THE COST OF MELANIZATION: BUTTERFLY WING COLORATION UNDER ENVIRONMENTAL STRESS

Evolutionary studies typically focus on adaptations to particular environmental conditions, thereby often ignoring the role of possible constraints. Here we focus on the case of variation in dorsal wing melanization in a satyrine butterfly Pararge aegeria. Because melanin is a complex polymer, its s...

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Bibliographic Details
Published in:Evolution 2004-02, Vol.58 (2), p.360-366
Main Authors: Talloen, W, Van Dyck, H, Lens, L
Format: Article
Language:English
Subjects:
Adult insects
Animal Nutritional Physiological Phenomena
Animals
Belgium
Butterflies
Butterflies & moths
Butterflies - physiology
Crosses, Genetic
Developmental constraint
Drought
Environment
Evolution
Evolutionary biology
fluctuating asymmetry
Genetic diversity
Host plants
Insect larvae
Larval development
Melanin
Melanins - biosynthesis
Melanization
Phenotypic traits
Pigmentation - physiology
Plants - chemistry
REGULAR ARTICLES
resource allocation
thermoregulation
Wings, Animal - physiology
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Summary:Evolutionary studies typically focus on adaptations to particular environmental conditions, thereby often ignoring the role of possible constraints. Here we focus on the case of variation in dorsal wing melanization in a satyrine butterfly Pararge aegeria. Because melanin is a complex polymer, its synthesis may be constrained if ambient conditions limit the resource budget. This hypothesis was tested by comparing melanization among butterflies that fed as larvae on host grasses experiencing different drought-stress treatments. Treatment differences were validated both at the level of the host plant (nitrogen, carbonate, and water content) and of the butterfly (life-history traits: survival, development time, and size at maturity). Melanization rate was measured as average gray value of the basal dorsal wing area. This area, close to the thorax, is known to be functionally significant for basking in order to thermoregulate. Individuals reared on drought-stressed host plants developed paler wings, and development of darker individuals was slower and less stable as estimated by their level of fluctuating asymmetry. These results provide evidence that melanin is indeed costly to synthesize, and that differences in environmental quality can induce phenotypic variation in wing melanization. Therefore, studies dealing with spatial and/or temporal patterns of variation in wing melanization should not focus on adaptive explanations alone, but rather on a cost-benefit balance under particular sets of environmental conditions.
ISSN:0014-3820
1558-5646
DOI:10.1554/03-250