Characteristics and drivers of high-altitude ladybird flight: insights from vertical-looking entomological radar

Jeffries, Daniel L., Chapman, Jason, Roy, Helen E. , Humphries, Stuart, Harrington, Richard, Brown, Peter M. J. and Lawson Handley, Lori J. (2013) Characteristics and drivers of high-altitude ladybird flight: insights from vertical-looking entomological radar. PLoS ONE, 8 (12). ISSN 1932-6203

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Characteristics and drivers of high-altitude ladybird flight: Insights from vertical-looking entomological radar
� 2013 Jeffries et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Understanding the characteristics and drivers of dispersal is crucial for predicting population dynamics, particularly in range-shifting species. Studying long-distance dispersal in insects is challenging, but recent advances in entomological radar offer unique insights. We analysed 10 years of radar data collected at Rothamsted Research, U.K., to investigate characteristics (altitude, speed, seasonal and annual trends) and drivers (aphid abundance, air temperature, wind speed and rainfall) of high-altitude flight of the two most abundant U.K. ladybird species (native Coccinella septempunctata and invasive Harmonia axyridis). These species cannot be distinguished in the radar data since their reflectivity signals overlap, and they were therefore analysed together. However, their signals do not overlap with other, abundant insects so we are confident they constitute the overwhelming majority of the analysed data. The target species were detected up to ~1100 m above ground level, where displacement speeds of up to ~60 km/h were recorded, however most ladybirds were found between ~150 and 500 m, and had a mean displacement of 30 km/h. Average flight time was estimated, using tethered flight experiments, to be 36.5 minutes, but flights of up to two hours were observed. Ladybirds are therefore potentially able to travel 18 km in a "typical" high-altitude flight, but up to 120 km if flying at higher altitudes, indicating a high capacity for long-distance dispersal. There were strong seasonal trends in ladybird abundance, with peaks corresponding to the highest temperatures of mid-summer, and warm air temperature was the key driver of ladybird flight. Climatic warming may therefore increase the potential for long-distance dispersal in these species. Low aphid abundance was a second significant factor, highlighting the important role of aphid population dynamics in ladybird dispersal. This research illustrates the utility of radar for studying high-altitude insect flight and has important implications for predicting long-distance dispersal. © 2013 Jeffries et al.

Keywords:rain, air temperature, altitude, aphid, article, biological monitoring, climate change, Coccinella septempunctata, female, flight, Harmonia axyridis, long distance migrant, male, nonhuman, population abundance, population dispersal, population dynamics, prediction, seasonal variation, summer, temperature, time series analysis, trend study, United Kingdom, velocity, vertical looking entomological radar, warming, wind
Subjects:C Biological Sciences > C340 Entomology
Divisions:College of Science > School of Life Sciences
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ID Code:15248
Deposited On:03 Oct 2014 10:31

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