ANALYSIS OF STEM COLOR AND CORRELATED MORPHOLOGICAL CHARACTERS FOR GROUPING PHRAGMITES (POACEAE) TAXA IN EASTERN ONTARIO

摘要

Phragmites australis subsp. australis is an invasive alien of major importance in natural habitats in many parts of North America but methods of distinguishing it from the native subsp. americanus required more research. A study of the value of basalstem internode color was conducted in eastern Ontario where the long history of collections enables characteristics of the native subspecies to be evaluated, since the invasive alien subspecies is believed to have arrived only recently. Although there issome overlap, correlation analysis indicated that basal stem internode color was highly correlated with ligule height and lower glume length, the latter characters being considered the most important for differentiation. With regard to ligule height, ameasurement excluding the fringe of hair proved most valuable. Collections of native plants prior to the post-1970 spread of Phragmites along roads have reddish-purple lower stem internodes, whereas many collected after 1970 have yellow-brown lower steminternodes. Plants from interior wetlands, presumed to be native, also have reddish-purple lower stem internodes, while those from roadsides are either yellow-brown or reddish-purple. The plants with reddish-purple lower stem internodes have longer lowerglumes and longer ligules on middle leaves than the plants with yellow-brown lower stem internodes. They are thus referable to the native subsp. americanus based on morphological as well as circumstantial evidence. Lower glume length and ligule height are confirmed as valuable characters for separating subsp. australis and subsp. americanus. Basal stem internode color is a valuable character, particularly for field identification and especially when combined with morphological measurements. Basal steminternode color was also indicated to be useful for studying the history of invasion of subsp. australis in eastern Ontario, and may prove similarly useful in other parts of northeastern North America, as well.