The origins of polyploids in western North American fawn-lilies (Erythronium)This paper is one of a selection of papers published in the Special Issue on Systematics Research.

Abstract

Two rare tetraploid fawn-lilies, Erythronium elegans P.C. Hammond & K.L. Chambers in western Oregon and Erythronium quinaultense G.A. Allen in northwestern Washington, are hypothesized to be of hybrid origin, on the basis of morphological evidence. I tested these hypotheses using DNA sequences of the nuclear ribosomal ITS region and of two plastid intergenic spacer regions (trnH-psbA and trnS-trnG) from the two tetraploids and the five relevant diploid taxa. ITS sequences indicated that the low-elevation diploid species Erythronium revolutum Sm. and Erythronium oregonum Applegate are recently diverged, and gave rise (at least in part) to the two tetraploids. Both E. elegans and E. quinaultense yielded multiple chloroplast DNA haplotypes that were of two distinct types. One plastid haplotype found in both E. elegans (four populations) and E. quinaultense (one population) exactly matched the most common haplotype of E. revolutum; other haplotypes of E. elegans (four populations) and E. quinaultense (two populations) were similar to those of E. oregonum. These results are consistent with derivation of the plastid genomes of different polyploid populations from either E. revolutum or E. oregonum (or their respective recent ancestors), and suggest recurrent formation of each tetraploid species. The two tetraploids are examples of allopolyploid species in which morphological and molecular evidence of their origins are in striking contrast, reflecting very different aspects of their genomes.