Abstract Detail

Pollination Biology

Mickley, James [1], Schlichting, Carl [1].

Mating System as a Driver of Variation in Floral Petal Number: Is There Evidence for Adaptation to Pollinators?

Across angiosperms, floral petal number varies broadly with clades ranging from few to many petals. Many clades are fixed for a certain petal number, and strikingly, the superclade Pentapetalae within Eudicots, with thousands of species, is overwhelmingly five-petaled. One longstanding hypothesis explaining petal number fixation is that pollinator preferences have selected for particular petal numbers, yet this has been poorly tested and a causal or mechanistic basis for why pollinators should have a preference is lacking. An alternative hypothesis is that petals are costly, either energetically or in terms of water loss, and thus lower petal numbers are favored. In combination, these two hypotheses could lead to some optimal petal number. If pollinators act as agents of selection on petal number, then autogamous species should experience relaxed selection, leading to higher variance in petal number compared to outcrossing congeners. Furthermore, if petals are costly, autogamous species should reduce petal number to minimize costs. If both are true, then autogamous species should have more variation in petal number than outcrossing species, and that variation should be biased towards losses of petals. In the family Polemoniaceae, low levels of petal number variation within natural populations are a common feature across many species. I test the above hypotheses by comparing patterns of natural petal number variation between closely related pairs of autogamous and outcrossing species in three genera Phlox, Gilia, and Saltugilia. Many of these species grow in dry environments where water loss via petals could be influential. My results reveal no evidence for higher levels of petal number variation within autogamous species, suggesting that selection via pollinators is not a strong determinant of petal number. Support for overall reduction in petal number within autogamous species is equivocal, with only some autogamous species showing the trend. Together, these are some of the first tests on the putatively adaptive basis of petal number.

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1 - University of Connecticut, Department of Ecology and Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, United States

Keywords:
merosity
pentamery
floral evolution
Polemoniaceae
petal number
adaptation
subindividual variation
pentapetalous
flower petals
petal variation.

Presentation Type: Oral Paper
Session: 36, Pollination Biology
Location: 203/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 9:15 AM
Number: 36006
Abstract ID:666
Candidate for Awards:None