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121.
The response of species to global warming depends on how different populations are affected by increasing temperature throughout the species'' geographic range. Local adaptation to thermal gradients could cause populations in different parts of the range to respond differently. In aquatic systems, keeping pace with increased oxygen demand is the key parameter affecting species'' response to higher temperatures. Therefore, respiratory performance is expected to vary between populations at different latitudes because they experience different thermal environments. We tested for geographical variation in respiratory performance of tropical marine fishes by comparing thermal effects on resting and maximum rates of oxygen uptake for six species of coral reef fish at two locations on the Great Barrier Reef (GBR), Australia. The two locations, Heron Island and Lizard Island, are separated by approximately 1200 km along a latitudinal gradient. We found strong counter-gradient variation in aerobic scope between locations in four species from two families (Pomacentridae and Apogonidae). High-latitude populations (Heron Island, southern GBR) performed significantly better than low-latitude populations (Lizard Island, northern GBR) at temperatures up to 5°C above average summer surface-water temperature. The other two species showed no difference in aerobic scope between locations. Latitudinal variation in aerobic scope was primarily driven by up to 80% higher maximum rates of oxygen uptake in the higher latitude populations. Our findings suggest that compensatory mechanisms in high-latitude populations enhance their performance at extreme temperatures, and consequently, that high-latitude populations of reef fishes will be less impacted by ocean warming than will low-latitude populations. 相似文献
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Philip L. Munday 《Environmental Biology of Fishes》2000,58(4):355-369
Coral-dwelling fishes from the genus Gobiodon are some of the most habitat specialised fishes on coral reefs. Consequently, we might expect that their population dynamics will be closely associated with the abundance of host corals. I used a combination of log-linear modelling and resource selection ratios to examine patterns of habitat use among eight species of Gobiodon in Kimbe Bay, Papua New Guinea. I then used multiple regression analysis to investigate relationships between the abundance of each species of Gobiodon and the abundance of the corals they inhabited. Each species of Gobiodon used one or more species of coral more frequently than expected by chance. The pattern of habitat use exhibited by each species of Gobiodon did not vary among reef zones or among reefs with different exposures to prevailing winds, despite changes in the relative abundances of corals among reef zones. This consistency in habitat use might be expected if the coral species inhabited confer considerable fitness advantages and, therefore, are strongly preferred. For most species of Gobiodon, abundances among reef zones and exposure regimes were correlated with the abundance of the coral species usually inhabited. Therefore, it appears that habitat availability helps determine abundances of most species of Gobiodon in Kimbe Bay. In addition to correlations with habitat availability, the abundances of G. histrio, G. quinquestrigatus, G. rivulatus (dark form) and the group others were also associated with particular reef zones and exposure regimes. Therefore, in these species, reef type appears to influence patterns of abundance independently of coral availability. In contrast to other species of Gobiodon, the abundance of the most specialised species, Gobiodon sp.A, was not closely associated with the abundance of the only coral species it inhabited. This study demonstrates that even for habitat specialised species, the relationship between habitat availability and abundance varies widely and is multiscale. 相似文献
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J. Oleksyn Mark G. Tjoelker Gabriela Lorenc-Plucińska Agata Konwińska Roma Żytkowiak Piotr Karolewski Peter B. Reich 《Trees - Structure and Function》1997,12(2):82-89
Pinus heldreichii Christ is a long-lived, slow-growing Tertiary relict from the Balkans. In this study we evaluated the physiological characteristics
of eight needle-age classes of P. heldreichii grown at the Arboretum of the Institute of Dendrology in Kórnik, Poland. At the end of the growing season, current-year foliage
had the highest rates of mass-based light-saturated net photosynthesis (Asat) of 33.5 nmol CO2· g–1· s–1. Asat decreased with needle age, but older needle classes retained from approximately 62 to 26% of the current needles’ rate. The
relationship between leaf N and chlorophyll a concentration among all needle-age classes was highly significant (r = 0.96, P = 0.0006). The variation in Asat of 1- to 7-year-old needles was linearly related to needle N concentration (r = 0.98, P = 0.0001). Needle dark respiration rates among these needle age classes ranged from 0.8 to 2.2 nmol · g–1· s–1 and decreased with needle age and nitrogen concentration. Total phenols and glucose concentrations increased linearly with
needle age. A similar pattern was observed in acid buffering capacity and the pH of tissue homogenates. The water content
ranged from 62% for the current needles to 51% for the 6-year-old needles. Greater investment in leaf structural tissue and
increased chemical defense is associated with higher structural cost of older needles and may reduce their photosynthetic
activity. Significant declines in water and nitrogen content with needle age and an increase in content of phenolics is most
likely a defense adaptation of P. heldreichii related to the species’ long-lived leaves.
Received: 8 January 1997 / Accepted: 4 March 1997 相似文献
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M. Akhtar I. A. Watkinson A. D. Rahimtula D. C. Wilton K. A. Munday 《The Biochemical journal》1969,111(5):757-761
The biosynthesis of cholesterol from squalene and tritiated water is described. Degradation of the cholesterol indicated that C-15 may be involved in cholesterol biosynthesis. In accordance with this view it is shown that in the conversion of [2RS-(3)H(2)]mevalonic acid into cholesterol one of the hydrogen atoms at C-15 is removed. A mechanism for the removal of the 14alpha-methyl group in steroid biosynthesis that involves the labilization of a C-15 hydrogen atom is outlined. In accordance with the requirement of this scheme it is shown that 4,4'-dimethyl-cholesta-8,14-dien-3beta-ol is converted into cholesterol. 相似文献