1
The Origin of Reproductive
Isolation: Biological Mechanisms
of Genetic Incompatibility
KYo/CHI SAWAMURA
Drosophila Genetic Resource Center, Kyoto Institute of Technology, Matsugasaki,
Sakyo-ku, Kyoto 606-8585, Japan
Abstract
The origin of species has been the mystery of mysteries since Charles Darwin's era.
According to the biological species concept advocated by the founders of the Modern Synthesis, the question 'how new species evolve' can be substituted by a more
answerable question 'how reproductive isolation is established between populations'. Mechanisms preventing gene exchange between species are various, and
most of them are thought to be the result, not the cause, of genetic diversity. Some
disturb species recognition systems (prezygotic isolation), and others terminate
generations of mixed genomes (postzygotic isolation). Examples of the latter whose
biological mechanisms have recently been documented well (tumorigenesis, sexual
reversion, irregular dosage compensation, nucleolar dominance, homeotic transformation, spermatogenic defects, mitotic defects, and maternal/zygotic transition
failure in interspecific hybrids) are reviewed here. Gene interactions between loci
from different species play important roles. As has been shown in developmental
biology, transcriptional regulation may be a key factor. Genetic incompatibility in
hybrids may be the manifestation of improper transcriptional regulation resulting
from the coevolution of DNA-binding proteins and their binding sites.
Key words. biological species concept, dosage compensation, Drosophila, genetic incompatibility, homeotic transformation, hybrid inviability, hybrid sterility, maternal/zygotic transition, mitosis, nucleolar dominance, postmating reproductive isolation, sex determination,
speciation, spermatogenesis, tumorigenesis
3
The Origin of Reproductive
Isolation: Biological Mechanisms
of Genetic Incompatibility
KYo/CHI SAWAMURA
Drosophila Genetic Resource Center, Kyoto Institute of Technology, Matsugasaki,
Sakyo-ku, Kyoto 606-8585, Japan
Abstract
The origin of species has been the mystery of mysteries since Charles Darwin's era.
According to the biological species concept advocated by the founders of the Modern Synthesis, the question 'how new species evolve' can be substituted by a more
answerable question 'how reproductive isolation is established between populations'. Mechanisms preventing gene exchange between species are various, and
most of them are thought to be the result, not the cause, of genetic diversity. Some
disturb species recognition systems (prezygotic isolation), and others terminate
generations of mixed genomes (postzygotic isolation). Examples of the latter whose
biological mechanisms have recently been documented well (tumorigenesis, sexual
reversion, irregular dosage compensation, nucleolar dominance, homeotic transformation, spermatogenic defects, mitotic defects, and maternal/zygotic transition
failure in interspecific hybrids) are reviewed here. Gene interactions between loci
from different species play important roles. As has been shown in developmental
biology, transcriptional regulation may be a key factor. Genetic incompatibility in
hybrids may be the manifestation of improper transcriptional regulation resulting
from the coevolution of DNA-binding proteins and their binding sites.
Key words. biological species concept, dosage compensation, Drosophila, genetic incompatibility, homeotic transformation, hybrid inviability, hybrid sterility, maternal/zygotic transition, mitosis, nucleolar dominance, postmating reproductive isolation, sex determination,
speciation, spermatogenesis, tumorigenesis
3