Starvation-Induced Reproductive Isolation in Yeast
Speciation in eukaryotes is one of the central issues in evolutionary biology. Retrospective studies of existing species may not reveal the molecular events underlying speciation, as it is frequently impossible to distinguish changes which preceded specia
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Starvation-Induced Reproductive Isolation in Yeast Eugene Kroll, R. Frank Rosenzweig, and Barbara Dunn
Abstract Speciation in eukaryotes is one of the central issues in evolutionary biology. Retrospective studies of existing species may not reveal the molecular events underlying speciation, as it is frequently impossible to distinguish changes which preceded speciation from those which happened after speciation has occurred. We propose a model for experimental speciation using a well-studied Eukaryotic organism, the yeast Saccharomyces cerevisiae, and starvation as an agent of speciation. Starvation can be viewed as a general and widespread consequence of catastrophic environmental change that leads to a decrease in survival or reproductive success. We find that yeast populations subjected to a month-long starvation exhibit a drastic increase in genomic rearrangements compared with a modest increase in point mutation. We subsequently find that starved yeast populations become reproductively isolated from their ancestor, which we attribute to chromosomal abnormalities in the starved clones’ genomes. Our model provides direct molecular evidence – that speciation can rapidly occur without the precondition of geographic separation or divergent selection.
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Continuing Uncertainty over Species Definitions Among the Eukarya
Two central questions in eukaryotic evolutionary biology are: how do new species emerge and how are they perpetuated? We can provisionally define a species as group of organisms that shares a complex genetic network of interacting alleles and E. Kroll, and R.F. Rosenzweig Division of Biological Sciences, University of Montana, 32 campus dr., Missoula, MT 59812, USA e-mail: [email protected] B. Dunn Department of Genetics, Stanford University, Stanford, CA 94305, USA
P. Pontarotti (ed.), Evolutionary Biology – Concepts, Molecular and Morphological Evolution, DOI 10.1007/978-3-642-12340-5_3, # Springer-Verlag Berlin Heidelberg 2010
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preserves its integrity by restricting the exchange of genetic material with other such networks (Mayr 1966). The processes by which new networks emerge, i.e., speciation, appear to be diverse and their relative contributions remain the subject of considerable controversy. While Darwin explicitly linked the process of speciation to the adaptation of organisms to novel environments (Darwin 1859, Ch. 4), neo-Darwinists have emphasized the role of interpopulation isolation (Fisher 1930; Dobzhansky 1937; Muller 1940; Mayr 1942). Uncertainty persists as to which of these emphases is correct (Lande 1989; Vulic et al. 1999; Orr and Presgraves 2000; Schilthuizen 2000; Turelli et al. 2001; Sinervo and Svensson 2002; Herrmann et al. 2003), largely due to the dearth of knowledge about the specific molecular mechanisms that underlie eukaryotic speciation and the fact that species can be defined in various ways. The most widely used definition for speciation is based on the biological species concept, i.e., the cessation of gene flow between groups of or
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