Genetic Analysis of Sexual Dimorphism in the Toothed Earwig Spongovostox apicedentatus

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The PI proposes to examine the ultimate causes of variability in the forceps of S.apicedentatus by estimating the potential for a further evolutionary response and clarifying evolutionary constraints on the evolution of earwig. This will be accomplished by combining a partitioning and quantification of selection with a quantitative genetic analyses of forceps morphology. Computerized image analysis will be used to relate the morphological variability in forceps to success in intra and intersexual interactions. This provides a measure of relative fitness. Quantitative genetic analysis that estimate heritabilities and genetic correlations will indicate potential genetic influences and constraints on variability. The genetic analysis yields a measure of the potential for response to selection. Combining the analysis of selection with the estimated response to selection will provide a detailed description of the evolution of forceps in S. apicedentatus. This, this study will provide a detailed analysis of the evolution of a sexually dimorphic structure. In addition to this laboratory study, the PI will continue to collect preliminary field observations on the use of forceps by S. apicedentatus in the Sonoran desert of Arizona. Thus, the laboratory observations can be compared to a more natural situation. In addition, the field work will also generate preliminary data for future comparative analyses of variability between populations and species, and information useful in designing future field studies of other species of earwigs.