Biology Reference
In-Depth Information
were in the reverse order. The data indicate a few genes with additive effects
determine the behavior.
“Domesticity” in
Ae. aegypti
is a complex phenomenon that includes a vari-
ety of behaviors, including a preference for ovipositing in man-made contain-
ers, the ability of larvae to develop in drinking water stored in clay pots with a
low nutritional content, and preferences for feeding on man (rather than birds)
inside houses, as well as resting and mating indoors. It is likely that
Ae. aegypti
speciated long before man began to build houses, but
Ae. aegypti
has adapted
rapidly to human habitats, and the domestic form of
Ae. aegypti
is the only one
known that is entirely dependent on humans (
Trpis and Hausermann 1978
).
11.4.1.3 Foraging in
Drosophila
Drosophila melanogaster
larvae feed on yeast growing on decaying fruit.
Naturally occurring populations contain individuals that vary in the distance
the larvae travel while foraging for food, a difference attributed to a single
foraging
gene (
Osborne et al. 1997, Sokolowski et al. 1997
). Natural populations
comprise approximately 70% “rovers” (who forage long distances) and 30%
“sitters” (short-distance foragers), with the rover phenotype dominant to sit-
ter, indicating a single-gene mode of inheritance (
de Belle and Sokolowski 1987,
Sokolowski 2001
).
Sitter larvae grow at a normal rate and are of normal size. Both sitters and
rovers are maintained in the field by natural selection; density-dependent selec-
tion can shift allele frequencies so that rovers are selected for in crowded lar-
val environments and sitters in less-crowded ones. The
foraging
gene encodes
a cyclic guanosine monophosphate (cGMP)-dependent protein kinase, and
rovers have higher kinase activity levels than sitters. Subtle differences in this
kinase lead to naturally occurring variation in behavior (
Shaver et al. 1998
).
Sleep deprivation and starvation studies with
D. melanogaster
individuals with
natural variants of the
foraging
gene suggest one of the reasons
foraging
gene
polymorphisms persist in wild populations is due to fitness tradeoffs (
Donlea
et al. 2012
). The
foraging
gene influences sleep, learning and memory, as well
as feeding behavior. Flies with the “rover” genotype have a better short-term
memory than “sitters,” but sitter flies have better long-term memory. Rover
flies do not lose their short-term memory if well fed, but do so if starved over-
night. Sitter flies have reduced short-term memory after sleep deprivation, but
are able to learn after 12 hours of starvation. Thus, the
foraging
gene alleles
appear to provide benefits in some environments, but not others.
Donlea et al.
(2012)
conclude that “understanding how these tradeoffs confer resilience or
vulnerability to specific environmental challenges may provide additional clues
