Daniel Janzen

Dr. Daniel Janzen

Professor of Biology; Thomas G. and Louise E. DiMaura Term Chair


Research Interests

Currently not accepting new graduate students

Ph.D., University of California, Berkeley, 1965

Research Interests


ecology and biodiversity of ecosystems


Why do caterpillars eat the plants they eat? Why do parasitoids (wasps and flies) eat the caterpillars they eat? And why do they do it that way in a complex dry forest, rain forest and cloud forest in northwestern Costa Rica? I have long pursued these questions because I am curious about them and their answers. But the answers, and the research processes themselves, also have very broad application to how one may use the biodiversity of a conserved tropical wildland without destroying it - biodiversity development.


How can we insure that tropical wildlands, and all of their biodiversity, are still with us centuries from now? Through non-destructive use of lands explicitly allocated to this land use. But to use biodiversity without damage requires detailed natural history knowledge, tracking of demography, and ecosystem-level understanding. And to use requires a user.


So it is that very basic research on the interactions of animals and plants in complex tropical forest quite serendipituously finds itself being key intellectual infrastructure and technological know-how for biodiversity prospecting, biological control of pests, biotechnology, ecotourism development, biocultural education, environmental monitoring, silviculture, agriculture and very much more - all the kinds of things that have to accompany conservation of large tropical wildlands.


My research over the past 55 years has evolved from a Victorian study of natural history of tropical animal-plant interactions to an exploration of the ecology of the interface between society and tropical wildland biodiversity. The administrative structure of institutions such as wildland administrations and Ministries of the Environment, the biodiversity development of conserved wildlands to where they can pay their own direct costs, and the integration of wildlands into society, are all major and essential tools in the engineering of the tropical countryside. Costa Rica as a whole is the ecosystem, and Area de Conservacion Guanacaste, in the northwestern corner, is the place.


My research is done where the organisms are, i.e., Costa Rica.

Selected Publications

Publications Featuring Dr. Janzen and his Research:

Wolf, G. 2008. Barcode of Life. Wired 16(10)(October):200-212.

Rosner, H. 2013.  Survival of the flexible.  Nature 494:22-23.

Pringle, R. M. 2017.  Upgrading protected areas to conserve wild biodiversity.  Nature 546:91-99.

Representative recent publications by Dr. Janzen:

Fleming, A.J., Wood, D.M, Smith, M. A., Hallwachs,W., and Janzen, D. H. 2018. Revision of the Mesoamerican species of Calolydella Townsend (Diptera: Tachinidae) and descriptions of twenty-three new species reared from caterpillars in Area de Conservación Guanacaste, northwestern Costa Rica.  Biodiversity Data Journal  5: https://bdj.pensoft.net/articles.php?id=11223.  151 pp.

Dias, F. M. S., Janzen, D. H., Hallwachs, W., Chacon, I., Willmott, K., Ortiz-Acevedo, E., Mielke, O. H. H., and Casagrande, M. M.  2018.  DNA barcodes uncover hidden taxonomic diversity behind the variable wing patterns in the Neotropical butterfly genus Zaretis (Lepidoptera: Nymphalidae: Charaxinae). Zoological Journal of the Linnean Society 20:1-61.  https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zly036/5066255?guestAccessKey=e443010e-cd38-49ee-b61b-8efb48903ea8

Hebert, P. D. N., Braukmann, T. W. A., Prosser, S. W. J., Ratnasingham, S., deWaard, J. R., Ivanova, N. V., Janzen, D. H., Hallwachs, W., Naik, Sones, J. E., and Zakharov, E. V. 2018.  A Sequel to Sanger: amplicon sequencing that scales.  BMC Genomics 19:219, 14 pp. https://doi.org/10.1186/s12864-018-4611-3

Espinoza, B.A., Janzen, D.H., and Hallwachs, W. 2017.  17 new species hiding in 10 long-named gaudy tropical moths (Lepidoptera: Erebidae: Arctiinae).  Tropical Lepidoptera Research 27 (Supplement 1): 1-29. https://doi.org/10.5281/zenodo.1092749.

Chacon, I. A., Janzen, D. H., Hallwachs, W., Dapkey, T., Harvey, D. J., and Grishin, N.V. 2017.  Six new cryptic species of Xylodonta Becker, 2014 (Notodontidae: Nystaleinae) from Costa Rica.  Tropical Lepidoptera Research 27(1): 33-58.

