Biology Reference
In-Depth Information
invest their inspection and detection efforts. It also is relevant if sterile Medflies
are to be released in an eradication program; potentially, sterile Medflies of
one “type” might not mate with an invasive wild population if there are suffi-
cient genetic differences in behavior, or other premating isolating mechanisms.
With regard to the California Medfly eradication efforts, the origin or genetic
makeup of the different Medfly invasions could answer the question as to
whether the expensive eradication efforts were successful.
Malacrida et al. (1996)
used enzyme electrophoresis to analyze genetic simi-
larities among 11 tephritid species. A later study focused on tracking the coloni-
zation of
C. capitata
throughout the world using samples from 17 populations
(
Malacrida et al. 1998
). Variability at 26 polymorphic enzyme loci revealed “that
the geographical dispersal of medfly from its ancestral source area (East Africa)
is associated with a great reduction in variability. The pattern of decreasing vari-
ability occurs at two regional levels: in the African-Mediterranean region where
the differentiation is gradual, and in the Latin American-Pacific region where
some ancestral variability is still present as a consequence of recent coloniza-
tion” (
Malacrida et al. 1998
).
The molecular data confirm that the common name “Medfly” is inappropri-
ate; because the ancestral home of
C. capitata
is Africa, it ought to be called
“Africafly.”
Malacrida et al. (1998)
concluded that the “population genetic
changes observed in the species range are consistent with both the chronology
and the historical circuitous course of the medfly colonization process.” Thus,
these molecular data are congruent with what is known about its movements
out of Africa.
13.7.4.4 Is the Medfly Established in California?
A critical question regarding the success of eradication in California is, “Is the
Medfly permanently established in California?” The question was approached
by assuming that independent introductions of Medflies from different geo-
graphic sources would result in populations with unique genetic markers; if each
invasive population had different markers, it would be evidence that each inva-
sion is independent. By contrast, if the markers found in the California popula-
tions during the different “invasions” were the same, the conclusion could be
that it is more likely that a single Medfly population is established in California.
However, an alternative explanation for Medflies having the same markers
is that multiple invasions occurred from a particular geographic source, and it
would be impossible to exclude this possibility.
Obtaining definitive data to discriminate between populations depends on
having markers that are diagnostic. These markers need to be validated with
