Taxonomy of autumn-flowering Spiranthes species of southern Nova Scotia

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Abstract
Identification difficulties with the autumn-flowering Spiranthes species of southern Nova Scotia resulted in questions regarding their discreteness and required determination of the most reliable diagnostic characters. Thirty-three morphological features were measured in each of 200 individual plants from 15 stations with no more than 30 plants randomly selected from each station. Principal components analysis did not establish groups clearly. Discriminant analysis of nine groups derived from the distance matrix using UPGMA clustering resulted in three major groups on the first two discriminant axes, representing S. cernua, S. ochroleuca, and S. casei. The Nova Scotian S. casei and S. ochroleuca are shown by further discriminant analysis to differ from their more western counterparts. Spiranthes casei var. novaescotiae is described as a new variety differing from var. casei in many characters including the relatively short, acute, and uniformly fleshy lip with indexed distal margins. Nova Scotian plants referrable to S. ochroleuca differ from more western S. ochroleuca principally in having larger ovaries and polyembryonic seed, these features being associated with apomixis. Minor differences in floral structure are also apparent. Formal recognition of the Nova Scotian race of S. ochroleuca is rejected since the distinctions are such that it is unlikely that it could be distinguished with an acceptable misclassification rate. The identification difficulties with the autumn-flowering Spiranthes species of southern Nova Scotia appear to have resulted from the fact that (1) the Nova Scotian race of S. ochroleuca is apomictic and has lost some of the distinctive features of floral morphology associated with sexuality throughout the rest of the range of this species, and consequently it closely approaches S. cernua, and (2) the Nova Scotian plants of S. casei differ from the typical variety in both floral and vegetative features. These Spiranthes species are among several taxa with a distinct morphological expression in southern Nova Scotia. A diagnostic key to the autumn-flowering Spiranthes species of southern Nova Scotia is provided.

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