Systematics of three North American polyploid arctic alkali grasses (Puccinellia, Poaceae): morphology, ploidy, and AFLP markersThis paper is one of a selection of papers published in the Special Issue on Systematics Research.

We used flow cytometry, amplified fragment length polymorphisms (AFLP), and macromorphology from field and common garden specimens to delimit and identify parental taxa of three polyploid species of Puccinellia from the North American Arctic. Tetraploid Puccinellia bruggemannii T.J. Sørensen, hexaploid Puccinellia angustata (R. Br.) E.L. Rand & Redfield, and octoploid Puccinellia andersonii Swallen were generally separable based on ploidy and AFLP pattern, and showed allopolyploid origin. All three shared AFLP bands with at least two diploids and with Puccinellia phryganodes (Trin.) Scribn. & Merr., shown here to have both triploid and tetraploid populations in Canada. Approximately 10% of hexaploid individuals had AFLP patterns that were intermediate between P. angustata and P. bruggemannii, or P. angustata and P. andersonii, and occupied corresponding intermediate positions in morphological ordinations. Geographic distributions provide better support for introgression than for multiple polyploid events to account for these intermediate patterns. In common garden experiments, half of the characters had significantly different values between field and common garden specimens, but these plastic characters varied depending on the species pair analyzed and between experiments. Moreover, several characters were significantly different among species, but these characters were also different in each of the two experiments. Given this variation, we pooled the field and common garden data to determine important key characters by discriminant analysis of species pairs.