(1) there are more generalist parasites in tropical versus temperate forests,
(2) there are more specialist parasites in second-growth than mature tropical forest,
(3) there are fewer trophic levels in tropical food webs than in less diverse temperate forests,
i. e., parasites and hyperparasites are rarer in tropical than temperate forests,
(4) seasonal flight patterns of parasitic wasps respond to host phenologies rather than to plant phenologies or to changes in abiotic factors such as rainfall,
(5) weaker-flying (smaller) species are rarer in tropical areas in which hosts are more dispersed than in temperate areas.
For 7 subfamilies (Agathadinae, Campopleginae, Ichneumoninae, Mesochorinae, Metopiinae, Pimplinae and Rogadinae), we will estimate species richness (alpha diversity) at La Selva and BCI/Pipeline Road and compare species composition between the sites. Thus, we will quantify changes in community composition as a function of distance (beta diversity) and extrapolate to obtain global estimates of species richness. To interpret our trapping data with regard to the biologies of selected hosts and parasitoids, we propose supplemental research on (1) interactions involving Dipteryx trees, their herbivores and parasitoids, and (2), Rogas parasitoids that feed on a number of lepidopteran families. We aim to facilitate a larger study to compare additional taxa between La Selva and BCI and to gain a more integrated understanding of the interactions of the plants, herbivores, parasites and hyperparasites in tropical forests.
In collaboration with Drs. David Smith, David Wahl, and Donald Windsor, we have
assembled a team of ecologists and systematists to test hypotheses related to insect diversity in
temperate and tropical forests. Our broad scientific goals include (1) comparing insect diversity
within habitats, between habitats and over distance, (2) understanding the trophic structure of
temperate and tropical landscapes, (3) investigating how life history parameters, abiotic factors,
and heterogeneity in plant and herbivore densities affect the abundance, movement and species
richness of parasitic wasps, and how these affect lower trophic levels, and ultimately (4),
understanding the ecological processes that contribute to the evolution and maintenance of high
biodiversity in the tropics. Supported by the University of Georgia, Athens (UGA), Agriculture
Canada, STRI's Environmental Sciences Program, the USDA Forest Service, and NSF's Biotic
Surveys and Inventories Program, we have run 44 Malaise traps at 6 sites in North America
(Ontario, Maryland, Georgia and Florida) and 2 sites in Panama (BCI and Nusagandi) for a total of
over 95 trap-years. We have an efficient system for processing specimens and have mounted over
165,000 Hymenoptera (ants, bees, wasps and sawflies) since 1992.
The superfamily Ichneumonoidea contains the families Braconidae and Ichneumonidae, 64 subfamilies, and an estimated 100,000 species (Wahl & Sharkey, 1993; Gauld & Bolton, 1988). These biologically diverse subfamilies differ significantly in many life history variables and lend themselves to comparative ecological and evolutionary studies. The majority are primary parasitoids of holometabolous insects. Others, such as the ichneumonid subfamily Mesochorinae, are hyperparasites and attack other parasitoids. Generally species can be categorized at the generic or subfamily level as either host specialists or generalists. Koinobiont parasitoids allow hosts to grow after oviposition. Because koinobionts must coexist with their host and overcome specialized immunological and chemical defenses, they have more specialized host ranges than idiobiont parasitoids that kill or paralyze hosts immediately (Salt, 1968; Askew & Shaw, 1986; Gauld et al., 1992). Thus, koinobioncy or idiobioncy predicts whether a species is a specialist or generalist, respectively (Askew & Shaw, 1986; Gauld & Bolton 1988; Pschorn-Walcher & Altenhofer 1989; Sheehan & Hawkins 1991; Kato 1994; Gaasch, Pickering & Wahl 1995). We will use koinobiont to idiobiont ratios in testing Hypotheses (1) and (2).
