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Alexander Flecker


Alexander Flecker

E145 Corson Hall

Educational Background

Ph.D., Zoology, University of Maryland (1990)

M.S., Zoology, University of Maryland (1984)

B.S, Zoology, Oregon State University (1980)



I am a Professor in the Department of Ecology and Evolutionary Biology. I am also a member of the graduate fields of Ecology and Evolutionary Biology, International Development, Natural Resources, and Conservation and Sustainable Development, and an Associate Member of the Latin American Studies Program. After receiving my Ph.D. in Zoology (Ecology and Evolution concentration) in 1990, I was a Postdoctoral Fellow at the University of Otago in New Zealand (1991-1993), and joined the Cornell faculty in 1995. My lab has worked extensively in the Neotropics, including research sites in Venezuela , Bolivia, Ecuador, Mexico, Peru, Trinidad, and the Dominican Republic.

In addition to teaching courses such as BioEE 1610 Ecology and the Environment; BioEE 4560/NTRES 4560 Stream Ecology and BioEE 990 Independent Undergraduate Research in Biology at Cornell, I have served as an invited course instructor in Costa Rica for the Organization for Tropical Studies and at the University of Coimbra in Portugal.




Food webs, tropical stream ecosystems, ecosystem engineers, ecological stoichiometry, ecosystem subsidies, eco-evolutionary interactions, fishes, biogeochemistry, biodiversity and ecosystem function



  • Ecology and Evolutionary Biology

Graduate Fields

  • Ecology and Evolutionary Biology
  • Natural Resources


Research in my lab is at the interface between community and ecosystem ecology and aims to understand the functional significance of biodiversity. Much of the research focuses on stream ecosystems in both the tropics and temperate zone, addressing questions pertaining to the importance of species diversity and identity for ecosystem functioning. My research team has found that species that engineer their physical and chemical environments can be particularly important drivers of ecosystem structure and function. For example, in river systems of South America, migratory fishes can be significant material subsidies as nutrient vectors, or can act as important modulators of ecosystem processes such as carbon and nitrogen cycling or as seed dispersal agents in vast flooded forests. In addition, my lab is interested in interactions between evolutionary and ecosystem processes in natural systems, working on the influence of phenotypic variation in Trinidadian guppies on stream ecosystem functioning. A further research theme is to use trait-based approaches for understanding the relative vulnerability of species to climate change in tropical versus temperate riverine systems. Our research team is especially interested in placing their work in the context of ecosystem-level consequences of biodiversity loss due to factors such as overharvest and habitat destruction, or species additions via invasions. Part of the research has an international focus, especially in freshwater ecosystems of South America, Mesoamerica, and the Caribbean. The research integrates a variety of approaches for testing ideas including observations of natural ecosystems over space and time, lab and mesocosm experiments, and whole-ecosystem manipulations. Major research topics include: (1) Role of animals in influencing community and ecosystem processes in aquatic systems. Research projects include work in Neotropical streams (Venezuela, Trinidad, Mexico, Ecuador, Peru), high Andean hypersaline lagoons (Bolivia), desert streams (New Mexico), and north temperate streams (Colorado, New York); (2) Importance of migratory fish as ecosystem subsidies, and the influence of overharvest on migratory species; (3) Community and ecosystem consequences of biological invasions and species loss; (4) Interactions between evolutionary and ecosystem processes.



