The amount and distribution of genetic variation in 51 native (Eurasian and northern African) populations of Bromus tectorum were assessed at 25 loci using starch gel electrophoresis and were compared with our previous results for introduced (North American) populations of this predominantly cleistogamous grass. More alleles and variable loci were detected across populations in the native range than in North American populations. Within populations, however, the level of polymorphism is higher in the introduced range than in the native range. Deviation from Hardy-Weinberg expectation among native populations is almost as severe as for introduced populations. Eurasian populations exhibit greater genetic differentiation than those in North America; populations from Southwest Asia are the most genetically differentiated. Comparison of single-locus genotypes suggests possible source populations in both Europe and Southwest Asia for the populations now so prominent in western North America. Genetic differences between introduced and native populations of B. tectorum stem from two opposing factors: the reduction in genetic variability across populations produced by founder effects combined with an increase in the within-population component of genetic variation from multiple introductions.

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Two of the classic examples of recent allopolyploid speciation are Tragopogon mirus and T. miscellus. Previous studies have documented that both allotetraploids originated within the past 50-60 years; the diploid parents of T. mirus are T. dubius and T. porrifolius; those of T. miscellus are T. dubius and T. pratensis. It has now been 40 years since these allotetraploids were first described by Ownbey in 1950. To assess whether population size (the absolute number of plants) and population number of these species have changed during the past 40 years, we determined their distribution and numbers in the Palouse region of eastern Washington and northern Idaho in the spring of 1990. We visited 90 localities, 60 in Washington and 30 in Idaho. Tragopogon mirus is found in nine locations, with eight of these sites located in eastern Whitman County, Washington. Tragopogon miscellus is much more widespread, occurring in 38 of90 locations. The latter species is now one of the most common weeds in the vicinity of Spokane, Washington. Comparison of the current distributions of these species with historical records indicates that both allotetraploids, especially T. miscellus, have increased substantially in both geographic range and numbers. These Tragopogon species offer an excellent model system for testing questions concerning the ecology and population biology of recently derived allotetraploid species and their diploid progenitors.