The proposed project seeks to compare differences in parasitoid, host and plant communities between 1) xeric ridge and mesic coves, 2) old-growth and mature second-growth mixed deciduous cove forests, 3) and pine stands before and after fire in the Great Smoky Mountains National Park (GSMNP). Disturbances both natural and anthropogenic, influence community diversity within ecosystems. This proposal seeks to test two hypotheses: fire suppression lowers parasitoid diversity in previously fire maintained ecosystems, and second-growth forests are less species rich than old-growth forests. The project will focus on parasitic wasps in the superfamily Ichneumonoidea from both malaise trap samples and host rearing records. Plant communities within study sites will be sampled for between site comparisons. This project is a collaborative effort by the U.S. Park Service and the University of Georgia promoting ecological research and long-term monitoring. Seed money from Friends of the Great Smoky Mountains National Park (FGSMNP) was given to inventory selected taxa of parasitic wasps. The project began in April 1997 and seeks additional support to extend preliminary malaise trapping of ichneumonid parasitoids and link reared specimens from selected hosts.

Background and Rationale

Parasitoids, their hosts and host plants comprise a large portion of the world's biodivesity (Price 1980; Strong et al. 1984). The Hymenoptera are extremely species rich and economically important. Parasitoids comprise approximately 80% of the Hymenoptera developing on or in a wide variety of hosts and are important in regulating their host populations (Gauld and Bolton 1988). Cornell and Hawkins (1993) reported that parasitism was the most identifiable mortality in 30.8% of 123 holometabolous insect host species. Many parasitoids have also been shown to be important in biological control programs. Despite their importance in ecosystems, many species remain undescribed and little is known about how parasitoid species respond under variable patterns of disturbance (ie., logging and fire). Key points governing insect response to disturbance are dispersal and host selection behavior, and resource quality and quantity (Schowalter 1985). It is important to link host biologies in interpreting parasitoid trapping data. Therefore, this proposal seeks to extend preliminary malaise trapping of ichneumonid parasitoids and link reared specimens from selected hosts. This will allow for more accurate comparisons of parasitoid, host and host-plant species diversity between 1) old-growth and mature second-growth mixed deciduous cove forests, 3) and pine stands before and after fire in the Great Smoky Mountains National Park (GSMNP). This proposal seeks to test two hypotheses: fire suppression lowers parasitoid diversity in previously fire maintained ecosystems, and second-growth forests are less species rich than old-growth forests. By using standard collecting methods, we will have quantitative estimates of how effective these methods are at estimating parasitoid diversity locally and regionally (Colwell and Coddington 1994).

The Ichneumonidae, consisting of 35 subfamilies (Wahl 1993) and an estimated 60,000 species worldwide, are thought to be the most speciose family in the world, with the possible exception of the Curcuclionidae (Townes 1969). They are large parasitoids and very strong fliers. The subfamilies within the Ichneumonidae are highly diverse biologically including both idiobiont and koinobiont lifestyles (Askew and Shaw 1986). Idiobionts include endo- and ectoparasitoids, that kill or immobilize the host upon oviposition. The host is then consumed in the location and developmental stage it is in when attacked. Idiobiont endoparasites generally oviposit in concealed hosts in leaf litter or soil. Contrastingly, koinobionts allow for further host development to occur before the host is destroyed. Koinobiont endoparasitism allows the parasitoid to oviposit inside conspicuous hosts, while using the host's pupation concealment to secure continued development (Gauld 1988). This strategy requires the parasitoid to overcome the immunodefensive encapsulation system of the host leading to a more specialized host range (Salt 1968; Askew and Shaw 1986; Gauld et al. 1992). Idiobionts have a wider host range because they are often ectoparasitoids avoiding internal host defense (Spradberry 1968). Hence, ichneumonid koinobionts are considered specialists and idiobionts generalists (Askew and Shaw 1986; Gauld and Bolkton 1988; Pschorn-Walcher and Altenhofer 1989; Sheehan and Hawkins 1991; Kato 1994).