Spring 2022

Fall 2022


  • Hammerschlag, N., O.J. Schmitz, A.S. Flecker, K. Lafferty, A. Sih, T.B. Atwood, A.J. Gallagher, D.J. Irschick, R. Skubel, and S.J. Cooke. 2019. Ecosystem function and services of aquatic predators in the Anthropocene. Trends in Ecology and Evolution 34(4):369-383
  • Simon, T., A. Binderup, A. Flecker, J. Gilliam, M. Marshall, S. Thomas, J. Travis, D. Reznick, and C. Pringle. 2019. Landscape patterns in top-down control of decomposition: omnivorous fish decouples a detrital-based trophic cascade. Ecology
  • Carvalho, D.R., A.S. Flecker, C.B.M. Alves, J.P. SParks, and P.S. Pompeu. 2019. Trophic responses to aquatic pollution of native and exotic livebearers fishes. Science of the Total Environment 681:503-515
  • Rosero-López, D., M.T. Walter, A.S. Flecker, P. Llorte, B. De Biévre, D.P. González-Zeas, R. Calvez, and O. Dangles. 2019. Streamlined eco-engineering approach helps define environmental flows for tropical Andean headwaters. Freshwater Biology 64:1315-1325
  • Polato, N.R., B.A. Gill, A.A. Shah, M.M. Gray, K.L. Casner, A Barthelet, P.W. Messer, M. Simmons, J.M. Guayasamin, A.C. Encalada, B.C. Kondratieff, A.S. Flecker, A.A. Thomas, C.K Ghalambor, N.L. Poff, W.C. Funk, and K.R. Zamudio. 2018. Narrow thermal tolerance and low dispersal drive higher speciation in tropical mountains. Proceedings of the National Academy of Sciences 115: 12471-12476
  • Wu, X., J. Gomes-Selman, Q. Shi, Y. Xue, R. García-Villacorta, E. Anderson, S. Sethi, S. Steinschneider, A. Flecker, and C.P. Gomes.   2018.  Efficiently approximating the Pareto Frontier: hydropower dam placement in the Amazon Basin.  Proc. 32nd AAAI Conference on Artificial Intelligence.
  • Shi, Q., J.M. Gomes-Selman, R. García-Villacorta, S. Sethi, A.S. Flecker, and C.P. Gomes. 2018. Efficiently optimizing for dendritic connectivity on tree-structured networks in a multi-objective framework. Submitted to: Proceedings of ACM Conference on Computing and Sustainable Societies. COMPASS 2018: 26:1-26:8; 
  • Larson, E.I., N.L. Poff, C.L. Atkinson, and A.S. Flecker.  2018.  Extreme flooding decreases stream consumer autochthony by increasing detrital resource availability.  Freshwater Biology. 
  • Dalton, C.M., K.E. Tracy, N.G. Hairston, Jr., and A.S. Flecker.  2018.  Disentangling the roles of predation risk and food deprivation in the nitrogen metabolism of consumers.  Ecology 99: 681–689; doi: 10.1002/ecy.2132.
  • Poff, N.L., E. Larson, P. Salerno, S. Morton, B. Kondratieff, A. Flecker, K. Zamudio, W.C. Funk.   2018.  Extreme streams: Species persistence mechanisms and evolutionary change in montane stream insect populations across a flood disturbance gradient.  Ecology Letters doi:10.1111/ele.12918.
  • Atkinson, C.L., A. Encalada, A. Rugenski, S. Thomas, A. Landeira-Dabarca, L. Poff, and A. Flecker.  2018.  Determinants of food resource assimilation by stream insects along a tropical elevation gradient.  Oecologia. 187:731-744. doi: 10.1007/s00442-018-4142-2. 
  • Vanni, M., et al.  2017.  A global database of nitrogen and phosphorus excretion rates of aquatic animals. Ecology DOI: 10.1002/ecy.1792.
  • Alexiades, A.V., A.S. Flecker, and C.E. Kraft.   2017.  Nonnative fish stocking alters stream ecosystem nutrient dynamics.   Ecological Applications 27:956-965. DOI: 10.1002/eap.1498.
  • Rubio-Gracia, F., et al.  2017. Combined effects of hydrologic alteration and cyprinid fish in mediating biogeochemical processes in a Mediterranean stream.  Science of the Total Environment 601–602 (2017) 1217–1225.  DOI:10.1016/j.scitotenv.2017.05.287.
  • Zandonà, E., C. Dalton, R. El-Sabaawi, J. Howard, M. Marshall, S. Kilham, D. Reznick, J. Travis, T.  Kohler, A. Flecker, S. Thomas, and C. Pringle.  2017.  Population variation in the trophic niche of the Trinidadian guppy from different predation regimes.  Scientific Reports 7: 5770; DOI:10.1038/s41598-017-06163-6
