Annual plants colonizing the Arctic? Phylogeography and genetic variation in the Euphrasia minima complex (Orobanchaceae)

作者：Gussarova Galina^*; Alsos Inger Greve; Brochmann Christian

来源：Taxon, 2012, 61(1): 146-160.

• amplified fragment length polymorphism (AFLP)
• annual plants
• Arctic
• cpDNA
• Euphrasia
• phylogeography

The high-arctic environment supports very few annual plants, but more annuals can be expected to move northwards following climate warming. Here we address the history of the amphi-Atlantic, hemiparasitic Euphrasia minima complex, which is taxonomically intricate and consists of annuals typically growing in alpine, north boreal, and low-arctic habitats. Recently it has also been discovered at three distantly separated sites in the high-arctic archipelago of Svalbard. We analyzed Amplified Fragment Length Polymorphism (AFLP) and chloroplast DNA (cpDNA) variation in populations from most of the range of the complex. The main split observed in both datasets, dated to nearly 6 Ma ago, was between one central/southern European alpine lineage (E. minima s.str.) and one northern amphi-Atlantic lineage (E. wettsteinii). The E. wettsteinii lineage consisted of two cpDNA sublineages, both amphi-Atlantic and partly sympatric, estimated to have diverged 1.7 Ma ago. Two main northern subgroups were also revealed in the AFLP dataset, partly consistent with the cpDNA sublineages: one E Atlantic subgroup (N Russia, extending into Scotland and Colesdalen in Svalbard), and one mainly W Atlantic subgroup (NE Canada, Greenland, and Iceland, extending into N Norway). A third subgroup was restricted to two of the three Svalbard populations, Bockfjorden and Ossian Sarsfjellet. Assignment tests of the Svalbard populations suggest that Colesdalen was derived from N Russian source populations and Bockfjorden from N Norwegian ones; the assignment of the Ossian Sarsfjellet population was uncertain. However, as all Svalbard populations were distinctly divergent from each other as well as from all other populations in AFLP marker frequencies, it is unlikely that their establishment in Svalbard is caused by the current climate warming or recent human activities. Their divergence is probably due to founder effects and genetic drift following independent earlier immigrations, possibly during the postglacial warm period 9500 to 4000 years ago.

• 出版日期2012-2