Evolution of water conservation mechanisms in Drosophila
Allen G. Gibbs1,*,
Fernando Fukuzato2 and
Luciano M. Matzkin3
1 Department of Ecology and Evolutionary Biology, 1041 E. Lowell St,
University of Arizona, Tucson, AZ 85721, USA
2 College of Veterinary Medicine, 105 Magruder Hall, Oregon State
University, Corvallis, OR 97331, USA
3 Department of Ecology and Evolution, State University of New York, Stony
Brook, NY 11794, USA
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Fig. 1. Phylogeny of Drosophila species used for measurements of metabolic
and water-loss rates. Cactophilic species are indicated by thick lines.
Additional species were used in analyses of cuticular hydrocarbons
(Table 1).
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Fig. 2. Representative water-loss recording from a group of 16 female
Drosophila mercatorum. Excretory losses were calculated by
integrating the areas of intermittent water-loss peaks, which reflect
defecation or oral losses.
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Fig. 3. Excretory water loss from Drosophila species. (A) Effects of body
size on fecal water content. Filled symbols, females; open symbols, males.
Circles, mesic species; triangles, cactophilic species. (B) Excretion rates of
xeric (open bars; means ± S.E.M.) and mesic (filled bars)
Drosophila.
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Fig. 4. Effects of size on metabolic rates of mesic and desert Drosophila.
Filled symbols, mesic species; open symbols, cactophilic species.
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Fig. 5. Correlation between metabolic rates and water-loss rates of
Drosophila species, after correction for body size. Filled symbols,
females; open symbols, males. Circles, mesic species; triangles, cactophilic
species.
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Fig. 6. Relationship between metabolic rates and water-loss rates of
Drosophila species, after controlling for evolutionary history using
phylogenetically independent contrasts
(Felsenstein, 1985 ). Filled
symbols and solid line, females (P=0.008); open symbols and broken
line, males (P=0.093).
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Fig. 7. Representative recordings of activity in individual Drosophila.
Abscissa labels indicate the amount of time each fly had been in the activity
chamber. Panels B and C depict consecutive recordings from the same
individual. Note that activity recorders differ in their sensitivities, and
their output may also be affected by the size of the fly. Thus, the scales
only indicate relative activity and cannot be directly compared for different
individuals.
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Fig. 8. Overall activity patterns for the same two flies as in
Fig. 7. Values are standard
errors of regression lines through the data, calculated for each hour of the
recording. Values are expressed relative to the S.E.M. values calculated after
the flies had ceased movement (i.e. relative to detector noise).
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Fig. 9. Activity patterns for Drosophila species, grouped by their
abilities to survive desiccation stress (circles, <10 h; open triangles,
10–24 h; filled triangles, >24 h). Individual flies were classified
as either active or inactive for each hour of the recordings, and the
percentage of active flies was calculated for each species. Flies were assumed
dead and removed from the analysis after their last active period. Data are
means of 4–6 species per category, with 5–10 individuals assayed
for each sex from each species.
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Fig. 10. Carbon dioxide release from individual Drosophila. (A) Cyclic
CO2 release by a single Drosophila mojavensis. This
individual walked around its chamber during the first 12 min of the recording,
then stopped moving for the last three minutes. (B) Representative recordings
from two Drosophila melanogaster. The first individual performed
cyclic CO2 release, whereas the second one did not.
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© The Company of Biologists Ltd 2003
