Latitudinal variation in sexual dimorphism of wing morphology in geometrid moths
|Author:||Eberinwa, Ijeoma Cynthia1|
1University of Oulu, Faculty of Science, Biology
|Online Access:||PDF Full Text (PDF, 1.7 MB)|
|Persistent link:|| http://urn.fi/URN:NBN:fi:oulu-202206213101
Oulu : I. Eberinwa,
|Publish Date:|| 2022-06-22
|Thesis type:||Master's thesis
Sexual dimorphism is notable in insect populations and latitudinal regions. Varying sizes and shapes between the sexes help insects to optimize performance for the different roles or environments they occupy. In this study, I analyse sexual dimorphism of wing length and shape across latitudinally distinct populations of two geometrid moths.
This study aims to analyse the morphological differences between males and females in Cabera pusaria and Chiasmia clathrata, using their fore wing length and fore wing aspect ratio to investigate the wing length and shape dimorphism across a gradient of growing season length and in relation to body size. I use linear mixed models to test for effects of sex, body (femur) size and mean growing season length on wing length and aspect ratio. I expected both species (C. pusaria and C. clathrata) to show same sexual dimorphism and to follow the same scaling along the latitudinal gradient. This is because they are relatively closely related within their family: Geometridae: Ennominae. Some of these assumptions proved to be wrong. The analysis reveals that both Chiasmia clathrata and Cabera pusaria display sexual wing dimorphism. In Chiasmia clathrata, the dimorphism occurs in the forewing length, while Cabera pusaria exhibits their sex difference in the forewing aspect ratio.
When their body size (estimated using mid femur length) was plotted against the season length with sex as the interacting factor, their forewing aspect ratio and fore wing length also show a similar pattern of scaling with season length; they all decrease or remain constant (show no changes) with growing season length. The results show evidence of sexual dimorphism in wing size of geometrid moths, while along the gradient of growing season there little is variation in the strength of the sexual dimorphism for these two species. The general implication is that size dimorphism of both sexes of C. pusaria and C. clathrata is not related to the length of the growing season, it is more related to their morphology such as body size, life history and ecological behaviour.
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