Climate Change and Caterpillars 2012 FIELD REPORT

Transcription

1 Climate Change and Caterpillars 2012 FIELD REPORT Background Information Lead PI: Lee Dyer Project scientists: Report completed by: Lee Dyer Period Covered by this report: 2012

2 Dear Earthwatch Volunteers, The 2012 field season was action-packed and included multiple trips to our 5 research sites and 9 excellent research teams in Ecuador, Louisiana, Arizona, Nevada, and California. One of these teams was a course with students from MIT and two of these teams were new teams focused both on our research and on climate-change/sustainability training for employees of HSBC, an international bank. As a group, our Earthwatch teams have continued to carefully document the relationships between climate, plants, plant chemistry, caterpillars, parasitoids, and interaction diversity across a complex set of ecosystems in the New World. One highlight for me this season was a new look at the data from all of our sites, which have matured enough to address some of the large scale questions that we set out to examine when we first started this project, over 15 years ago. We were able to fit a unique statistical distribution (with the fancy name, inverse discrete pareto!) to all caterpillar-plant and parasitoid-caterpillar feeding relationships across over a dozen sites that encompass various climatic and biotic gradients, including our 5 Earthwatch sites. Our findings were relevant to our two major research objectives: documenting biodiversity and understanding the effects of climate on interactions between organisms. We found that these distributions were very stable across all sites, suggesting that estimates of biodiversity based on simple assumptions of specialization are correct and that some of the particulars of these feeding relationships are not affected by latitude or climate. We are still trying to figure out what this means for predicting current levels of biodiversity and for understanding how interactions between plants, herbivores, and parasitoids will be affected by climate change. The final report provides more details on these and other interesting results from I hope this report provides you with a sense of how successful the Climate Change and Caterpillars project has been because of your excellent assistance in the field and laboratory. I continue to be impressed with the amount of high quality data that Earthwatch volunteers have collected with us over the past 17 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. I also hope that our research will help us understand how diverse ecosystems will respond to dramatic changes in climate as well as other global change. In the face of continual bad news about increases in extreme weather events, rising

3 sea levels, massive extinctions, and loss of our favorite habitats, it is important to continue the hard work of documenting and protecting the amazing diversity that lives on through the consequences of human impacts. If you are wondering about the rest of the team of plant-insect investigators, feel free to send an asking for their addresses. Wilmer and Lucho are still working on the project in Ecuador, collecting and rearing amazing numbers of caterpillars. Harold Greeney is still the owner of Yanayacu, but he is currently living in Los Angeles, considering getting a job at a university in the US. Rebecca and Mark are still doing an outstanding job leading the New Orleans portion of the project and continue to make excellent progress towards completing their PhD dissertations. Angela is about to sign a contract for a faculty position at UNR; she will continue to teach classes and conduct research and will be involved in all of our future Earthwatch expeditions. Dave Wagner is still as intense as ever and will not stop sending me amazing plates of caterpillars for the Western Caterpillar guide. I thank all of you for your hard work in As an extended team, we have a strong database and positive memories of diverse and thoughtful people. You contributed to field collections of caterpillars, collecting diversity of interaction data from field plots, helping with laboratory experiments, data entry, discussion of preliminary results, and to many other components of our overall research program. My collaborators and I have enjoyed working with all volunteers, and our project would not be successful without your help. 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, Principle Gusanero

4 SECTION ONE: Scientific research achievements Top highlight from the past season This is super nerdy, but for the PI, one of the major highlights of the year 2012 was seeing results from our group s mathematical models that confirmed our assumptions about interaction diversity and how it is a more tractable variable than species diversity. Of course, each exciting discovery of new caterpillars, rare parasitoids, and novel host associations is central to why we love our project, but our statistics and models will help us efficiently estimate biodiversity in complex ecosystems and to predict how it will change in our changing world. The results of our interaction diversity models, inspired and parameterized by our rich Earthwatch databases, constituted exciting progress towards clarifying relationships between global warming, extreme weather, and biodiversity. Perhaps the strengths of diverse trophic interactions will continue, for a while, to buffer ecosystems from all that we do to disrupt them? Reporting against research objectives Objective 1: Determine how hurricanes and variation in climate affect insect diversity. We have made considerable progress towards determining effects of hurricanes and climatic variation on interaction diversity through our modeling approach. Our models, including analytical (not displayed here), simulation (Fig. 1), and statistical (Fig. 2) approaches were parameterized using all of the Earthwatch data from all of our sites. These models have provided us with the appropriate quantitative tools to examine how diversity of interactions will respond to hurricanes and other extreme perturbations. As we reported previously at our hurricane damaged sites, and as predicted by our previous papers, there were 6-8 caterpillar species that reached outbreak proportions in response to storm damage and overall species diversity is still lower at the heaviest hit sites. We are still examining the details of this complex relationship and are (in 2013) analyzing time series at all sites to rigorously test hypotheses about extreme weather events and biodiversity. The most relevant published paper from 2012 for this objective: Dyer et al. (2012, American Entomologist) and Wilson et al. (2012, Journal of Evolutionary Biology).

