EARTHWATCH INSTITUTE
FIELD REPORT
Section I: UNEP- WCMC Weblink Information
Project
Title:
Principal Investigator: Lee Dyer
Position/Affiliations: Professor,
E-mail address: ldyer@tulane.edu
Research Sites and Local Management Status:
Scientific
names of primary species being studied (if appropriate):
Lepidoptera,
Hymenoptera, Diptera, Angiosperms, Nemata
Key
Research Objectives (5-8 brief bullet points):
· What affects diversity and abundance of caterpillars and parasitoids in natural forests and adjacent agriculture (banana and alfalfa)?
· What parasitoids might be good candidates for biological control in banana plantations and alfalfa fields?
·
How do
variation in precipitation and temperature affect levels of parasitism (and
subsequently affect caterpillar densities)?
Date
this report was completed: January
29, 2006
Data
Collection and Results
Diversity relationships
One objective of our Earthwatch caterpillar
research was to determine the effects of plant-herbivore-predator interactions
on biodiversity. We measured grassland plant and insect diversity at our
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MANAGED
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UNMANAGED
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Figure 1. Path diagrams based on analyses of
Earthwatch plot data, as well as experimental data from managed and unmanaged
grasslands. Arrows indicate positive effects, lines with a circle-head
indicate negative effects. Numbers next to effects are values of significant
path coefficients and indicate the size of the effect. H’ = arthropod
diversity, ni = arthropod abundance. |
Climatic unpredictability
and parasitism of caterpillars: implications of global warming
Numerous
Earthwatch teams quantified parasitism at our research sites in
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Figure 2. A linear regression of total parasitism
levels of caterpillars from fifteen extensive rearing programs against year-to-year
variability in precipitation (CV; R2 = 0.33). Letter codes
correspond to sites of rearing studies; AZ = Arizona, USA; ACGd = Guanacaste Conservation Area, Costa
Rica, dry forest; ACGr = rain forest; LS = La Selva Biological Station, Costa
Rica; YBS = Yanayacu Biological Station, Ecuador; NO = Southeast Louisiana,
USA; Braz = Reserva Ecológica do IBGE, Brazil; BCI = Barro Coloardo
Island, Panama; PNM = Parque Nacional Metropolitana, Panama; FS = Fort
Sherman, Panama; Can = Southern Ontario, Canada; MD = Maryland, USA; MO =
Southern Missouri, USA; VA = Virginia and West Virginia, USA. |
Predicting caterpillar
parasitism in agricultural systems
Leaf damage caused by Lepidoptera as they are
responsible for the majority of the herbivory suffered by rainforest plants as
well as many agricultural systems, including banana plantations. We used Earthwatch parasitism data
to link ecological theory to the biological control of insect pests in banana
plantations. Through our established predictive approach, ecological data on
plant-caterpillar-parasitoid interactions from natural systems were used to
formulate simple recommendations for biological control in banana plantations.
The specific goals were (1) to determine the most effective parasitoid enemies for
biological control of caterpillars in banana plantations and (2) to examine the
impact of nematicides on enemy populations. To assess percent parasitism,we
reared 1,121 caterpillars collected from six plantations managed under two
nematicide regimens. Attack by parasitoids in the families Tachinidae
(Diptera), Braconidae, Eulophidae, and Chalcididae (Hymenoptera) closely
paralleled rates reported for species with similar characteristics at our
Earthwatch site at La Selva, and statistical models predicted the relative
importance of these parasitoids as sources of mortality. We found that tachinid
flies were the most important source of early instar larval parasitism in
banana plantations, and their importance increased with more intensive
nematicide applications. The statistical models that we derived from data at La
Selva were useful in predicting which parasitoids would be important in banana
and which larval characteristics they would preferentially attack. We provided
predictions for caterpillars that can occur in other banana plantations (Table
1), especially those that shift from insecticide use to biological control.