Comparisons of generalists and specialist ichneumonids in varying age loblolly pine stands by Gaasch et al. (1995) support Price's (1991) earlier prediction of more specialist (koinobionts) parasitoids in earlier successional stages with the proportions of generalists (idiobionts) increasing in later successional stages. For numbers of individuals in 22 ichneumonid subfamilies, Gaasch et al. (1995) reported more koinobionts in earlier successional stages and significantly more idiobionts in more mature stands. This was not true for the species composition between earlier and later successional stages. Ichneumonids may therefore be well distributed throughout the landscape, but congregate in specific habitats based on host availability. We would therefore expect shifts from more generalists in old-growth coves and old growth pine stands to more specialists in second growth coves. Host rearing records would help clarify which species are using the habitats and which are simply passing through.

The National Park Service (NPS) has had a policy of fire suppression in the GSMNP since the park opened in 1934. The park service seeks to reintroduce the natural fire regime within the GSMNP and manage this ecosystem within the boundaries of historical and ecological fire cycles. However, gaps in knowledge concerning the role of fire management still exist, including its role in maintaining deciduous forests, rare communities, vegetation composition and biodiversity (SAMAB 1996). The ecological effects of fire are extremely complex, and researchers often overlook the relationships between plants and animals with respect to fire regimes (Whelan 1995). Modification of disturbance patterns and predictable patch generation by human intervention (i.e., fire suppression) can alter landscapes yet little is known about how landscape structure changes (Baker 1992). This project seeks to fill gaps in knowledge about the role of fire in maintaining biodiversity of parasitoids.

Vegetation of the GSMNP has been well documented in R. H. Whittaker's (1956) classic study of population and community distributions along environmental gradients. There is support for the idea that vegetation influences upper trophic levels (Southwood 1975, 1977, 1988; Brown 1984; Crawley 1989; Hunter and Price 1992, Price 1992), and that disturbance may be a source of mortality for certain species through changes in temporal and spatial heterogeneity of habitats (Harmon et al. 1983, Bond and van Wilgen 1996, Runkle 1982, Denslow 1985). Forest communities can be viewed as open systems where interactions of disturbances, including variation in frequencies and intensities, and the life histories of species determine the pattern of succession in a given patch. In ecological time, maximum species diversity may therefore be expected in systems where disturbances are consistent with historical patterns (Denslow 1985).

Natural and anthropogenic disturbances have shaped plant communities of the GSMNP, although little is known about how disturbance influences higher trophic levels in the park. In protected coves, Runkle (1982) reported that even small disturbances, at the level of a single tree fall, were adequate to provide regeneration of light tolerant plant species. Larger scale disturbances may affect species colonization by reducing community heterogeneity and eliminating adequate refugia (Denslow 1985). Disturbance frequency, predictability, area, cycle and severity greatly influence plant community composition, and modification of disturbance patterns from activities such as fire suppression may result in shifts in distributions of both species and communities (Harmon et al. 1983). These shifts in species distributions may ultimately lead to the loss of species diversity (Denslow 1983). Parasitoid species richness of external feeders has been shown to increase in later successional stages with higher diversity associated with increasingly complex host plant architecture (Hawkins 1994). We would therefore expect higher parasitoid diversity in old-growth forests than in logged, second growth forests. By examining species richness under different disturbance regimes park managers can begin to address impacts of different disturbances on our protected lands.

Project Description

The GSMNP is over 500,000 acres and contains enormous biological diversity. It contains the largest stands of rare eastern old-growth forest, totaling over 100,000 acres. The flora and fauna are sampled at eight study sites within the GSMNP. Each site includes a 1-hectare plot in 2 old growth mesic coves: Porter's Creek and Ramsey's Cascade, 2 mature second-growth mesic coves: Goshen Prong and Meigs Post Prong, 2 xeric burn treatments and 2 xeric control plots: Lynn Hollow. Porter's Creek and Goshen Prong are matched in elevation (3400 ft.), aspect, slope and soil type. Ramsey's Cascade and Meigs Post Prong are similarly matched at a higher elevation of approximately 3800 ft. The second-growth cove stands are 70+ years-old. After one year of pre-burn sampling, two plots on the xeric ridge will be burned in the spring of 1998. Sampling of plant and parasitoid communities will continue after completion of the burn. Through standard collecting and databasing methods, we will be able to quantify effects on parasitoid diversity of 1) climate and seasonality, 2) forest age, 3) and fire suppression.

