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Apex Melanization in Native and Introduced Ranges of Pieris Rapae

Pieris rapae is a species of butterfly found in a wide range of habitats, which have white wings with black spots, where the white pigment is due to pterins, and the black pigment is formed by melanin. Studies have shown that melanization in Pieris rapae has a strong correlation to the temperature in its environment.  However, studies have shown that other environmental factors such as diet also contribute to melanization.  Our study aims to analyze the scope of limitations of temperature as a prediction for apex melanization.  Our hypothesis is that there will be a significant variation in the apex melanization of Pieris rapae in introduced and native ranges of the same climate, due to differences in available diet.  We choose to only consider apex melanization because the spots on the butterfly are a secondary sex characteristic.  For our sample, we use the iDigBio digital database for records of Pieris rapae specimens, measured by our group as well as students from the class. We record the measurements of the M3 melanization spots from 200 specimens from both the native and introduced populations in temperate zones from Europe and North America, from the summer seasons. We summarize our data using an ANOVA test.  As a result, we fail to reject our null hypothesis; meaning that there is no significant variation in apex melanization in Pieris Rapae to suggest a difference in native and introduced ranges.

Isabelle Scott '24, Kerin Johnson '25   
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