5 Figure 1. An example of output from our interaction diversity simulation models, using 17 years of Earthwatch data for parameter estimation. The red data points are simulated numbers of new species of plants, caterpillars, and parasitoids expected to be discovered from our Earthwatch plots, while the blue data points are simulated numbers of unique interactions. The pattern in which the blue points reach an asymptote (i.e. level off) before the red points is caused by differences in frequencies of species versus interactions. Although there are far more interactions in any ecosystem (such as the Great Basin Desert), most of these interactions are rare and unimportant in maintaining stability. As a result of these features, diversity of relevant interactions is easier to estimate than species diversity. This is convenient, because interaction diversity is a better measure of ecosystem function and stability than species diversity and it is apparently (according to our models) easier to measure Objective 2: Determine how hurricanes and variation in climate affect levels of parasitism and caterpillar densities. Most climate change scenarios predict that insect outbreaks will increase in frequency and intensity as a result of increases in CO2 and mean global temperatures, based on direct positive effects of temperature on insect populations as well as through complex effects on tritrophic interactions. Models of climate change have predicted greater

6 frequency and duration of droughts and floods and a widespread increase in the frequency of extreme weather events. Such increased unpredictability and variability in regional climates, particularly with regard to precipitation, will likely impact interaction diversity, yet the potential effects are largely unknown. As we reported previously at our hurricane damaged sites, and as predicted by our previous papers, there were 6-8 caterpillar species that reached outbreak proportions in response to storm damage and outbreaks are more likely at sites which experience more variance in precipitation. We continued to use our databases to follow up on our work comparing plant-caterpillar-parasitoid interactions across a precipitation gradient in the Americas. In addition to the modeling approaches summarized under Objective 1, we continue to document the details of phenological asynchrony between parasitoids and their hosts when weather events such as floods and droughts create temporal shifts in caterpillar populations such that they are unavailable to specialized wasp parasitoids during their hostsearching phase. To this end, we hope to accumulate 2-3 more years of data to allow us to determine which subfamilies and genera of parasitoids are most affected by specific extremes in weather. In addition to examining relationships between extreme weather events and trophic interactions, we have used our Earthwatch data and modeling efforts to help make progress on understanding insect outbreaks that are likely to arise in response to tropical hurricanes and other extreme weather. Very little is known about outbreaks in tropical ecosystems, and there was a false paradigm that insect herbivore outbreaks are rare or nonexistent in tropical forests. To help guide future research on global change and insect outbreaks, we published a book chapter synthesizing all published work to date, including both published and unpublished results from our Earthwatch rearing projects. In the chapter, we: 1. Quantitatively defined an outbreak, identified different general types of outbreaks, and outlined challenges associated with quantifying and detecting outbreaks in tropical forests. 2. Pointed out potential biotic linkages between outbreaks in managed landscapes and those in more natural forests. 3. Identified taxa that are known to outbreak and traits that make species prone to outbreak. 4. Predicted where outbreaks are likely to occur both within a stand and across gradients from dry to wet forests. 5. Modeled the consequences of outbreaks for plant communities and species coexistence. 6. Made predictions about how global climate change will alter the frequency and severity of outbreaks. 7. Proposed a series of testable hypotheses concerning outbreaks in the tropics to serve as a guide for future research (which includes clear guidelines for our future

7 Earthwatch research). are: The most relevant published papers from 2012 for this objective Dyer et al. (2012, American Entomologist), Dyer et al. (2012, Insect Outbreaks), and Massad et al. (2012). Figure 2

