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| Titel |
Isotopes and trace elements as geo-location markers for biosecurity: determining the origin of exotic pests. |
| VerfasserIn |
Peter W. Holder, Karen Armstrong, Tim Clough, Russell Frew, Robert Van Hale, Joel A. Baker, Marc-Alban Millet |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038104
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| Zusammenfassung |
| Background. The benefits of accurate point of origin discrimination in biosecurity include
achieving appropriate operational responses in exotic pest eradication and post-border
incursion campaigns, and identifying risk pathways. Reading natural abundance
biogeochemical markers via mass spectrometry methods is a powerful tool for tracing
ecological pathways and provenance determination of agricultural products and items of
forensic interest. However, the application of these methods to trace insects – man’s most
damaging competitors – has been underutilised to date and our understanding in this field is
still in a phase of basic development.
Stable isotope ratio analyses using δ2H, δ13C have given spatial resolution in the
monarch butterfly, single host system in eastern North America. Subsequently, the
same method was employed in an attempt to determine the origin of important
biosecurity pests in New Zealand. However, the results were contentious as the
accuracy and limitations of the method in a biosecurity application were unknown.
Further investigation has shown the value of existing invertebrate stable isotope
geo-location methodology (i.e., using only two light elements) is tenuous in the
biosecurity context, where the sample sizes are usually only one or two insects, and the
specimens are generally polyphagous and accidentally introduced, and so from an
unknown and unpredictable place, point in time and host: The spatial distribution
of 2H in New Zealand may not be reliable over insect life-span time-scales; and
fractional variables are un-quantified and potentially overwhelm any New Zealand
signal. Further, the geo-location value of 13C is uncertain, especially for polyphagous
insects.
Research aims. The internationally distributed Helicoverpa armigera [Noctuidae] is
being used to examine the processes fundamental to the location-to-plant-to-insect
biogeochemical profile imprinting in phytophagous insects, including the turn over of
elements in adult insects, the influence of polyphagy and local variation in precipitation 2H.
This improved understanding is being applied to assess the validity of using heavy and light
element isotope ratio and trace element profiles to differentiate insects of New Zealand natal
origin from insects of exotic origin.
Results. An integrated method of TC-IRMS, TI-MS, MC-ICP-MS and ICP-MS analyses
of natural abundance 2H, 87Sr/86Sr, 207Pb/206Pb and 208Pb/206Pb isotope ratios and trace
element profiles from single insect specimens has been developed. No single geo-location
marker has been found in a preliminary comparison of international moths, although the
latitudinal cline of δ2H on a continental scale is confirmed. However, multivariate analysis
revealed that successful geo-location discrimination between the study regions is
possible.
Conclusion. The promising but imperfect geo-location demonstrated provides solid leads
for further investigation. Any geo-location system developed is likely to be applicable to
other disciplines, including forensics, ecological studies and pest management. |
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