Even slight differentiation between the respective pheromones by Marble and Wardle females was surprising because these populations are separated by a distance of only 20 miles over which tridens is c... Even slight differentiation between the respective pheromones by Marble and Wardle females was surprising because these populations are separated by a distance of only 20 miles over which tridens is continuously distributed. The extremely strong discrimination between Marble and Wardle males by females of Swan and Rodgers indicated that the volatiles produced by males of the two populations were even more different than could have been suspected from the reciprocal tests. This discrimination may have resulted from differences in pheromone bouquets which were of little consequence to the Marble and Wardle populations, but important for response by Swan and Rodgers. The same phenomenon may explain the relatively high response of Trogoderma stemale males to T. grassmani females despite its zero response to four other species, which, on the basis of reciprocal attraction, appear to be pheromonally identical to T grassmani (table 9.1) according to http://sundowndivers.org/athena-10x-pheromones-hands-review/ Genetic control of pheromone systems No direct information on the genetics of pheromone specicity has been published. However, insight into genetic control of pheromones and pheromone receptors can be gleaned from bioassays of hybrids of species in the following three groups of lps: (1) hybrids of I. tridens (=amiskwiensis Hopping) with I. borealis and I. pilifrons (Lanier l970a); (2) 1. plastographus and]. integer (Lanier l970b); (3) 1. pini from Idaho and New York (Piston and Lanier 1973). In all cases, hybrid males were intermediate in attractiveness to the parental types. When males of the backcross generations (B1) were included in the bioassays, levels of response by the parent population were again in direct order of ‘blood’ relationship. For example, the indices of response of female I. pilifrons to male I. pilzfrons, B, P(t—p*, F, t—p, B, t(p~t) and]. tridens were 100, 35, 27, 13, and II, respectively (Lanier 1970a). The only exception was that the ability of I. tri- dens to discriminate among its backcrosses broke down in the presence of the F , top. The only hybrid females bioassayed were those of the spruce Ips. females were slightly more attracted to males of their own kind than to those of the two parent species. Backcross females were generally most attracted to pure males of the backcross species. For example, B, p(t—p) females had indices of response of 143, 100 and 30 to males of I. pilifrons, the B1, and I . tridens, respectively. All of the F, and B, individuals tested appeared to be inuenced by genotypes of their parents in both their attractant and response behavior. This clearly showed that genes controlling pheromone production and reception were not sex-linked. It seems unlikely that hybrids produce ‘new’ compounds which evoke intermediate response in receptors of the parent species or that hybrids have ‘new’ receptors which are sensitive to both parental pheromones It is especially unlikely that ‘new’ hybrid receptors are automatically ‘keyed’ to new hybrid pheromones ~ as would be necessary to explain the preference of F, t-p females for their brother’s pheromone. The simplest explanation for the observed results is that hybrids have pheromones and pheromone receptors of both parental types. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger from Los Angeles that studies pheromones.