Alien Species.vp - IUCN

Richard N. Mack
acceptance of a food may result from repeated contact, i.e., formerly novel food becomes
acceptable by repeated contact alone (Capaldi, 1996; Rozin, 2000). Among immigrants,
conditions of extreme food deprivation force such familiarity; initial reluctance is overturned
by the desire for self-preservation. European immigrants in the Western Hemisphere were
reluctant to adopt the white potato as food (Crosby, 1972), although eventually they and many
native Europeans, most conspicuously the Irish, clearly adopted the potato to the point that it
became a staple food (Speed, 1976). European colonists in 16 th
century Mesoamerica initially
preferred wheat to maize, but maize along with manioc became acceptable when neither a
reliable local nor a foreign source of wheat emerged (Crosby, 1972). As a cultural result, the
descendants of early immigrants to Brazil today readily include both maize and manioc in their
diet.
Each ethnic group of immigrants brings familiar edible plants, including seasonings, to a
new homeland. For example, Europeans from the Mediterranean Basin have introduced olives,
garlic, and fennel, wherever they have settled. One of these plant immigrants, olives, has
become invasive in South Australia; Olea europaea now forms a prominent new arboreal layer
in eucalypt parklands (Parsons and Cuthbertson, 1992). Northern European colonists have
widely introduced brassicas (cabbage, kale, rape) as well as many root crops (radishes, carrots,
beets, and parsnip) (Harlan, 1975; Simmonds, 1979). Many of these edible species have
become naturalized, including Taraxacum officinale, Rorippa nasturtium-aquaticum, and
Rubus spp. (Harlan, 1975). Asian cuisines have quite different plant ingredients from those
employed in Europe. As a result, Indian, Indonesian, Thai and especially Chinese immigrants
have widely introduced plants they prefer to eat. Among these plant culinary immigrants are
now such naturalized species as Brassica juncea and Coriandrum sativum, which despite its
native European range has been adopted in Chinese cuisine (Wagner et al., 1990). Unable to
import a familiar edible food, immigrants may even inadvertently adopt a substitute that proves
invasive. The recent Cambodian immigrants to Australia mistook the highly invasive
Alternanthera philoxeroides (alligator weed) for a favorite aquatic plant in Cambodia
(Alternanthera sessilis). Thus, they fostered and spread the plant in their adopted home, until
the mistake was pointed out (J. Virtue, pers. comm).
Along with its traditional importance in human nutrition and animal behaviour, psychology,
cultural anthropology, and sociology, food preference becomes a legitimate area of interest in
invasion biology. Immigrants’ cultural heritage clearly influences the plants that are introduced
for food into potential new ranges (Rozin, 2000). These strong biases have repeatedly placed
crops in far-flung locales where they have not only become naturalized but in some cases have
also become invasive (Harlan, 1975; Mack, 1991, 1999).
The Call Home Syndrome: pleas for the essential
No colonists could predict all the crop species that would be needed in a distant locale, despite
careful planning and even prior knowledge of the locale’s biota and physical environment. The
ability to “call home”, i.e., to request essential plants from their homeland for unanticipated
needs, has long characterized colonization attempts worldwide. By 1524 Cortes, writing from
Mexico, was imploring the King of Spain to include essential plants within future shipments: “I
have also explained to your Caesarian Majesty the need for plants of all kinds; for every species
of agriculture may flourish here; but nothing has been so far provided, and I again pray your
majesty to order a provision from the Casa de contracion at Seville, so that no ship be allowed to
sail without bringing a certain number of plants which would favour the population and
prosperity of the country” (MacNutt, 1908). He assessed that among deficiencies in the newly
conquered lands were plants to treat a host of human afflictions that Spanish settlers were
already encountering (Kay, 1996). These early pleas were apparently answered; Bernardo
Cobo, a 17th century Spanish commentator, stated that, “All the regions of the globe have
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