Considerations, Cautions, and Caveats
There are many cautions that need to be heeded before conducting
a molecular genetic study. A frequent mistake made by many researchers
is to assume that simply sending noninvasive samples to a laboratory
will yield answers to all questions of interest. It is not unusual
for someone to send samples to a laboratory and to expect a report
without ever having posed a question or explicitly described the
desired data. It is even more common for wildlife researchers
to underestimate the effort required to conduct an analysis for
a given project; after all, on television, human forensic samples
are analyzed between commercials. For instance, most biologists
are aware that molecular markers can determine parentage (to estimate
the relative abundance of offspring in a sample), yet it is frequently
assumed that this is a trivial exercise. Often, numerous molecular
markers are required to provide adequate power for assigning paternity
and maternity simultaneously-sometimes more than are readily available
or affordable. By comparison, determining paternity given known
maternity (or other information acquired in the field) is far
less intensive. Thus, combining field data with genetic data can
save analysis time and money. Similar caveats hold true for
a suite of other questions, including those related to estimating
absolute abundance and distribution.
Here we review some practical issues associated with genetic
monitoring and offer some guidance on how to be successful despite
the many logistical and analytical challenges. Some of this material
is covered in ohter sections of this website (e.g., sample preservation,
data management); however, this section provides a directional
overview of potential problems beginning with sample collection
and working through various analyses.
I. Defining your objective:
* Do you have a clear idea of exactly what you want to achieve? Properly
defining your objective is the single most important step in
successfully designing and executing any research or monitoring
II. Project design:
* Will the proposed sampling methodology provide appropriate
data for the study's objectives? Don't assume that published
methods will meet your objectives. more
* Have you determined the appropriate marker type? Different
markers answer different questions. more
* Have I taken advantage of all available information and
expertise? Go beyond the literature! Directly contact experts
for added insight and to avoid pitfalls. more
* Will the sampling design adequately represent the full
population of interest? Inadequate sampling can bias results,
reduce precision, and limit inferences.
III. In the field:
* Will the data you collect support your objectives? Don't
waste time collecting data you will not use. Be sure to collect
everything you need; you may not get another chance.
* Are you confident that your data will be accurate? Missing,
incorrect, or illegible data cannot be used.
* Is training adequate? The quality of your data will
be only as good as the skill level of those collecting it.
* Have you ensured the quality and security of your data
and samples? Lost samples or corrupted data can undermine
your hard work.
IV. Preservation and archiving:
* Are samples properly stored to minimize DNA degradation? Degraded
samples result in low genotyping success rates and increased
* Are you maximizing the information that can be derived
from your samples? Your choice of preservation method can
facilitate or impede future analyses.
* Have you made plans for long-term storage? Think beyond
the life of your project.
V. In the laboratory:
* Which loci and how many loci do you need? A pilot study
might be needed to optimize your marker selection. more information
* Have you minimized genotyping error? Modern methods
can reduce error rates to levels that do not bias results.
* How do you identify a reliable lab? Not all labs are
created equal. Do your homework.
* Are your analytical methods appropriate given your sampling
methods and objectives? It's never too early to consult
with experts in genetics and statistics. Seek recommendations from colleagues for geneticists and statisticians that deal with the type of genetic data you have. Experts may be identified in journal publications related to your study or in unpublished reports.
* Results often require interpretation to be useful to managers. For example, are differences between Fst values significant, either statistically or, more importantly, biologically? Don't hesitate to seek help in understanding the significance of your results.