Dr. S. Kathleen Lyons
Assistant Professor of Biological Sciences
Education:
- National Center for Ecological Analysis and Synthesis, Post-doc (2003-2006)
- University of New Mexico, Post-doc (2001-2003)
- University of Chicago, Ph.D. (2001)
- University of Chicago, M.S. (1997)
- Texas Tech University, M.S. (1994)
- Wayland Baptist University, B.S. (1991)
Research focus:
I am interested in the factors affecting and controlling species diversity at multiple scales across both space and time. Moreover, I am particularly interested in the effects of global climate change on species diversity and use the fossil record of mammals over the last 40,000 years to evaluate how current changes in global climate may affect diversity patterns in the future.
Species and community level responses to climate change:
The late Pleistocene offers a unique opportunity to study the ecological processes involved in the structuring of communities because of the climate change engendered by the last glaciation. I quantitatively assessed changes in the distributions of mammals to determine the degree to which species shifted their ranges independently over broad time scales. Although it is difficult to make generalizations about the range shifts of the different orders of mammals, many species exhibited very small range shifts. The prediction that the individualistic responses of species to climate change should result in non-analogue communities likely is over simplified. Certainly, some communities should be non-analogue, but not all ( Lyons, 2003). Next, I examined changes in community composition over broad time scales and assessed the effect of range shifts on community composition using simulation models. Although there was some degree of turnover in all communities, results indicate that the geographic pattern of community similarity through time was more complex than a strict prediction using independent range shifts would imply ( Lyons, 2005).
Current and future work involves evaluating other aspects of community structure, such as body size distributions as a function of climatic variables across the globe today. Once predictive models are formulated and tested, the results will be applied to late Pleistocene communities to determine if changes in body size distributions through time are a result of changes in climate associated with glaciation.
References:
Extinction Risk:
With Felisa Smith and Jim Brown, I have compared the body size distributions of mammals on four continents before and after the extinction of the megafauna at the end of the Pleistocene. We concluded that human hunting played a large role in this extinction event. On each continent, the arrival of humans occurred just prior to the extinction, whereas significant climate change occurred on only two continents coincident with the extinction. Moreover, examination of present day patterns of endangered species indicates that only large-bodied species are affected by human hunting practices (Lyons et al., 2004a). A companion paper examines the likelihood that a hyperdisease played a role in this extinction event using the spread of West Nile virus in birds in the United States. We argue that West Nile virus meets all the criteria of a hyperdisease, but is unlikely to cause an extinction with a size signature like that of the end-Pleistocene extinctions (Lyons et al., 2004b).
Currently, Joshua Madin and I are evaluating the effect of geographic range size on extinction of marine invertebrates across the Phanerozoic. In future research, I will examine communities with greater and lesser degrees of turnover for evidence of morphological adaptation and changes in relative abundance.
References:
Macroecological patterns across space and time:
Although progress has been forthcoming concerning macroecological patterns across large spatial scales, relatively little attention has focused on their temporal dynamics. Investigation of the macroecological patterns of mammalian body size distributions suggests that modern patterns from North America have been strongly affected by the end-Pleistocene extinction event (Lyons et al. 2004, Smith et al., 2004). Moreover, mammalian body size distributions settled into a bimodal distribution early in mammalian evolution (~40 ma) and remained that way until the extinction of large mammals 10,000 ya (Lyons and Smith, submitted). Other macroecological patterns are consistent across time. For example, body size/range size patterns in mammals have not changed over the last 40,000 years despite considerable changes in climate and a size biased extinction event (Lyons and Smith, submitted).
I am also investigating the role of body size in structuring communities through time and across the globe. Examination of ~300 local assemblages over the last 40,000 years indicates that despite the considerable turnover in community composition, body size distributions have stayed relatively uniform. Such results imply that body size is an important factor in determining membership in communities. However, extension of this work to include ~300 Recent communities across the globe indicates a significant latitudinal gradient in the shape of local body size distributions. Tropical communities have higher kurtosis values and thus more peaked distributions than temperate ones ( Lyons, in prep). Preliminary analyses indicate that the shape of these distributions is correlated with climatic variables. Moreover, the ecological traits of the organisms that make up these communities differ among communities with the same general habitat characteristics, climate and elevation.
Future work will focus of the role of ecological traits in structuring communities across space and time. In particular, I am interested in the interaction between ecological traits and body size distributions.
References:
- S. K. Lyons and F. A. Smith. Macroecological patterns in body size of mammals over space and time. In: Body Size: Linking pattern and process across space, time and taxonomic group (F. A. Smith and S. K. Lyons, eds). University of Chicago Press (in review).
- S. K. Lyons, F. A. Smith and J. H. Brown. 2004. Of mice, mastodons and men: human mediated extinction on four continents. Evolutionary Ecology Research. 6: 339-358.
- F. A. Smith, J. H. Brown, J. P. Haskell, S. K. Lyons, J. Alroy, E. L. Charnov, T. Dayan, B. J. Enquist, S. K. M. Ernest, E. A. Hadly, K. E. Jones, D. M. Kaufman, P. A. Marquet, B. A. Maurer, K. J. Niklas, W. P. Porter, B. Tiffney, and M. R. Willig. 2004. Similarity of mammalian body size across the taxonomic hierarchy and across space and time. The American Naturalist. 163:672-691.
