. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 6789 AGE (yr) 10 11 12 Figure 2. Arcsine square root compound E allele frequency as a function of age at Croyde high shore (+ and solid line) and Croyde low shore (A and broken line). cant length-at-age differences exist between the genotypes. It is at this stage that viability differences between the genotypes are most pronounced, resulting in greatest dif- ferential mortality of edulis mussels. Third, following this period of maximum differential mortality, the oldest sur- viving mussels exhibit nonsignificant differe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 6789 AGE (yr) 10 11 12 Figure 2. Arcsine square root compound E allele frequency as a function of age at Croyde high shore (+ and solid line) and Croyde low shore (A and broken line). cant length-at-age differences exist between the genotypes. It is at this stage that viability differences between the genotypes are most pronounced, resulting in greatest dif- ferential mortality of edulis mussels. Third, following this period of maximum differential mortality, the oldest sur- viving mussels exhibit nonsignificant differences in length- at-age values. Thus, during the second stage, the highest mortality rates are experienced by the echilis individuals with the lowest viabilities (and also the smallest length- at-age values), resulting in the significant differences in mean length-at-age values observed at this time. The edulis with (by definition) the highest viabilities (and the greatest length-at-age values) survive this period so that among the oldest age classes, when viability differences are once again less pronounced, there are no significant differences in length-at-age values. The positive association between length-at-age values and viability among the echilis indi- viduals can be explained in one of two ways. One, the association is noncausal, resulting from, for example, pleiotropy ( Falconer. 1989). Two. it is causal, and occurs because increased shell length offers a refuge from predators (Gardner and Skibinski, 1991) and confers a fitness advantage in terms of increased byssal strength of attachment to the substrate, which decreases the chance of being dislodged from the rock face and swept out to sea (Gardner and Skibinski, 1991; Willis and Skibinski, 1992). Based on genotype frequency differences between young and old mussels, relative viability coefficients were cal- culated that demonstrate a high selective mortality against echilis. Increasingly more evidence points to
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
