Presentation Detail

Evolutionary Ecology

Koski, Matthew [1], Ashman, Tia-Lynn [2].

Variation, heritability, and functional significance for a common ultraviolet floral pattern.

The ecological and evolutionary significance of variation in human-visible flower color is understood for many systems, yet numerous angiosperms possess floral UV reflectance that contributes to color and petal patterning. The floral UV bull's eye pattern, where petal tips reflect UV while the bases absorb UV, is common and thought to be important for mediating plant-insect interaction. We use Argentina anserina (Rosaceae), a perennial herb with floral UV pattern to answer the following broad questions: a) what is the degree of variation and heritability for UV pattern, and b) does the UV bull's eye pattern and/or UV reflectance influence pollinator visitation and/or foraging and orienting behavior? We sampled flowers in 13 populations and found that UV proportion, the relative area of the petal that absorbs UV, showed quantitative variation within and among populations in the field (~0.30 to ~0.99), where some individuals display a small bull-s eye while others are fully UV absorptive. Field-collected plants from eight populations were cloned and phenotyped in the greenhouse to estimate broad-sense heritability from clonal repeatability. Heritability for UV proportion was ~0.85, and population mean UV proportion in the field was tightly correlated with that in a common garden (r=0.82) suggesting genetic determination of phenotypic variation. To examine the function of floral UV pattern with respect to plant-pollinator interaction, we compared pollinator visitation and behavior at flowers with a UV bulls-eye pattern to flowers with a) fully UV-absorbing petals, b) fully UV-reflecting petals, and c) an inverse bull’s eye pattern (UV reflection at petal bases, absorbance at petal apices). Experiments revealed that the presence of pattern, but not increased UV reflective area, lead to increased visitation rates by bees and flies. Basal UV-absorbance was more attractive than the inverse pattern. The likelihood of pollinator foraging and orienting to the center of the flower however, was not influenced by floral manipulation—that is, the bull's eye pattern did not function as a proximate nectar guide. Our studies show substantial quantitative variation for a floral UV trait that may be ignored in many systems, and suggest that possession of a ubiquitous UV floral pattern, not UV reflectance alone, contributes to increased floral attractiveness to pollinators. Variation, heritability, and functional significance suggest that a floral UV phenotype could be under natural selection.

1 - University Of Pittsburgh, Biological Sciences, 4249 Fifth Avenue, 216 Clapp Hall, Pittsburgh, PA, 15260, USA
2 - University Of Pittsburgh, Department Of Biological Sciences, 4249 Fifth Avenue & Ruskin, Pittsburgh, PA, 15260, USA

Keywords:
flower color
heritability
pollination
quantitative variation
ultraviolet.

Presentation Type: Regular Oral Presentation
Session: 42
Location: Alpine C/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 4:45 PM
Number: 42006
Abstract ID:607
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation,Student Travel Awards from the ASN