Entomology. insect. Sexual Selection - Essay Example

Sexual Selection al Affiliation: Sexual selection Sexual selection occurs in two major ways; intersexual selection whereby males fight among themselves in order to be attractive to the females and the intra-sexual selection whereby members of the limited sex fight with each other to gain access to the limiting sex. In the process of sexual selection due to the competition, organisms tend to develop various adaptations. Sexual selection explains why the females and males of similar species usually vary in shape and size.

This for instance it explains why the stag beetle has fearsomely oversized mandibles that cannot be used for eating as it is with other insects. The two point mandibles found in the male beetle are because of sexual selection. In the case of stag beetles, the males fight and the females choose the strongest. This ensures that the female choose and reproduce with males who posses their favourable characters. Sexual selection is only for male and that is why the male develop adaptive and non-adaptive features to attract the female.

The male beetle genital morphology comprises of two outstanding and general models of morphological variation. This morphological variation includes swift evolutionary divergence both in shape and in complexity as well as poor relationship with body size as suggested by Simmons, Tomkins and Hunt (1999). The aspect of sexual selection causes these variations. Some of the variations are non-adaptive, for instance, the reduction of the scaling relationship between the genital size and the body size.

The idea that evolution of new traits is followed by trade-offs is important in evolutionary studies. The weapons used by the male stag beetle in fighting can be physiologically expensive and are mostly trade offs with investment in other characters, like spermatogenic investment and wings. This investment into other weapons results in the evolution of mating strategies for the male beetles. For instance, the enlarged mandibles used for male-to-male competition. The male-male fight in sexual selection accounts for the evolution of exaggerated traits used as weapons in male competition.

The exaggerated characters can be responsible for the dispersal and ejaculatory strategies. The change of investment into other traits or weapons for competition can lead to evolutionary changes in life history characters. Since investment in exaggerated traits can cause trade-offs alongside other traits related to fitness, life history tactics are affected by evolution of sexually selected behaviour. During evolution, the males’ population fitness for the females is depressed due to the cost associated with finding female mating partners.

At this time, the female develops resistance to trauma resulting from injury by the male genitalia that result from female savings in immune capacity. The females also tend to develop an immune system which is well adapted to survive any injuries and scarring. Hence, this result in a pattern of evolution that is co-related. The female sex is mostly responsible for the non-adaptive male features. This is because it is in the process of competing among the males in order to please the females that the male adopt such features.

ReferenceSimmons L. W., Tomkins J. L. &Hunt J. (1999). Sperm competition games played by dimorphic male beetles. London: Routlage.