Abstract Detail

Functional Genetics/Genomics

Liao, Irene [1], Rausher, Mark [1].

Floral trait modularity in the selfing syndrome of morning glories.

A composite trait is composed of traits that appear to be phenotypically integrated, suggesting that these components may have evolved together as a unit. If component traits are genetically correlated - through pleiotropy, tight linkage, or regulatory networks - changes in one component trait can indirectly affect other traits. Such correlations can facilitate or constrain the evolutionary trajectories to forming a composite trait. However, if these component traits are not genetically correlated, each component trait must evolve independently.
One example of a composite trait in flowering plants is the selfing syndrome, a suite of traits associated with the transition from outcrossing to selfing. This transition and the associated phenotypic changes have occurred in multiple plant lineages, making the selfing syndrome a compelling system to study the evolutionary mechanisms for the formation of a composite trait. The selfing syndrome typically consists of reductions in the following traits: overall flower size, anther-stigma separation, pollen-ovule ratio, scent, and nectar. Despite its importance as a pollinator reward that is potentially costly to produce, nectar has been overlooked in studies of the selfing syndrome and how nectar traits evolved remains unexamined.  
Here, we address whether nectar traits have evolved independently or in a coordinated fashion with other traits in the selfing syndrome in the highly selfing morning glory, Ipomoea lacunosa (Convolvulaceae). Ipomoea lacunosa displays the components of the selfing syndrome compared to its sister mixed-mating species, I. cordatotriloba. Using a quantitative trait locus (QTL) mapping approach on F5 recombinants derived from a I. cordatotriloba X I. lacunosa cross, we found that nectar traits are polygenic, with several QTLs underlying each nectar trait. Phenotypically, nectar traits form a distinct trait module, but weak correlations do exist between flower and nectar modules. These results are reflected in QTL analyses, which indicate that nectar traits share overlapping QTLs, but little to no overlapping QTLs exist between nectar and flower traits. The lack of genetic correlation between flower size and nectar traits suggests that reduced nectar traits may have evolved independently, such that selection on each trait is necessary for the formation of the selfing syndrome. This raises future questions of whether independent evolution of component traits is common for generating similar composite traits in separate lineages.

1 - Duke University, Biology, 130 Science Drive, Room 137, Biological Sciences Building, Durham, NC, 27708, United States

none specified

Presentation Type: Oral Paper
Number: 0005
Abstract ID:427
Candidate for Awards:Margaret Menzel Award

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