Daniel H. Janzen
Community Ecology
Brittany Owens
Daniel Janzen: C.V.
Degree in Biology from University of Minnesota in
Ph.D. from University of California, Berkeley in 1965
Teaching positions (US):
-(1965-1968) University of Kansas
-(1969-1972) University of Chicago
-(1972-1976) University of Michigan
-(1976- present) University of Pennsylvania
Teaching positions (outside US):
(1965-1966): Universidad de Oriente, Cumana
(1969): Universidad de Puerto Rico, Rio Piedras
(Puerto Rico)
(1973): Universidad de Los Andes (Venezuela)
OTS Affiliation:
(1963) Student at OTS tropical biology course in
Costa Rica
(1965) Returned as an instructor
-since has served annually as an instructor
Influenced work in tropics, particularly Costa Rica
Conservation/Restoration Projects
• Currently ad honorem technical advisor for
Area de Conservacion Guanacaste (ACG) and
Instituto Nacional de Biodiversidad (INBio)
1975 Gleason Award (Amercian Botanical Society)
1984 Crafoord Prize, Coevolutionary ecology (Royal Swedish Academy of Sciences)
1987 Hijo Ilustre de Guanacaste (Governor of Guanacaste province)
1897 “Global 500” Roll of Honor (UNEP)
1989 MacArthur Fellowship
1991 Founder’s Council Award of Merit (Field Museum of Natural History)
1992 Member, National Academy of Sciences (USA)
1993 Award for Improvement of Costa Rican Quality of Life (Universidad de Costa
1994 Silver Medal Award (International Society of Chemical Ecology)
1995 Conservation Society Award
1997 Kyoto Prize, Basic Sciences Field (Inimori Foundation)
2002 Albert Einstein World Award for Science (Consejo Cultural Mundial, Mexico)
2002 Honorary Fellow of the Association for Tropical Biology, and Conservation (ATBC)
2006 National Outdoor Book Award, Design and Artistic Merit for 100 Caterpillars
2011 FBBVA Foundation Frontiers of Knowledge Award of Ecology and Conservation
220 publications
55 journals
~10,000 citations
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.
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.
Miller, J. C., Janzen, D. H. and Hallwachs, W. 2006. 100 Caterpillars. Harvard University Press, Cambridge, Massachusetts. 264 pp.
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. 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.
“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.”
-Dan Janzen
• “Victorian Era Natural History Studies”
Coevolution of Plants and Insects
– Ant-Acacia mutualisms in the Neotropics
– Spondias mombin seed dispersal by mammals
– Effect of herbivory on tropical plant diversity
• “Exploration of the Interface between Humans and
Habitat Conservation/Restoration
– Area de Conservacion Guanacaste (ACG)
– Instituto Nacional de Biodiversidad (INBio)
What is Coevolution?
• “The term coevolution is used to describe
cases where two (or more) species reciprocally
affect each other’s evolution”
– evolution.berkeley.edu
• “Coevolution is a change in the genetic
composition of one species in response to a
genetic change in another.”
– biomed.brown.edu
• Concept of coevolutionary “races” in
ecologically intimate species
Coevolution: Ant-Acacia Mutualisms
“Ant-plants” and “Plant-ants”
• “Swollen Thorn Acacias”
• Genus Acacia (<10% of genus in C. America)
Enlarged stipular thorns which house ants
Enlarged foliar nectaries
Modified leaflet tips (Beltian bodies)
Year-round production of leaves (even in areas with dry
Ant-plants and Plant-ants
• “Obligate acacia ants”
• All in genus Pseudomyrmex
– Solely build colonies in swollen thorn acacias
*Taxonomic Issues
*Not obligate on one species of acacia, but on the
life form
“Fully developed interdependency”
1. Queen ant finds unoccupied sapling and chews
entrance hole.
2. Lays eggs in thorn and forages for foliar
3. Forages for Beltian bodies to feed larvae.
4. Colony grows to occupy all thorns of plant.
5. Queen becomes physogastric with workers
performing daily duties.
*9 months of colony growth are required to produce
enough workers to police area outside of acacia and
provide protection for the plant.
