Computation and uses of central trend lines

Ricker, W. E.

doi:10.1139/z84-279

Cited by 292 publications

(204 citation statements)

References 6 publications

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“…The r 2 value of the ordinary linear regression ( on H ) was so high ( , ) that the slope of the 2 J rp 0.87 P ! .0001 reduced major axis, or geometric mean regression (GMR), was not very different from the linear regression (Ricker 1984 fig. 2C, 2D).…”

Section: Overall Relationshipsmentioning

confidence: 85%

Empirical Relationships between Species Richness, Evenness, and Proportional Diversity

Stirling¹,

Wilsey²

2001

The American Naturalist

168

220

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Diversity (or biodiversity) is typically measured by a species count (richness) and sometimes with an evenness index; it may also be measured by a proportional statistic that combines both measures (e.g., Shannon-Weiner index or ). These diversity measures are hypothesized to be positively and strongly correlated, but this null hypothesis has not been tested empirically. We used the results of Caswell's neutral model to generate null relationships between richness (S), evenness ( ), and proportional diversity (). We tested predictions of the null model against empirical relationships describing data in a literature survey and in four individual studies conducted across various scales. Empirical relationships between or and differed from the null model when <10 species were tested and in>plants, vertebrates, and fungi. The empirical relationships were similar to the null model when >10 and <100 species were tested and in invertebrates. If>100 species were used to estimate diversity, the relation between and was negative. The strongest predictive models included and . A path analysis indicated that and were always negatively related, that empirical observations could not be explained without including indirect effects, and that differences between the partials may indicate ecological effects, which suggests that S and act like diversity components or that diversity should be measured using a compound statistic. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. abstract: Diversity (or biodiversity) is typically measured by a species count (richness) and sometimes with an evenness index; it may also be measured by a proportional statistic that combines both measures (e.g., Shannon-Weiner index or ). These diversity measures H are hypothesized to be positively and strongly correlated, but this null hypothesis has not been tested empirically. We used the results of Caswell's neutral model to generate null relationships between richness (S), evenness ( ), and proportional diversity ( ). We tested predictions J H of the null model against empirical relationships describing data in a literature survey and in four individual studies conducted across various scales. Empirical relationships between or and differed from log S J H the null model when !10 species were tested and in plants, vertebrates, and fungi. The empirical relationships were similar to the null model when 110 and !100 species were tested and in invertebrates. If 1100 species were used to estimate diversity, the relation between and log S was negative. The strongest predictive models included and H log S . A path analysis indicated that and were always negatively J log S J related, that empirical observations could not be explained without including indirect effec...

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Section: Overall Relationshipsmentioning

confidence: 85%

Empirical Relationships between Species Richness, Evenness, and Proportional Diversity

Stirling¹,

Wilsey²

2001

The American Naturalist

168

220

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“…Slope comparisons between orders were not possible due to small sample sizes. The reduced major axis regression was chosen because error variance is assumed to exist for both variables and the ratio of these variances is also assumed to be proportional to the population variances (Ricker, 1984;Rayner, 1985;Plotnick, 1989;Harvey and Krebs, 1990). The expected line of isometry between convergence and binocular visual field overlap has a slope of 2.…”

Section: Discussionmentioning

confidence: 99%

On the relationship between orbit orientation and binocular visual field overlap in mammals

2004

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The orbital apertures of Primates are among the most convergent (i.e., facing in the same direction) among mammals. It is often assumed that orbit convergence is associated with binocular visual field overlap and stereoscopic depth perception in primates. Likewise, it is also assumed that orbit orientation reflects the shape of the visual field across mammals. To date, however, no study has demonstrated that orbit and visual field orientation are correlated, much less comparable, across mammals. In this study, data on orbit convergence were collected for a representative sample of mammals for which data on the extent of the visual field are available. Both standard and phylogenetically controlled comparisons were made. The results demonstrate that orbit convergence and binocular visual field overlap are significantly correlated and display a linear relationship. Based on orbit convergence, Primates as a group have the largest binocular visual fields among mammals.

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“…Univariate statistics used are described in standard textbooks (Neter and Wasserman, 1974 log Y (linearly) regressed on log X and the inverse of that derived from regressing log X on log Y (Ricker, 1984). We employed all of these methods, although we present only linear and GMR estimates and relied most heavily on the latter.…”

Section: Statistical Analysesmentioning

confidence: 99%

FLIGHTLESSNESS IN STEAMER‐DUCKS (ANATIDAE: TACHYERES ): ITS MORPHOLOGICAL BASES AND PROBABLE EVOLUTION

Livezey¹,

Humphrey

1986

Evolution

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Abstract. -Flightlessness in Tachyeres is caused by wing-loadings in excess of 2.5 gcm", which result from the large body size and small wing areas of the flightless species. Reduced wing areas offlightless species are related to absolutely shorter remiges, and to relatively or absolutely shortened wing bones, although these reductions differ among species. Reduced lengths of the ulna, radius, and carpometacarpus are associated most strongly with flightlessness. Pectoral muscles and the associated sternal keel are well developed in all species of Tachyeres, largely because of the use of wings in "steaming," an important locomotor behavior. Relative size ofthese muscles was greatest in largely flighted T. patachonicus; however, sexual dimorphism in wing-loadings results in flightlessness in some males of this species. Proportions in the wing skeleton, intraspecific allometry, and limited data on growth indicate that the relatively short wing bones and remiges of flightless Tachyeres are produced developmentally by a delay in the growth of wing components, and that this heterochrony may underlie, in part, skeletal sexual dimorphism. Increased body size in flightless steamer-ducks is advantageous in territorial defense of food resources and young, and perhaps diving in cold, turbulent water; reductions in wing area probably reflect refinements for wingassisted locomotion and combat. Flightlessness in steamer-ducks is not related to relaxed predation pressure, but instead was permitted selectively by the year-round habitability ofthe southern South American coasts. These conditions not only permitted the success ofthe three flightless species of Tachyeres, but at present may be moving marine populations of T. patachonicus toward flightlessness.

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Computation and uses of central trend lines

Cited by 292 publications

References 6 publications

Empirical Relationships between Species Richness, Evenness, and Proportional Diversity

Empirical Relationships between Species Richness, Evenness, and Proportional Diversity

On the relationship between orbit orientation and binocular visual field overlap in mammals

FLIGHTLESSNESS IN STEAMER‐DUCKS (ANATIDAE: TACHYERES ): ITS MORPHOLOGICAL BASES AND PROBABLE EVOLUTION

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