MORPHOLOGICAL VARIATION AMONG MEMBERS OF THE STELLARIA-LONGIPES COMPLEX - S-LONGIPES, S-LONGIFOLIA, AND S-PORSILDII (CARYOPHYLLACEAE)

Morphological relationships were investigated among diploid Stellaria porsildii, polyploid S. longipes, and diploid S. longifolia. Canonical discriminant analysis, based on a priori assumptions to maximize differences among groups, showed that S. longipes clusters equally distant between the two diploid species along an axis connecting the diploids' centroids, but it differs along an axis perpendicular to this axis. The intermediacy along the former axis is evidence that S. longipes is an amphiploid derived from S. longifolia and S. porsildii. The divergence along the latter axis may be attributable to adaptively valuable heterotic traits which were retained following amphidiploidization. The only morphological discontinuity occurred between the two diploids, whereas the morphological range of S. longipes overlapped the range of both diploids forming a continuum. The lack of discrete clusters is likely due to hybridization and introgression with S. longifolia on one hand, and convergence of traits between S. longipes var. monantha and S. porsildii on the other. High a posteriori assignments in classificatory discriminant analysis supports the separation of S. longipes var. monantha from other S. longipes specimens. Although S. longipes var. monantha grouped close to S. porsildii, the two groups separate based on leaf shape traits. Overall results support, firstly, the hypothesis that S. porsildii is a diploid parent species which by hybridizing with S. longifolia gave rise to polyploid S. longipes. Secondly, results suggest that S. longipes var. monantha converged morphologically towards S. porsildii relatively recently due to ecological specialization, and merits distinction at least as a variety of S. longipes.