出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/11/13 15:13:11」(JST)
| Drosophila pseudoobscura | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Family: | Drosophilidae |
| Genus: | Drosophila |
| Subgenus: | Sophophora |
| Species group: | obscura group |
| Species subgroup: | pseudoobscura subgroup |
| Species: | D. pseudoobscura |
| Binomial name | |
| Drosophila pseudoobscura Frolova & Astaurov, 1929 [1] |
|
Drosophila pseudoobscura is a species of fruit fly, used extensively in lab studies of speciation.
In 2005, D. pseudoobscura was the second Drosophila species to have its genome sequenced, after the model organism Drosophila melanogaster.[2]
Allopatric speciation has been induced by reproductive isolation in D. pseudoobscura after only eight generations using different food types, starch and maltose.[3]
Females Drosophila pseudoobscura mate through polyandry meaning they mate with more than one male. Polyandrous females can take advantages by enhancing their offspring fitness.[4] There are no additional costs to polyandrous females, because there are not big differences in life expectancy between monandrous female experiencing multiple copulations and polyandrous female experiencing multiple copulations.[5]
In the D. pseudoobscura population, some males have a harmful chromosome called sex ratio (SR), where an inactive Y-chromosome is transmitted.[6] Hence, if an SR male mates with a female, the female will produce only daughters. Monandry permits the spread of SR, which increases the population loss of males in species with the SR chromosome.[7] However, polyandry decreases the SR gene frequency because the non-SR male sperms outcompete the SR male sperms.[8] Therefore, polyandry results in a decreased risk of extinction in the population.
Monandrous female D. pseudoobscura do not obtain sufficient sperm or a plenty of suitable sperm for the fertilization. Even though monandrous female experiencing multiple copulations can produce more eggs than polyandrous female experiencing multiple copulations, monandrous females produce less adult offspring than polyandrous females do.[5] This means that polyandrous females have higher egg-to-adult survival ratio than monandrous females, making the polyandrous females more fit.
Polyandrous relationships benefit females D. pseudoobscura. By having multiple male mates, the female is able to select from multiple genes. In males D. pseudoobscura, the sperm is beneficial in several ways. Males D. pseudoobscura ejaculate more sperm than any other Drosophila species, increasing the survival of offspring.[5] Additionally, the sperm provides important nourishing factors to females and their offspring.[5] As a result, the female is able to access to the best male genes, thereby increasing her fitness.[5]
Polyandry, in general, may have a few fitness consequences. Population dense areas may have lower rates of polyandry. A larger population tend to be in restricted areas with a limited number of resources. This can greatly limit the number of survival and reproduction of offspring.[9] Therefore, in population dense areas, polyandrous behavior may actually be a fitness consequence since the environment significantly controls the number of offspring that survive.[9]
Polyandry could also pose genetic fitness consequences. Polyandry does not always result in the spread of the most adaptive genes. For example, some individuals may appear to be attractive due to genes that code for increased pheromone production.[10] As a result, attractive individuals are more likely to reproduce more often.[10] However, since these individuals do not always contain adaptive genes, multiple mating events do not always result in the propagation of adaptive genes.[10]
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| リンク元 | 「D. pseudoobscura」「ウスグロショウジョウバエ」 |
| 関連記事 | 「Drosophila」「pseudoobscura」 |
ショウジョウバエ、ョウジョウバエ属、ドロソフィラ属、Drosophila属