Treuer, T. L. H., Choi, J. J., Janzen, D. H., Hallwachs, W., Perez-Aviles, D., Dobson, A., Powers, J. S., Shanks, L. C., Werden, L. K., and Wilcove, D. S. 2017.  Low-cost agricultural waste accelerates tropical forest regeneration.  Restoration Ecology 9 pp. https://doi.org/10.1111/rec.12565

Hammer, T. J., Janzen, D. H., Hallwachs, W., Jaffe, S. P., and Fierer, N. 2017. Caterpillars lack a resident gut microbiome.  Proceedings of the National Academy of Sciences 114(36):9641-9647 doi/10.1073/pnas.1707186114

Janzen, D.H., Burns, J.M., Cong, Q., Hallwachs,W., Dapkey, T., Manjunath, R., Hajibabaei, Hebert, P.D.N., and Grishin, N.V. 2017.  Nuclear genomes distinguish cryptic species suggested by their DNA barcodes and ecology.  Proceedings of the National Academy of Sciences 114(31):8313-8318. doi/10.1073/pnas.1621504114

Ge, D., Wu, G., Yang, L., Kim, H-N., Hallwachs,W., Burns, J. M., Janzen, D. H., and Yang, S. 2017.  Varying and unchanging whiteness on the wings of dusk-active and shade-inhabiting Carystoides escalantei butterflies.  Proceedings of the National Academy of Sciences 114(28):7379-7384 https://doi.org/10.1073/pnas.1701017114

Janzen, D. H. and Hallwachs, W. 2016.  DNA barcoding the Lepidoptera inventory of a large complex tropical conserved wildland, Area de Conservacion Guanacaste, northwestern Costa Rica.  Genome 59:641-660 dx.doi.org/10.1139/gen-2016-0005.

Miller, S. E., Hausmann, A., Hallwachs, W. and Janzen, D. H. 2016.  Advancing taxonomy and bioinventories with DNA barcodes.  Philosophical Transactions of the Royal Society B 371: 20150339.  http://dx.doi.org/10.1098/rstb.2015.0339

Janzen, D.H. and Hallwachs, W. 2016.  Biodiversity Conservation History and Future in Costa Rica: The Case of Area de Conservacion Guanacaste (ACG).  Chapter 10.  In Costa Rican Ecosystems, Kappelle, M. ed. University of Chicago Press, Chicago,  pp. 290-341.

Hansson, C., Smith, M.A., Janzen, D.H. and Hallwachs,W. 2015.  Integrative taxonomy of New World Euplectrus Westwood (Hymenoptera, Eulophidae), with focus on 55 new species from Area de Conservacion Guanacaste, northwestern Costa Rica.  ZooKeys 485:1-236. Doi: 10.3897/zookeys.458.9124.

Phillips-Rodriguez, E., Powell, J. A., Hallwachs,W. and Janzen, D. H. 2014.  A synopsis of the genus Ethmia Hubner in Costa Rica: biology, distribution, and description of 22 new species (Lepidoptera, Gelechioidea, Depressariidae, Ethmiinae), with emphasis on the 42 species known from Area de Conservacion Guanacaste.  ZooKeys 461:1-86.  Doi:10.3897/zookeys.461.8377

Brown, J. W., Janzen, D. H., Hallwachs,W., Zahiri, R., Hajibabaei, M., and Hebert, P.D.N. 2014.  Cracking complex taxonomy of Costa Rican moths: Anacrusis Zeller (Lepidoptera: Tortricidae: Tortricinae).  Journal of the Lepidopterists’ Society.  68:248-263.

Bertrand, C., Janzen, D. H., Hallwachs, W., Burns, J. M., Gibson, J. F., Shokralla, S. and Hajibabaei, M. 2014.  Mitochondrial and nuclear phylogenetic analysis with Sanger and next-generation sequencing shows that, in Area de Conservación Guanacaste, northwestern Costa Rica, the skipper butterfly named Urbanus belli (family Hesperiidae) comprises three morphologically cryptic species.  BMC Evolutionary Biology 2014, 14:153. 18 pp.  http://www.biomedcentral.com/1471-2148/14/153

Gibson, J., Shokralla, S., Porter, T.M., King, I, van Konynenburg, S., Janzen, D.H., Hallwachs, W., and Hajibabaei, M. 2014.  Simultaneous assessment of the macrobiome and microbiome in a bulk sample of tropical arthropods through DNA metasystematics.  Proceedings of the National Academy of Sciences 111:8007-8012. https://doi.org/10.1073/pnas.1406468111.

