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Abstract Detail


Pollination Biology

Kalisz, Susan [1], Faigeles, Melissa [2], Chaiffetz, David [1], Butera, Aileen [1].

Testing predicted morphological and developmental correlates of mating system evolution in the tribe Collinseae.

Flower size is often used as a surrogate for assessing a species’ mating system—with small-flowered species generally considered selfing. However, for species to move to the selfing mode and autonomously self, a change within a flower in either the relative positions of male and female parts (herkogamy) or the timing of male and female phases (dichogamy) or both are necessary and predicted to evolve. Such developmental traits are rarely quantified, yet are central to understanding the trajectories that species follow during mating system evolution. The tribe Collinseae is comprised of ~24 self-compatible species that range from large-flowered, putatively outcrossing to small-flowered, putatively selfing. The tribe has a well-resolved phylogenetic tree that conforms to a molecular clock and allows us to assign relative species ages. In addition, small- and large-flowered sister taxa pairs exist in the tribe, allowing us to compare developmental traits of species with divergent mating systems and to explore these predicted developmental correlates of mating system evolution.
We 1) quantified the multidimensional floral phenotype space for the tribe Collinseae using Principle Components Analysis (PCA) of flower size and shape variables, 2) tested the relationship of floral size/shape with developmental correlates of mating system (longevity, herkogamy, dichogamy and autonomous pollen deposition), and 3) explored common pathways in phenotype space that define transitions between selfing and outcrossing of the sister taxa pairs. The first three PC explain 88% of the variance in floral morphology among species [PC1=flower size (75%), PC2=dorsal-lateral petal angle (9%) and PC3=corolla tube shape (4%)]. Interestingly, floral lifespan, herkogamy, and dichogamy were all significantly and positively correlated with floral size (PC1), suggesting a general co-evolution of floral size and developmental traits. However fine-scale analyses reveal significant differences among sister taxa pairs in which developmental traits contribute to the transition between selfing and outcrossing.


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1 - University of Pittsburgh, Department of Biological Sciences, Langley Hall, Pittsburgh, Pennsylvania, 15260, USA
2 - University of Pittsburgh, Department of Biological Sciences, Langley Hall, Pittsburgh, Pennsylvania, 15260, USA

Keywords:
mating system
Collinsia
evolution of selfing
floral evolution
Floral development
floral longevity
flower size
herkogamy
dichogamy.

Presentation Type: Oral Paper:Papers for Topics
Session: CP37
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 5:00 PM
Number: CP37005
Abstract ID:2064


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