Quantitative Genetics of Bryozoan Phenotypic Evolution. I. Rate Tests for Random Change Versus Selection in Differentiation of Living Species

Cheetham, Alan H.; Jackson, Jeremy B. C.; Hayek, Lee‐Ann C.

doi:10.2307/2410165

Cited by 38 publications

(92 citation statements)

References 25 publications

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“…However, words of caution have been set forth by a number of researchers against that procedure (Phillips et al, 2001;Steppan et al, 2002;Willis et al, 1991), because the genetic and phenotypic covariances can differ by a number of reasons, and more research on that subject is certainly needed before genetic covariances can be replaced by phenotypic covariances with confidence (Lynch and Walsh, 1998). The multivariate selection tests used are based on the fact that, under genetic drift, the G matrix will be modified by a constant proportional to t/N e (Lande, 1979), and the G matrices of diverging populations or species should remain proportional (Cheetham et al, 1993;Lofsvold, 1988). Recent evidence indicates that genetic drift might change the G matrices by more than a proportionality constant (Phillips et al, 2001), and a theory is still needed to describe the expected evolution of genetic covariances under genetic drift.…”

Section: Sensitivity Analysis and Robustness Of Resultsmentioning

confidence: 99%

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Morphological divergence rate tests for natural selection: uncertainty of parameter estimation and robustness of results

Monteiro

Gomes‐Jr

2005

Genet. Mol. Biol.

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In this study, we used a combination of geometric morphometric and evolutionary genetics methods for the inference of possible mechanisms of evolutionary divergence. A sensitivity analysis for the constant-heritability rate test results regarding variation in genetic and demographic parameters was performed, in order to assess the relative influence of uncertainty of parameter estimation on the robustness of test results. As an application, we present a study on body shape variation among populations of the poeciliine fish Poecilia vivipara inhabiting lagoons of the quaternary plains in northern Rio de Janeiro State, Brazil. The sensitivity analysis showed that, in general, the most important parameters are heritability, effective population size and number of generations since divergence. For this specific example, using a conservatively wide range of parameters, the neutral model of genetic drift could not be accepted as a sole cause for the observed magnitude of morphological divergence among populations. A mechanism of directional selection is suggested as the main cause of variation among populations in different habitats and lagoons. The implications of parameter estimation and biological assumptions and consequences are discussed.

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Section: Sensitivity Analysis and Robustness Of Resultsmentioning

confidence: 99%

“…Genetic drift has not been rejected in some cases (Lynch, 1990;Cheetham et al, 1993), but studies claiming directional selection (such as Clegg et al, 2002) as a mechanism are rare, probably because of the reversals in directional selection patterns during longer periods of time.…”

Section: Introductionmentioning

confidence: 99%

Morphological divergence rate tests for natural selection: uncertainty of parameter estimation and robustness of results

Monteiro

Gomes‐Jr

2005

Genet. Mol. Biol.

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“…Temporal and spatial patterns of variation in fossils may be interpreted using studies of related recent species. Such an approach has rarely been followed, although it has proven fruitful (e.g., in Bryozoa, Cheetham et al 1993Cheetham et al , 1995. In this respect, molluscs are model organisms because they are well represented both in living faunas and in fossil series (Bayer and Seilacher 1985, p. 4).…”

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Variation of Shell Shape in the Clonal Snail Melanoides Tuberculata and Its Consequences for the Interpretation of Fossil Series

