Neutral Mutations (neutral + mutation)

Distribution by Scientific Domains

Selected Abstracts

Microbial diversity , insights from population genetics

Ted H. M. Mes
Summary Although many environmental microbial populations are large and genetically diverse, both the level of diversity and the extent to which it is ecologically relevant remain enigmatic. Because the effective (or long-term) population size, Ne, is one of the parameters that determines population genetic diversity, tests and simulations that assume selectively neutral mutations may help to identify the processes that have shaped microbial diversity. Using ecologically important genes, tests of selective neutrality suggest that adaptive as well as non-adaptive types of selection act and that departure from neutrality may be widespread or restricted to small groups of genotypes. Population genetic simulations using population sizes between 103 and 107 suggest extremely high levels of microbial diversity in environments that sustain large populations. However, census and effective population sizes may differ considerably, and because we know nothing of the evolutionary history of environmental microbial populations, we also have no idea what Ne of environmental populations is. On the one hand, this reflects our ignorance of the microbial world. On the other hand, the tests and simulations illustrate interactions between microbial diversity and microbial population genetics that should inform our thinking in microbial ecology. Because of the different views on microbial diversity across these disciplines, such interactions are crucial if we are to understand the role of genes in microbial communities. [source]

Emerging model systems in evo-devo: cavefish and microevolution of development

William R. Jeffery
SUMMARY Cavefish and their conspecific surface-dwelling ancestors (Astyanax mexicanus) are emerging as a model system to study the microevolution of development. Here we describe attributes that make this system highly promising for such studies. We review how the Astyanax system is being used to understand evolutionary forces underlying loss of eyes and pigmentation in cavefish. Pigment regression is probably explained by neutral mutations, whereas natural selection is a likely mechanism for loss of eyes. Finally, we discuss several research frontiers in which Astyanax is poised to make significant contributions in the future: evolution of constructive traits, the craniofacial skeleton, the central nervous system, and behavior. [source]

The end of regressive evolution: examining and interpreting the evidence from cave fishes

A. Romero
The evolution of hypogean fauna in general and hypogean fishes in particular has been controversial. Explanations regarding the reduction or loss of phenotypic characters such as eyes and pigmentation range from neo-Lamarckism to neutral mutations, with ,regressive evolution' being a catch-all characterization for such processes. The assumptions required for special evolutionary mechanisms underlying the evolution of cave dwellers have been based on generalizations about the animals and their environments drawn from relatively few observations. The evidence offered for notions such as pre-adaptation of colonizing fauna and the purported impoverished nutrients in all caves is examined and it appears that the generalizations cannot be supported. Some major accomplishments in field and laboratory studies of hypogean fishes are summarized, including work highlighting developmental phenotypic plasticity. At the end, it is argued that evolution of hypogean fauna can be explained by well-known mechanisms within the current context of evolutionary biology. [source]

How neutral networks influence evolvability

COMPLEXITY, Issue 2 2001
Marc Ebner
Abstract Evolutionary algorithms apply the process of variation, reproduction, and selection to look for an individual capable of solving the task at hand. In order to improve the evolvability of a population we propose to copy important characteristics of nature's search space. Desired characteristics for a genotype,phenotype mapping are described and several highly redundant genotype,phenotype mappings are analyzed in the context of a population-based search. We show that evolvability, defined as the ability of random variations to sometimes produce improvement, is influenced by the existence of neutral networks in genotype space. Redundant mappings allow the population to spread along the network of neutral mutations and the population is quickly able to recover after a change has occurred. The extent of the neutral networks affects the interconnectivity of the search space and thereby affects evolvability. 2002 Wiley Periodicals, Inc. [source]