  • Boyero, L., et al.  2017.  Riparian plant litter quality increases with latitude.  Scientific Reports 7: 10562; DOI:10.1038/s41598-017-10640-3.  
  • Norman, B., et al.  2017.  Drivers of nitrogen transfer efficiencies in stream food webs across continents. Ecology 98: 3044–3055; DOI: 10.1002/ecy.2009.
  • Twining, C.W., D.C. Josephson, C.E. Kraft, J.T. Brenna, P. Lawrence, and A.S. Flecker.  2017.  Limited seasonal variation in food quality and foodweb structure in an Adirondack stream: insights from fatty acids. Freshwater Science 36:877-892. 
  • Shah, A., B. Gill, A. Encalada, A. Flecker, C. Funk, J. Guayasamin, B. Kondratieff, N.L. Poff, S. Thomas, K. Zamudio, and C. Ghalambor.  2017. Climate variability predicts thermal limits of aquatic insects across elevation and latitude.   Functional Ecology 31:2118-2127; doi: 10.1111/1365-2435.12906. 
  • Boyero, L., et al. 2016.  Biotic and abiotic variables influencing plant litter breakdown in streams: a global-scale study. Proceedings of the Royal Society B. 283:20152664; DOI: 10.1098/rspb.2015.2664.
  • Gill, B., B. Kondratieff, K. Casner, A.Encalada, A. Flecker, D. Gannon, C. Ghalambor, J. Guayasamin, L. Poff, M. Simmons, S. Thomas, K. Zamudio, and W.K. Funk.  2016.  Cryptic species diversity reveals biogeographic support for the ‘Mountain passes are higher in the tropics Hypothesis’. Proceedings of the Royal Society B 283: 20160552; DOI: 10.1098/rspb.2016.0553.   
  • Buchanan, B.P., D.A. Auerbach, R.A. McManamay, A.S. Flecker, J. Taylor, J A. Archibald, D.G. Fuka, and M.T. Walter.   2016.   Environmental flows in the context of unconventional natural gas development in the Marcellus Shale.  Ecological Applications 27: 37-55. DOI: 10.1002/eap.1425
  • Collins, S.M., S.A. Thomas, T. Heatherly II, K.L. MacNeill, A. Leduc, A. López-Sepulcre, B. Lamphere, R.W. El-Sabaawi, D.N. Reznick, C.M. Pringle, and A.S. Flecker.  2016. Fish introductions and light modulate food web fluxes in tropical streams: a whole-ecosystem experimental approach. Ecology 97: 3154–3166; DOI: 10.1002/ecy.1530.
  • Lessmann, J., et al.  2016.   Freshwater vertebrate and invertebrate diversity patterns in an Andean-Amazon basin: implications for conservation efforts. Neotropical Biodiversity 2: 99-114, DOI: 10.1080/23766808.2016.1222189
  • Auerbach, D. A., B.P. Buchanan, A.V. Alexiades, E.P. Anderson, A.C. Encalada, E.I. Larson, R.A. McManamay, G.L. Poe, M.T. Walter, and A.S. Flecker.  2016. Towards catchment classification in data-scarce regions.  Ecohydrology 9: 1235-1247. doi: 10.1002/eco.1721. 
  • Bassar, R.D., T. Heatherly II, M.C. Marshall, S.A. Thomas, A.S. Flecker, and D.N. Reznick.  2015. Population size structure dependent fitness and ecosystem consequences in Trinidadian guppies.   Journal of Animal Ecology 84: 955–968.  doi: 10.1111/1365-2656.12353.
  • Collins, S.M., T.J. Koher, S.A. Thomas, W.W. Fetzer and A.S. Flecker.  2015.  The importance of terrestrial subsidies in stream food webs varies along a stream size gradient. Oikos doi:10.1111/ oik.07213.
  • Twining, C.W., J.T. Brenna, N.G. Hairston Jr., and A.S. Flecker.  2015.  Highly unsaturated fatty acids in nature: what we know and what we need to learn.  Oikos 125: 749-760. doi: 10.1111/oik.02910.
  • Dodds, W. K., et al.  2014.  You are not always what we think you eat: selective assimilation across multiple whole-stream isotopic tracer studies. Ecology 95:2757-2767.
  • Capps, K. A., and A. S. Flecker. 2013. Invasive aquarium fish transform ecosystem nutrient dynamics.  Proceedings of the Royal Society B 280: 20131520. doi: 10.1098/rspb.2013.1520.


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