2010

Great Smoky Mountains NP

Research

Anita Juen

00435125075692

Anita Juen
University of Innsbruck, Institute of Ecology
Technikerstrasse 25
A-6020 Innsbruck
A-6020
Austria

 

anita.juen@uibk.ac.at

Impact of biotic invasion on food web interactions: Tracking predation on native and invasive earthworms by molecular techniques

GRSM-01005

GRSM-2010-SCI-0016

May 01, 2010

Dec 31, 2010

May 01, 2010

Dec 31, 2010

Continuing

___ A final report has been provided to the park or will be provided to the park within the next two years

___ Copies of field notes, data files, photos, or other study records, as agreed, have been provided to the park

___ All collected and retained specimens and retained material originating from such specimens have been cataloged into the NPS catalog system and NPS has processed loan agreements as needed.

Research

Ecology (Aquatic, Marine, Terrestrial)

The introduction of foreign species is one of the most important causes of global change. The consequences of non-indigenous species for native ecosystems are divers, ranging from minor impacts to dramatic changes in ecosystems and sever losses of local species diversity.
Earthworms are among the many examples of deliberately or unintentionally introduced species that can change ecosystems dramatically. They are well known for their economic impact on soil structure, nutrient cycle and crop yield in agricultural habitats and are utilised for vermicomposting and waste management. Therefore, earthworms have been shipped all over the world and have been released repeatedly sometimes in high numbers. When non-indigenous earthworms became invasive and spread into natural habitats it was often ignored but recent studies found that they can alter soil structure, seed banks, plant communities and vegetation cover, influence microbial communities and change the composition of the soil living invertebrates.
The proposed project concentrates on the Asian earthworm Amynthas agrestis (Oligochaeta, Megascolicidae), which has been introduced to the Great Smoky Mountain National Park (GSMNP). First studies indicated changes in the soil structure and an impact on the highly diverse diplopod fauna of the National Park. As earthworms are well known to be an important food source for many invertebrates and vertebrates, it is very likely that there are sever impacts on the native predator community. This is a topic that deserves more attention, but difficulties to track trophic interactions among earthworms and their predators have long hampered such studies. Many of these difficulties can be overcome by recently developed molecular tools and this allows investigating whether A. agrestis (i) changes composition and/or dominance structure of the native predator community (ii) is accepted as food by native generalist predators and (iii) changes the prey spectrum of predators and the food-web established in the National Park. The focus of this project is on invertebrate predators, mainly predatory beetles and centipedes. However, if we are successful in developing a non-lethal, harmless approach to analyse the diet of salamanders, we will include salamanders in this studies.
The primary objective of the first year was the characterisation of the invertebrate community at invaded and un-invaded sites. It was essential to find appropriate study areas that provide habitats invaded and not-invaded by A. agrestis and it was necessary to identify the invertebrates present at these sites. Additional experiments with selected invertebrate predators and salamanders should provide important information to refine the methodological approaches for the subsequent molecular studies on the predator-prey interactions.

The following results are all preliminary, as the analyses are still going on and may take several more months to be finished.
Altogether 87 sites have been search for the presence of A. agrestis and other earthworms. Fifty nine sites were searched by turning litter and logs and 12 sites have been probed using the octet device. Sixteen sites have been sampled by a specially developed sample design to confirm the absence of A. agrestis. This special sample design included five extractions using the octet device and an intensive hand search within an area of about 40m in diameter. Amynthas has been found on 62 of the searched sites. Many of the collected individuals are juveniles that cannot be identified morphologically to species level. Based on found adult individuals we know that there are two abundant species A. agrestis and A. corticis. A molecular marker to identify the juveniles is currently under development. So far we can verify the presence of A. agrestis at Elkmont, at Tremont, at Deep Creek, along Little River Road near Fighting Creek Gap and near Sugarlands Visitor Center, at Huskey Gap Trail near HW 441, around Twin Creeks Research Station, at Old Sugarlands Trail and along Greenbrier Road. Based on these findings we established 15 sites, 7 sites invaded by A. agrestis and 8 sites free of A. agrestis.
To describe the invertebrate community at the selected sites, we established pitfall traps (one at each site) and searched litter and soil-samples by hand. The identification of the collected animals is not finished yet. Altogether 13,434 specimens have been collected, the most abundant taxa being Coleoptera, Formicidae and Diplopoda, followed by Chilopoda, Oligochaeta, Orthoptera and Aranae. The most abundant predators among the epigeic invertebrate community identified so far are the carabid beetles Carabus goryi Dejean and Cyclotrachelus blatchleyi (Casey), and the Scolopendromorpha Scolopocryptops sexspinosus (Say) and S. nigridus McNeill. Three more taxa comprise important and abundant predators, Staphylinidae, Geophilomorpha and Opilionidae. Community analysis will be performed as soon as the species lists are available by a correspondence analysis including abiotic factors and vegetation data collected from the 15 sites.
Several small experiments provided information to improve methodological approaches. One question important to answer was: “How to ship samples for DNA analysis”. The most often suggested methods are (i) conserved in ethanol, (ii) frozen and (iii) freeze-dried. Hundred eighty samples of earthworm tissue digested between 0 and 50min in 1% bleach have been sent with each of the three shipping methods. Molecular analyses are still ongoing, but first results indicate that all three methods of shipping are possible.
A series of feeding experiments should help to develop non-lethal sampling approaches. Unfortunately these experiments could not be performed as planned due to time limits. Nevertheless preliminary experiments resulted in a method that enables us to collect the gut content of carabid beetles by forcing them to regurgitate. Similarly, experiments with three specimens of salamander indicated that it is possible to collect faecal samples and use these to study the diets of salamanders without harming them.

Yes

University of Innsbruck
Institute of Ecology
Technikerstrasse 25
6020 Innsbruck
Austria

$0.00

$40,760.00