Temperature has been shown to have a significant effect on swimming performance in teleost fish. ... more Temperature has been shown to have a significant effect on swimming performance in teleost fish. This thermal dependence has usually been attributed to correlated changes in muscle contractile physiology. However, the physical properties of all materials, including both water and living tissues, are profoundly affected by changes in temperature. In particular, both the kinematic viscosity of water and the flexible body dynamics of the fish (independent of muscle contractile activity) are substantially higher at lower temperatures. In this study, we investigated the extent to which the observed thermal dependence of locomotor performance of fish simply reflects changes in the biophysical properties of the aqueous medium independent of the changing physiology of the animals. C-starts (escape swimming) of adult goldfish (Carassius auratus, length approximately 8 cm) were video-taped (400 frames s-1) at 5 degreesC and 20 degreesC in fresh water and at 20 degreesC in fresh water containi...
In this study, we use the bacterium Escherichia coli to examine evolutionary responses to environ... more In this study, we use the bacterium Escherichia coli to examine evolutionary responses to environmental acidity fluctuating temporally among pH 5. 3, 6.3, 7.0, and 7.8 (5,000-15 . Two experimental protocols of temporal variation were used. One group (six replicate lines) of populations evolved for 2,000 generations during exposure to a cycled regime fluctuating daily between pH 5.3 and 7.8. The other group (also in six replicate lines) evolved during exposure for 2,000 generations to a randomly shifting regime fluctuating stochastically each day among pH 5.3, 6.3, 7.0, and 7.8. Adaptation to these fluctuating acidity regimes was measured as a change in fitness relative to the common ancestor by direct competition experiments in both constant and fluctuating pH regimes. For comparisons with constant pH evolution, a group evolved at a constant pH of 5.3 and another group evolved at pH 7.8 were also tested. This study initiated the first long-term laboratory natural selection experimen...
One of the major potential disadvantages to asexual reproduction is believed to be a reduction in... more One of the major potential disadvantages to asexual reproduction is believed to be a reduction in phenotypic variability. This study represents an empirical test for such a reduction in the variance of physiological traits in parthenogenetic species of the lizard genus Cnemidophorus. Five performance traits (burst speed, endurance, maximal exertion, standard metabolic rate and evaporative water loss rate) were examined in four asexual species and the sexual species that hybridized to produce them. A phylogenetically controlled analysis revealed less trait variance in asexual species for the first three traits, but no detectable differences between asexual and sexual species for the other two traits. A second analysis examining the average shape of trait distributions in the two types of species suggests that sexual populations produce distributions with more elongate tails than do asexual populations. Thus, part of the reason for increased variance in sexual populations may be a gre...
Temperature has been shown to have a significant effect on swimming performance in teleost fish. ... more Temperature has been shown to have a significant effect on swimming performance in teleost fish. This thermal dependence has usually been attributed to correlated changes in muscle contractile physiology. However, the physical properties of all materials, including both water and living tissues, are profoundly affected by changes in temperature. In particular, both the kinematic viscosity of water and the flexible body dynamics of the fish (independent of muscle contractile activity) are substantially higher at lower temperatures. In this study, we investigated the extent to which the observed thermal dependence of locomotor performance of fish simply reflects changes in the biophysical properties of the aqueous medium independent of the changing physiology of the animals. C-starts (escape swimming) of adult goldfish (Carassius auratus, length approximately 8 cm) were video-taped (400 frames s-1) at 5 degreesC and 20 degreesC in fresh water and at 20 degreesC in fresh water containi...
In this study, we use the bacterium Escherichia coli to examine evolutionary responses to environ... more In this study, we use the bacterium Escherichia coli to examine evolutionary responses to environmental acidity fluctuating temporally among pH 5. 3, 6.3, 7.0, and 7.8 (5,000-15 . Two experimental protocols of temporal variation were used. One group (six replicate lines) of populations evolved for 2,000 generations during exposure to a cycled regime fluctuating daily between pH 5.3 and 7.8. The other group (also in six replicate lines) evolved during exposure for 2,000 generations to a randomly shifting regime fluctuating stochastically each day among pH 5.3, 6.3, 7.0, and 7.8. Adaptation to these fluctuating acidity regimes was measured as a change in fitness relative to the common ancestor by direct competition experiments in both constant and fluctuating pH regimes. For comparisons with constant pH evolution, a group evolved at a constant pH of 5.3 and another group evolved at pH 7.8 were also tested. This study initiated the first long-term laboratory natural selection experimen...
One of the major potential disadvantages to asexual reproduction is believed to be a reduction in... more One of the major potential disadvantages to asexual reproduction is believed to be a reduction in phenotypic variability. This study represents an empirical test for such a reduction in the variance of physiological traits in parthenogenetic species of the lizard genus Cnemidophorus. Five performance traits (burst speed, endurance, maximal exertion, standard metabolic rate and evaporative water loss rate) were examined in four asexual species and the sexual species that hybridized to produce them. A phylogenetically controlled analysis revealed less trait variance in asexual species for the first three traits, but no detectable differences between asexual and sexual species for the other two traits. A second analysis examining the average shape of trait distributions in the two types of species suggests that sexual populations produce distributions with more elongate tails than do asexual populations. Thus, part of the reason for increased variance in sexual populations may be a gre...
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Papers by Alistair Cullum