Biology Reference
In-Depth Information
discussed often. Molecular-genetic techniques allow for rapid assessment of
intraspecific genetic variation, changes in host preferences, insecticide-resistance
levels, and pest and natural enemy biotypes significant in biological control of
pest arthropods and weeds. The following examples illustrate some of the diver-
sity of methods and goals used when molecular tools are applied for applied
pest-management programs. However, molecular methods are not a panacea
and
Curtis (2002)
recently raised a relevant question (see Section 13.8.5).
13.8.1 Monitoring Biotypes, Species, and Cryptic Species
Real-time PCR assays based on TaqMan technology and RFLP analyses of the COI
mitochondrial gene were used to distinguish the B and Q biotypes (cryptic spe-
cies) of
Bemisia tabaci
(
Papayiannis et al. 2009
). The RFLP assay and real-time
PCR assay were equivalent except that the real-time PCR was more sensitive and
more rapid.
Distinguishing early immature stages of the screwworms
Cochliomyia homini-
vorax
and
C. macellaria
(Calliphoridae) is difficult, but important, in the eradica-
tion and exclusion program to prevent reintroduction of screwworms into the
United States, Mexico, and Central America (
Alamalakala et al. 2009
). AFLP-PCR
was evaluated for strain and species identifications and all ten primers tested
resulted in AFLP banding patterns. The 10-primer combinations generated
10-35 bands per individual and resulted in 52 useful bands, with seven bands
found in both species. 22 bands were specific for
C. macellaria
populations, 10
were specific for
C. hominivorax
, and 13 diagnostic for different populations of
C. hominivorax
. The authors concluded, “AFLP-PCR is a good tool for differen-
tiating species and has tremendous potential for studies of intraspecific genetic
variation.” Diagnostic bands could be isolated from the gels and sequenced to
develop specific primers for future screens.
Although barcoding of the COI gene is often useful in identifying species, it
does not always work.
Whitworth et al. (2007)
found that it could not identify
species of the blowfly genus
Protocalliphora
. Assignment of unknown individu-
als to species was impossible for 60% of the species.
Barcoding was useful in identifying bees (Apoidea) in Nova Scotia, Canada
(
(Sheffield et al. 2009
). A survey of the fauna of this region not only identified
the known bee species but also revealed two undescribed species, one each in
the genera
Ceratina
and
Andrena
. It allowed identification of the two sexes in
dimorphic species so that synonymies could be resolved.
Lefort et al. (2012)
wanted to identify scarab larvae without killing them, so
that they could be studied in the laboratory. They discovered it was possible to
