2012

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-2011-SCI-0032

Apr 15, 2011

Dec 31, 2012

Apr 15, 2011

Dec 31, 2012

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 can cause dramatic changes in ecosystems and is, besides climatic change, one of the main factors responsible for the global loss of species diversity. In North America non-indigenous earthworm species provide a complex and instructive example of the possible consequences of deliberately or unintentionally introduced species. European as well as Asian earthworms are known to alter soil structure, seed banks, plant communities and vegetation cover, influence microbial communities and change the composition of the soil living invertebrates.
This project concentrates on the Asian earthworm Amynthas agrestis (Goto and Hatai 1899) (Oligochaeta, Megascolicidae), which has established populations alongside roads, parking areas and some hiking trails. First studies indicated changes in the soil structure and an impact on the highly diverse diplopod fauna of the National Park (Snyder et al. 2011). As earthworms are well known to be an important food source for many invertebrates and vertebrates, it is expected that there are sever impacts on the native predator community. There are three main questions to answer during this projects (i) Does A. agrestis induced changes in composition and/or dominance structure of the native predator community? (ii) Which of the native generalist predators feed on the invading Asian earthworms? (iii) Does A. agrestis influence the prey spectrum of predators and thus the food-web established in the National Park?
The focus of the study during the first year (2010) was the detection of areas invaded by A. agrestis and the identification of the species communities at selected research areas comparing invaded and non-invaded sites. During the second summer (2011) we (i) conducted extensive feeding experiments with beetles, scolopenders and salamanders, which enabled the development of non-invasive investigation methods to study the diets of these predators and (ii) we collected carabid beetles to obtain gut content samples for diet analyses.
During the summer 2012 we mainly collected salamanders to obtain faecal pellets. These faecal pellets will tell us about the diet of the salamanders. Besides we finished the collection of soil-living animals for the description of the invertebrate species communities, collected additional carabid beetles for gut content analyses and finally dismantled the research sites by removing all traps and data-logger.

The analyses to detect correlations between the presence of A. agrestis and the invertebrate species communities are still under progress. The final identification of important invertebrate groups is delayed, due to a lack of identification literature and taxonomic specialists. A molecular key for the identification of juvenile earthworm has been developed and successfully applied to half of the collected specimen. An additional project has been approved to identify Geophilomorpha and there are on-going discussions with specialists about the identification of some less abundant taxa.
Based on the feeding experiment in the second summer we developed reliable non-invasive approaches to analyse the diets of carabid-beetles and salamanders. Details about these methods are currently prepared for publication. The methods have been applied to analyse the gut content and faecal samples of carabid beetles from research sites invaded and not-invaded by A. agrestis. Preliminary results indicate that all abundant epigeic carabid beetles except those of the genus Sphaeroderus feed on the invasive Asian earthworms, but there is no significant influence on the overall diet of the beetle predators. Final results and analyses on the diet of carabid beetles and of salamanders are expected until the end of 2013.

Yes

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