Advice on Workflow for Asymmetry Analysis Using bilat.symmetry in Triatomines

[Federico Fiad]

Dear Geomorph community,

I hope this message finds you well. I would like to ask about the correct workflow for analyzing asymmetry using the bilat.symmetry function in geomorph. Specifically, I aim to study whether there are changes in wing asymmetry of triatomines associated with three levels of anthropization (high, intermediate, low). My data include two species (Triatoma garciabesi and Triatoma guasayana) and both sexes (males and females). Previous studies have shown the presence of sexual dimorphism in morphological traits of triatomines, and both species have structures with different shapes.

My question is: would it be better to perform the analysis using the complete dataset or to separate it by species and sex? In the first case, I assume that the mean shape would be calculated from the combined shape changes of both species and sexes. In the second case, I believe it might yield more accurate results in terms of shape changes by sex and species.

I would appreciate your advice on this approach.

Thank you for your time and help!

Best regards,

Federico Fiad

[Adams, Dean [EEOB]]

Federico,

 

Any GM study requires a common GPA prior to downstream tests or analyses. The common GPA, which is part of bilat.symmetry, ensures that all objects are aligned in common and reside in the same tangent space. Doing separate GPA will not do that.

 

Once a common GPA is performed, one may then subset the data for any specific analyses that are question-specific.

 

Dean

 

Dr. Dean C. Adams

Distinguished Professor of Evolutionary Biology

Department of Ecology, Evolution, and Organismal Biology

Iowa State University

https://faculty.sites.iastate.edu/dcadams/

phone: 515-294-3834

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[Federico Fiad]

Hi Dean,

Thanks so much for your response and for clarifying that! It makes perfect sense now why a common GPA is necessary before moving forward with the analyses. I'll follow your suggestion and perform the common GPA with bilat.symmetry, and then subset the data as needed for my specific questions.

I really appreciate your guidance on this!

Best regards,
Federico

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