Abstract
Establishment of polyploid individuals within diploid populations is theoretically unlikely unless polyploids are reproductively isolated, pre-zygotically, through assortative pollination. Here, we quantify the contribution of pollinator diversity and foraging behaviour to assortative pollen deposition in three mixed-ploidy populations of Chamerion angustifolium (Onagraceae). Diploids and tetraploids were not differentiated with respect to composition of insect visitors. However, foraging patterns of the three most common insect visitors (all bees) reinforced assortative pollination. Bees visited tetraploids disproportionately often and exhibited higher constancy on tetraploids in all three populations. In total, 73% of all bee flights were between flowers of the same ploidy (2x–2x, 4x–4x); 58% of all flights to diploids and 83% to tetraploids originated from diploid and tetraploid plants, respectively. Patterns of pollen deposition on stigmas mirrored pollinator foraging behaviour; 73% of all pollen on stigmas (70 and 75% of pollen on diploid and tetraploid stigmas, respectively) came from within-ploidy pollinations. These results indicate that pollinators contribute to high rates of pre-zygotic reproductive isolation. If patterns of fertilization track pollen deposition, pollinator–plant interactions may help explain the persistence and spread of tetraploids in mixed-ploidy populations.
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Acknowledgments
We thank Jeff Warner for his assistance in the field, Ralph Cartar for help identifying pollinators and Elizabeth Elle for comments on the manuscript. This work was supported by an Alberta Conservation Association Grant in Biodiversity to HS and an NSERC Discovery Grant, Premier’s Research Excellence Award and a Canada Research Chair Award to BCH. All research complied with the current regulations of landowners and the Canadian Government.
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Communicated by Jacqui Shykoff.
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Kennedy, B.F., Sabara, H.A., Haydon, D. et al. Pollinator-mediated assortative mating in mixed ploidy populations of Chamerion angustifolium (Onagraceae). Oecologia 150, 398–408 (2006). https://doi.org/10.1007/s00442-006-0536-7
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DOI: https://doi.org/10.1007/s00442-006-0536-7