The response of Dendroctonus frontalis to frontalin was inhibited by endobrevicomin in the southwestern U.S.A. (Vité and Renwick 1971a) but in Mexico D. frontalis was attracted to endobrevicomin (Vité and Islas 1973). As pheromones become more widely tested additional reports of geographic variation are certain to follow. In some instances the entities revealed by pheromonal differences will prove to be sibling species. Sympatric sibling species of moths have already been discovered by their differential response to attractant compounds (Roelofs and Comeau 1969, 1970).
Reproductive isolation, and hence the species status according to the definition of the biological species by Mayr (1969), is not proven by the demonstration of different pheromonal preferences among geographical isolates. It is unwarranted to assume that, since pheromones are important in mate-ï¬nding, differences in pheromone systems per se constitute reproductive isolation of the best pheromones at http://baids.org/?p=9 and http://www.jasminedirectory.com/shopping-ecommerce/cosmetics/detail,647082228,pheromones-planet-com.html .
Eastern and western are less cross attractive than are a number of âgoodâ species â i.e.,1. paraconfusus, I. confusus and I. montanus (Wood 1970; Lanier and Wood 1973). Nevertheless, cross attraction is sufficient to insure cross insemination between individuals of eastern and western if they were present together in the ï¬eld. Interpopula- tional hybrids of are highly fertile and hybrid males are intermediate in attractiveness at least to the eastern population (Piston and Lanier 1973). The pheromonal differences, like the slight morphological differences in both the insect (Hopping 1964) and its parasitic mites (Lindquist 1969), probably intergrade in the Rocky Mountains of the northern U.S.A. and Canada. Check out the top pheromones at http://anatomist.info/?p=28 .
The most complex intrapopulational variation in pheromone systems discovered to date is exhibited in I. tridens and 1. borealis Swaine. The concepts of these species were revised considerably following the discovery that seven names (considered synonyms here) were based on different forms of polymorphic females (Lanier 1973). The two remaining species are basically western and eastern in their respect.
They exist sympatrically along the eastern ranges of the Canadian Rocky Mountains. Near Banff, Alberta, the two species were found in discrete gallery systems in the same spruce trees; reproductive isolation was enforced by speciï¬city of attractant pheromones (Lanier 1970a). Field and laboratory bioassays of seven populations of each species demonstrated high degrees of pheromone speciï¬city between sympatric populations of the two species. The same tests revealed a startling variability in pheromone systems among populations of the same species. The following discussion illustrates this variability among five populations of from the Rocky Mountain National Parks region of British Columbia (fig. 9.1). A detailed description of methods and results is published elsewhere (Lanier 1974).
Males of I. tridens from Marble Canyon (Marble), Wardle Creek (Wardle), and Donald Station (Donald) were tested concurrently in each of these three areas and at White Swan Lake (Swan) and Rodgers Pass (Rodgers) (fig. 9.1). In all cases males used in the tests were reared in the laboratory in bolts of the same spruce tree and introduced into fresh bolts cut from another tree.
In most tests, females responded preferentially to males of the same population. Exceptions to this generality are that Marble females showed no clear preference for Marble males over Wardle males in two ï¬eld tests and Donald females did not discriminate between Wardle and Donald males in four laboratory tests (table 9.8).