Smith, M.A., Hallwachs, W., and Janzen, D.H. 2014.  Diversity and phylogenetic community structure of ants along a Costa Rican elevational gradient.  Ecogeography 37:720-731  DOI: 10.1111/j.1600-0587.2013.00631.x

Fernandez-Triana, J.L., Whitfield, J.B., Rodriguez, J.J., Smith, M.A., Janzen, D.H., Hallwachs, W., Hajibabaei, M., Burns, J.M., Solis, M.A., Brown, J., Cardinal, S., Goulet, H., and Hebert, P.D.N. 2014.  Review of Apanteles sensu strictu (Hymenoptera, Braconidae, Microgastrinae) from Area de Conservación Guanacaste, northwestern Costa Rica, with keys to all described species from Mesoamerica.  ZooKeys 383:1-565. doi: 10.3897/zookeys.383.6418

Smith, M. Alex, Fernández-Triana, J.L., Eveleigh, E., Gómez, J., Guclu, C., Hallwachs, W.,  Hebert, P.D.N., Hrcek, J., Huber, J.T., Janzen, D. H., Mason, P.G., Miller, S., Quicke, D.L.J., Rodriguez, J.J., Rougerie, R. Shaw, M. R., Várkonyi, G.,  Ward, D., Whitfield, J.B., and Zaldivar-Riveron, A. 2012.  DNA barcoding and the taxonomy of Microgastrinae wasps (Hymenoptera, Braconidae): impacts after 8 years and nearly 20,000 sequences.  Molecular Ecology Resources doi: 10.1111/1755-0998.12038

Rodriguez, J. J., Fernandez-Triana, J. L., Smith, M. A., Janzen, D. H., Hallwachs, W., Erwin, T. L. and Whitfield, J. B. 2013.  Extrapolations from field studies and known faunas converge on dramatically increased estimates of global microgastrine parasitoid wasp species richness (Hymenoptera: Braconidae).  Insect Conservation and Diversity. 6:530-536  doi: 10.1111/icad.12003

Janzen, D.H., and Hallwachs,W. 2011.  Joining inventory by parataxonomists with DNA barcoding of a large complex tropical conserved wildland in northwestern Costa Rica.  PLoS ONE 6(8): e18123. doi:10.1371/journal.pone.0018123

Janzen, D. H., Hallwachs, W., and Burns, J. M. 2010.  A tropical horde of counterfeit predator eyes.  Proceedings of the National Academy of Sciences 107:11659-11665. doi:10.1073/pnas.0912122107

Smith, M.A., Rodriguez, J.J., Whitfield, J.B., Deans, A.R., Janzen, D.H., Hallwachs, W., and Hebert, P.D.N. 2008. Extreme diversity of tropical parasitoid wasps exposed by iterative integration of natural history, DNA barcoding, morphology, and collections. Proceedings of the National Academy of Sciences 105:12359-12364.

Burns, J.M., Janzen, D.H., Hajibabaei,M., Hallwachs,W., and Hebert, P.D.N. 2008. DNA and cryptic species of skipper butterflies in the genus Perichares in Area de Conservacion Guanacaste, Costa Rica. Proceedings of the National Academy of Sciences 105:6350-6355.

Miller, J. C., Janzen, D. H. and Hallwachs, W. 2007. 100 Butterflies and moths. Harvard University Press, Cambridge, Massachusetts. 256 pp.

Miller, J. C., Janzen, D. H. and Hallwachs, W. 2006. 100 Caterpillars. Harvard University Press, Cambridge, Massachusetts. 264 pp.

Smith, M. A., Woodley, N. E., Janzen, D. H., Hallwachs, W., and Hebert, P. D. N. 2006. DNA barcodes reveal cryptic host-specificity within the presumed polyphagous members of a genus of parasitoid flies (Diptera: Tachinidae). Proceedings of the National Academy of Sciences 103:3657-3662.

Janzen, D. H. 2005. How to conserve wild plants? Give the world the power to read them. Forward, Plant conservation: a natural history approach, eds. Krupnick, G. and Kress, J., University of Chicago Press, Chicago, 346 pp.

Janzen, D. H., Hajibabaei, M., Burns, J. M., Hallwachs, W., Remigio, E. and Hebert, P. D. N. 2005. Wedding biodiversity inventory of a large and complex Lepidoptera fauna with DNA barcoding. Philosophical Transactions of the Royal Society B 360 (1462):1835-1846.

Hebert, P. D. N., Penton, E. H., Burns, J. M., Janzen, D. H. and Hallwachs, W. 2004. Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator. Proceedings of the National Academy of Sciences 101:14812-14817.

