Neutral Genetic Diversity (neutral + genetic_diversity)

Distribution by Scientific Domains

Selected Abstracts


EVOLUTION, Issue 6 2009
Andrew R. Whiteley
Anthropogenic-induced change is forcing organisms to shift their distributions and colonize novel habitats at an increasing rate, which leads to complex interactions among evolutionary processes. Coastrange sculpin (Cottus aleuticus) have colonized recently deglaciated streams of Glacier Bay in Alaska within the last 220 years. We examined divergence among populations in background matching coloration and tested the hypothesis that observed variation is due to morphological color plasticity. To examine how color-change plasticity has interacted with other evolutionary processes, we also determined the influence of colonization on neutral genetic diversity. We observed clinal variation in substrate-matching fish color along the chronological continuum of streams. Microsatellites provided little evidence of genetic subdivision among sculpin populations. Fish color was significantly correlated to substrate color, but was not correlated to neutral population genetic structure. Furthermore, a laboratory experiment revealed that morphological color plasticity could explain much, but not all, of the observed fish color divergence. Our study demonstrates that sculpin in Glacier Bay have colonized and adapted to recently deglaciated habitat and suggests that color change plasticity has aided in this process. This research, therefore, highlights the important role phenotypic plasticity may play in the adaptation of species to rapid climate change. [source]


EVOLUTION, Issue 5 2003
John R. Pannell
Abstract Many species exist as metapopulations in balance between local population extinction and recolonization. The effect of these processes on average population differentiation, within-deme diversity, and specieswide diversity has been considered previously. In this paper, coalescent simulations of Slatkin's propagule-pool and migrant-pool models are used to characterize the distribution of neutral genetic diversity within demes (,s), diversity in the metapopulation a whole (TTT), the ratio FST= (,t,,S)/,T, Tajima's D statistic, and several ratios of gene-tree branch lengths. Using these distributions, power to detect differences in key metapopulation parameter values is determined under contrasting sampling regimes. The results indicate that it will be difficult to use sequence data from a single locus to detect a history of extinctions and recolonizations in a metapopulation because of high genealogical variance, the loss of diversity due to reductions in effective population size, and the fact that a genealogy of lineages from different demes under Slatkin's model differs from a neutral coalescent only in its time scale. Genetic indices of gene-tree shape that capture the effects of extinction/recolonization on both external branches and the length of the genealogy as a whole will provide the best indication of metapopulation dynamics if several lineages are sampled from several different demes. [source]

Community genetics in the Northwestern Atlantic intertidal

J. P. Wares
Abstract Our ability to make inferences about the processes acting upon a biological system can be dramatically improved through integration of information from other fields. In particular, this is true of the field of phylogeography, a discipline that attempts to describe geographical variation in species using neutral genetic diversity as a correlate of time. Through comparisons of information from multiple species, as well as background information about the abiotic environment and how it has changed over time, we should be able to reassemble many of the forces that were important in assembling the communities and community interactions found in a given region. Here I review the information available for coastal species in the northwestern Atlantic, and argue that an integration of ecological, genetic, geological and oceanographic information can illustrate emergent patterns of community genetics. [source]

Microsatellite diversity and genetic structure of fragmented populations of the rare, fire-dependent shrub Grevillea macleayana

Phillip R. England
Abstract Recent habitat loss and fragmentation superimposed upon ancient patterns of population subdivision are likely to have produced low levels of neutral genetic diversity and marked genetic structure in many plant species. The genetic effects of habitat fragmentation may be most pronounced in species that form small populations, are fully self-compatible and have limited seed dispersal. However, long-lived seed banks, mobile pollinators and long adult lifespans may prevent or delay the accumulation of genetic effects. We studied a rare Australian shrub species, Grevillea macleayana (Proteaceae), that occurs in many small populations, is self-compatible and has restricted seed dispersal. However, it has a relatively long adult lifespan (c. 30 years), a long-lived seed bank that germinates after fire and is pollinated by birds that are numerous and highly mobile. These latter characteristics raise the possibility that populations in the past may have been effectively large and genetically homogeneous. Using six microsatellites, we found that G. macleayana may have relatively low within-population diversity (3.2,4.2 alleles/locus; Hexp= 0.420,0.530), significant population differentiation and moderate genetic structure (FST = 0.218) showing isolation by distance, consistent with historically low gene flow. The frequency distribution of allele sizes suggest that this geographical differentiation is being driven by mutation. We found a lack mutation-drift equilibrium in some populations that is indicative of population bottlenecks. Combined with evidence for large spatiotemporal variation of selfing rates, this suggests that fluctuating population sizes characterize the demography in this species, promoting genetic drift. We argue that natural patterns of pollen and seed dispersal, coupled with the patchy, fire-shaped distribution, may have restricted long-distance gene flow in the past. [source]