Numerous studies document and attempt to explain why floral and faunal diversity generally increase towards the equator (Dobzhansky 1950, Darlington 1957, Miller 1958, Fischer 1960, Simpson 1964, Pianka 1966, Goodman 1975, Stevens 1989). Certain taxa of parasitic Hymenoptera are notable exceptions to this pattern. Owen and Owen (1974) first documented that the trend for the Ichneumonidae runs contrary to most plant and insect families, reporting more species in samples from temperate Europe than tropical Africa. Because the forces governing parasitoid distribution are poorly defined, the processes that determine the relationship between species richness and latitude are unclear (Hawkins, Shaw & Askew, 1992). In contrast to the Ichneumonidae, other parasitic families such as the Chalcididae (Hespenheide 1979) and the Encyrtidae (Noyes 1989) appear to be more speciose in the tropics. Resource fragmentation (Janzen 1981, Janzen & Pond 1975, Askew & Shaw 1986, Hawkins 1990), plant-host-parasitoid interactions (Hawkins & Lawton 1987; Gauld, Gaston & Janzen 1992; Price 1973, 1991; Gaasch, Pickering & Wahl 1995; Gaasch & Pickering 1995), competition (Hawkins, 1990), predation (Rathcke & Price 1976) and environmental factors (Townes, 1972; Hawkins, 1990; Gauld, 1991; Hawkins et al. 1992) may influence parasitoid diversity. A goal of our research is to quantify and test the merits of these factors.
Janzen (1981) analyzed published distribution maps of North American ichneumonid species and concluded that their peak species richness lies at mid-latitudes between 38 and 42 N. He hypothesized that as host species richness increases towards the equator, densities of individual host species decrease, and consequently, it is increasingly difficult for specialized parasitoids to find hosts. This Resource Fragmentation Hypothesis (RFH) predicts a decrease in parasitoid species richness in areas of high host diversity, because species with narrow host ranges drop out. Thus, fewer koinobionts are expected in the tropics than in temperate areas. As a corollary to the RFH, we predict that there are fewer hyperparasites in tropical than temperate forests. Thus, Hypotheses (1), (3) and (5) stem from the RFH. In testing these, we will analyze the relative composition of subfamilies within our samples. For example, regarding Hypothesis (3), we predict fewer mesochorine hyperparasites in the tropics relative to other ichneumonoid subfamilies.
More recently, Gauld and Gaston examined latitudinal trends for a number of ichneumonid subfamilies. Their results are equivocal. Some subfamilies appear more diverse in the tropics; others, in temperate areas. Gauld (1986) presented evidence that Australian collections have a slight decrease in the overall ichneumonid diversity nearer the equator. This is in part because of the absence in northern Australia of taxa such as the Ctenopelmetinae that feed on sawflies--a relatively rare taxa in the tropics. Gauld (1987) examined 5 major taxa in Finland (70 N), England (53 N), Okinawa (27 N), Santa Rosa National Park, Costa Rica (11 N) and Brunei (4 N). He reports higher diversity for the Mesostenini, Pimplini and Ophioninae towards the equator and lower diversity of sawfly parasitoids away from it. Gauld (1991) and Gaston & Gauld (1993) consider the lower pimpliformes from an extensive survey of Costa Rica. They show that local and regional richness of these wasps is generally higher in the tropics than elsewhere. The proposed research extends Gauld and Gaston's subfamily approach and examines additional subfamilies using standardized sampling across sites.
Landscape effects further complicate understanding parasitoid community composition. Spatial heterogeneity, movement between habitats, and ecological succession are critical processes in the development of landscapes and the ecological processes within them (Connell and Slatyer 1977; Turner 1988, 1989; Dunning et al. 1992; Turner et al. 1993; McCook 1994; Pulliam & Dunning 1994). Community structure in one habitat, for example, can be confounded by movement between source areas of positive population growth and sinks with negative growth (Pulliam 1988; Pulliam & Danielson 1991) and, at a larger scale, between local and regional faunas (Wilson 1988). Relatively little is known about how landscape structure affects community interactions and diversity. Ecological studies are typically conducted within habitats and do not address emergent landscape properties such as dispersal. In patchworks of fields and forest stands in different stages of succession, transient individuals passing through habitats may be an important part of alpha diversity and play havoc with conventional attempts to understand communities in the context of trophic interactions within habitats. Clearly, to understand biodiversity within habitat patches, landscapes or regions, we must learn how species move within and between habitats in searching for resources and mates. Wayman (1994) presents evidence that the sex ratio of specimens caught in Malaise traps may indicate whether a species is using a habitat or moving through it. Our proposed rearing of parasitoids from Dipteryx flowers parallels Wayman's temperate study and may confirm it. We will test whether trap sex ratios reflect habitat use for the tropical parasitoids that we rear. Thus, in addition to host records, we hope to use the sex ratio and relative abundance of species in Malaise trap samples to infer which species are using particular habitats and which are transients.
