• Lamar Michaelsen posted an update 1 week, 4 days ago

    The intensity of sexual selection in these buckets was estimated from the standardized Bateman Gradient to be in the region of 0.8 (Simmons and Garc��a-Gonz��lez 2008). After the mating period, females were established in individual breeding chambers to produce F2 offspring. The number of broods each female produced was counted. Experimental evolution was conducted for INK 128 research buy a second generation, providing F3 offspring. Male offspring were sampled for strength and testes mass. At 1 week of age, a sample of males were weighed and their pronotum width measured. Some were dissected and their testes removed and weighed. Others were assessed for strength using the methods described in Knell and Simmons (2010). In brief, a length of cotton was attached to the elytra and the male allowed to enter an artificial tunnel between two pieces of glass, lined with fine sandpaper allowing the beetles to attain a firm grip on the substrate. A small polythene bag was attached to the end of the cotton, and the tunnel inclined to an angle of 60�� from the horizontal. The cotton was pulled gently to encourage the beetle to grip onto the sandpaper. Water was then dripped into the bag at a constant rate until the beetle was unable to maintain its grip and was pulled from the tunnel. The weight of the bag plus water was determined and converted to Newtons to give a measure of the beetle’s strength. We assayed samples of males from the F1, F2, and F3 generations. Data were log transformed where necessary and analyzed using general linear models. For male sexual traits, treatment, selection regime, generation, and male morph were entered as main effects; males were assigned to a morph based on their pronotum width (minors < 5.0 mm �� majors; Simmons et al. 1999). Body weight was also entered as a covariate. Nonsignificant interaction terms were removed from the models. All means are provided ��1 standard error. Induced mutations in their heterozygous state had only weak effects on male sexual traits (Table?1). Although male body size, strength, and testes weight of F1 males were lower when their fathers had been exposed to ionizing radiation, the differences among treatment groups were not statistically significant (Tables S1�CS3). The number of broods produced by F1 female offspring did not differ between treatment groups or the mating regime to which they were subjected (Tables?2, S4). However, when induced mutations could occur in their homozygous state, in the F2 and F3 offspring, male sexual traits were affected. Male body size among the F2 and F3 generations did not vary across selection regimes or treatments (Table S5). However, selection regime (F1,90 = 5.82, P < 0.001), treatment (F1,90 = 24.32, P < 0.001) and generation (F1, 90 = 32.64, P < 0.001) all influenced beetle strength (Table S6). Importantly, the interaction between selection and treatment was significant (F1,90 = 5.90, P = 0.017).