Chromosome polymorphisms and natural selection in Leptysma argentina (Orthoptera): External phenotype affected by a centric fusion predicts adult survival
The relationship between fitness variation associated with a quantitative trait and a Mendelian factor affecting that trait was examined in a natural population of the South American grasshopper Leptysma argentina. Previous studies have shown that a centric fusion between chromosomes 3 and 6 (fusion...
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| Autores principales: | , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00221333_v78_n1_p57_Norry |
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| Sumario: | The relationship between fitness variation associated with a quantitative trait and a Mendelian factor affecting that trait was examined in a natural population of the South American grasshopper Leptysma argentina. Previous studies have shown that a centric fusion between chromosomes 3 and 6 (fusion 3/6) increases adult survival and body size in this grasshopper. Here we examined the possible relationships among fusion 3/6, a size-related trait (prothorax height) and adult survival in a natural population. The study was based on two generations, comparing samples taken at the beginning and at the end of the adult life span. All individuals were karyotyped and scored for prothorax height (PH). A nonparametric regression analysis revealed that adult survival monotonically increased with PH in both generations. Moreover, fusion 3/6 was found to have an additive effect on this trait. Within generations, fusion frequency increased with adult survival in males (but not significantly so), as expected if phenotypic selection on PH influences the fusion polymorphism. Using regression analyses, we show that the correlation between PH and adult survival is not a purely environmental correlation genetically independent from the fusion polymorphism. A simple model is proposed for testing similar hypotheses in studies of selection on a trait influenced by a known genetic polymorphism. |
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