The Geography of Phytochemical Races

46 2 Examples Within Continents
southern Finnish ports in that manner. [Other examples of seed transport via ballast
will be met later in this review in a discussion of beach rocket (Cakile).] The more
fundamental question—how to explain the chemical variation in tansy— however,
remains, to use the authors’ word, “elusive.” It seems reasonable to suggest that
tansy, over a considerable period of time, has been subjected to human intervention
with an eye to improving one or another of its properties, and it is the seeds of those
improved lines that have found their way to northern Europe and subsequently into
Scandinavia. Environmental factors may also have played an important role (Sorsa
et al., 1968). As is the case with most of these highly variable systems, carefully
controlled studies focusing on likely environmental factors, coupled with a thorough
understanding of the biosynthetic processes involved, should lead to a better
appreciation of why such complex systems occur in nature.
The fi nal Finnish example here deals with the question of susceptibility of Scots
pine (Pinus sylvestris L.) to insect herbivory. Manninen et al. (1998) studied the terpene
and resin acids and growth characteristics of trees from four provenances that
ranged over a distance of about 1200 km: Muonio (67°56′N), Suomussalmi (65°10′N),
and Korpilahti (62°0′N) in Finland, and Saaremaa (58°22′N) in Estonia. Experiments
were run either in petri plates or in pots under common garden conditions. Host plant
selection was tested using two species of aphids, the gray pine aphid (Schizolachnus
pineti) and the spotted pine aphid (Eulachnus agilis), while measures of oviposition
behavior employed the tarnished plant bug (Lygus rugulipennis). The terpenes, separated
by HPLC, were identifi ed as bornyl acetate [95] (see Fig. 2.26 for structures
95–103, others above), camphene [96], 3-carene [97], caryophyllene [98], copaene [99],
Fig. 2.26 Compounds 95–105 from Pinus sylvestris in Finland and Estonia