Supporting information
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Respirometry methods
The acclimation time needed to obtain resting levels of oxygen consumption in the
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species examined here, 90 min., is shorter thanwhat is necessary forother species, especially
larger fishes or those that are more active. The damselfishes and cardinalfishes investigated
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here, and in other recent studies (Nilsson et al., 2009; Gardiner et al., 2010; Couturier et al.,
2013;Rummer et al., 2013;) exhibit minimal handling stress and quickly become accustomed
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to the respirometry chamber. We conducted pilot studies to determine how long it takes for
ṀO2Restvalues to stabilize after fish were placed in the respirometry chamber. Even after a
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fish had been chased to exhaustion, which would be far more stressful and energetically
costly than handling stress, ṀO2 values stabilized earlier than 2h. See Fig. S1 for chase and
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post-chase ṀO2 values for three C. atripectoralisindividuals (Rummer, unpublished data).
The pilot data show that the fish return to a low, very stable rate of oxygen
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consumptionrapidly following disturbance (Fig. S1).
We could not detect significant differences between the average ṀO2Maxand average
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ṀO2Restof two of our species (D. melanurus and C. quinquelineatus) acclimated to 34°C and,
over the course of the entire study, we observed 5 individual fish that had a ṀO2Max value that
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was numerically, albeit only slightly below their ṀO2Rest value. We note that resting rates
increased significantly upon acclimation to34°C, if not by 33°C, in all except for one of the
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species investigated, and thatṀO2Maxvalues had already peaked and fallen in all except for
twospecies. The patterns of change resulted in a very low aerobic scope nearing zero at 34°C.
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We believe this was the result of the fish being unable to exhibit a maximum swimming
performance and the overall stress of high temperatures. This interpretationisfurther
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supported by the variability around the means; which is small across all species and
temperatures for both ṀO2Max and ṀO2Rest, except at the highest temperature where the error
1
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bars are noticeably larger.
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Latitudinal comparisons and reanalysis of data
It was necessary to re-analyze data from the two previous studies (Nilsson et al., 2009;
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Gardiner et al., 2010) becauseone higher acclimation temperature (at 33C) was added for the
Heron Island populations andadditional replicates were obtained for the other temperatures to
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make the latitudinal comparisons more robust. After incorporating the additional replicates
and the additional acclimation temperature for the Heron Island populations, we found that
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the overall patterns were retained. However, there was less variability around the means, and
with the addition of33°Cdata, it was clear that performance was starting to fall at the higher
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temperatures, which could be due to an increase in ṀO2Rest, a decrease in ṀO2Max, or both.
Both sets of reanalyzed data – plotted in the same way as we did for the PNG populations – in
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addition to aerobic scopes for the PNG populations are summarized in Fig. S2.
Re-analysis of the previously published data with the inclusion of the additional
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replicates and temperature group was also necessary in the present study in order to more
appropriately make comparisons across the three separate data sets. In particular, we aimed to
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compare the temperatures at which the representatives from each population performed best,
not directly compare values of absolute scope among populations, because the magnitude of
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the absolute aerobic scope may not be what dictates performance. Therefore,we estimated the
temperatures at which performance is the greatest within populations and then compared those
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temperaturesamong the different sites.
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Local adaptation
While we found no evidence for a consistent pattern of local adaptation of aerobic
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scope to the average and maximum temperatures among the populations we studied, this does
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not mean that adaptation is irrelevant. High latitude populations may be adapted to the greater
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range of seasonal temperatures that they experience when compared with low latitude
populations, leading to improved capacity to perform at a range of temperatures, including
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higher temperatures outside the normal range experienced. This could produce an apparent
mismatch between the average temperatures experienced in high latitude populations and the
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temperatures where aerobic scope is the greatest. Consequently, our results could indicate that
reef fish populations are more closely adapted to seasonal temperature variation than they are
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to the average temperatures they experience. There could also be other traits that provide
evidence for local thermal adaptation (e.g. reproductive timing). Furthermore, despite no
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obvious adaptation of aerobic scope to different temperatures across latitudes, it does not
follow that local adaptation of aerobic scope could not occur once temperatures exceed the
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natural range. The magnitude of selection and trade-offs in genetic correlations among
traits(Mundayet al., 2013) may be very different at temperatures outside the normal range
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when compared with temperatures within the normal range. As a consequence, there could be
adaptation to rapid climate change in the future, even in cases where there is no strong
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evidence for local adaptation to existing natural temperature variation (Mundayet al., 2013).
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Fig. S1Representative traces from three individual C. atripectoralis chased to exhaustion and
then immediately placed into respirometry chambers where ṀO2 could be monitored until
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recovery, which was sooner than 2h (Rummer, unpublished data).
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Fig. S2Absolute aerobic scope (ṀO2Max - ṀO2Rest) for five coral reef fish species from three
populations (see legend for symbols) investigated upon acclimation to 27, 29, 31, 32, 33,
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and/or 34°C. Note: D. melanurus was only investigated at the equatorial site; whereas,D.
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aruanus was investigated only at Lizard and Heron Islands.All data are means ±S.E.M., n≥8
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for each species and each temperature.
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Supporting References(not cited in main text)
Couturier CS, Stecyk JAW, Rummer JL, Munday PL, Nilsson GE (2013) Species-specific effects of
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near-future CO2 on the respiratory performance of two tropical prey fish and their predator.
Comparative Biochemistry and Physiology, Part A: Molecular and Integrative
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Physiology,166, 482-489.
Rummer JL, Stecyk JAW, Couturier CS, Watson S-A, Nilsson GE, Munday PL (2013) Elevated CO2
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enhances aerobic scope of a coral reef fish. Conservation Physiology,1.
Munday PL, Warner RR, Munro K, Pandolfi JM, Marshall DJ (2013) Predicting evolutionary
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responses to climate change in the sea. Ecology Letters, doi: 10.1111/ele.12185.
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