First published online September 9, 2005
Journal of Experimental Biology 208, 3593-3602 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01777
Allometric scaling of flight energetics in orchid bees: evolution of flux capacities and flux rates
Charles-A. Darveau1,
Peter W. Hochachka1,
,*,
David W. Roubik2 and
Raul K. Suarez3
1 Department of Zoology, University of British Columbia, Vancouver, BC,
Canada V6T 1Z4
2 Smithsonian Tropical Research Institute, Balboa, Republic of
Panama
3 Department of Ecology, Evolution and Marine Biology, University of
California Santa Barbara, Santa Barbara, CA 93106-9610, USA
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Fig. 1. Relationships between body mass and (A) trehalase (TR) and (B) glycogen
phosphorylase (GP) activity measured in 27 species of orchid bees. Filled
circles represent the genus Euglossa, open circle Exaerete,
filled squares Eulaema, and open squares Eufriesea.
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Fig. 2. Relationships between body mass and (A) hexokinase (HK), (B)
phosphoglucoisomerase, (C) phosphofructokinase, and (D) glycerol 3-phosphate
dehydrogenase activity measured in 28 species of orchid bees. Symbols as in
Fig. 1.
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Fig. 3. Relationships between body mass and (A) citrate synthase (CS) and (B)
cytochrome c oxidase activity measured in 28 species of orchid bees.
(C) The relationship between body mass and homogenate respiration rate was
measured in eight species. Symbols as in
Fig. 1.
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Fig. 4. Relationship between hovering flight mass-specific metabolic rate and the
activity of (A) hexokinase (HK), (B) cytochrome c oxidase (COX) and
(C) glycogen phosphorylase (GP). Symbols as in
Fig. 1.
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Fig. 5. Allometric scaling relationship of orchid bee hovering flight wingbeat
frequency (solid line: n=106Mb-0.31,
r2=0.86) and mass-specific metabolic rate (broken line:
 CO2=44Mb-0.31,
r2=0.80), and hexokinase activity (dotted line:
HK=27Mb-0.33, r2=0.82).
Symbols as in Fig. 1.
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Fig. 6. (A) Correlation between hovering flight mass-specific metabolic rate and
hexokinase activity residuals (r2=0.29,
F1,12=4.85, P=0.048) obtained from the body mass
relationships in Fig. 5. (B)
The same relationship (non-significant in both cases) presented for
independent contrast obtained from the cyt b phylogeny using gradual
(filled circles) and speciational (open circles) models of character
evolution.
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Fig. 7. Relationships between body mass and the fractional velocity
(%Vmax) of (A) glycogen phosphorylase (GP; open triangles,
r2=0.39, P<0.01) and trehalase (TR; filled
triangles, r2=0.80, P<0.001), (B) the
glycolytic enzyme hexokinase (HK; open circles, P=0.65),
phosphoglucoisomerase (PGI; open triangles, r2=0.47,
P<0.005), phosphofructokinase (PFK; filled circles,
r2=0.76, P<0.001) and glycerol 3-phosphate
dehydrogenase (GPDH; filled triangles, r2=0.73,
P<0.001), and (C) the mitochondrial enzymes citrate synthase (CS;
open squares, r2=0.91, P<0.001) and cytochrome
c oxidase (COX; filled squares, r2=0.49,
P<0.005).
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Fig. 8. Correlation coefficients between the independent contrasts in body mass and
enzyme activities of (A,B) hexokinase (HK), (C) citrate synthase (CS), (D)
glycogen phosphorylase (GP) and (E) trehalase (TR). Solid lines represent
analyses performed using the gradual model of character evolution while broken
lines represent the speciational model. The relationship between independent
contrasts obtained from cyt b phylogeny is only presented for HK (A).
The cyt b independent contrasts relationships are superimposed on the
distribution of correlation coefficient results from analyses performed with
10 000 different trees (see Materials and methods). The correlation
coefficients obtained from cyt b sequence information are presented
for HK (gradual: r=-0.77, P=0.003; speciational:
r=-0.73, P=0.007), CS (gradual: r=0.75,
P=0.008; speciational: r=0.76, P=0.007), GP
(gradual: r=-0.69, P=0.013; speciational: r=-0.64,
P=0.025) and TR (gradual: r=-0.58, P=0.047;
speciational: r=-0.65, P=0.023). The shaded areas represent
non-significant relationships, given that the critical values of the
correlation coefficient r for significance at the P=0.05
level (two-tailed) is 0.576 for HK, GP and TR (d.f.=10) and 0.602 for CS
(d.f.=9).
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Fig. 9. Correlation coefficients between the independent contrasts in hovering
flight mass-specific metabolic rate and the activity of (A) hexokinase (HK),
(B) cytochrome c oxidase (COX) and (C) glycogen phosphorylase (GP).
The distribution of correlation coefficients results from analyses performed
with 10 000 different trees (see Materials and methods). The correlation
coefficient obtained from cyt b sequence information using a gradual
(solid lines) and speciational (broken lines) model of evolution are presented
for HK (gradual: r=0.77, P=0.004; speciational:
r=0.71, P=0.010), COX (gradual: r=0.35,
P=0.27; speciational: r=0.43, P=0.16) and GP
(gradual: r=0.53, P=0.07; speciational: r=0.67,
P=0.02). The shaded areas represent non-significant relationships,
given that the critical values of the correlation coefficient r for
significance at the P=0.05 level (two-tailed) is 0.576 (d.f.=10).
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© The Company of Biologists Ltd 2005
