Biology ETDs

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Plant mating systems include a variety of mechanisms that result in non-random success of self- and outcross pollen, pollen from different compatible mates, and pollen from the same or different species. Although some of these mechanisms have received considerable attention (i.e., Charlesworth et al. 2005; Pannell and LaBouche 2013), most previous study has been of only one of these mechanisms at a time. Further in the field, a plant might simultaneously receive pollen of several types; thus, it is likely that multiple mechanisms of sorting among pollen operate simultaneously. If these mechanisms interact in ways that alter sorting among mates, we may be missing important pieces in our understanding of plant mating systems. To begin to ask whether different types of sorting among mates (e.g., sorting against self pollen, sorting among compatible mates, and sorting against heterospecific pollen) interact, I conducted two experiments that ask whether sorting among compatible mates changes when self incompatibility and/or sorting against heterospecific pollen also occur. By using two different Raphanus sativus types with different histories of introgression with R. raphanistrum, I also asked whether past history of hybridization affects ability to discriminate against heterospecific pollen. I applied different mixes of pollen to recipient plants and investigated the ability to sire seeds when different identities of pollen were present. I found that the regardless of the identity of the pollen, sorting compatible mates did not change in either type of R. sativus (California wild radish; P=0.15 and Purple plum; P=0.34). This result suggests that the mechanisms involved in sorting different pollen types are independent in this species. I also found differences in ability to discriminate against the R. raphanistrum in the two types of R. sativus. The relative proportion of seeds sired by R. raphanistrum on California wild radish was significantly less than on the cultivar Purple plum (P<0.0001), but Purple plum showed seed abortion and reduced size of seeds when R. raphanistrum pollen was used. Thus, it appears that the mechanism for discriminating against heterospecific pollen acted earlier (prior to fertilization) in California wild radish than in Purple plum. This may give an advantage to California wild radish, since seed abortion has a negative impact on reproductive fitness.




Radish, sexual selection, pollen sorting, heterospecific pollen, pollen discrimination, Brassicaceae

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Department Name

UNM Biology Department

First Committee Member (Chair)

Hanson, David

Second Committee Member

Whitney, Kenneth