Samadi¹,

David

Jarne

2000

Evolution

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Abstract.Interpreting paleontological data is difficult because the genetic nature of observed morphological variation is generally unknown. Indeed, it is hardly possible to distinguish among several sources of morphological variation including phenotypic plasticity, sexual dimorphism, within-species genetic variation or differences among species. This can be addressed using fossil organisms with recent representatives. The freshwater snail Melanoides tuberculata ranks in this category. A fossil series of this and other species have been studied in the Turkana Basin (Kenya) and is presented as one of the best examples illustrating the punctuated pattern of evolution by the tenants of this theory. Melanoides tuberculata today occupies most of the tropics. We studied variation of shell shape in natural populations of this parthenogenetic snail using Raup's model of shell coiling. We considered different sources of variation on estimates of three relevant parameters of Raup's model: (1) variation in shell shape was detected among clones, and had both genetic and environmental bases; (2) sexual dimorphism, in those clones in which males occur, appeared as an additional source of shell variation; and (3) ecophenotypic variation was detected by comparing samples from different sites and years within two clones. We then tested the performance of discriminant function analyses, a classical tool in paleontological studies, using several datasets. Although the three sources of variation cited above contributed significantly to the observed morphological variance, they could not be detected without a priori knowledge of the biological entities studied. However, it was possible to distinguish between M. tuberculata and a related thiarid species using these analyses. Overall, this suggests that the tools classically used in paleontological studies are poorly efficient when distinguishing between important sources of within-species variation. Our study also gives some empirical bases to the doubts cast on the interpretation of the molluscan series of the Turkana Basin.

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“…All rights reserved. (u~) partitioned by parentage (left) and by membership in colonies (right) in two living species of the cheilostome bryozoan Stylopoma (Cheetham et al 1993). Components are proportions of phenotypic variance averaged for 10 traits of skeletal morphology in each species; numerical values are averaged across the two species.…”

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confidence: 99%

“…For two living bryozoan species ( fig. 1), genetic parameters based on repeatability were reconstructed with sufficient precision to reproduce estimates of forces of selection and random change based on breeding data (Cheetham et al 1993). This precision was possible because nonadditive genetic variance (attributable to dominance and epistasis) and among-colonies environmental variance are so small in these species, and their genetic and phenotypic covariances are so closely proportional.…”

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Quantitative Genetics of Bryozoan Phenotypic Evolution. Ii. Analysis of Selection and Random Change in Fossil Species Using Reconstructed Genetic Parameters

1994

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Abstract. -The roles of natural selection and random genetic change in the punctuated phenotypic evolution of eight Miocene-Pliocene tropical American species of the cheilostome bryozoan Metrarabdotos are analyzed by quantitative genetic methods. Trait heritabilities and genetic covariances reconstructed by partitioning within-and among-colony phenotypic variance are similar to those previously obtained for living species of the cheilostome Stylopoma using breeding data. The hypothesis that differences in skeletal morphology between species ofMetrarabdotos are entirely due to mutation and genetic drift cannot be rejected for reasonable rates of mutation maintained for periods brief enough to account for the geologically abrupt appearances of these species in the fossil record. Except for one pair of species, separated by the largest morphologic distance, directional selection acting alone would require unrealistically high rates of selective mortality to be maintained for these periods. Thus, directional selection is not strongly implicated in the divergence ofMetrarabdotos species. Within species, rates ofnet phenotypic change are slow enough to require stabilizing selection, but mask large, relatively rapid fluctuations, all of which, however, can be attributed to chance departures from the mean phenotype by mutation and genetic drift, rather than to tracking environmental fluctuation by directional selection. The results are consistent with genetic models involving shifts between multiple adaptive peaks on which phenotypes remain more or less static through long-term stabilizing selection. Regardless of the degree to which directional selection may be involved in peak shifts, phenotypic differentiation is thus related to processes different than the pervasive stabilizing selection acting within species.

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Quantitative Genetics of Bryozoan Phenotypic Evolution. I. Rate Tests for Random Change Versus Selection in Differentiation of Living Species

Cited by 38 publications

References 25 publications

Morphological divergence rate tests for natural selection: uncertainty of parameter estimation and robustness of results

Morphological divergence rate tests for natural selection: uncertainty of parameter estimation and robustness of results

Variation of Shell Shape in the Clonal Snail Melanoides Tuberculata and Its Consequences for the Interpretation of Fossil Series

Quantitative Genetics of Bryozoan Phenotypic Evolution. Ii. Analysis of Selection and Random Change in Fossil Species Using Reconstructed Genetic Parameters

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