For the past year, I have examined the courtship song
and
mating behavior of local and wide-ranging populations of Drosophila
robusta. I have observed patterns in acoustic signals for
eight geographically isolated populations of D. robusta.
I have and am currently examining courtship behavior in both
wild and lab-reared populations to determine if what we see in
studies of lab-reared populations accurately represents what
occurs in nature. My goals are 1) to describe in ethological
terms the similarities/differences between lab-reared and wild
populations and 2) to determine the function of courtship song
of D. robusta.
Links to information on:
Drosophila
robusta - Courtship Song
Figure 2 - Areas from which
we collect and make observations that are representative of the
natural habitat of D.
robusta.
They inhabit deciduous forests near a source of flowing water.
The first image was taken at a more recent sample site on Cornie
Bayou, LA, and the second image was taken near the Lake Sequoyah
Spillway in Fayetteville, AR.
Drosophila
robusta - Life History
Drosophila
robusta - Courtship Behavior
Figure 1 -
Populations used in the preliminary studies and areas they were
collected from.
Flies were collected from the wild by baiting
for them in their natural habitat (see figure 2). The bait
consists of a concoction of cooked banana, syrup, and yeast that
has fermented for a period of several days. The bait is poured
into buckets (see figure 3) which are placed close to a source
of flowing water surrounded by deciduous forest.
Figure 3 - This image was taken on a hot afternoon in August 2005.
The flies were observed to cluster around the drainage holes of the bait
buckets
which are moist and shielded from the sun.
Courtship songs were recorded by placing a mature male and
female fly together into a mating chamber. The
chamber is then placed in the INSECTOVOX (see figure 4) upon a
condenser microphone and the flies
are observed throughout the courtship (see figure 5). Songs are
recorded onto a portable cassette recorder with a second
output designed for high impedance headphones for observational
purposes. Patterns in acoustic signals were examined for eight
geographically isolated populations of D. robusta (see Figure
1).The courtship songs of thirty
male flies were recorded and analyzed using Sound Ruler
(Gridi-Papp, 2003) software compiling the mean values for IPI,
IPF and pulse duration for each population.
Figure 4 - An INSECTOVOX is used to record near field sounds
produced by small organisms such as Drosophila.
Figure 5 - The mating chamber can be viewed during the
mating/recording process via a magnified viewing hole.
The data analysis for this research was generated using the SAS
software package (SAS Institute, 2004). No significant variation
was found among populations for pulse duration (P=0.9086) or
interpulse interval (P=0.5325); however, variation was found for
intrapulse
frequency (P<.0001). While interpulse interval and pulse
duration
tend to
vary greatly between species (Ritchie & Kyriacou, 1996;
Bennet-Clark & Ewing, 1969) they vary little between
populations; however, populations do tend to show variance in
intrapulse frequency as found among all populations in this
study; therefore, D. robusta seem to fit these
previously studied systems in trait variation. All results were
adjusted for the effects of temperature. It is interesting to
note from figure 6 how the plotted least square population means
for intrapulse frequency increase
in value (amplitude) from southerly to northerly populations.
Figure 6 - Plotted least square population means showing the
geographic
effects of temperature upon intrapulse frequency.
Observed patterns of character change within these populations
imply a focus for research by identifying the origin and
direction of important changes in courtship behavior.
My Homepage