Holocene environmental changes in the lower Thames Valley, London, UK: implications for our understanding of the history of Taxus woodland

A radiocarbon-dated multiproxy palaeoenvironmental record from the Lower Thames Valley at Hornchurch Marshes has provided a reconstruction of the timing and nature of vegetation succession against a background of Holocene climate change, relative sea level movement and human activities. The investigation recorded widespread peat formation between c. 6300 and 3900 cal. yr BP (marine ‘regression’), succeeded by evidence for marine incursion. The multiproxy analyses of these sediments, comprising pollen, Coleoptera, diatoms, and plant and wood macrofossils, have indicated significant changes in both the wetland and dryland environment, including the establishment of Alnus (Alder) carr woodland, and the decline of both Ulmus (Elm; c. 5740 cal. yr BP) and Tilia (Lime; c. 5600 cal. yr BP, and 4160–3710 cal. yr BP). The beetle faunas from the peat also suggest a thermal climate similar to that of the present day. At c. 4900 cal. yr BP, Taxus (L.; Yew) woodland colonised the peatland forming a plant community that has no known modern analogue in the UK. The precise reason, or reasons, for this event remain unclear, although changes in peatland hydrology seem most likely. The growth of Taxus on peatland not only has considerable importance for our knowledge of the vegetation history of southeast England, and NW Europe generally, but also has wider implications for the interpretation of Holocene palaeobotanical records. At c. 3900 cal. yr BP, Taxus declined on the peatland surface during a period of major hydrological change (marine incursion), an event also strongly associated with the decline of dryland woodland taxa, including Tilia and Quercus, and the appearance of anthropogenic indicators.

Variability in life-history and ecological traits is a buffer against extinction in mammals

Anthropogenic degradation of the world's ecosystems is leading to a widespread and accelerating loss of biodiversity. However, not all species respond equally to existing threats, raising the question: what makes a species more vulnerable to extinction? We propose that higher intraspecific variability may reduce the risk of extinction, as different individuals and populations within a species may respond differently to occurring threats. Supporting this prediction, our results show that mammalian species with more variable adult body masses, litter sizes, sexual maturity ages and population densities are less vulnerable to extinction. Our findings reveal the role of local variation among populations, particularly of large mammals, as a buffering mechanism against extinction, and emphasise the importance of considering trait variation in comparative analyses and conservation management.

Earworms ("stuck song syndrome"): towards a natural history of intrusive thoughts

Two studies examine the experience of “earworms”, unwanted catchy tunes that repeat. Survey data show that the experience is widespread but earworms are not generally considered problematic, although those who consider music to be important to them report earworms as longer, and harder to control, than those who consider music as less important. The tunes which produce these experiences vary considerably between individuals but are always familiar to those who experience them. A diary study confirms these findings and also indicates that, although earworm recurrence is relatively uncommon and unlikely to persist for longer than 24 hours, the length of both the earworm and the earworm experience frequently exceed standard estimates of auditory memory capacity. Active attempts to block or eliminate the earworm are less successful than passive acceptance, consistent with Wegner’s (1994) theory of ironic mental control.