COMPARATIVE FLORAL ECOLOGY OF BICOLOUR AND CONCOLOUR MORPHS OF VIOLA PEDATA L. (VIOLACEAE) FOLLOWING CONTROLLED BURNS

Peter Bernhardt, Retha Edens-Meier, Dowen Jocson, Justin Zweck, Zong-Xin Ren, Gerardo Camilo, Michael Arduser
2016 Journal of Pollination Ecology   unpublished
We compared pollinators, pollination rates and seed set of bicolour and concolour morphs in self-incompatible, Viola pedata over two seasons. The two populations grew on a wooded slope (CR) vs. an exposed glade (SNR) and were of unequal sizes. Both were burned in 2014. The number of flowers produced by concolour plants at SNR was higher in 2014 while the number of flowering bicolour plants increased significantly at CR in 2015. Petal temperatures, regardless of site, showed that the dark
more » ... posterior petals of bicolours were consistently warmer than their own mauve-lilac, anterior (lip) petals and the all mauve petals of concolours. Major pollen vectors were polylectic/polyphagic bees (Andrenidae, Apidae and Halictidae) but females of Andrena carlinii dominated at both sites. Bees foraged on flowers upside down or right side up but neither mode correlated with either morph. Bees foraged preferentially on concolour at both sites. Pollen tube counts were higher in concolours at both sites with a marginally greater number of pollen tubes penetrating concolour ovules regardless of site or year. While both populations produced more seeds in 2014 SNR plants always produced more seeds than CR plants. The increasing numbers of bicolour plants at CR in 2015 suggested that bicolours may equal or outnumber concolours as dark petals offer additional warmth to ecto-thermic pollinators foraging in a cooler, shady forest vs. an open, sunny glade. Subtle environmental factors may give a floral trait a selective advantage influencing fitness when an unbalanced polymorphism persists in discrete and localized populations.
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