. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 156 A. PHILLIPPI ET AL. Table 1 Analysis of variance results for effects of population size and density on fertilization in the manipulative experiment Effect df MS SS F-ratio P Size 1 Density 1 Trial 5 Error 55 icant (P = , r = ). The power analysis indicated that a slope estimate of double the value obtained would have been necessary for significance at a = In contrast to the absence of a pattern in overall fertil
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 156 A. PHILLIPPI ET AL. Table 1 Analysis of variance results for effects of population size and density on fertilization in the manipulative experiment Effect df MS SS F-ratio P Size 1 Density 1 Trial 5 Error 55 icant (P = , r = ). The power analysis indicated that a slope estimate of double the value obtained would have been necessary for significance at a = In contrast to the absence of a pattern in overall fertilization level, a nonlinear (exponentially declining) relationship did exist between the variance in fertilization and colony density (r = <P < ; Fig. 4B). Discussion Effects of population size and density on fertilization Population density did not significantly affect fertilization in either experimental or natural populations of Botryllus schlosseri (Figs. 2. 3, 4; Table 1), although density varied across more than an order of magnitude and spanned most of the range relevant to local populations (Yund and Stires, 2002). Mean fertilization levels were generally very high (Figs. 2, 3). In the experimental manipulation, population size also had no effect on fertilization (Fig. 2: Table 1). This result contrasts with previous work on a species that broad- casts its eggs (the red sea urchin Strongylocentrotus fran- ciscanus), in which population size was found to have an interactive effect (with density) on fertilization levels (Levi- tan et til., 1992). 24 26 26 30 32 34 36 38 40 4. Week Figure 3. Percent of eggs fertili/ed (circlesI. embryos completing development (squares), and population density estimates (bars) for two natural populations ot H<iir\llu\ \.7i/ov«'n. Open bars and circles represent population DM; solid bars, circles, and squares represent population Cl. Error bars represent one standard error. I 80 OJ N 1 60 • § 40 20. Please note
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
