Alpine melanism, a tendency to become darker with increased elevation and latitude, occurs in many species of butterflies. In Parnassius phoebus
(Papilionidae) it has been assumed that alpine melanism is the result of adaptation to colder environments at higher elevations and latitudes, owing to the ability of darker wings to transfer more solar energy to the body as heat. I examined five independently variable components of wing melanism for agreement with this hypothesis, as well as the subsidiary hypothesis that size is inversely correlated to melanism because it also affects thermoregulation. Basal patch blackness (proportion of scales which are black) in both sexes is well correlated with elevation, latitude, and air temperature during the flight season. In males, increased basal patch blackness is advantageous because it increases the proportion of total time spent in flight looking for mates, but is locally disadvantageous because it increases the probability of dispersal. Basal patch width is only poorly correlated with elevation, latitude, and air temperature during the flight season in males, and not correlated in females. Increased patch width also results in increased flight activity, but does not affect dispersal. Basal wing transparency has little correlation with elevation, and no effect on activity, although it does slightly affect body temperature. Within individual mountains, distal wing blackness and transparency are correlated with elevation, but show no correlation when many mountains are considered together. Distal wing characters have no effect on flight activity or dispersal. Size is well correlated with elevation and latitude, but is less well correlated with air temperature. Smaller males disappear from the population more rapidly than large males, apparently through increased mortality because small males do not disperse more rapidly. Females disperse more than males, with larger females dispersing more than smaller females. Variation in basal patch blackness may have a similar adaptive significance in both sexes, but all the other melanism characters appear to have a different significance for each sex. I develop a new hypothesis for the mechanism of the effect of wing color on thermoregulation in dorsal basking butterflies. I suggest that most transfer of solar radiation to the body by the wings occurs while in flight, rather than while dorsal basking on a substrate. This hypothesis is used to explain the observation that the minimum levels of air temperature and solar radiation at which flight can occur does not depend on wing color in Parnassius phoebus, in contrast to phenotype dependent flight thresholds in lateral basking Colias. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/24675 |
| Date | January 1984 |
| Creators | Guppy, Crispin Spencer |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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