The Smithsonian Institution , established in 1846 "for the increase and diffusion of knowledge," is a group of museums and research centers administered by the United States government. Originally organized as the "United States National Museum," that name ceased to exist as an administrative entity in 1967.Termed "the nation's attic"for its eclectic holdings of 137 million items, the Institution's Washington, D.C., nucleus of nineteen museums, nine research centers, and zoo—many of them historical or architectural landmarks—is the largest such complex in the world. Additional facilities are located in Arizona, Maryland, New York City, Virginia, Panama and elsewhere, and 168 other museums are Smithsonian affiliates.The Institution's thirty million annual visitors are admitted without charge;funding comes from the Institution's own endowment, private and corporate contributions, membership dues, government support, and retail, concession and licensing revenues.Institution publications include Smithsonian and Air & Space magazines. Wikipedia.
Slater G.J.,Smithsonian Institution
Methods in Ecology and Evolution | Year: 2013
Summary: Phylogenetic comparative methods provide a powerful way of addressing classic questions about tempo and mode of phenotypic evolution in the fossil record, such as whether mammals increased in body size diversity after the Cretaceous-Palaeogene (K-Pg) extinction. Most often, these kinds of questions are addressed in the context of variation in evolutionary rates. Shifts in the mode of phenotypic evolution provide an alternative and, in some cases, more realistic explanation for patterns of trait diversity in the fossil record, but these kinds of processes are rarely tested for. In this study, I use a time-calibrated phylogeny of living and fossil Mammaliaformes as a framework to test novel models of body size evolution derived from palaeontological theory. Specifically, I ask whether the K-Pg extinction resulted in a change in rates of body size evolution or release from a constrained adaptive zone. I found that a model comprising an Ornstein-Uhlenbeck process until the K-Pg event and a Brownian motion process from the Cenozoic onwards was the best supported model for these data. Surprisingly, results indicate a lower absolute rate of body size evolution during the Cenozoic than during the Mesozoic. This is explained by release from a stationary OU process that constrained realized disparity. Despite a lower absolute rate, body size disparity has in fact been increasing since the K-Pg event. The use of time-calibrated phylogenies of living and extinct taxa and realistic, process-based models provides unparalleled power in testing evolutionary hypotheses. However, researchers should take care to ensure that the models they use are appropriate to the question being tested and that the parameters estimated are interpreted in the context of the best fitting model. © 2013 British Ecological Society.
McInerney F.A.,Northwestern University |
Wing S.L.,Smithsonian Institution
Annual Review of Earth and Planetary Sciences | Year: 2011
During the Paleocene-Eocene Thermal Maximum (PETM), ∼â̂ 56 Mya, thousands of petagrams of carbon were released into the ocean-atmosphere system with attendant changes in the carbon cycle, climate, ocean chemistry, and marine and continental ecosystems. The period of carbon release is thought to have lasted <20 ka, the duration of the whole event was ∼ 200 ka, and the global temperature increase was 5-8°C. Terrestrial and marine organisms experienced large shifts in geographic ranges, rapid evolution, and changes in trophic ecology, but few groups suffered major extinctions with the exception of benthic foraminifera. The PETM provides valuable insights into the carbon cycle, climate system, and biotic responses to environmental change that are relevant to long-term future global changes. Copyright © 2011 by Annual Reviews. All rights reserved.
Slater G.J.,Smithsonian Institution
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015
A long-standing hypothesis in adaptive radiation theory is that ecological opportunity constrains rates of phenotypic evolution, generating a burst of morphological disparity early in clade history. Empirical support for the early burst model is rare in comparative data, however. One possible reason for this lack of support is that most phylogenetic tests have focused on extant clades, neglecting information from fossil taxa. Here, I test for the expected signature of adaptive radiation using the outstanding 40-My fossil record of North American canids. Models implying time- and diversity-dependent rates of morphological evolution are strongly rejected for two ecologically important traits, body size and grinding area of the molar teeth. Instead, Ornstein-Uhlenbeck processes implying repeated, and sometimes rapid, attraction to distinct dietary adaptive peaks receive substantial support. Diversity-dependent rates of morphological evolution seem uncommon in clades, such as canids, that exhibit a pattern of replicated adaptive radiation. Instead, these clades might best be thought of as deterministic radiations in constrained Simpsonian subzones of a major adaptive zone. Support for adaptive peak models may be diagnostic of subzonal radiations. It remains to be seen whether early burst or ecological opportunity models can explain broader adaptive radiations, such as the evolution of higher taxa. © 2015, National Academy of Sciences. All rights reserved.
Potts R.,Smithsonian Institution
Quaternary Science Reviews | Year: 2013
Investigations into how climate change shaped human evolution have begun to focus on environmental dynamics, i.e., the nature and tempo of climate and landscape variability, an approach that de-emphasizes static reconstructions of early hominin habitats. The interaction among insolation cycles is especially apparent in the paleoenvironmental records of the East African Rift System, where the longest records of human evolution are preserved. However, environmental indicators such as deep-sea oxygen isotopes, terrestrial dust flux, paleosol carbon isotopes, and lake sediments do not point consistently to any simple trend or climate driver of evolutionary change. Comparison of environmental indicators cautions against an exclusive focus on any given end-member of environmental fluctuation (driest or wettest, warmest or coolest), and argues for the impact of the entire range of variability in shaping evolutionary change. A model of alternating high and low climate variability for tropical Africa further implies that specific environmental indicators reflect different aspects of East African environmental dynamics. The model may thus help reconcile some of the conflicting interpretations about the environmental drivers of hominin evolution. First and last appearances of hominin lineages, benchmark biogeographic events, and the emergence of key adaptations and capacities to alter the surroundings are consistently concentrated in the predicted longest intervals of high climate variability. The view that emerges is that important changes in stone technology, sociality, and other aspects of hominin behavior can now be understood as adaptive responses to heightened habitat instability. © 2013.
Smith B.D.,Smithsonian Institution
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2011
Niche construction efforts by small-scale human societies that involve 'wild' species of plants and animals are organized into a set of six general categories based on the shared characteristics of the target species and similar patterns of human management and manipulation: (i) general modification of vegetation communities, (ii) broadcast sowing of wild annuals, (iii) transplantation of perennial fruit-bearing species, (iv) in-place encouragement of economically important perennials, (v) transplantation and in-place encouragement of perennial root crops, and (vi) landscape modification to increase prey abundance in specific locations. Case study examples, mostly drawn from North America, are presented for each of the six general categories of human niche construction. These empirically documented categories of ecosystem engineering form the basis for a predictive model that outlines potential general principles and commonalities in how small-scale human societies worldwide have modified and manipulated their 'natural' landscapes throughout the Holocene. © 2011 The Royal Society.