This approach could be used in other managed ecosystems (e.g., near our sites
in
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Table 1. Percent parasitism predictions (with SE
in parentheses) for common species of Lepidoptera found in Costa Rican banana
plantations based on logit models from Earthwatch data collected over the past
10 years. Parasitism levels over 30% are likely to result in successful
biological control. |
Significance/Benefits of Research
Diversity
and natural history
Our most
significant accomplishment is the compilation of natural history data related to
approximately 2800 species of caterpillars, plants, and parasitoids. We share
this natural history information with locals and scientists alike (refer to the
list of talks and publications), including talks in Spanish to Costa Rican and
Ecuadorian students, naturalists, and local workers; the local talks have
increased awareness and respect for insect diversity. Many of the naturalist
guides at our research sites now point out caterpillars in their tourist walks
and discuss the role they play in the forest. We also share these data with
anyone who has internet access by publishing it on caterpillar web pages at www.caterpillars.org. The web pages are
currently undergoing major improvements and should be a very useful tool for
managing and studying biodiversity for many years to come. In addition, our
basic research on diversity relationships between trophic levels will
contribute to a growing understanding of how parasitoids and other natural
enemies affect entire biotic communities.
Sustainable
agriculture
Managers of
banana plantations, alfalfa fields, and other agricultural systems who are
attempting to control pests without using pesticides will benefit from
increased knowledge of the parasitoid community. First, we discovered at least
12 new species of parasitoids (that are still being treated by taxonomists) in
the families Braconidae and Tachinidae, all of which are potentially important
biological control agents. Second, our modeling approach identified the most
important biological control agents in banana plantations under different
pesticide management, which allows plantation owners to manage for caterpillar
pests without resorting to harmful insecticides.
Sustainable
employment in the rainforest
Although it is not a direct benefit from the research, our
Earthwatch project benefits the local communities by supporting the research
stations and by continuing collaborations with local naturalists and
scientists. Field stations generally benefit the local community by providing
excellent employment opportunities that are not destructive to the forest and
by boosting the local economy. At the
Environmental
education
Finally, our work has directly benefited the educational community
because many volunteers have been school teachers and have incorporated ideas
learned from this project into their classes. It has indirectly benefited the
educational community because the research addresses basic theoretical
questions in ecology. One of the most important issues to which our Earthwatch
project has contributed is the idea of “trophic cascades.” Theory
predicts that the effects of predators and parasitoids on plant biomass and
diversity should not be great in complex systems such as rainforests, but we
have demonstrated that the enemies of caterpillars significantly enhance plant
biomass and diversity by killing caterpillars. This means that the consequences
of tropical predator extinctions are more severe than previously thought, and
predators of all sizes and all predatory guilds (i.e. including parasitoids)
should be a major focus for conservation efforts.
Dissemination
of Results (all publications
below are available in pdf format at: http://caterpillars.unr.edu/papers.htm)
Peer reviewed articles and book chapters
Stireman III, J.O., L.A.
Dyer, D.H. Janzen, M.S. Singer, J.T. Lill, R.J. Marquis, R.E. Ricklefs, G.L.
Gentry, W. Hallwachs, P.D. Coley, J.A. Barone, H.F. Greeney, H. Connahs, P.
Barbosa, H.C. Morais, and I.R. Diniz. 2005. Climatic unpredictability and
caterpillar parasitism: implications of global warming. Proceedings of the
Dyer,
Stireman,
J.O. III, Dyer,
Letourneau,
D.K. and
Irschick,
D., Dyer,
Presentations
Organization for Tropical Studies,
Yanayacu Biological
Ecological Society of
Bodega Marine Laboratory, 2005
Section II: Volunteers
February 3, 2006
Dear Volunteers,
While I write this letter from a FEMA trailer (without
electricity), I am reflecting on a year that was filled with ups and downs. The
last 5 months have been difficult for everyone in
I have been impressed with the amount of high quality
data that Earthwatch volunteers have collected with us over the past 9 years. I
am sure that I will continue leading this research for at least 20 more years,
and I hope to keep discovering new species and new associations. Perhaps the
most important paper that we published from these data was our paper in the
Proceedings of the National Academy of Sciences in November (2005 – the
paper is available here: http://www.pnas.org/cgi/reprint/0508839102v1). We
discuss how extreme weather events (like hurricanes) cause a decrease in
parasitism – this means that increases in extreme weather events as a
result of climate change may cause parasitoid extinctions and increases in
caterpillar outbreaks in forests and agricultural systems. We hope that this
paper helps land managers plan for future conservation of natural enemy
communities.
If you are wondering about the rest of the team of
plant/caterpillar/enemy investigators, feel free to send an email asking for
their addresses. Unfortunately, Marco and
I would like to thank all of you for your hard work.
As an extended team, we have a strong database and positive memories of great
people. My collaborators and I have enjoyed working with all of you, and our
project could not have been done without your help. We also want to thank all
of you for sending us great emails, cards, pictures, slides, and other
thoughtful items. We definitely appreciate all this correspondence. Please feel
free to keep in touch and we will do our best to respond. Hopefully we'll see
you again in the field.
