Journal Article

Broad geographic covariation between floral traits and the mating system in <i>Camissoniopsis cheiranthifolia</i> (Onagraceae): multiple stable mixed mating systems across the species' range?

Sara R. Dart, Karen E. Samis, Emily Austen and Christopher G. Eckert

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 109, issue 3, pages 599-611
Published in print February 2012 | ISSN: 0305-7364
Published online October 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcr266
Broad geographic covariation between floral traits and the mating system in Camissoniopsis cheiranthifolia (Onagraceae): multiple stable mixed mating systems across the species' range?

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  • Ecology and Conservation
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Background and Aims

Plants vary widely in the extent to which seeds are produced via self-fertilization vs. outcrossing, and evolutionary change in the mating system is thought to be accompanied by genetic differentiation in a syndrome of floral traits. We quantified the pattern of variation and covariation in floral traits and the proportion of seeds outcrossed (t) to better understand the evolutionary processes involved in mating system differentiation among and within populations of the short-lived Pacific coastal dune endemic Camissoniopsis cheiranthifolia across its geographic range in western North America.

Methods

We quantified corolla width and herkogamy, two traits expected to influence the mating system, for 48 populations sampled in the field and for a sub-sample of 29 populations grown from seed in a glasshouse. We also measured several other floral traits for 9–19 populations, estimated t for 16 populations using seven allozyme polymorphisms, and measured the strength of self-incompatibility for nine populations.

Key Results

Floral morphology and self-incompatibility varied widely but non-randomly, such that populations could be assigned to three phenotypically and geographically divergent groups. Populations spanned the full range of outcrossing (t = 0·001–0·992), which covaried with corolla width, herkogamy and floral life span. Outcrossing also correlated with floral morphology within two populations that exhibited exceptional floral variation.

Conclusions

Populations of C. cheiranthifolia seem to have differentiated into three modal mating systems: (1) predominant outcrossing associated with self-incompatibility and large flowers; (2) moderate selfing associated with large but self-compatible flowers; and (3) higher but not complete selfing associated with small, autogamous, self-compatible flowers. The transition to complete selfing has not occurred even though the species appears to possess the required genetic capacity. We hypothesize that outcrossing populations in this species have evolved to different stable states of mixed mating.

Keywords: Allozymes; Camissoniopsis cheiranthifolia; corolla width; flower size; geographic variation; herkogamy; mating system; Onagraceae; outcrossing; self-fertilization; self-incompatibility

Journal Article.  9429 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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