Diel surface temperature range scales with lake size

Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored

Thermal Variability Increases the Impact of Autumnal Warming and Drives Metabolic Depression in an Overwintering Butterfly

Increases in thermal variability elevate metabolic rate due to Jensen's inequality, and increased metabolic rate decreases the fitness of dormant ectotherms by increasing consumption of stored energy reserves. Theory predicts that ectotherms should respond to increased thermal variability by lowering the thermal sensitivity of metabolism, which will reduce the impact of the warm portion of thermal variability. We examined the thermal sensitivity of metabolic rate of overwintering Erynnis propertius (Lepidoptera: Hesperiidae) larvae from a stable or variable environment reared in the laboratory in a reciprocal common garden design, and used these data to model energy use during the winters of 1973–2010 using meteorological data to predict the energetic outcomes of metabolic compensation and phenological shifts. Larvae that experienced variable temperatures had decreased thermal sensitivity of metabolic rate, and were larger than those reared at stable temperatures, which could partially compensate for the increased energetic demands. Even with depressed thermal sensitivity, the variable environment was more energy-demanding than the stable, with the majority of this demand occurring in autumn. Autumn phenology changes thus had disproportionate influence on energy consumption in variable environments, and variable-reared larvae were most susceptible to overwinter energy drain. Therefore the energetic impacts of the timing of entry into winter dormancy will strongly influence ectotherm fitness in northern temperate environments. We conclude that thermal variability drives the expression of metabolic suppression in this species; that phenological shifts will have a greater impact on ectotherms in variable thermal environments; and that E. propertius will be more sensitive to shifts in phenology in autumn than in spring. This suggests that increases in overwinter thermal variability and/or extended, warm autumns, will negatively impact all non-feeding dormant ectotherms which lack the ability to suppress their overwinter metabolic thermal sensitivity

Stable carbon and nitrogen isotope enrichment in primate tissues

Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate species could lead to variable offsets between apatite carbonate and collagen. To improve our understanding of the isotopic chemistry of primates, we explored the apparent enrichment (ε*) between bone collagen and muscle, collagen and fur or hair keratin, muscle and keratin, and collagen and bone carbonate across the primate order. We found that the mean ε* values of proteinaceous tissues were small (≤1‰), and uncorrelated with body size or phylogenetic relatedness. Additionally, ε* values did not vary by habitat, sex, age, or manner of death. The mean ε* value between bone carbonate and collagen (5.6 ± 1.2‰) was consistent with values reported for omnivorous mammals consuming monoisotopic diets. These primate-specific apparent enrichment values will be a valuable tool for cross-species comparisons. Additionally, they will facilitate dietary comparisons between living and fossil primates

Climate change and freshwater zooplankton: what does it boil down to?

Recently, major advances in the climate–zooplankton interface have been made some of which appeared to receive much attention in a broader audience of ecologists as well. In contrast to the marine realm, however, we still lack a more holistic summary of recent knowledge in freshwater. We discuss climate change-related variation in physical and biological attributes of lakes and running waters, high-order ecological functions, and subsequent alteration in zooplankton abundance, phenology, distribution, body size, community structure, life history parameters, and behavior by focusing on community level responses. The adequacy of large-scale climatic indices in ecology has received considerable support and provided a framework for the interpretation of community and species level responses in freshwater zooplankton. Modeling perspectives deserve particular consideration, since this promising stream of ecology is of particular applicability in climate change research owing to the inherently predictive nature of this field. In the future, ecologists should expand their research on species beyond daphnids, should address questions as to how different intrinsic and extrinsic drivers interact, should move beyond correlative approaches toward more mechanistic explanations, and last but not least, should facilitate transfer of biological data both across space and time

Damaliscus niro horns from Wonderwerk Cave and other Pleistocene sites: morphological and chronological considerations

Wonderwerk Cave, situated near Kuruman in the Northern Cape Province of South Africa, has yielded well-preserved horns of many antelope, including three horn fragments of Damaliscus niro. These specimens were discovered in the course of guano-mining operations in the 1940s. Remarkably, they retain a keratinous sheath. Dimensions of Pleistocene horn cores from Sterkfontein, Olduvai, Cornelia-Uitzoek, Florisbad and Maselspoort are used to assess the Wonderwerk specimens. Assuming that morphological variability can be used to assess relative chronology, we suggest that the Wonderwerk specimens date to the Middle Pleistocene, intermediate in age between specimens from Florisbad (between 400 000 and 100 000 years BP) and Cornelia-Uitzoek (c. 800 000 years BP). One of the Wonderwerk specimens has a radiocarbon date of close to the limit of the method.We interpret this to reflect an indefinite age of greater than 40 000 years ago. This is not in conflict with the suggested Middle Pleistocene age of the specimens. The horns are of further interest in that the keratin sheaths have carbon-nitrogen ratios that suggest the presence of protein suitable for ancient-DNA analysis.National Research Foundatio

Standardized analyses of glass trade beads from Mgungundlovu and Ondini, nineteenth century Zulu capitals

Renewed interest has been generated in studies of beads from southern African Iron Age sites. Statistical analyses of bead frequencies can now be undertaken, making use of a standardized, internationally recognized classification scheme. Large samples from two nineteenth-century Zulu capitals, Mgungundlovu and Ondini, have been examined according to this typology. Results of statistical analyses are presented to demonstrate variability in bead frequencies within and between sites. The results show that the recovery methods of four excavators have not introduced systematic biases in the consolidated Mgungundlovu bead collection. Assemblages from different parts of the site more closely resemble each other than any of them resemble the bead collection of Ondini. These findings clear the way for more detailed physical and chemical analyses of the beads, so as to quantify the spatial and temporal variability of different bead types

Migrating microbes: what pathogens can tell us about population movements and human evolution

Background: The biology of human migration can be observed from the co-evolutionary relationship with infectious diseases. While many pathogens are brief, unpleasant visitors to human bodies, others have the ability to become life-long human passengers. The story of a pathogen’s genetic code may, therefore, provide insight into the history of its human host. The evolution and distribution of disease in Africa is of particular interest, because of the deep history of human evolution in Africa, the presence of a variety of non-human primates, and tropical reservoirs of emerging infectious diseases. Methods: This study explores which pathogens leave traces in the archaeological record, and whether there are realistic prospects that these pathogens can be recovered from sub-Saharan African archaeological contexts. Results: Three stories are then presented of germs on a journey. The first is the story of HIV’s spread on the back of colonialism and the railway networks over the last 150 years. The second involves the spread of Schistosoma mansoni, a parasite which shares its history with the trans-Atlantic slave trade and the origins of fresh-water fishing. Finally, we discuss the tantalising hints of hominin migration and interaction found in the genome of human herpes simplex virus 2. Conclusions: Evidence from modern African pathogen genomes can provide data on human behaviour and migration in deep time and contribute to the improvement of human quality-of-life and longevity.CJH was funded by the University of Cambridge. JBR was funded by the University of Pretoria and the South African National Research Foundation (ERTTG 2016 grant UID 105197). RFR was funded by the National Geographic Society/Waitt Foundation Scientific Exploration Grant (Nr. W420–15) and the University of Pretoria. SJU was funded by Oxford Brookes University