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Biology Letters (1)
Microbial Ecology (1)
Wilkinson, David M. (2)
Ju, Lihua (1)
Liu, Lemian (1)
Ruxton, Graeme D. (1)
Yang, Jun (1)
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Diversity and Distribution of Freshwater Testate Amoebae (Protozoa) Along Latitudinal and Trophic Gradients in China
Freshwater microbial diversity is subject to multiple stressors in the Anthropocene epoch. However, the effects of climate changes and human activities on freshwater protozoa remain poorly understood. In this study, the diversity and distribution of testate amoebae from the surface sediments were investigated in 51 Chinese lakes and reservoirs along two gradients, latitude and trophic status. A total of 169 taxa belonging to 24 genera were identified, and the most diverse and dominant genera were Difflugia (78 taxa), Centropyxis (26 taxa) and Arcella (12 taxa). Our analysis revealed that biomass of testate amoebae decreased significantly along the latitudinal gradient, while Shannon-Wiener indices and species richness presented an opposite trend (P < 0.05). The relationship of diversity and latitude is, we suspect, an artifact of the altitudinal distribution of our sites. Furthermore, biomass-based Shannon-Wiener index and species richness of testate amoebae were significantly unimodally related to trophic status (P < 0.05). This is the first large-scale study showing the effects of latitude and trophic status on diversity and distribution of testate amoebae in China. Therefore, our results provide valuable baseline data on testate amoebae and contribute to lake management and our understanding of the large-scale global patterns in microorganism diversity.
Electronic supplementary material
The online version of this article (doi:10.1007/s00248-014-0442-1) contains supplementary material, which is available to authorized users.
The energetics of low browsing in sauropods
Ruxton, Graeme D.
It has recently been argued that the probable high cost of travel for sauropod dinosaurs would have made exploiting high forage energetically attractive, if this reduced the need to travel between food patches. This argument was supported by simple calculations. Here, we take a similar approach to evaluate the energetics of foraging close to the ground. We predict that small extensions of the neck beyond the minimum required for the mouth to reach the ground bring substantial energetic savings. Each increment of length brings a further saving, but the sizes of such benefits decrease with increasing neck length. However, the observed neck length of around 9 m for Brachiosaurus (for example) is predicted to reduce the overall cost of foraging by 80 per cent, compared with a minimally necked individual. We argue that the long neck of the sauropods may have been under positive selection for low foraging (instead of, or as well as, exploitation of high foraging), if this long neck allowed a greater area of food to be exploited from a given position and thus reduced the energetically expensive movement of the whole animal.
sauropod; dinosaur; neck; feeding; energy expenditures; Brachiosaurus
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