“Fully developed interdependency”
Experimentally demonstrated that the swollen-thorn
acacias have evolutionarily lost their ability to withstand
insect damage and competition with neighboring plants
in the absence of obligate acacia-ants (Janzen 1966a)
-Experimentally removed ants from acacias
-Total of 50 subplots were observed for 11 months
-After 7-9 months, unoccupied acacias were compared
with occupied acacias in control plots
-Death of unoccupied acacias usually occurs within 6-12
months due to repeated defoliation via herbivores or
overshadowing by neighboring vegetation
“Fully Developed Interdependency”
Mean Sucker Length
Presence of
Weight of Biomass
(Janzen 1996)
Ant-Plant Traits
• “In a sense, the obligate acacia-ants are the secondary
plant substances and micromorphology of the swollenthorn acacias, and they are the means through which
the swollen-thorn acacias interact with a large number
of the other organisms in the community…
consideration of the ant x acacia interaction system
leads to the hypothesis that evolutionary abilities of
the entire group of organisms in the community is
responsible for the structure and properties of the
plants in the community, especially at the
microstructure level…” (Janzen 1996)
Plant-Ant Traits
• “The obligate acacia-ants are completely
dependent, as a colony in nature, on the
swollen-thorn acacias… The obligate acaciaants have committed themselves to the fate of
the swollen-thorn acacias, provided that
something happens to the swollen thorn
acacias so rapidly that the obligate acacia-ants
cannot evolve out of the interaction system.”
(Janzen 1996)
Beyond Mutualism
Looking beyond the single system of ant-acacia
coevolution to discuss basic properties of such
1. Coevolution of mutualistic coevolution is the
product of evolutionary feedback systems.
-one population must supply the other with a
benefit, and the receptive population must be able
to favor the donating genotype of the donating
- “increasing a flow from a trickle”
Beyond Mutualism
2. Within the ant-acacia system, a hypothesis for
the production of a coevolutionary relationship
between species is provided by examples of
-There are several species of Pseudomyrmex
which exhibit a range of affinity for acacias.
-There are at least five independent
evolutions of the acacias into the swollenthorn lifestyle.
Beyond Mutualism
3. This study adds support to the idea that the
chemical and microphysical properties of plants
may have partly evolved as a response to insect
-The services provided by the acacia-ants
appear to be a substitute for many of the
physical and chemical traits that other acacias
use in their defense.
Beyond Mutualism
4. When looking at coevolution, preadaptations on
both sides are important to facilitating the
coevolutionary system.
-Magnification or reduction of pre-interaction
properties may have led to many of the traits
essential to the ant x acacia mutualism.
-However, the production and consupmtion of
Beltian bodies, along with the aggression of ants
towards neighboring plants do not fall under this
Beyond Mutualism
5. The existence of such coevolutionary
relationship contributes to our understanding of
high plant density in the tropics.
-Ant-acacia coevolution appears more
common in warmer, wetter areas
-As one moves away from the tropics, plantinsect interspecific interactions appear to
decrease in density.
Coevolution Summary
“The interaction system between obligate acaciaants and swollen-thorn acacias is clearly an example
of mutualism between a higher plant and an
animal. The present deductive discussion of the
evolution of the traits of the ant and the acacia
leads without reasonable doubt the conclusion that
the system evolved through mutually exclusive
interactive evolution, or coevolution, rather than by
chance coincidence in time and space of two highly
specialized yet mutually beneficial organisms.”
(Janzen 1966)
Habitat Conservation/Restoration
Area de Conservacion Guanacaste (ACG)
• 163,000 hectare national park in Costa Rica
(2% of the country’s total area)
• 325,000 species (2.6% of the world’s
• Includes diverse habitats including dry forest
lowlands, cloud forests, rainforest, and marine
• 1971 established as one of the first National
Parks in Costa Rica
• 1999 established as UNESCO World Heritage Site
• “ACG conducts research and conservation action
at the leading edge of ecology, evolutionary
biology, biotechnology, biodiversity development,
schoolchild education, decentralized
administration, and integration with local,
national and international society.”
