Biology Reference
In-Depth Information
Wolbachia
can influence mating behavior and kill males in populations of
the butterfly
Acraea encedon
across Africa. In many populations, females pro-
duce only female progeny, whereas other populations produce both males and
females in a normal 1:1 sex ratio.
Wolbachia
kills males, resulting in the produc-
tion of all-female progeny in this butterfly (
Jiggins et al. 1998
).
Acraea encedon
females typically deposit clutches of 50-300 eggs and newly hatched larvae often
cannibalize unhatched eggs, only gradually dispersing into smaller groups.
Jiggins
et al. (1998)
speculated that the evolution of male-killing behavior by
Wolbachia
may be favored when the behavior and ecology of a species makes antagonis-
tic interactions between siblings or sib cannibalism likely. Under field conditions,
Wolbachia
infections in
A. encedon
females may result in populations with a seri-
ous shortage of males. As a consequence, the mating behavior of
Wolbachia
-
infected
A. encedon
has been altered. Normally males seek out and compete for
individual females near larval food plants. However, when male-killing
Wolbachia
are present in high frequency in a population, females instead form dense aggre-
gations in grassy areas near trees, perhaps to attract rare males as mates.
In adzuki bean borer
Ostrinia scapulalis
(Lepidoptera: Crambidae) popula-
tions infected with
Wolbachia
, sexual mosaics are produced (
Sugimoto 2010
).
The female-specific form of the
doublesex
+
gene is transcribed as well as the
male-specific form, indicating that
Wolbachia
manipulates the sex of this insect
by interfering either with the sex-specific splicing of
dsx
+
itself or with another
upstream sex-determination process.
Wolbachia
have been proposed as “drive” mechanisms to introduce trans-
genes into arthropod populations (
Turelli and Hoffman 1999
), as is discussed fur-
ther in Chapter 14.
Wolbachia
infections may reduce the ability of mosquitoes to
transmit pathogens (viruses, nematodes, and protozoa); this also is being evalu-
ated as a pest-management method and is described in Chapter 14. However,
Cordaux et al. 2011
) noted that resistance to feminization by
Wolbachia
and
resistance to male killing by
Wolbachia
has developed in wild populations. This
suggests that there could be an arms race between symbionts and their hosts.
10.11.5
Cardinium
The false spider mite
Brevipalpus phoenicis
(Acari: Tenuipalpidae) consists
entirely of females that have only a haploid chromosome set (
Weeks et al. 2001
).
This unusual genetic system is due to the presence of an endosymbiotic bac-
terium,
Cardinium
, discovered relatively recently by
Zchori-Fein et al. (2001)
.
The
Cardinium
in
Brevipalpus
results in feminized haploid males, but how the
bacterium induces feminization of genetic males is unknown.
