The allotetraploids (2n=24) Tragopogon mirus and T.miscellus have become textbook examples of recently and recurrently formed allopolyploids. Both species formed following the introduction of three diploids, T.dubius, T.porrifolius and T.pratensis (each with 2n=12), from Europe into the Palouse region of eastern Washington and adjacent Idaho, USA, in the early 1900s. The parentage of both allotetraploids is well documented (T.mirus=T.dubius×T.porrifolius; T.miscellus=T.dubius×T.pratensis), and both allotetraploids have formed repeatedly in the past approximately 80 years in the Palouse. On a larger geographical scale, T.mirus has also been reported from Flagstaff, Arizona (AZ), and more recently from Oregon (OR). However, the populations from OR and AZ have not been previously analysed with molecular markers to test the hypothesis of separate origin (vs. long-distance dispersal). Here, we show that both the AZ and OR collections of T.mirus combine distinctive parental genotypes and are genetically differentiated from the T.mirus genotypes found in the Palouse. The OR sample of T.mirus has a genetically distinct T.dubius contribution that forms a clade in our analyses with a sample of what has been referred to as T.major (now considered a subspecies of T.dubius). Consistent with other naturally occurring T.mirus populations, plastid sequences indicate that T.porrifolius was the maternal parent for both the AZ and OR collections. Microsatellite data are also consistent with local formation of T.mirus from co-occurring populations of T.dubius and T.porrifolius in OR and AZ. As with sequence data, T.dubius from OR is distinct from other samples of T.dubius at microsatellite loci, contributing a unique signature to T.mirus from this location. It will be useful to include these additional geographical origins of T.mirus, particularly the more genetically distant sample from OR, in ongoing investigations of the genetic and genomic consequences of recent allopolyploidy.
- DNA sequence data
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Plant Science