8 Figure 3

9 Figure 4

10 Figures 2-4. Plots showing the relative fit of Pareto (open circles), Geometric (triangles), and Poisson (squares) distributions to the data (solid points) for family diet breadth. The Geometric and Poisson distributions are those that are normally assumed for ecological relationships, such as frequency distributions of parasite hosts and herbivore food plant species. The y-axis is the natural log of the probability that X > x. A close fit to a particular distribution is indicated by the alignment of the solid points (data) and predicted values (open symbols) it is obvious from these graphs that the pareto is the best fit, meaning that ecosystems are dominated by specialists, with many species of relatively rare generalists, all of which have different diet breadths. All plots are for unique sites, including our 5 Earthwatch sites, and unless otherwise indicated the data are from frequency of novel host plant species for individual caterpillar species. The PNG sites are Vojtech Novotny s data from Papua New Guinea, and include a variety of herbivorous insects (not just caterpillars). Data for parasitoid hosts are also displayed: tachinid flies from our Ecuador site and braconid wasps from Dan Janzen s site in the Guanacaste Conservation Area of Costa Rica (ACG). Objective 3: Specialization and biodiversity The diet breadth or host range of insect herbivores has been a focal point for understanding current levels of biodiversity, which are increasingly threatened by global change. Numbers of species for the most diverse forests on earth are only crude approximations and the methods for estimating biodiversity rely on poor natural history data and untested assumptions about herbivore specialization. For years our Earthwatch data have facilitated investigation of latitudinal gradients in diversity and specialization, a major challenge in community ecology and evolutionary biogeography. For herbivorous insects, high specialization may be one mechanism allowing for high diversity at a given locale. We previously tested this hypothesis with our Earthwatch data by comparing host specialization in lepidopteran larvae for eight different New World forests ranging in latitude from 15 S to 45 N and found that the diets of tropical Lepidoptera larvae are more specialized than their temperate forest counterparts, allowing for vastly greater numbers of herbivore species within an ecosystem. In 2012, we combined our Earthwatch data with our collaborators datasets to create a global dataset that we used to investigate the distribution of taxonomic and phylogenetic host range for over 20,000 species of Lepidoptera (butterflies and moths) interacting with over 6,000 species of plants. We asked if relatively specialized and generalized herbivores are characterized by discontinuity in host range, or if they form a continuum from few to many hosts attacked. We also investigated the consistency of the distribution of diet breadth

11 among geographic regions, families of Lepidoptera, herbivores associated with different plant families, and also among parasitic wasps and flies. A distinct shape to taxonomic diet breadth was revealed, characterized by a unimodal, high peak at one host (most herbivores at any one location attack a single host plant species) and a long, thin tail of more generalized species. The observed patterns of diet breadth are fit with a discrete, truncated Pareto power law distribution that is qualitatively identical across most of the subsets of our data (Figures 2-4, above). Analyses of phylogenetic diet breadth are consistent with the predominance of specialists in plant-insect communities and also with the presence of a consistent, long tail of generalists across latitudes. In addition to presenting a definitive portrait of the distribution of diet breadth, these results raise interesting directions for future empirical and theoretical work, and more importantly, help efforts to quickly calculate biodiversity in forests around the world that are quickly changing in response to climate change and other global change parameters. These results are important for understanding determinants of biodiversity and for guiding conservation efforts that try to focus on specialized or endemic species. The most relevant publications we produced for this work are: Wilson et al. (2012, Journal of Evolutionary Biology) and Forister et al. (2012, Ecology). Objective 4: Discovery and descriptions of new species and new life histories In 2012, we focused on creating our sister site to caterpillars.org this is a site created in collaboration with the Encyclopedia of Life (EOL). The URL for the site is: In addition to updates to the life history data and images newly available on the web, we published several new life history descriptions for our focal taxa, many of which are the first biological information known for particular genera (Fig. 5). We continue to rear out new species from the project at a rapid rate and we continue to publish species descriptions for as many of these as possible. At the North American sites (Louisiana, Arizona, California, Nevada), we focused on contributing new life histories to the existing limited life history data for moths and butterflies of North America. Here we provide several examples from the Arizona site that will eventually be part of the sequel to Dave Wagner s Eastern Caterpillars book (Figures 6-9). The most relevant publications we produced for this work are: Dyer et al. (2012, American Entomologist), Smilanich et al. (2012, Insects), Wilson et al. (2012, Journal of Evolutionary Biology), Greeney et al. (2012), and Inclan and Stireman (2013).