There is general support for a bottom-up theory that vegetation influences upper trophic levels (Southwood 1975, 1977, 1988; Southwood et al. 1979, 1983; Brown & Southwood 1983; Brown 1984; Hunter & Price 1992; Power 1992; Price 1992), and that insect species composition changes with ecological succession (Southwood et al. 1979; Ashmole et al. 1992; Sanderson 1992; Kato 1994). Parasitoid complexes develop in relation to plant succession (Price 1973, 1991; Gathman et al. 1994). Early-successional plants are often ephemeral and defended by toxins such as alkaloids, mustard oils and cardenolides while later-successional plants are often more evenly dispersed and defended by digestibility reducers such as tannins, lignins and high fiber content (Feeny 1976; Rhoades and Cates 1976; Coley et al. 1985; Coley and Aide 1991). Parasitoids that occur earlier in succession must be specialized to combat the toxin sequestration by herbivores, while parasitoids that occur later in succession can be more generalized without the risk of sequestered toxins in the herbivores (Price 1991). Price (1991) predicted that early successional stages have a predominance of specialists (koinobionts) and that the proportion of generalists (idiobionts) increases in later stages of succession. Gaasch, Pickering and Wahl (1995) found strong evidence in support of this prediction. For 22 ichneumonid subfamilies in a temperate landscape, in terms of the number of individuals, they found significantly more idiobionts in mature stands and more koinobionts in early-stages of succession. In terms of species composition, rather than individuals, this was not true. Ichneumonid species appear to be well dispersed throughout the landscape, while their members are often concentrated in particular habitats. Our Hypothesis (2) concerns whether tropical landscapes are similar in these regards.
(2) Seasonality -- We have completed 1-2 year studies of the flight phenology of the Ichneumonoidea and alate ants on BCI (Wright 1995), of 22 ichneumonid subfamilies in Georgia (Gaasch & Pickering 1995), and of the Campopleginae and Ichneumoninae at all our North American sites (Lockard 1995; Wayman 1994). Gaasch & Pickering (1995) speculate that ichneumonids fly in response to host phenologies rather than abiotic factors, per se. We propose to examine the flight phenology of all ichneumonoid subfamilies on BCI and at La Selva. The difference in rainfall patterns between the two sites gives us the opportunity to compare subfamilies under different environmental conditions in the tropics. How much does BCI's harsher dry season affect their seasonality? Does the seasonality of species that attack folivorous lepidoptera larvae, for example, differ from species that attack fungus-feeding beetles? Ultimately, we aim to link flight phenology with the availability of specific hosts using rearing data.
(3) Second Tropical Site -- In addition to the opportunities that La Selva offers us for between site comparisons with BCI, it will provide us with an essential second tropical site to compare with our 6 sites in eastern North America. This aspect of the study has two facets. We propose to (a) compare the subfamily composition across sites with regard to certain life history variables (e. g., host taxa, koinobioncy versus idiobioncy, flight ability (wing length:body size), primary parasitism versus hyperparasitism, diurnal versus nocturnal flight, sex ratio), and (b) compare communities in mature and second growth areas, thus addressing the role of succession as a confounding variable in tropical versus temperate comparisons.
(4) Pooled Expertise -- Our research will benefit from shared information and stronger interactions with individuals working in Costa Rica. Because of the systematic work on Costa Rican wasps by Drs. Gauld, Hanson, Shaw and Ugalde, the Costa Rican fauna is generally better known. The reference collections of Project ALAS, the Universidad de Costa Rica and INBio are valuable resources for our work. Individuals working with ALAS, most notably Drs. Longino and Hanson, could help us considerably. For example, Dr. Sharkey has arranged for funding for Dr. Hanson to have the braconids from ALAS processed for us. Dr. Janzen should be able to provide us with valuable information on reared Costa Rican material that links host and parasitoid species. Such data will help us understand the natural history on BCI. In return, we will reciprocate with information and specimens we collect. We are already collaborating with Drs. Shaw and Wahl on systematic work using specimens from both Costa Rica and Panama.
