Rare electrophoretic variants in a hybrid zone

Barton, Nicholas H.; Halliday, R. B.; Hewitt, Godfrey M.

doi:10.1038/hdy.1983.15

Cited by 65 publications

(49 citation statements)

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“…Allozyme and morphological divergence in the Ozark region suggests that genetic isolation persists despite potential for migration and gene flow through corridors virtually indistinguishable (in terms of linear distance and environmental conditions) from those in Ohio and Ouachita regions. Incongruence of the two measures of gene flow may thus arise through dynamics associated with hybridization and genetic introgression of genetically distinct groups (Barton et al 1983). Conversely, the expected positive association between gene flow based on a and private alleles was ob- Karlin and Ricketts (1990). served in Ohio region, suggesting that extinction and recolonization after the Wisconsin glacial period did not affect congruence of gene flow estimates from the two methods.…”

Section: Discussionmentioning

confidence: 99%

Ecological and Historical Associations of Gene Flow in Darters (Teleostei: Percidae)

Turner

Trexler

1998

Evolution

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Abstract.-Life history should relate to gene flow (Nm) through its influence on dispersal and effective population size. Comparative studies designed to elucidate this relationship must contend with historical events that can yield misleading estimates of gene flow and statistical problems associated with inclusion of life-history traits correlated with phylogeny. We studied the relationships of life-history characters and gene flow in 15 species of darters, a monophyletic group of stream fishes. Populations of coexisting species were sampled in three geographic regions with different Pleistocene glaciation histories. Gene flow was estimated indirectly from allozymes using two methods, 6 and private alleles. Isolation-by-distance was also tested using regression of pairwise estimates of gene flow (M) on distance. Theta and private-alleles methods produced congruent estimates of Nm, except in a study region hypothesized to have been historically fragmented and then united following Pleistocene glaciation. A relatively weak association between life-history traits and Nm (based on 6) was observed when species from the historically fragmented region were included in stepwise regression analysis, because Nm was low despite life-history differences among taxa in this region. Excluding observations from this region produced stronger associations between clutch size and Nm (r 2 = 0.57), and between female size, egg size, and Nm (r 2 = 0.95). Additional analyses that corrected for female body size and phylogenetic nonindependence agreed that darters with high fecundity and small eggs exhibited high gene flow, whereas darters with small clutches and large eggs had low gene flow. The latter combination of life-history traits primarily is exhibited in species from headwater habitats where parental investment presumably confers survivorship on offspring. Reduced gene flow and genetic divergence among demes appear to be evolutionary consequences of this strategy.Key words.-Allozymes, comparative approach, Etheostoma, life history, mitochondrial DNA, Percina, population history.Received July 7, 1998. Accepted August 18, 1998 Life history should relate to gene flow (Nm) through its influence on dispersal and effective population size. A number of comparative studies have shown that interspecific lifehistory variation and gene flow are only weakly related (reviewed in Avise 1994). This probably results from the effects of historical events on genetic structure, for example, vicariant fragmentation, range expansion, and extinction and recolonization. Such events can produce patterns of genetic divergence that are similar to patterns resulting from ongoing migration (Felsenstein 1982;Templeton et al. 1995). Thus, comparing taxa with different population histories can diminish the explanatory power of life-history traits as predictors of gene flow (Loveless and Hamrick 1984;Boileau et al. 1992; Schulman and Bermingham 1995).Comparisons of unrelated and ecologically dissimilar taxa can obscure the relationship between life-history ...

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Section: Discussionmentioning

confidence: 99%

Ecological and Historical Associations of Gene Flow in Darters (Teleostei: Percidae)

Turner

Trexler

1998

Evolution

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“…the one from Djemila. Several mechanisms, including higher mutation rate and relaxed selection, have been proposed to explain both the production and maintenance of these peculiar allelic variants, but they cannot reliably be distinguished (Barton et a!., 1983;Barton & Hewitt, 1985;Woodruff, 1989). Whatever is the explanation for such a local increase in peculiar allozymes, introgressed and private alleles apparently lead to different patterns of migration but both reflect the existence of gene exchanges between western and eastern populations.…”

Section: Discussionmentioning

confidence: 99%

Genetic relationships among suspected contact zone populations of Helix aspersa (Gastropoda: Pulmonata) in Algeria

1996

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“…This is made possible by the availIntroduction ability of neutral genetic markers and appropriate Gene flow, the movement of genes among populagenetic models with which to interpret their distributions, is of interest to evolutionary biologists because tion (Wright, 1951;Barton et a!., 1983; of its influence on genetic differentiation. Because it 1985b), the most common of these being Wright's is difficult to observe directly, gene flow is often island model.…”

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Estimates of gene flow in Eichhornia paniculata (Pontederiaceae): effects of range substructure

Husband

Barrett

1995

Heredity

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Gene flow in the annual aquatic plant, Eichhomia paniculata, was inferred from estimates of genetic differentiation at 24 isozyme loci among 44 populations from north-east Brazil. Population differentiation, estimated as the correlation among genes of different individuals (4)), was 0.45 (range among loci, 0.10-0.69). Based on Wright's island model, this heterogeneity would result from gene flow equivalent to 0.31 immigrants (Nm) entering each population per generation. The distribution of E. paniculata in north-eastern Brazil is geographically and genetically subdivided, and therefore, the assumption that migrants are a random draw from all populations is likely to be violated for this range-wide estimate of gene flow. We investigated the importance of range subdivision on indirect estimates of gene flow through computer simulation and through a hierarchical analysis of FST and Nm in populations of E. paniculata from northeastern Brazil.Simulations indicated that estimates of Nm in the presence of range substructure consistently underestimated the actual values of gene flow. The degree to which Nm was underestimated increased in proportion to the magnitude of genetic differentiation among range subdivisions. In E. paniculata, northern and southern regions of the geographical range and local clusters within regions were genetically differentiated (4) = 0.10, 4) = 0.14, respectively) and there was a strong negative relationship between Nm estimated for pairs of populations and the geographical distance between them. Average estimates of population differentiation decreased and gene flow increased with successive reductions in spatial scale, from the complete range sampled (Nm = 0.31), to regions (Nm = 0.44), to local areas within regions (Nm = 0.64), and to neighbouring population pairs within local areas (Nm = 0.58). Similarity in estimates for neighbouring pairs and local areas suggests that, below the spatial scale of local area, gene flow estimates are not influenced by range substructure and can be considered to occur at random. Our results suggest that range substructure can have a substantial influence on gene flow estimates, and that ecologically relevant rates are likely to be higher than those indicated by range-wide analyses in organisms with geographical subdivision.

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Rare electrophoretic variants in a hybrid zone

Cited by 65 publications

References 14 publications

Ecological and Historical Associations of Gene Flow in Darters (Teleostei: Percidae)

Ecological and Historical Associations of Gene Flow in Darters (Teleostei: Percidae)

Genetic relationships among suspected contact zone populations of Helix aspersa (Gastropoda: Pulmonata) in Algeria

Estimates of gene flow in Eichhornia paniculata (Pontederiaceae): effects of range substructure

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