Flora of North America species comparison

H. J. Thompson and W. R. Ernst (1967) called attention to two different floral size morphs among populations of Eucnide bartonioides, and Turner recognized them formally as different varieties. Thompson, in a personal communication to Turner, suggested that the small-flowered var. edwardsiana may be a highly autogamous derivative of the larger flowered form, and observations for this treatment showed the stigma of this form to be closely surrounded by dehisced anthers. Turner indicated that var. edwardsiana, which is found on the Edwards Plateau (Comal, Edwards, Hays, Kerr, Llano, and Travis counties), grades into var. bartonioides in Edwards County. Flowers of var. edwardsiana from Edwards County are at the large end of their size range, and a survey of specimens showed that both relatively large-flowered plants and more typical forms of var. edwardsiana occur near each other in some localities. Turner characterized var. edwardsiana as perennial, but most of the examined specimens appear to be annuals. Across its range in Mexico, E. bartonioides displays variation in flower size, with small-flowered plants that appear to be annuals found in different regions. These are likely to be separate evolutionary origins of small-flowered annuals that converge on the characteristics of var. edwardsiana.

(Discussion copyrighted by Flora of North America; reprinted with permission.)