(2) Sorting -- We will mount all ichneumonoids and give each a conventional label and unique barcode. We will store residual taxa in ethanol and make them available to other investigators. We will deposit reference material at the end of the study at the Canadian National Collection, American Entomological Institute, UGA, INBio, STRI, Universidad de Panama and in institutional collections designated by collaborating systematists.
(3) Identification -- We will sort all ichneumonoids to subfamily and the 7 subfamilies listed earlier to species. We will make specimens in taxa being worked on by other ichneumonoid systematists available to them. Thus, it is likely that several additional subfamilies will eventually be identified to species. We will record the sex of all ichneumonoids.
(4) Analysis -- We will store data in a UNIX database and analyze them by the methods in Cowell & Coddington (1994), Kay (1994), Lockard (1995), and Gaasch, Pickering & Wahl (1995).
(5) Dipteryx system -- Last summer, we put Malaise traps in the canopy of 2 Dipteryx and 2
Anacardium trees on BCI. These are paired with ground traps. With Dipteryx, we propose to
study the parasites associated with the lepidoptera larvae that cause flowers to abort. Dr. Windsor
has done preliminary work on this system and will collaborate with us. By collecting Dipteryx
flowers at La Selva and BCI, we propose to rear parasitoids and compare their sex ratios and
phenologies with those of same species in the Malaise and light traps. Thus, we will rear large
numbers of parasitoids and link their biology to our trapping data.
(6) Rearing records -- A focal taxon in our study is the braconid genus Rogas. To date we have trapped 54 species on BCI and have got rearing records from Panama for 4 species, only two of which were also trapped. While looking for Rogas in the forest would be too time consuming, we anticipate that we will be able to a get a much larger sample of rearing information from individuals working with lepidoptera and ultimately start to link the trapped species with their natural histories.
The resulting data will permit us to test the hypotheses concerning community structure, succession, trophic interactions, seasonality, and life history traits as outlined in the Overview.
In the summer and fall of 1996, we propose to meet with potential collaborators, visit potential study sites, examine existing collections, and plan and write grant proposals. The above Methods outline our base plan for studying Ichnumonoidea at La Selva and BCI/Pipeline Road. This base plan will be expanded to include additional taxa, trophic levels and sites depending on our ability to attract additional collaborators and students and justify additional funds. Over 40 systematists have agreed to help in the identification of Hymenoptera, Coleoptera and Diptera from our existing traps. Many of these individuals may wish to collaborate on a BCI-La Selva comparison. Our primary goal in 1996 will be to submit an NSF proposal with STRI and OTS personnel for funding in 1997. We propose to do 2 years of field work starting in the summer of 1997 and anticipate completing the sorting and analysis 2 years after the Mellon award ends.
Phone: 706-542-1115 FAX: 706-542-3344 E-mail: firstname.lastname@example.org
B.S., Honors Biology with High Honors, University of Illinois, 1973
A. M., Biology, Harvard University, 1976
Ph. D., Biology, Harvard University, 1980
1979-1981 Miller Postdoctoral Fellow
Department of Entomological Sciences, University of California, Berkeley
1981-1982 Research Associate
Div. of Entomology & Parasitology, University of California, Berkeley
1982-1984 Postgraduate Research Entomologist
Div. of Biological Control, University of California, Berkeley
1984- Faculty Member
University of Georgia, Athens
Department of Entomology (1984-1995)
Institute of Ecology (1994- )
1973 Bronze Tablet, University of Illinois
1974-1979 Richmond Fellow, Harvard University
1976-1977 Predoctoral Fellowship, Smithsonian Tropical Research Institute
1979-1981 Postdoctoral Fellowship, Miller Institute for Basic Research in Science,
University of California, Berkeley
1991 Outstanding Conference Paper Presentation, GRASS Users Conference, Berkeley
1994 Special Sandy Beaver Award for Teaching Excellence
University of Georgia
Biodiversity, trophic interactions, landscape ecology, natural history of parasitic wasps
My research focuses on community structure, host-parasite interactions, and the exploitation of patchy resources. I study ecological and evolutionary questions associated with how individuals, populations and communities use host resources. What regulates insect population abundance and species diversity? How much does weather and the surrounding landscape determine the outcome of interactions? Through comparative field studies at temperate and tropical sites, I am testing the importance of such factors as habitat type, climate, land-use practices and landscape effects on community composition, structure and stability of parasitic wasps and their hosts.
