The origins of Erigeron trifidus (Asteraceae), an agamospermous rare species in Alberta 1

Erigeron trifidus Hook. (Asteraceae) is a rare species in Alberta thought to have originated via hybridization be- tween Erigeron compositus Pursh and Erigeron lanatus Hook., and is disjunct in three alpine regions of Alberta. An analy- sis of uni- and bi-parentally inherited molecular markers from E. trifidus and its putative parents yielded data that support the hybridization hypothesis for some of the populations. In most cases, cpDNA haplotypes in E. trifidus were the same as in E. lanatus, suggesting that E. lanatus is the maternal parent. Sequencing and cloning the nuclear ETS region revealed multiple repeat types in most individuals. Erigeron trifidus contained only the repeat types also present in the putative pa- rents. In addition, E. trifidus displayed the highest percentage of intra-individual repeat type polymorphism, consistent with a hybrid origin. All northern populations of E. trifidus exhibited a particular pattern of repeat type variation that was absent in central and southern populations. Since E. lanatus is absent from Ram Mountain (in central Alberta), it is likely that populations from this locality, previously identified as E. trifidus, are instead a different agamospermous variant of E. compositus. In southern Alberta (Waterton Lakes), populations of E. trifidus are thought to be the product of local hy- bridization, and are therefore of different origin from the northern populations. The identity of the putative parents in the southern region remains uncertain.