Macroevolutionary dynamics of mammals
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I am also interested in the evolution of body size in mammals and the role of constraints on minimum and maximum size over the last 65 ma. Using a global database of mammalian body sizes (Smith et al. 2003), we have shown that mammals under 18 g show differences in their diversification patterns compared to mammals over 18 g suggesting that when faced with novel environments small bodied mammals are more likely to evolve by changing body size than large bodied mammals (Smith et al., 2004). Biomechanical constraints are thought to play a role in limiting the maximum size of terrestrial mammals. Because the effect of these constraints should be limited in marine mammals because of the aquatic habitat, terrestrial and marine mammals should show differences in body size diversification. However, late Pleistocene terrestrial and marine mammals show no differences in their patterns of body size diversification, suggesting that biomechanical constraints do not play a major role in limiting maximum size of terrestrial mammals (Smith and Lyons, in revision). With Felisa Smith and Morgan Ernest, I am a co-PI on a 5 year NSF grant to investigate the macroevolutionary dynamics of body size in mammals and the constraints on minimum and maximum size. This work will focus on the role of life history characteristics, ecology and phylogeny on the evolution of body size in mammals.
References:
- F. A. Smith, J. H. Brown, J. P. Haskell, S. K. Lyons, J. Alroy, E. L. Charnov, T. Dayan, B. J. Enquist, S. K. M. Ernest, E. A. Hadly, K. E. Jones, D. M. Kaufman, P. A. Marquet, B. A. Maurer, K. J. Niklas, W. P. Porter, B. Tiffney, and M. R. Willig. 2004. Similarity of mammalian body size across the taxonomic hierarchy and across space and time. The American Naturalist. 163:672-691.
- F.A. Smith, S.K. Lyons, S.K. M. Ernest, K.E. Jones, D.M. Kaufman, T. Dayan, P.A. Marquet, J.H. Brown, and J.P. Haskell. 2003. The body mass of late Quaternary mammals. Ecology 84:3403.
- F. A. Smith and S. K. Lyons. Body size patterns of very large mammals: does water matter? (in revision).
Latitudinal gradients in species richness:
Although it is not the main focus of my research, I am interested in documenting and understanding mechanisms for latitudinal patterns of range size and species diversity. As such, I examined the effect of scale on patterns of species diversity with latitude (Lyons and Willig, 1999, 2002). I am also interested in latitudinal patterns of range size. My particular contribution consisted of pointing out flaws in existing techniques, designing an alternative statistical test, and applying it to patterns for bats and marsupials (Lyons and Willig, 1997). In addition, I helped develop a theoretical mathematical model predicting the number of species expected at each latitude based on the bounded nature of land masses, also known as the mid-domain effect (Willig and Lyons, 1998). My collaboration with Michael Willig is on going as we continue to explore the implications and limitations of the mid-domain effect.
References:
Selected Publications:
- V. Millien, S. K. Lyons, L. Olson, F. A. Smith, T. Wilson, Y. Yom-Tov. 2006. Ecotypic variation in the context of global climate change: revisiting the rules. Ecology Letters. 9(7): 853-869.
- S. K. Lyons. 2005. A quantitative model assessing the community dynamics of Pleistocene mammals. The American Naturalist. 165(6):E168-E185.
- J. S. Madin and S. K. Lyons. 2005. Incomplete sampling of geographic ranges weakens or reverses the positive relationship between animal species geographic range size and its body size. Evolutionary Ecology Research, 7:607-617.
- S. K. Lyons, F. A. Smith, P. J. Wagner, E. P. White, and J. H. Brown. 2004. Was a "hyperdisease" responsible for the late Pleistocene megafaunal extinction? Ecology Letters. 7:859-868.
- S. K. Lyons, F. A. Smith and J. H. Brown. 2004. Of mice, mastodons and men: human mediated extinction on four continents. Evolutionary Ecology Research. 6: 339-358.
- S. K. Lyons. 2003. A quantitative assessment of the range shifts of Pleistocene mammals. Journal of Mammalogy (Special Feature). 84: 385-402.
- S. K. Lyons and M. R. Willig. 2002. Species richness, latitude, and scale-sensitivity. Ecology 83: 47-58.
- S. K. Lyons and M. R. Willig. 1999. A hemispheric assessment of scale-dependence in latitudinal gradients of species richness. Ecology. 80(8): 2483-2491. (Special Feature)
- M. R. Willig and S. K. Lyons. 1998. An analytical model of latitudinal gradients of species richness with an empirical test for Marsupials and Bats in the New World. Oikos 80:93-98.
- S. K. Lyons and M. R. Willig. 1997. Latitudinal patterns of range size: methodological concerns and empirical evaluations for New World Bats and Marsupials. Oikos 79:568-580.
Contact Information:
S. Kathleen Lyons
Department of Biological Sciences
Old Dominion University
302-N Mills Godwin Building/45th St.
Norfolk , VA 23529
ph: 757-683-4202
fax: 757-683-5283
email: sklyons@odu.edu
