Why Small Is Beautiful: Wing Colour Is Free from Thermoregulatory Constraint in the Small Lycaenid Butterfly, Polyommatus icarus.
We examined the roles of wing melanisation, weight, and basking posture in thermoregulation in Polyommatus Icarus, a phenotypically variable and protandrous member of the diverse Polyommatinae (Lycaenidae). Under controlled experimental conditions, approximating to marginal environmental conditions for activity in the field (= infrequent flight, long duration basking periods), warming rates are maximised with fully open wings and maximum body temperatures are dependent on weight. Variation in wing melanisation within and between sexes has no effect on warming rates; males and females which differ in melanisation had similar warming rates. Posture also affected cooling rates, consistent with cooling being dependent on convective heat loss. We hypothesise that for this small sized butterfly, melanisation has little or no effect on thermoregulation. This may be a factor contributing to the diversity of wing colours in the Polyommatinae. Because of the importance of size for thermoregulation in this small butterfly, requirements for attaining a suitable size to confer thermal stability in adults may also be a factor influencing larval feeding rates, development time and patterns of voltinism. Our findings indicate that commonly accepted views of the importance of melanisation, posture and size to thermoregulation, developed using medium and large sized butterflies, are not necessarily applicable to small sized butterflies.
Centre for Ecology, Environment and Conservation, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, United Kingdom.
Rien
R
De Keyser
Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, United Kingdom.
Casper J
CJ
Breuker
Centre for Ecology and Hydrology, Maclean Building, Wallingford, OX10 8BB, United Kingdom.
Rosemary S
RS
Hails
Centre for Ecology, Environment and Conservation, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, United Kingdom.
Roger L H
RL
Dennis
Centre for Ecology, Environment and Conservation, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, United Kingdom.
Tim G
TG
Shreeve
D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation; D002080:Butterflies / Q000033:anatomy & histology* / Q000502:physiology*; D005260:Female; D008297:Male; D008543:Melanins / Q000032:analysis; D010858:Pigmentation; D011187:Posture; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology
D008543:Melanins