To investigate the time course of speciation, literature data is gathered on 119 pairs of closely related Drosophila species with known genetic distances, mating discrimination, strength of hybrid sterility and inviability, and geographic ranges to provide a cross‐section of taxa at different stages ofSpeciation.
The frequently disproportionate effects of the sex chromosomes on interspecific inviability or sterility are consistent with the hypothesis that the gene differences concerned involve recessive or partially recessive alleles fixed by selection.
These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution.
The data from Drosophila are unique-and are likely to remain so-because of the large number of crossable species and the ease of estimating sexual and postzygotic isolation in the laboratory, and some estimates of reproductive isolation and phylogenetic relatedness when better data became available are revised.
The key aspect of sympatric speciation is that it occurs when incipient species are in physical contact with each other, potentially able to interbreed and exchange genes.
The study of speciation has become one of the most active areas of evolutionary biology, and substantial progress has been made in documenting and understanding phenomena ranging from sympatric…
The origins and divergence of Drosophila simulans and close relatives D. mauritiana and D. sechellia were examined using the patterns of DNA sequence variation found within and between species at 14 different genes, and revealed little evidence of gene flow between the species.
The length of time it takes to attain genealogical species status is investigated when an ancestral population divides into two descendant populations of equal size with no gene exchange, and when genetic drift and mutation are the only evolutionary forces operating.
Defining speciation as 'the origin of reproductive isolation between two taxa' is defined, and some important and tractable questions about speciation that have been neglected are pointed out.