• Guanacaste National Park (GNP) was created with the
idea that it’s long-term survival would be supported by
the creation of the idea of “ownership”
– “owners” being both its direct custodians and society, at
• Mission Statement of GNP included:
– Restoration via use of existing fragments
– Inclusion of a large enough area to facilitate intense
visitation and research use
– Maintenance of forested area to provide a variety of
material resources and biological data to the local culture
– Exposure of the local, national, and international audience
to the benefits of the natural world
(Janzen 2000)
Orange You Glad…
20,000 hectares of pastureland were purchased to allow restoration back into
hardwood forest
In 1992 an industrial- level orange plantation was established along the
northern boundary of the ACG on thousands of hectares of pastureland along
its northern boundary.
The ACG requested an experimental 100 truckloads of orange peels from the
neighboring orchard to be dumped on the reclaimed pastureland, which aided
in the beginning of the forest regeneration process.
ACG then negotiated a contract with the orange plantation in which organisms
from the park would degrade 1000 truckloads of peel a year for 20 years in the
same manner, along with providing 20 years of other environmental services
such as water and biological control. In return, orange farmers would pay the
ACG with 1400 hectares of Del Oro forested land neighboring the ACG forests.
Controversial, but successful so far!
(Janzen 2010)
Gmelina Plantations
• Gmelina have traditionally resulted in deforestation and erosion.
• However, unweeded Gmelina plantations overshadow pastureland,
killing grasses and aiding in the regeneration of forest (typically
difficult to start on such lands)
• ACG has partnered with local Gmelina planters, which pay the cost
of the plantation, leaving it unweeded and sharing profits with the
• After one 8-12 year rotation of Gmelina the planter harvests the
logs and ACG conservationists herbicide the stumps, leaving the
remaining unweeded understory to grow up as rainforest.
• Although controversial, a grant from a conservation NGO has now
put this concept into practice in the eastern ACG, providing jobs,
funds for further restoration, and community involvement.
(Janzen 2010)
"Acacias." Www.entangledbank.com. N.p., n.d. Web. 15 Apr. 2013. Website
"Ants Collecting Food Bodies." Www.ecolibrary.edu. N.p., n.d. Web. 15 Apr. 2013. Website
"Coevolution." Www.biomed.brown.edu. Brown Biomedical Sciences, n.d. Web. 15 Apr. 2013. Website
Janzen, D.H. 2000.
Costa Rica’s Area de Conservacion Guanacaste: a long march to survival through non-damaging
biodevelopment.Biodiversity 1(2)
Janzen, D.H. 2000. "Daniel H Janzen." Wikipedia. Wikimedia Foundation, n.d. Web. 15 Apr. 2013.Website
"Daniel H Janzen." Www.jouralogy.edu. N.p., n.d. Web. 15 Apr. 2013.Website
"Department of Biology." Department of Biology. N.p., n.d. Web. 15 Apr. 2013.Website
" Guanacaste Dry Forest Conservation." Acguanacaste.ac.cr. N.p., n.d. Web. 15 Apr. 2013.Website
Janzen, D.H. 2010. Hope for tropical biodiversity through true bioliteracy. Biotropica.
Janzen, D.H. 1987. How to grow a national park.Experientia 43. "Instituto Nacional De Biodiversidad." Wikipedia.
Wikimedia Foundation, n.d. Web. 15 Apr. 2013.Website
Janzen, Daniel H. "Coevolution of Mutualism Between Ants and Acacias in Central America." Evolution 20.3
(1966): 249-75. Web.Journal Article
Janzen, Daniel H. "The Interaction of the Bull's-horn Acacia (Acacia Cornier L.) with One of Its Ant Inhabitants
(Pseudomyrmex Ferruginea F.Smith) in Easter Mexico." University California Publ. Ent (n.d.): n. pag. Print.Journal
"Moreless." Guanacaste Dry Forest Conservation Fund. N.p., n.d. Web. 15 Apr. 2013.Website
"Understanding Evolution." Understanding Evolution. N.p., n.d. Web. 15 Apr. 2013.

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