12 Figure 5. Examples of new species descriptions resulting from our rearing projects in Ecuador, Louisiana, and Costa Rica. These species of flies are parasitoids that are responsible for preventing caterpillar outbreaks and are less susceptible to climate change than parasitic wasps. All images are of new species. The Earthwatch project discovered approximately 50 new species of parasitoids in The images include dorsal view of males of Erythromelana jaena species group. 19. Erythromelana abdominalis (Townsend). 20. Erythromelana jaena Townsend. 21. Erythromelana leptoforceps sp. nov. 22.

13 Erythromelana nigrithorax (Wulp). 23. Erythromelana curvifrons sp. nov. Scale bar = 1.0 mm. In addition to the results described here, participation of Earthwatch volunteers in our research contributed to the training and career development of the following personnel: 1) several postdoctoral researchers (Robinson, Miller, Greeney), 2) UNR graduate students (Lumpkin, Glassmire, Pardikes, Krauss), 3) Tulane graduate students (Hazen, Fox), 4) CU Boulder graduate student (Whitehead), 5) UNR undergraduate students (Fredrickson, Pirtle, Morrison, Blaustein, Lindgren, Chipman, Salls, Holman), 6) Reno school teachers (Habdas and Robinson), and 7) crews of local field technicians and graduate students in Latin America (Costa Rica, Ecuador). The work has also contributed to and enhanced an international collaboration that includes Dan Janzen (University of Pennsylvania and ACG Costa Rica), Vojtech Novotny (Czech Academy of Sciences and Papua New Guinea field institute), Scott Miller (Smithsonian Institute), Massuo Kato (University of Sao Paulo, Brazil), Yvonne Diniz (University of Brasilia, Brazil), and many other scientists with interests in multitrophic interactions, biodiversity, and conservation. Figures 6-9. Examples of new species descriptions and host affiliations for caterpillars collected by our project. Captions are included for each species.

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15 SECTION TWO: Impacts Partnerships 1) American Museum of Natural History, New York, NY: Provided office space to our project, including a microscope and computer; provided 24/7 access to insect collections and library; provided mail service for specimens. 2) United States National Museum, Washington, DC: Provided 24/7 access to moth and butterfly collections during visits by our project. 3) The Natural History Museum, London: Provided access to moth and butterfly collections during visits by our project. 4) Southwest Research Station (AMNH), Portal, AZ: Collaborates with the Earthwatch project, provides additional volunteer support, provides lab space, internet access and accommodations. 5)Yanayacu Biological Station, Cosanga, Ecuador: hosts all researchers, staff, students, and volunteers. Acts as a full collaborating partner institution with the Earthwatch project. 6)Museo Ecuatoriano de Ciencias Naturales, Quito, Ecuador: provides in-country logistical support and research/export permits. 7)Universidad Central Ecuatoriano, Quito, Ecuador: undergraduate students from various biological disciplines work with PI's and associated researchers on completing their undergraduate thesis requirements.

