Inter- and Intraspecific Variation in the Superfamily Pneumoroidea
Date of Award
Doctor of Philosophy (Ph.D.)
Moira van Staaden
This dissertation concerns phenotypic plasticity of male morphology within South African bladder grasshoppers (Orthoptera: Pneumoroidea) from an individual to the species level. Wings and a large inflated abdomen used for acoustic courtship and communication are characteristic of adult male pneumoroids. However, a secondary (‘alternate’) male morph has been identified in three species, which completely lacks the appearance and associated dispersal and signaling behaviors. These characteristics are shared with three monotypic genera formerly raised to accommodate taxa with atypical males. As the aforementioned characteristics are critical for mate localization, the absence of such structures and behaviors demands explanation. The first chapter examines three pneumoroid species that possess both male morphs to determine how similar the uninflated morph is across taxa. The morphology of each species and morph was compared using Multivariate Analysis of Variance (MANOVA) and linear regression. Results show that the morphological differences between inflated and uninflated males is similar across species. This demonstrates that the uninflated phenotype is largely conserved within the Bullacris genus. The second chapter takes a broader comparative approach. It expands the morphometric analysis to investigate three strictly uninflated species and asks whether they are in fact uninflated morphs of inflated species with which they are sympatric. Based on results from chapter 1, we propose that the known differences between morphs can be used to create ‘hypothetical’ uninflated males for any inflated taxa. MANOVA and Discriminant Function Analysis (DFA) then compare the hypothetical males to the actual uninflated taxa. Our results suggest that each of the uninflated male taxa can be placed into inflated taxa. This now places dual morphologies in at least three genera and perhaps the entire superfamily. The third chapter uses geographic and morphological data of two widespread species to determine whether environmental characteristics: predict species presence, influence morphology, and form distinct populations. This study also examines whether clinal rules hold across the species. Results from MANOVA, logistic regression, and DFA show that, while environmental conditions are highly predictive of morphology for one species, the second does not display predictable morphological responses to environmental variation.
Donelson, Nathan, "Inter- and Intraspecific Variation in the Superfamily Pneumoroidea" (2007). Biology Ph.D. Dissertations. 16.