This paper is about the sexual selection. It shows how sexual selection has an enormous effect on the evolutionary changes with different characteristics selected for and against (Brewster and Houde 2003, p. 1057). The common result of this phenomenon is the directional selection. This is where phenotypes indicate high fitness level resulting to an increased number of offspring in this phenotype (Brooks and Endler 2001, p. 1007). By increasing the rate of directional selection and opportunity for the sexual selection methods, the ability of survival and the average fitness will increase. The processes involve dauer processes. Dauer entry is the entry into the facultative diapauses of the dauer, the enduring larval level of nematode development. Direct selection can result into a sympatric speciation (Casalini et al. 2010, p. 1037). In a species that has variable genetic factors, some population may have high chances of sexual selection. This will make their fitness increase rapidly. Many factors of population genetic affect the degree of sexual selection (Head et al. 2008, p. 140).
Specialists use microarrays survey the expression of thousands of genes in one experiment. Applied creatively, the specialists test the genes as generate new hypotheses. This technology becomes accessible; microarray analysis finds its applications in diverse areas of biology. Microarrays is methods for visualizing the genes that need to be used in a tissue at a particular time in particular set of conditions. The output of a microarray analysis is the gene expression profile. One of the factors that affect the degree of sexual selection is the Operation sex ratio (OSR). This is the ratio of sexual receptive male to the ration of sexual receptive female. Population density has an effect on the sexual selection (Head et al. 2008, p. 138).
Traditionally, male biased OSR increase the chances for sexual selection. This is because of the increased competition and variations between males and the mates (Head et al. 2008, p. 139). The opposite has been proved true. Male biased OSR reduces the chances of sexual selection. This is due to the harassment of the female genes by their male counterparts. This leads to random behavior in the selection (Head et al. 2008, p. 142). This commentary discusses the effects that are found when OSR and population density are manipulated in poecilia retiulate (Guppies).
Population and OSR are linked and their effect on the sexual selection varied and dependent on the mating system (Jirotkul 2003, p 738). In the selection systems where females selects their own mates and the male engage to mate, male biased OSR and massive population density increases the selectiveness of the level of competition between males and the number of females (Head et al. 2008, p. 144). Females suffer harassment in the male biased OSR and dense population. This is because the male adopt behaviors that undermine the selective process of the female. This makes the female become less selective than the male. The level of choosiness is too high (Head et al. 2008, p. 144). The density behavior and OSR manipulation can be served in the reticulate. Male exhibits two types of mating behavior: these are sneak mating, and courtship. Courtship displays the male courting the female while sneak mating is whereby the male inseminate the female without the female’s permission. Sneak mating undermines the choice of the female, and it is costly to the females as they try to escape the sneak mating (Head et al. 2008, p. 144).
Traits of male sexual ornament like pattern and color are inherited; therefore, they are subject to sexual selection (Brook and Endler 2001, p. 1011). Females judge male’s attractiveness by his tail’s area, areas of pattern and coloration, involving contrasting colors. It is expected that in high population and male OSR. Females will select attractive males and produce attractive offspring. The female influences the insemination process (Pilastro et al. 2004, p. 669). The female may allow a male whom she perceives not attractive or limit the sperm count. She does this by shortening the copulation time or ejecting the sperm (Pilastro et al. 2004, p. 667).
The P. Reticulate male biased OSR increases the sexual selection and evolution of secondary sexual characteristics acts faster in these conditions (Jirotkul 2003, p. 740). Independently altered male OSR and population density in P. Reticulate recorded female and male behavior in the entire conditions and estimated the reproduction success of the male. This is by paternity testing of the offspring through the process of DNA microsatellite. Other studies show that the male OSR and the increased population do not alter the male directional selection and ornaments of the male.
After the permutation test, no change was found in the male mating behavior, in the various OSR. Permutation test is the way scientists shuffle observed data in order to observe and determine the reaction of an unusual outcome. Females were pursed more than their male counterparts in the biased male OSR were. The male did not harass the female. Therefore, there was no change for sexual selection (Ryder et al. 2012. P. 986). A female avoiding male increases the chances of injury, risk and predation. The cost of mating may have a high risk of fleeing their courting mate. These findings are in contrast to the previous studies (Wang et al. 2009, p. 88). The OSR and population changes have a significant effect on the male mating in the nysius huttoni. The population density has a strong effect on the sexual selection in migrating songbird (Gasparini et al. 2010, p. 125).
There was no evidence found in the directional selection on the male ornamental and behaviors (Head et al. 2008, p. 143). This may be due to the high sperm number that is indicative of the high fertility. Males expel varied amount of sperm numbers and quality (Gasparini et al. 2010, p. 126). It is evident that the OSR and density effect on the sexual selection are inconsistent. The sexual selection may have affected the way that the selection cannot be reduced to the demographic parameters. Mate encounter rates, breeding cost and variations may influence the mate quality (Head et al. 2008, p. 125). It is crucial for the females to select their sexual mates. This may be the reason why the OSR and density do not affect the sexual selection in the study.
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