Methods

Malaise Trapping

Within each one hectare plot two malaise traps will be run continuously for two field seasons. The length of each field season will be determined by the flight activity of ichneumonids at each site. Collaborators will service each trap bi-weekly. Malaise traps are meshed fabric, open-sided, tent-like structures designed to collect flying insects in a container of 70% ethanol (Owen 1991). Our standard trapping method is the fine mesh (.33 mm) Townes-style Malaise trap (1972) from Sante Traps, Lexington, KY. This trap has been used as a standard method by Dr. John Pickering at UGA since 1991 to compare insect diversity between sites in Canada, USA, Costa Rica and Panama.

Specimen Preparation

All Ichneumonoids except the Orthocentrinae (Hymenoptera: Ichneumonidae) and the Alysiinae (Hymenoptera: Braconidae) will be mounted for identification. The Orthocentrinae and Alysiinae will be counted and databased separately from residual insects. Certain host taxa (ie, Coleoptera) may be identified, counted and databased as host rearing data become available. We will assign each specimen a conventional label, and a unique identifier linking that specimen to the database containing location, trap number, and sample dates. See Wayman (1994) for a detailed description of sorting techniques. Specimens collected during this project will be deposited at the natural history museum at the GSMNP and at UGA.

Rearing Records

In an effort to link parasitoid biologies with data from malaise trap samples this project proposes rearing parasitoids from selected hosts. Rearing studies will be conducted during peak ichneumonid flight periods recorded from malaise trap data (Figure 1). Those taxa targeted for collection will be based on known hosts of parasitoids active during peak flight. Host collecting efforts will be conducted within the one hectare plots at each of the study sites where malaise traps are located. Records of host plants and host instars will be noted with collection of parasitoid host material when known, and all host material will be kept after parasitoid emergence (Gauld and Bolton 1988).

Vegetation Studies

Plant diversity will be sampled in each one hectare plot in collaboration with the help of park botanists. Plots will be divided into 10 x 10 meter subplots and all vascular plants within the area will be recorded. Comparisons between burned and unburned sites at Lynn Hollow will be made to see how reintroduction of fire affects plant communities.

Database and Analysis

Each Ichneumonoid specimen will be mounted and receive two labels, one with traditional collecting information including a LOG_ID number, and a second consisting of a barcode label with a unique identifier. The barcode links each specimen to an electronic database that contains specific site, and taxonomic data. Reared material will be specified as such within the database for comparison with malaise trap material. Data collected from this work will be stored as part of the UGCA database established at UGA by John Pickering in 1991. The primary platform for the UGCA database is a Sun SparcUltra 140 workstation. The database can be accessed on the internet: Insect Diversity Project (IDP), http://dial.pick.uga.edu, under databases.

Data analysis will be completed using UNIX shell and the SPLUS (Becker 1988) programming environments. Six models for species estimations will be used to evaluate between site differences in parasitoid diversity: Eadie-Hofstee, Chao 1 and 2 (Chao 1984), Jackknife 1-5 (Burnham and Overton 1978, 1979), Lamas (Lamas et al. 1991), and the Ratio Method (Bailey 1952) reviewed by Colwell and Coddington (1994).

Time Table

We request support for three years, from September, 1998 - June, 2001. In the first year, we plan to finish processing the estimated 540 bulk malaise trap samples collected between April, 1997 - November 1997 and April, 1998 - November, 1998. Additional time may be need to sort and identify mounted ichneumonoid specimens. Host rearing studies will be conducted during peak flight periods determined from malaise trap samples at each study site for selected taxa. Preliminary results indicate peak flight for ichneumonoidea to be between 7 May - 18 June in the old - growth cove forests (Figure 1). Host rearing studies will be continued for two field seasons. Data tabulation and analysis will be started by the end of the summer, 2000. Expected graduation date is in June of 2001.

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