What’s Behind Wing Size in Pieris rapae? A Look at Migration, Adaptation, and Sexual Selection

Presenter: Leila Demi Lendon

Faculty Sponsor: Kathryn Weglarz

School: Westfield State University

Research Area: Biology

Session: Poster Session 3, 1:15 PM - 2:00 PM, Auditorium, A13

ABSTRACT

Pieris rapae, the cabbage white butterfly, is a cosmopolitan species with varied migration
behavior. Our study compared migratory and non-migratory populations to test how migration
contributes to wing size. We hypothesized that migratory populations of P. rapae would display
longer and wider wings than non-migratory populations, since larger wings may allow more
efficient long-distance flight. To test this hypothesis, we measured wing length, width, and
melanization from P. rapae specimens obtained from iDigBio.org. These specimens represented
three geographic regions: migratory North America (n=273, 272, 293 ), non-migratory Europe
(n=611, 611, 610), and non-migratory Australia (n=40, 45, 47). In which the specimens were
collected from the year 1800 to 1993. Australia, although non-migratory, was included to
determine whether wing size differences reflect only migration and/or other environmental
factors. We measured wing dimensions using ImageJ software and used ANOVA and
Tukey-Kramer tests to determine statistically significant wing differences among regions. Our
results showed that North American and Australian butterflies had larger wings than European
butterflies, supporting our hypothesis that longer wings are selected for in migratory butterflies.
Non-migratoryAustralian butterfly wings were similar to migratory North American butterflies,
suggesting other selective pressures may be involved. Our data support a relationship between
migration and increased wing size, and our findings contribute to the understanding of how
physical traits evolve in response to migration and competing environmental pressures.

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