SUPPORT RECEIVED since 1989 totals $555,000 including the current project:
Pickering J. 1995-1996. Calibration of Malaise traps for studying insect diversity. Biotic
Surveys and Inventories Program, The National Science Foundation (DEB-9522581)
RELEVANT THESES DIRECTED:
Crawford, Kelly B. 1994. Biodiversity, abundance, and distribution of Rogadinae (Hymenoptera: Braconidae) in a Panamanian tropical forest and North American temperate habitats. Senior honors thesis, Univ. of Georgia, Athens, 69pp.
Gaasch, Christine M. 1996. Flight phenology and species distribution of parasitic wasps in a heterogeneous landscape in Georgia's piedmont, with special reference to the Ichneumoninae and Campopleginae (Hymenoptera: Ichneumonidae). M. S. thesis, Univ. of Georgia, Athens, 200pp.
Kay, Melanie J. 1994. Estimating the biodiversity of Rogas (Hymenoptera: Braconidae) in a tropical moist forest in Panama using Malaise and light trap samples. Senior honors thesis, Univ. of Georgia, Athens, 61pp.
Lockard, Elizabeth I. 1995. Biodiversity and geographic distributions of parasitic Hymenoptera (Ichneumonidae: Campopleginae and Ichneumoninae) along a latitudinal gradient in eastern North America. M. S. thesis, Univ. of Georgia, Athens, 233pp.
Middleton, Sarah M. 1994. Species richness and abundance of sawflies (Hymenoptera: Symphyta) in different habitats along a latitudinal gradient from Panama to Canada. Senior honors thesis, Univ. of Georgia, Athens, 53pp.
Wayman, Linda D. 1994. Spatial distribution and sex ratios of parasitic Hymenoptera (Ichneumonidae: Campopleginae and Ichneumoninae; Braconidae: Aphidius ervi) in a distrurbed Georgia piedmont landscape. M. S. thesis, Univ. of Georgia, Athens, 123pp.
Wright, Lisa M. 1995. Seasonality of the Ichneumonoidea and alate Formicidae in a tropical moist forest at Barro Colorado Island, Panama. Senior honors thesis, Univ. of Georgia, Athens, 85pp.
Pickering, J. 1980. Larval competition and brood sex ratios in the gregarious parasitoid Pachysomoides stupidus. Nature 283: 291-292.
Getz, W. M., and J. Pickering. 1983. Epidemic models: thresholds and population regulation. American Naturalist 121: 892-898.
Holt, R. D., and J. Pickering. 1985. Infectious disease and species coexistence: a model of Lotka-Volterra form. American Naturalist 126: 196-211.
Pickering, J., J. A. Wiley, N. S. Padian, L. E. Lieb, D. F. Echenberg and J. Walker. 1986. Modeling the incidence of acquired immunodeficiency syndrome (AIDS) in San Francisco, Los Angeles, and New York. Mathematical Modelling 7: 661-688.
Pickering, J., W. W. Hargrove, J. D. Dutcher and H C Ellis. 1990. RAIN: A novel approach to computer-aided decision making in agriculture and forestry. Computers and Electronics in Agriculture 4: 275-285.
Pickering, J., J. D. Dutcher and B. S. Ekbom. 1990. The effect of a fungicide on fungal-induced mortality of pecan aphids (Homoptera: Aphididae) in the field. J. Economic Entomology 83: 181-1805.
Wenzel, J. W., and J. Pickering. 1991. Cooperative foraging, productivity, and the central limit theorem. Proc. Nat. Acad. Sci. USA 88: 36-38.
Pickering, J. and A. P. Gutierrez. 1991. Differential impact of the pathogen Pandora neoaphidis (R. & H.) Humber (Zygomycetes: Entomophthorales) on the species composition of Acyrthosiphon aphids in alfalfa. Canadian Entomologist 123: 315-320.
Holzman, S., M. J. Conroy and J. Pickering. 1992. Home Range, movements, and habitat use of coyotes in southcentral Georgia. J. Wildlife Management 56: 139-146.
Hargrove, W. W. and J. Pickering. 1992. Pseudoreplication: a sine qua non for regional ecology. Landscape Ecology 6: 251-258.
