[MARMAM] New Publication Announcement

Bromaghin, Jeffrey jbromaghin at usgs.gov
Wed Jun 28 11:18:03 PDT 2017


Colleagues,



I am pleased to announce the availability of an early-view paper that
presents a new model for the estimation of consumer diet composition using
quantitative fatty acid signature analysis, a method commonly used in
studies of marine species.



Citation:

Bromaghin, J. F., S. M. Budge, G. W. Thiemann, and K. D. Rode. 2017.
Simultaneous estimation of diet composition and calibration coefficients
with fatty acid signature data. Ecology and Evolution.
https://doi.org/10.1002/ece3.3179



Abstract:

Knowledge of animal diets provides essential insights into their life
history and ecology, although diet estimation is challenging and remains an
active area of research.  Quantitative fatty acid signature analysis
(QFASA) has become a popular method of estimating diet composition,
especially for marine species.  A primary assumption of QFASA is that
constants called calibration coefficients, which account for the
differential metabolism of individual fatty acids, are known.  In practice,
however, calibration coefficients are not known, but rather have been
estimated in feeding trials with captive animals of a limited number of
model species.  The impossibility of verifying the accuracy of feeding
trial derived calibration coefficients to estimate the diets of wild
animals is a foundational problem with QFASA that has generated
considerable criticism.  We present a new model that allows simultaneous
estimation of diet composition and calibration coefficients based only on
fatty acid signature samples from wild predators and potential prey.  Our
model performed almost flawlessly in four tests with constructed examples,
estimating both diet proportions and calibration coefficients with
essentially no error.  We also applied the model to data from Chukchi Sea
polar bears, obtaining diet estimates that were more diverse than estimates
conditioned on feeding-trial calibration coefficients.  Our model avoids
bias in diet estimates caused by conditioning on inaccurate calibration
coefficients, invalidates the primary criticism of QFASA, eliminates the
need to conduct feeding trials solely for diet estimation, and consequently
expands the utility of fatty acid data to investigate aspects of ecology
linked to animal diets.



Regards,

Jeff
-----------------------------------------------
Jeffrey F. Bromaghin, PhD
Research Statistician
USGS Alaska Science Center
Marine Ecosystems Office
4210 University Drive
Anchorage, AK 99508
907-786-7086
jbromaghin at usgs.gov
*http://alaska.usgs.gov/science/biology/quantitative_ecology/index.php
<http://alaska.usgs.gov/science/biology/quantitative_ecology/index.php>*
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