? Nature 538:E1-E2.

Bertelsmeier, C., and S. Ollier. 2016. Questioning Holocene community shifts. Nature 537:E4-E5.

Lyons, S. K., J. H. Miller, K. L. Amatange, A. K. Behrensmeyer, A. Bercovici, J. L. Blois, M. Davis, W. DiMichele, A. Du, J. T. Eronen, J. T. Faith, G. R. Graves, N. Jud, C. Labandeira, C. V. Looy, B. McGill, D. Patterson, S. Pineda-Munoz, R. Potts, B. Riddle, R. Terry, A. Tóth, W. Ulrich, A. Villaseñor, S. Wing, H. Anderson, J. Anderson, and N. J. Gotelli. 2016. Lyons et al. reply. Nature 538:E3-E4.

 

EFMy paper with Rebecca Rowe is out in PNAS!  Using the Homestead Cave fossil record, we discovered that energy flow through the small mammal community during today’s heightened climate warming differs from that experienced during natural rapid warming in the past. This discrepancy highlights a modern breakdown in energetic compensation among functional groups, and stresses the importance of novel anthropogenic impacts, such as the replacement of shrublands by invasive annual grasses introduced to North American deserts more than a century ago. Use of the fossil record to untangle the effects of climate and anthropogenic habitat change on ecosystem function today is thus critical for understanding how ecosystems will respond to future environmental change.

Terry, R. C., and R. J. Rowe. 2015. Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change. Proceedings of the National Academy of Sciences 112:9656-9661.

Also check out this commentary on our paper by Julio Betancourt:

Betancourt, J.L. 2015. Energy flow and the “grassification” of desert scrublands. Proceedings of the National Academy of Sciences 112:9504–9505.

 

 

20. June 2015 · Categories: Publications

AFD_modelKnowing how time is distributed within a fossil record is fundamental to paleobiology.  Time-averaging (the degree to which non-contemporaneous skeletal specimens are combined within the depositional layers of a fossil record) establishes the temporal scales at which questions can be addressed and dictates appropriate sampling and analytical frameworks.  In this new paper, Mark Novak and I present a new model of how “time” (i.e. the frequency distribution of fossil ages) gets distributed across the layers of a fossil record by the processes of specimen decay, mixing and burial. The predictions of our model are supported by the age-frequency distributions of AMS 14C-dated small mammal specimens collected from four different strata within the Homestead Cave record.

01. May 2015 · Categories: News

Predictions of species’ range shifts are routinely based on the direct impacts of climate change alone.  But this approach is widely acknowledged as overly simplistic, ignoring many interacting abiotic and biotic factors.  In collaboration with Rebecca Rowe (UNH) and with funding from the NSF (DEB-1457500, starting June 2015), we will be evaluating how the direct and indirect effects of resource use, species interactions, landcover, and climate change at local sites surveyed both a century ago and today have shaped landscape-scale range dynamics of small mammals in the mountains of the Great Basin.

The first paper from our Evolution of Terrestrial Systems working group (supported by the Smithsonian) is out in Ecography:

Blois, J. L., N. J. Gotelli, A. K. Behrensmeyer, J. T. Faith, S. K. Lyons, J. W. Williams, K. L. Amatangelo, A. Bercovici, A. Du, J. T. Eronen, G. R. Graves, N. Jud, C. Labandeira, C. V. Looy, B. McGill, D. Patterson, R. Potts, B. Riddle, R. Terry, A. Tóth, A. Villaseñor, and S. Wing. 2014. A framework for evaluating the influence of climate, dispersal limitation, and biotic interactions using fossil pollen associations across the late Quaternary. Ecography 37:1095-1108.

09. July 2011 · Categories: Publications

My research with Rebecca Rowe (Univ. New Hampshire) and Eric Rickart (Natural History Museum of Utah) was featured on the front cover of Ecology.  Our paper documents the impact of a century’s worth of landscape change on the small mammal community of the Ruby Mountains in Nevada. It’s also been highlighted by F1000 and Science.

02. November 2010 · Categories: News

An article by the Salt Lake Tribune discussing some of our work using the Homestead Cave record.