Camann, M. A., A. K. Culbreath, J. Pickering, J. W. Todd and J. W. Demski. 1995. Spatial and temporal patterns of spotted wilt epidemics in peanut. Phytopatholohy 85:879-885. Curriculum Vitae
MICHAEL JOSEPH SHARKEY
Biological Resources Division/CLBRR
Ottawa, Ontario K1A OC6
B. Sc., (hons.), University of Guelph, Guelph, Ontario, 1977
M. Sc., Macdonald College, McGill University, Ste. Anne de Bellevue, P.Q. 1981
Ph. D., Macdonald College, McGill University, Ste. Anne de Bellevue, P.Q. 1983
1979 Curatorial Assistant
Lyman Museum, McGill University, St. Anne de Bellavue
1978-1981 Teaching assistant
Macdonald College, McGill University, St. Anne de Bellavue
1981-1983 Biologist, Agriculture Canada
1983- Research Scientist, Agriculture Canada
1987- Adjunct Professor, McGill University, Montreal
1989-1990 Research Fellow, Japanese Science and Technology Agency
The major thrust of my research is in the systematics of parasitic wasps in the family Braconidae. I have also published on and maintain a keen interest in theoretical systematics, especially numerical cladistics. More recently I have become involved in several biodiversity studies that involve sampling large numbers of Braconidae. Collecting Braconidae is an activity that I ardently indulge in both to test phylogenetic and biogeographical hypotheses and to add to my primary data base, museum specimens. I have collected extensively in the neotropics (Guatemala, Mexico, Ecuador), the old world tropics (Malaysia), the Palearctic (Japan, Europe) and many localities in the Nearctic realm. As a result of this experience I have acquired some expertise in designing and operating sampling systems for Hymenoptera.
Sharkey, M. J. 1983. Marjoriella, a new Neotropical genus of Agathidinae (Hymenoptera: Braconidae). Cont. Am. Ent. Inst. 20: 90-93.
Sharkey, M. J. 1985. Notes on the genera Bassus Fabricus and Agathis Latreille, with a description of Bassus arthurellus n. sp. (Hymenoptera: Braconidae). Can. Ent. 117: 1497-1502.
Sharkey, M. J. 1987. Pharpa, a new genus of Neotropical Agathidinae (Hymenoptera: Braconidae) with a discussion of phylogenetic relationships. Can. Ent. 118: 1231-1239.
Sharkey, M. J., A. Arthur, G. Bisdee, C. Yoshimoto, J. Barron. 1987. The parasitic
Hymenoptera associated with sunflower (Helianthus spp.) in mid-western Canada. Can. Ent. 119: 611-628.
Sharkey, M. J. 1988. A taxonomic revision of Alabagrus (Hymenoptera: Braconidae: Agathidinae). Bull. Brit. Mus. Nat. Hist. 57: 311-437.
Sharkey, M. J. 1989. A hypothesis-independent method of character weighting for cladistic analysis. Cladistics 5: 63-86.
Chou, L. and M. J. Sharkey. 1989. The Braconidae (Hymenoptera) of Taiwan. I. Agathidinae. J. Taiwan Mus. 42: 147-223.
Sharkey, M. J. 1990. A revision of Zacremnops (Hymenoptera: Braconidae: Agathidinae). Proc. Ent. Soc. Wash. 92: 561-570.
Sharkey, M. J. 1992. Cladistics and tribal classification of the Agathidinae (Hymenoptera: Braconidae). J. Nat. Hist. 26: 425-447.
Sharkey, M. J. 1993. Superfamily Braconidae. pp. 362-394. In: H. Goulet and J.T. Huber (eds.), Hymenoptera of the world, an identification guide to families. Agriculture Canada Research Branch Monograph No. 1894E, 668pp.
Sharkey, M. J. 1993. Exact indices, criteria to select from minimum tree lengths. Cladistics 9: 211-222.
Sharkey, M. J. 1994. Discriminate compatibility measures and the reduction routine. Syst. Biol. 43: 526-542.
Sharkey, M. J. and R.. A. Wharton. 1994. A revision of the genera of the world Ichneutinae (Hymenoptera: Braconidae). J. Natural History 28: 873-912.
Sharkey, M. J. and D. H. Janzen. 1995. Review of the world species of Sigalphus (Hymenoptera: Braconidae: Sigalphinae) and biology of Sigalphus romeroi, new species. J. Hym. Res. 4: 99-109.