Chemotaxonomic characters

Seybold S. J., OhtsukaT., Wood D. L. and Kubo I. (1995a) Enantiomeric composition of ipsdienol A chemotaxonomic character for North American populations of Ips spp. in the pini subgeneric group (Coleoptera Scolytidae). J. Chem. Ecol. 21, 995-1016. 

One of the most widely studied chemotaxonomic characters in insects has been cutic-ular hydrocarbons (CHCs). The earliest descriptive papers on CHCs were by Jackson (1970), Jackson and Bayer (1970), Jackson and Blomquist (1976), Lockey (1976), and Lange et al. (1989). Carlson and collaborators (Carlson and Service 1979, 1980 Carlson et al., 1978 Carlson, 1988) were the first to recognize the special role of CHCs in chemical taxonomy. Since then, numerous reviews have devoted sections to CHCs (Lockey, 1980, 1988 Howard and Blomquist, 1982,2005 Blomquist and Dillwith, 1985 Blomquist et al., 1987 Kaib et al., 1991 Singer, 1998 Howard, 1993). Since the introduction of molecular techniques, the number of insect chemotaxonomy papers about hydrocarbons has dropped, but there are still many submissions and publications. Explanations for this continued interest in insect CHCs include not only their importance as chemical cues in recognition processes, but also the fact that insects are excellent bioindicators of nature conservation, and inversely, pests to control. 

A great deal of information on CHCs as chemotaxonomic characters and sex pheromones is available for Drosophilidae. Several species and populations within species have been identified on the basis of hydrocarbon patterns. Studies have shown that CHCs differing between close species or populations often act as pheromones and may participate in prezy-gotic isolation. This section presents examples in which sex-pheromone polymorphism has been used as a basis for quick determination of strain/species (see Table 7.1). In section four of this chapter we deal with the possible role of pheromones in speciation. 

C. A. (1990). Preliminary examination of cuticular hydrocarbons of worker termites as chemotaxonomic characters for some Australian species of Coptotermes (Isoptera Rhinotermitidae). Sociobiology, 16, 181-197. 

McDaniel, C.A., Howard, R. W., Blomquist, G. J. and Collins, A.M. (1984). Hydrocarbons of the cuticle, sting apparatus, and sting shaft of Apis mellifera L. Identification and preliminary evaluation as chemotaxonomic characters. Sociobiology, 8, 287-298. 

Page, M., Nelson, L. J. Blomquist, G. J., and Seybold, S. J. (1997). Cuticular hydrocarbons as chemotaxonomic characters of pine engraver beetles (Ips spp.) in the grandicollis subgeneric group. J. Chem. Ecol., 23, 1053-1099. 

Isoptera Rhinotermitidae) in Japan and neighboring countries as chemotaxonomic characters. Appl. Entomol. ZooL, 34,179-188. 

One or more species of nine of these genera have been examined and all but one contained arylphenalenones and/or closely related compounds. Phenalenones have not been found so far in any other family of higher plants so their presence may be a useful chemotaxonomic character. The single exception so far reported among the genera of... 

In Australian tenebrionid beetles, defensive compounds and their patterns seem to be of only low chemotaxonomic value. However, the aforementioned aromatic compounds are restricted to the genus Tribolium. Abdominal defensive compounds were used as chemosystematic characters in order to construct a phylogenetic tree for the genus Tribolium [330]. The defensive secretion of adults of Tenebrio molitor was shown to contain toluquinone 7 and m-cresol 89 [333]. The quantification of benzoquinones in single individuals of Tribolium castaneum at different days after adult eclosion indicates that the amount of toxic quinone only shows a maximum subsequent to cuticle sclerotization. Obviously, there is a need for an adequate cuticular barrier for self-protection from these defensive compounds [334]. 

It is clear that the use of a limited number of morphological characters may lead to artificial subdivisions in a family as complex as the Rubiaceae, and thus to an erroneous classification. A thorough understanding of plant interrelationships requires the accumulation and comparison of numerous data originating from complementary disciplines, e.g., anatomy, cytology. The contribution of chemotaxonomic correlations may be of help for clarifying the present situation. 

Chemotaxonomic Relevance. The existing data for an intrafamilial evaluation of this topic are full of gaps in case of the Solanaceae (Table 3.1). However, since simple pyrrolidines are plesiomorphic characters shared with the well-studied Convolvulaceae (Table 3.2) and at least the occurrence and distribution of cuscohygrine is also well-documented in the Solanaceae, it might be that there is a similar tendency in both Solanales families. 

For chetnotaxonomic considerations, it is necessary to know about the combinations of certain alkaloidal types and about their biosynthetic inter-relationships. The types of alkaloid present may be used as characters for assessing relationships of taxa at the levels of subfamily, tribe, genus, species, subspecies or chemical race. It is not always possible to make any significant chemotaxonomic conclusions where data is missing from the literature, e.g. the yields of individual alkaloids, the nature of the minor alkaloids present and the plant part analysed. It is also important to know about the locality of growth and the season of collection of the plant material. 

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