Saludos,
Lee Dyer,
gusanero, ldyer@tulane.edu
Volunteer Tasks and Accomplishments
In our 9th year of funding by Earthwatch, we were fortunate
to have the help of 30 volunteers. These volunteers helped us bring our rearing
total up to approximately 1800 species of butterflies and moths (26,000
individuals) and over 350 species of parasitoids. The four teams participated in all
aspects of our Forest Caterpillars project. Team members searched for and
collected caterpillars, noted possible morphological or behavioral characters,
and took care of the larvae. At La Selva and Tirimbina, they also assisted with
experiments on the understory pepper plants, Piper spp. and helped with
encapsulation experiments.
The four teams logged over 1400
total person hours in the field, searching for and recording data on caterpillars
and working on related experiments. At La Selva and Tirimbina, they found over
1900 caterpillars belonging to 55 butterfly and moth species in 21 families; at
least 9 of those were new species. From these caterpillars they reared over 20
species of parasitoid wasps and flies. At the Southwest Research Station,
volunteers collected 210 individual caterpillars for a total of 45 species in
16 families. At least 8 species of parasitoids were reared. The teams in
Ecuador contributed to our new NSF funded biotic survey and inventory of the
eastern slope of the Andes, collecting 1400 caterpillars, including 75 species
and 18 families, and a couple dozen new species. The site will continue to
yield many new species of caterpillars and parasitoids (Figure 3). The levels
of parasitism at our 3 Earthwatch sites were used in our important new finding
that climatic unpredictability is associated with lower levels of parasitism.
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Figure 3a. A new species in the family Geometridae.
It will be years before this caterpillar receives a name (the genus may be
undescribed). Tirimbina Biological |
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Figure 3b. A cryptic lycaenid caterpillar from
the Southwest Research Station, |
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Project Development
The data we have collected thus far at all sites support our hypotheses that the dynamics in these strikingly different habitats (Arizona, Ecuador, Costa Rica, Louisiana) are very similar, but the actors are different — species composition of the caterpillars and their parasitoids show almost zero overlap. The larvae that we studied exhibited a wide array of defenses, and we continued a focus on two specific defenses: frass-throwing and encapsulation. Several more years of data will allow us to make conclusions about how these defenses function against different types of parasitoids. For all sites, we will continue to focus on collecting new species (Figure 4), but we will also focus more on altitudinal gradients in parasitism, similar to the precipitation gradient that we’ve tested.
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Figure 4.
This Notodontid caterpillar, Nebulosa elicioi,
was parasitized by an ichneumonid wasp, which
has pupated in the old skin of the caterpillar (which is now dead). Both the
moth and the specialized parasitoid were new species. You can find more information
on the web page for this species:
http://caterpillars.unr.edu/lsacat/ecuador/species/notodontidae/Nelicioi/nelicioi.htm |
Educational Opportunities
Educational opportunities were provided to:
- Local communities. We hired and
trained four local naturalists and gave talks to local residents at all of
the research sties.
- Students. Seven graduate students in
Dyer’s laboratory participated in the projects, either directly or
by analysing data and working on papers. Eight undergraduates were also
involved with the Earthwatch research. One PhD dissertation was completed
with help from the Earthwatch funded work.
- Early career scientists. Two post
doctoral researchers (Stireman and Gentry) helped run Earthwatch teams.
Our
Earthwatch project has united workers from
Acknowledgements
Research assistants:
Costa
Rican paraecologists: Gerardo Vega, Humberto Garcia, Maylin Paniagua
Ecuadorian
paraecologists: Rafael Maitio, Wilmer Simbana, Maria de
Graduate
students: Angela Smilanich, Malia Fincher, Michael Olson, Clark Pearson, Tara
Massad, Genoveva Rodriguez, Kathleen Burke
Collaborators:
Dr. John
Stireman,
Dr.
Grant Gentry,
Dr.
Craig Dodson,
Dr.
Thomas Walla,
Dr.
Daniel Janzen,
Dr.
Deborah Letourneau,
Harold
Greeney, Yanayacu Biological Station
Cooperating Institutions:
Organization
for Tropical Studies
Grants from additional funding
sources:
National
Science Foundation – Ecology
National
Science Foundation – Biotic Surveys and Inventories
National
Geographic
United
States Department of Energy