Sexual Selection -- one of the Keys to the Fittest

Sexual Selection -- One of the Keys to the Fittest!

What are keys to natural selection? Evolution? Reproductive success? Fittest? Strongest? Clearly one of the key components that answers positively to all of these questions is sexual selection. "Sexual selection is a component of natural selection; Sexual selection is thus selection for traits associated with mating success and partner choices" (Stearns & Hoekstra, 2005, p. 249). This paper would be remiss if it did not also identify asexual reproduction as one of the equals to sexual selection, however this paper will focus mainly on the sexual selection research that supports the thesis. Even though offspring could still be produced without sexual selection, sexual selection is a vital part of natural selection and ultimately evolution itself because sexual selection is a key to reproductive success and enables the production of strong and fit offspring.

Survival of the Prettiest: Sexual selection can be inferred from the fossil record. This article relates to how we can determine if sexual selection was occurring in animals of the past utilizing fossils since we cannot observe these types of behaviors in animals of the past, like we can with animals of today. Paleontologists can determine from fossils that many animals of old have very distinct feathers, horns, and other things that make them "pretty or sexually attractive" to a would be mate. It was also determined that many of these "pretty" things cannot be identified as something that evolved into protection of this animal or survival in some way. So it is assumed that these "features" were used as part of the sexual selection process. The reason this is assumed is based on behaviors of current animals in the sexual selection process. This research was able to draw analogies between animals of today and those now extinct by using fossil records. Things such as male peacock feathers and male moose antlers used in clashes during mating season are just two of the things they discovered that were similar. Thus sexual selection has been around for a very long time based on fossil records and is clearly a key role in the evolution of many species. The reason this supports the thesis is that it shows that we can draw conclusions, using the behavior of current day animals, with extinct animal fossils to determine how certain features improve the success during courtship and breeding, and ultimately reproductive success.

Sexual Selection and the Potential Reproductive Rates of Males and Females. One of the key features of the animal breeding system is the pronounced sex differences in mating competition. This article discusses these differences, clearly distinguishing the relationship between reproductive rates (success) and mating competition (sexual selection). Currently we are unable to determine if the sex that has the most investment in parental care has a greater impact on sexual selection than the other sex. What we can determine from this article is that in species where the male partner cares for the young, that whatever sex has the highest reproductive rate (which is determined by the number of offspring produced per a unit in time) will fight harder for the potential mate (selection) than the other sex that has the lower reproductive rate. This implies that sexual selection has the greatest impact on producing the most offspring in these types of species.

Ecology, Sexual Selection and the Mating Systems. This is a great example of sexual selection that is found in different species and between populations of species. There is currently no "universal" theory when it comes to determining sexual selection. There is discussion regarding Darwin's theory of sexual selection which also supports the thesis of this research in that "when one sex becomes a limiting factor for the other, the result is an increase in intersexual competition among members of the available sex for access to mates of the limiting sex" (Emlen & Oring, 1977). This goes on to suggest that the more of a shortage, the more intense the battle for sexual selection. It is especially interesting that they discuss a hypothesis that fully supports the thesis. The hypothesis indicates the ability of a portion of the population to control the access of others to potential mates. By controlling resources they are able to control mate attraction -- you can't mate with what you can't see. They go on to imply that environmental factors support the degree of protection or monopoly of these potential mates. Thus not only do the species that control access to mates have an impact on sexual selection but the environment does as well, thereby supporting the key that in this case reproductive success can only be accomplished through access and eventual sexual selection.

Sexual Selection for Male Sacrifice in Redback Spiders. This article clearly supports the thesis of sexual selection leading to reproductive success, which is a key to the fittest and the strongest. The male redback spider basically performs a somersault type move during sperm transfer and the dorsal surface of the abdomen is placed over the female's mouth and remains there during copulation and eventual suicide due to the female eating the male. This seems to occur most of the time, however there is no courting or sharing of webs beforehand. Once the male selects the female and enters her web it happens. The fate is not necessarily because the female wants to kill the male, it's because the female is so hungry and the male is there, available, and in her grasps. These cannibalized spiders have two advantages because of sexual cannibalism. They copulated longer which clearly led to more eggs being fertilized (stronger reproductive success) than those that survived copulation (being eaten by the female), while also only producing the fittest as the female does not take on another male after eating the first one.

Evolution of Sexual Dichromatism in relation to nesting habits in European passerines: a test of Wallace's hypothesis. This article discusses the proposal that Wallace came up with in 1868 that natural rather than sexual selection could explain the differences in avian plumage dichromatism. Findings are discussed in relation to the debate that Darwin and Wallace maintained on the importance of natural and sexual selection in dichromatism in birds. Darwin felt that dichromatism came about through sexual selection and was the sole reason for this occurrence. A study was conducted using Wallace's claim that compared both natural and sexual selection and their affects on avian dichromatism. This study mainly focused on nesting habits and the chosen bird was the European passerine. The