Janzen, D. H. 2004.  Setting up tropical biodiversity for conservation through non-damaging use: participation by parataxonomists.  Journal of Applied Ecology 41:181-187.

Janzen, D. H. 2002. Tropical dry forest: Area de Conservación Guanacaste, northwestern Costa Rica. In Handbook of Ecological Restoration, Volume 2, Restoration in Practice, eds. Perrow, M. R., Davy, A. J., Cambridge University Press, Cambridge, UK, pp. 559-583.

Schauff, M. E. and Janzen, D. H. 2001. Taxonomy and ecology of Costa Rican Euplectrus (Hymenoptera: Eulophidae), parasitoids of caterpillars (Lepidoptera). Journal of Hymenoptera Research 10(2):181-230.

Janzen, D. H. 2001. Saving fractured oases of biodiversity (book review). Quarterly Review of Biology 76:327-330.

Burns, J. M. and Janzen, D. H. 2001. Biodiversity of pyrrhopygine skipper butterflies (Hesperiidae) in the Area de Conservación Guanacaste, Costa Rica. Journal of the Lepidopterist's Society 55:15-43.

Janzen, D. H. 2000. Wildlands as gardens. National Parks Magazine 74(11-12):50-51.

Janzen, D. H. 2000. Costa Rica's Area de Conservación Guanacaste: a long march to survival through non-damaging biodevelopment. Biodiversity 1(2):7-20.

Janzen, D. H. 1999. Gardenification of tropical conserved wildlands: Multitasking, multicropping, and multiusers. PNAS 96(11):5987-5994.

Janzen, D. H. 1999. La sobrevivencia de las areas silvestres de Costa Rica por medio de su jardinificación. Ciencias Ambientales No. 16:8-18.

Janzen, D. H. 1998. Gardenification of wildland nature and the human footprint. Science 279:1312-1313.

Janzen, D. H. and I. D. Gauld 1997. Patterns of use of large moth caterpillars (Lepidoptera: Saturniidae and Sphingidae) by ichneumonid parasitoids (Hymenoptera) in Costa Rican dry forest. In Forests and Insects, eds. A. D. Watt, N. E. Stork and M. D. Hunter, Chapman & Hall, London, pp. 251-271.

Reid, W. V., S. A. Laird, R. Gómez, A. Sittenfeld, D. H. Janzen, M. A. Gollin and G. Juma. 1993. Biodiversity Prospecting. World Resources Institute, Washington, D.C. 341 pp.

Janzen, D. H. 1993. Caterpillar seasonality in a Costa Rican dry forest. In: Caterpillars. Ecological and evolutionary constraints on foraging, N. E. Stamp and T. M. Casey, eds., Chapman and Hall, New York, pp. 448-477.

Janzen, D. H. 1988. Guanacaste National Park: tropical ecological and biocultural restoration. In Rehabilitating Damaged Ecosystems, vol. 11, pp. 143-192, J. Cairns, Jr., ed., CRC Press, Boca Raton, Florida.

Janzen, D. H. 1986. The future of tropical ecology. Ann. Rev. Ecol. Syst. 17, 305-24.

Janzen, D. H. ed. 1983. Costa Rican Natural History, University of Chicago Press, Chicago, 816 pp.

Janzen, D. H., and Martin, P. S. 1982.  Neotropical anachronisms:  the fruits the gomphotheres ate.  Science 215:19-27.

Janzen, D. H. 1978.  The ecology and evolutionary biology of seed chemistry as relates to seed predation.  In Biochemical aspects of plant and animal coevolution, J. B. Harborne, ed.,  Academic Press, London, pp. 163-206.

Janzen, D. H. 1977.  Why fruits rot, seeds mold, and meat spoils.  The American Naturalist 111:691-713.

Janzen, D. H. 1976.  Why bamboos wait so long to flower.  Annual Review of Ecology and Systematics 7:347-391.

Janzen, D. H. 1972.  Whither tropical ecology?  In Challenging biological problems, J. A. Behnke, Ed.,  Oxford University Press, New York, pp. 281-296.

Janzen, D. H. 1970.  Herbivores and the number of tree species in tropical forests.  American Naturalist 104:502-528.

Janzen, D. H. 1967.  Synchronization of sexual reproduction of trees with the dry season in Central America.  Evolution 21:620-637.

Janzen, D. H. 1967.  Why mountain passes are higher in the tropics.  American Naturalist 101:233-249.

Janzen, D. H. 1966.  Coevolution of mutualism between ants and acacias in Central America.  Evolution 20:249-275.