Three‐dimensional flight tracking shows how a visual target alters tsetse fly responses to human breath in a wind tunnel

Tsetse flies Glossina spp. (Diptera; Glossinidae) are blood‐feeding vectors of disease that are attracted to vertebrate hosts by odours and visual cues. Studies on how tsetse flies approach visual devices are of fundamental interest because they can help in the development of more efficient control tools. The responses of a forest tsetse fly species Glossina brevipalpis (Newstead) to human breath are tested in a wind tunnel in the presence or absence of a blue sphere as a visual target. The flight responses are video recorded with two motion‐sensitive cameras and characterized in three dimensions. Although flies make meandering upwind flights predominantly in the horizontal plane in the plume of breath alone, upwind flights are highly directed at the visual target presented in the plume of breath. Flies responding to the visual target fly from take‐off within stricter flight limits at lower ground speeds and with a significantly lower variance in flight trajectories in the horizontal plane. Once at the target, flies fly in loops principally in the horizontal plane within 40 cm of the blue sphere before descending in spirals beneath it. Successful field traps designed for G. brevipalpis take into account the strong horizontal component in local search behaviour by this species at objects. The results suggest that trapping devices should also take into account the propensity of G. brevipalpis to descend to the lower parts of visual targets.     

Success in the demographic expansion of Fraxinus excelsior L.

This review examines the ecological traits and ecophysiological characteristics of the common ash (Fraxinus excelsior L.) that help to explain the current spread of ash communities in Europe. As a consequence of anthropogenic disturbance, the common ash has experienced new environmental conditions and the frequency of the species has fluctuated over space and time. Owing to its ubiquity, over the last few decades the common ash has been greatly favoured in areas abandoned by agriculture and also along impounded rivers. F. excelsior is a mesophilic species that usually thrives on alluvial soils and can also survive the strong water deficit on hillslopes. Drought tolerance in ash trees is related to stomatal regulation, a decrease in osmotic potential and also an increase in the elastic modulus ). Malic acid plays a central role in drought tolerance, first as one of the major solutes involved in osmotic adjustment, and second as an effector for stomatal regulation through a drought-induced increase in its xylem concentration.