DAPHNIA-LUMHOLTZI IN NORTH-AMERICA - ANOTHER EXOTIC ZOOPLANKTER

Daphnia lumholtzi, whose natural distribution is restricted to Australia, southwest Asia, and Africa, has been detected recently at numerous localities in the southern U.S. The present study establishes that D. lumholtzi populations from two of these localities are allozymically distinct from an Australian population but genetically similar to each other, suggesting they share a common origin not from Australia. The inland distribution of D. lumholtzi suggests it was not introduced in ballast water of large ships. One of the first localities known to have D. lumholtzi is also the first North American site where Nile perch were introduced in 1983. If D. lumholtzi was introduced at this time, it has colonized sites across the southern U.S. extremely rapidly, suggesting that it will soon be common in lakes and reservoirs in warm temperate regions of North America.