16 Dissemination of research results Scientific peer-reviewed publications Massad, T.J., Dyer, L.A., and G. Vega C Costs of defense and a test of the Carbon- Nutrient Balance and Growth-Differentiation Balance Hypotheses for two co-occurring classes of plant defense. PLOS ONE 7(10): e Richards L.A., Lampert E.C., Bowers M.D., Dodson C.D., Smilanich A.M. and Dyer L.A Synergistic effects of iridoid glycosides on the survival, development, and immune response of a specialist caterpillar (Junonia coenia Nymphalidae). Journal of Chemical Ecology 38: Smilanich, A.M. and L.A. Dyer Effects of banana plantation pesticides on the immune response of lepidopteran larvae and their parasitoid natural enemies. Insects 3: Wilson, J.S., Forister, M.L., Dyer, L.A., O'Connor, J.M., Burls, K., Feldman, C.R., Jaramillo, M.A., Miller, J. S., Rodríguez-Castañeda, G., Tepe, E.J., Whitfield, J.B., Young, B Host conservatism, host shifts and diversification across three trophic levels in two Neotropical forests. Journal of Evolutionary Biology 25: Dyer, L.A., Wagner, D.L., Greeney, H.F., Smilanich, A.M., Massad, T.M., Robinson, M. Fox, M., Hazen, R., Glassmire, A., Pardikes, N., Fredrickson, K., Pearson, C., Gentry, G.L., and J.O. Stireman III Novel insights into tritrophic interaction diversity and chemical ecology using 16 years of volunteer supported research. American Entomologist 58: Forister, M. L., Dyer, L.A., Singer, M.S., Stireman III, J.O., and J.T. Lill Progress and perspectives in the study of ecological specialization, with emphasis on insect-plant interactions. Ecology 93: Greeney H.F., Dyer L.A., and Smilanich A.M Feeding by lepidopteran larvae is dangerous: A review of caterpillars chemical, physiological, morphological, and behavioral defenses against natural enemies. Invertebrate Survival Journal 9:7-34. Dyer, L.A., Carson, W.P., Leigh, E.G Insect Outbreaks in Tropical Forests: Patterns, Mechanisms, and Consequences. In: Barbosa, P., Letourneau, D.K. and Agrawal, A.A. Insect Outbreaks Revisited. Wiley-Blackwell, New Jersey.

17 Inclan, D.J. and Stireman III, J.O Revision of the genus Erythromelana Townsend (Diptera: Tachinidae) and analysis of its phylogeny and diversification. Zootaxa 3621: Grey literature and other dissemination "An ecological perspective on natural products chemistry and synthesis.", L. Dyer, University of Sao Paulo, Department of Chemistry, Brazil. (September 2012). "Interaction diversity, biological control, and pest physiology in tropical agriculture.", L. Dyer, International Congress of Biotechnology and Biodiversity., Centro de Investigaciones Biotecnologicas.. (May 2012). "Ecology and evolution of chemically mediated interactions between plants, herbivores, and natural enemies.", L. Dyer, University of California, Berkeley, Department of Integrative Biology. (March 2012). SECTION THREE: Anything else Project funding Collaborative Research: Caterpillars and Parasitoids in the Eastern Andes of Ecuador. National Science Foundation. $1,540,000 (total) $780,000 (Dyer) $320,000 (Whitfield) $180,000 (Shaw) $180,000 (Stireman) $180,000 (Walla); June 2007 May Supports the caterpillar project in Ecuador. Dyer, Lee (Principal), O'Brien, J J (Principal), Richards, J L (Principal). "Patterns and Processes: Monitoring and Understanding Plant Diversity in Frequently Burned Longleaf Pine Landscapes.", Sponsored by Department of Defense, Federal, $ (total) $ (Dyer); Date Awarded: August 2012; End Date: July 2017 Dyer, Lee (Co-Principal), Forister, Matthew L (Co-Principal), Smilanich, A M (Principal), Whitfield, J B (Co-Principal), Jeffrey, Christopher (Co-Principal). "Collaborative research: Phylogenetic cascades and the evolution of tropical diversity in a system of plants, caterpillars, and parasitoids", Sponsored by NSF, Federal, $ Acknowledgements We first thank all of the superb Earthwatch volunteers for hard work, patience, sharing their skills, and producing very high quality ecological data. The support of Earthwatch Institute and all the quality staff there is also greatly appreciated. This study was co-funded by NSF grants DEB , DEB , DEB , DEB , the Department of Defense, and the University of Nevada. Our projects would not have functioned without

18 expert assistance from many field technicians and colleagues who helped in the field and laboratory, gave lectures to volunteers, and discussed ideas with us; these include: N. Pardikes, A. Glassmire, C. Morrison, M. Robinson, G. Blaustein, W. Lumpkin, L. Robinson, J. Miller, S. Rab-Green, J. Jahner, R. Lindgren, A. Dietrick, K. Krauss, M. Forister, R. Hazen, H. Greeney, D. Wagner, M. Singer, L. Salazar Vega, W. Simbaña, J. Simbaña, T. Walla, K. Fredrickson, T. Barber, H. Garcia Lopez, W. Simbaña, M. Ryan, M. Fox, T. Massad, and C. Pearson.