Evol Ecol Res 1: 651-662 (1999)     Full PDF if your library subscribes.

Development of colour in an aposematic ladybird beetle: The role of environmental conditions

Christopher P. Grill*

T.H. Morgan School of Biological Sciences, Center for Ecology, Evolution and Behavior, University of Kentucky, 101 Morgan Building, Lexington, KY 40546-0091, USA

Address all correspondence to Christopher P. Grill, Division of Natural Sciences, University of Hawaii at Hilo, 200 West Kawili Street, Hilo, HI 96720, USA.
e-mail: grill@hawaii.edu


I investigate the role of food quality and the use of a chemical defence in determining variability of warning colouration in an introduced aposematic beetle, Harmonia axyridis. I compare the development of colour in adults reared on different semi-natural diets and examine the effects of use of a chemical defence response, reflex bleeding, on adult colour. Adult colour differences are investigated using a combination of spectral inflection point data and principal component analysis. The two analysis techniques provide similar conclusions. Adult diet has very strong effects on the development of colour over time. Almost immediately, diet treatments diverge, with the high-quality aphid diet producing vibrantly coloured red adults, whereas a lower-quality pollen diet produces pale orange adults. Reflex bleeding has almost no effect on any aspect of adult beetle colour. The timing of reflex bleeding does not influence colour development. Finally, reflex bleeding and dietary stress do not result in reductions in the brightness, chroma or hue of adult Harmonia colour once colour development has taken place. The implications of these results for the evolution of colour are discussed.

Keywords: aposematism, chemical defence, colouration, food quality, Harmonia axyridis, reflex bleeding.

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