Posted on: 02 March, 2017
Author: Alexander P
Thus, the hybrid was most responsive to hybrid males because the mixture of pheromones would excite the maximum number of pheromone receptors. The least complex genetic situation possible is single lo... Thus, the hybrid was most responsive to hybrid males because the mixture of pheromones would excite the maximum number of pheromone receptors. The least complex genetic situation possible is single loci for pheromone and pheromone receptor type. Thus, the genotype for receptors would be TP and those of the backcross to pilifrons would be zTP and PP. The response of backcross females with the TP genotype is expected to be similar to that of the F 1 female. Those with the PP genotype should respond in a manner similar to I. pilifrons. If the response levels of the two genotypes predicted by the attraction indices are summed, it is clear that the I. pilifrons pheromone will provide the greatest aggregate attraction to backcross females. If more than one locus is responsible for determining receptor type, this preference of the B1 to the backcross species should be accentuated according to http://sundowndivers.org/human-pheromones-attraction-science/ Mechanisms for pheromone system shift In the process of eld-screening a number of synthetic candidate compounds, three cases were discovered in which pairs of sympatric species of moths were attracted to geometric isomers (Roelofs and Comeau 1969, 1970). In each case the isomers can technically be classed as sex attractants but they cannot be termed pheromones because it has not been shown that they are actually produced by the moths. The geometric isomer of the attractant was not attractive and a mixture of both isomers inhibited response in the two cases tested. This is similar to the earlier discovery that the response of the red-banded leaf roller (Argyrotarnia velutinana Walker) to its sex pheromone (cis-1 l-tetradecenyl acetate) was inhibited by the trans isomer (Roelofs and Comeau 1968). Roelofs and Comeau (1969) proposed that these pairs of sibling species may have developed sympatrically by mutation of a gene to produce the geometric isomer of the pheromone. This would not be attractive to males of the parent population, but a simultaneous mutation of a gene controlling the perception of the ‘new’ compound could result in a strain which is reproductively isolated from the other members of the population. Thus the two entities would pursue separate courses of evolution. There are at least three major problems confronting this ‘instant species‘ hypo- thesis. One is that the resultant two entities would be competing for exactly the same niche, unless mutations for niche accompanied mutations for pheromone system. A second problem is that the mutant types would have vastly fewer potential mates than normal individuals. If the chance of mutant individuals nding mates is lower than that of the normal individuals, the percentage of mutant alleles in the population will decrease in each succeeding generation; in order for the mutant pheromone system to become established, it must convey more efficiency in mate-finding or be linked with genes for superior survival. The third problem is the difficulty of insuring the inbreeding necessary to consolidate the mutant alleles. One of the mutant alleles — either for pheromone production or reception — must occur on the Y chromosome in order that the progeny of a mutant mating have more than 50% chance of inbreeding. A mutation for pheromone production on the Y chromosome of a lepidopteran female would be passed on to all of her daughters; an equivalent mutation on the Y chromosome of a male Ips would be inherited by all of his sons. However, the Y chromosome is practically devoid of genes in those systems known genetically modified pheromone system. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger that studies pheromones. He lives in Los Angeles, CA.