Reproductive isolation can be achieved through multiple types of barriers and is essential for speciation. In flowering plants, pre-pollination barriers (e.g. differentiation in pollination niches) are believed to be the most efficient at preventing gene flow across species boundaries. In closely related species that come into secondary contact, such barriers can evolve to prevent competition for pollinator service and/or interspecific pollen transfer, which can have fitness costs. Hence pollination niche differentiation should be stronger in sympatric populations than in allopatric populations (i.e. character displacement). To investigate the differences in pollination niches and to see if it is consistent with a hypothesis of character displacement, I used the two closely related and phenotypically similar orchid species, Gymnadenia conopsea and G. densiflora. I sampled mixed and pure populations of G. conopsea and G. densiflora on Öland during the summer of 2020. In these populations, I used video cameras and pollinator catches to record pollinator activity and characterize the composition of pollinator communities. Estimation of pollinator efficiency was also assessed by analyzing the number of pollinia carried by each pollinator. Contrary to my expectations, I found that both orchids had their visitation peak during the night and that the most frequent and efficient pollinators were Autographa gamma or Deilephila porcellus for both of them. Furthermore, no increased differentiation between the two species was found in mixed compared to pure populations. My results suggest that plant-pollinator interactions do not act as efficient pre-pollination barriers in these two orchid species, and that competition for pollinator service and through interspecific pollen transfer seem to be too weak to drive pollination niche partitioning.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-435219 |
| Date | January 2021 |
| Creators | Olofsson, Caroliné |
| Publisher | Uppsala universitet, Institutionen för biologisk grundutbildning |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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