This purchase only includes chapter 21 of this title.
The primary cone volatiles of the cycads, Macrozamia machinii, pollinated solely by the weevils Tranes sp., and Macrozamia lucida, pollinated solely by the thrips Cycadothrips chadwicki, were studied for their effects on their species-speciï¬?c pollinators. Two monoter-penes, linalool and Î²-myrcene, are the major components in the cone fragrance of M. machinii. Cones of M. lucida release numerous monoterpenes, including Î²-myrcene, the dominant component, and lower quantities of the ocimene isomers, (Z)-Î²-, (E)-Î²-, and (allo-)ocimene. No linalool has been detected in M. lucida, and no (E)-Î²-or (allo-)ocimene has been detected in M. machinii. Results of electroantennographic and gas chromatographyâ€“electroantennographic detection techniques demonstrated that Tranes sp. and Cycadothrips responded physiologically to components within the suite of volatiles generated by their host cones. In particular, Cycadothrips from M. lucida responded to Î²-myrcene as well as to (E)-Î²- and (allo-)ocimene but not to (Z)-Î²-ocimene. Tranes sp. from M. machinii responded to both linalool and Î²-myrcene. In Y-tube olfactometer behavioral tests, both insects responded positively to the volatiles of their own host (male cone sporophylls), but their response levels to nonhost sporophylls were not signiï¬?cantly different from their response levels to the control arm, which contained only ï¬?ltered room air. The response of Cycadothrips to Î²-myrcene was dose dependent. Higher levels appeared to repel male and female thrips, whereas lower levels of Î²-myrcene slightly attracted male thrips but had no signiï¬?cant effect on female thrips (no repellency or attraction). Cycadothrips were attracted to a blend comprising three ocimene isomers, even in the presence of low levels of Î²-myrcene. The only level of Î²-myrcene tested on Tranes indicated a slightly repellent effect. These results are discussed in the context of cone thermogenesis studies and the nature of the Macrozamia pollination syndrome.