JOHNSON, LEIGH A. Department of Botany and Range Science, Brigham Young University, Provo, UT 84602. - Sinister speciation: elucidating phylogeny and taxonomy in a cryptic species complex in Polemoniaceae.
Gilia sinistra remains one of the more enigmatic species of
Polemoniaceae. Formally recognized in the early 1900's, this
small-flowered plant was afterward considered synonymous with G.
capillaris. A larger-flowered form was also later described as a
subspecies of G. leptalea. These two forms were united under
the name Gilia sinistra in 1993. Concomitantly, all three of
the above species were circumscribed in a new section of Gilia,
section Kelloggia. Cohesive in gross morphology but variable
in geographic distribution and breeding systems, the species of
section Kelloggia provide an interesting model for exploring
patterns of diversification among a putatively monophyletic group.
Isozyme analyses of 24 populations, however, reveal unexpected
divergence within Gilia sinistra. Analyses of chloroplast and
nuclear DNA sequences also reveal this remarkable divergence. Instead
of a monophyletic group, section Kelloggia comprises three
distinct lineages, all with affinities to Navarretia. Gilia
leptalea and G. capillaris form one lineage, and G.
sinistra occurs in two well-separated lineages. The geographic
distribution of the morphologically cryptic races of G. sinistra
were determined from sampling DNA sequences from over 30
populations throughout its range. The proper application of the
specific epithet to one of these races was determined by scrutiny of
micromorphological characters among these populations and the
nomenclatural type. Combined, these data suggest possible reticulate
evolution in the origin of at least one of the sinistra lineages.
These data also favor the recent realignment of the kellogioid gilias
in Navarretia, rather than in Allophyllum as also
recently proposed. Although these "gilias" are readily
distinguished in gross morphology from both genera, corroboration of
morphological and molecular data argue for expanding the concept of
Navarretia to include these species--but not as a single,
exclusive section within this genus.
Key words: cryptic species, Gilia, Navarretia, phylogeny, Polemoniaceae, taxonomy