klaassen-singlepoint-2010.pdf (394 kB)
Single-point isotope measurements in blood cells and plasma to estimate the time since diet switches
journal contribution
posted on 2010-08-01, 00:00 authored by Marcel KlaassenMarcel Klaassen, T Piersma, H Korthals, A Dekinga, M Dietz1. Understanding ecological phenomena often requires an accurate assessment of the timing of events. To estimate the time since a diet shift in animals without knowledge on the isotope ratios of either the old or the new diet, isotope ratio measurements in two different tissues (e.g. blood plasma and blood cells) at a single point in time can be used. For this ‘isotopic-clock’ principle, we present here a mathematical model that yields an analytical and easily calculated outcome.
2. Compared with a previously published model, our model assumes the isotopic difference between the old and new diets to be constant if multiple measurements are taken on the same subject at different points in time. Furthermore, to estimate the time since diet switch, no knowledge of the isotopic signature of tissues under the old diet, but only under the new diet is required.
3. The two models are compared using three calibration data sets including a novel one based on a diet shift experiment in a shorebird (red knot Calidris canutus); sensitivity analyses were conducted. The two models behaved differently and each may prove rather unsatisfactory depending on the system under investigation. A single-tissue model, requiring knowledge of both the old and new diets, generally behaved quite reliably.
4. As blood (cells) and plasma are particularly useful tissues for isotopic-clock research, we trawled the literature on turnover rates in whole blood, cells and plasma. Unfortunately, turnover rate predictions using allometric relations are too unreliable to be used directly in isotopic-clock calculations.
5. We advocate that before applying the isotopic-clock methodology, the propagation of error in the ‘time-since-diet-shift’ estimation is carefully assessed for the system under scrutiny using a sensitivity analysis as proposed here.
2. Compared with a previously published model, our model assumes the isotopic difference between the old and new diets to be constant if multiple measurements are taken on the same subject at different points in time. Furthermore, to estimate the time since diet switch, no knowledge of the isotopic signature of tissues under the old diet, but only under the new diet is required.
3. The two models are compared using three calibration data sets including a novel one based on a diet shift experiment in a shorebird (red knot Calidris canutus); sensitivity analyses were conducted. The two models behaved differently and each may prove rather unsatisfactory depending on the system under investigation. A single-tissue model, requiring knowledge of both the old and new diets, generally behaved quite reliably.
4. As blood (cells) and plasma are particularly useful tissues for isotopic-clock research, we trawled the literature on turnover rates in whole blood, cells and plasma. Unfortunately, turnover rate predictions using allometric relations are too unreliable to be used directly in isotopic-clock calculations.
5. We advocate that before applying the isotopic-clock methodology, the propagation of error in the ‘time-since-diet-shift’ estimation is carefully assessed for the system under scrutiny using a sensitivity analysis as proposed here.
History
Journal
Functional EcologyVolume
24Issue
4Pagination
796 - 804Publisher
Wiley-Blackwell PublishingLocation
London, EnglandPublisher DOI
Link to full text
ISSN
0269-8463eISSN
1365-2435Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2010, The AuthorsUsage metrics
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