Systematics

Established introduced insects are not a systematically random group. An order may be over- or underrepresented, reflecting primarily the reasons for its introduction and/or the means of its arrival. This pattern is exemplified in Fig. 1, which depicts the proportional fractions, by order, of insects of the world compared with introduced insects of the contiguous United States. Thus, far more species of homopterans, hemipterans, and thysanopterans are introduced than would be expected based on their numbers in the world, because these orders are associated with introduced agricultural and ornamental plants. Hymenopterans are overrepresented

FIGURE 1 Fractional representation of different insect orders of the world (cross-hatched) and established introduced insects of the United States (clear). [From Simberloff, D. (1986). Introduced insects: a biogeographic and systematic perspective. In "Ecology of Biological Invasions of North America and Hawaii (H. A. Mooney and J. A. Drake, eds.), Fig. 1.1, p. 6. © Springer-Verlag GmbH & Co. K G, Heidelberg. Data from Arnett, R. H. (1983). Status of the taxonomy of the insects of America north of Mexico: a preliminary report prepared for the subcommittee for the insect fauna of North America project. (Privately printed) and Sailer, R. I. (1983). History of insect introductions. In "Exotic Plant Pests and North American Agriculture" (C. Graham and C. Wilson, eds.), pp. 15—38. Academic Press, New York.]

FIGURE 1 Fractional representation of different insect orders of the world (cross-hatched) and established introduced insects of the United States (clear). [From Simberloff, D. (1986). Introduced insects: a biogeographic and systematic perspective. In "Ecology of Biological Invasions of North America and Hawaii (H. A. Mooney and J. A. Drake, eds.), Fig. 1.1, p. 6. © Springer-Verlag GmbH & Co. K G, Heidelberg. Data from Arnett, R. H. (1983). Status of the taxonomy of the insects of America north of Mexico: a preliminary report prepared for the subcommittee for the insect fauna of North America project. (Privately printed) and Sailer, R. I. (1983). History of insect introductions. In "Exotic Plant Pests and North American Agriculture" (C. Graham and C. Wilson, eds.), pp. 15—38. Academic Press, New York.]

perhaps partly because of their wide use in biological control and partly because their haplodiploidy allows a single female, which can produce both male and female offspring, to found a population. Haplodiploidy may also lower inbreeding depression in founding populations. Haplodiploidy is also found among homopterans and thysanopterans, both overrepresented groups. At the family level, 26 families are overrepresented, and other patterns become clear. In the contiguous United States, coccinellid beetles and anthocorid bugs are both overrepresented; species in both groups were introduced as biological control predators. Tephritid flies were introduced deliberately for control of knapweeds and inadvertently on cultivated plants. Ten overrepresented families are in the Hymenoptera, and seven of these were introduced for biological control. Two thrips families in this list are associated with cultivated plants, as are the adelgids (pine and spruce aphids). Oestrid flies are overrepresented, and these are internal parasites of mammals, including livestock; they probably arrived with their hosts. Dermestid and anobiid beetles are overrepresented, and these stored product pests probably arrived with their food sources.

0 0

Post a comment