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The cost of co-occurrence : reproductive interference between close relatives in an open-pollinated common garden Buckholtz, Gracy
Abstract
A widely observed pattern is closely related species typically do not co-occur, which can be a potential factor driving divergence in range. Close relatives often display similar traits and resource requirements, leading to more intensive ecological competition. However, reproductive interactions are also expected to be more intense in close relatives and therefore can also play a significant role in driving range divergence. We used a system in which one taxon reproduces sexually and the other asexually to disentangle these interactions. Townsendia hookeri (Easter Daisy) plants are either apomictic triploids, producing clonal offspring without fertilization of the ovule, or sexually reproducing diploids, requiring outcrossed pollen to produce offspring. As expected of close relatives, mixed populations are exceedingly rare, even in areas where the ranges overlap. Because apomicts produce vestigial pollen, reproductive interference is unidirectional; controlled hand crosses have shown that sexual plants produce fewer offspring when treated exclusively with apomictic pollen. Previous common garden work has shown that sexual plants can establish well in the northern range currently exclusively occupied by apomictic plants. We explore the reproductive dynamics between the two types when co-occurring in equal numbers in an open-pollinated garden. Achenes of sexual plants were collected, measured, germinated, and the offspring sequenced using GBS (genotyping-by-sequencing) techniques. We found evidence of early-stage reproductive interference in the form of reduced seed set of sexual plants closest to apomicts in our garden. Open-pollinated plants, assumed to receive a mixed pollen load, showed a similar decline in seed set as measured in previous controlled crosses but unlike previous results our plants showed no evidence of selfing. Among surviving offspring, 28% were hybrids sired by apomicts. Hybrid and outcrossed offspring did not significantly differ in their fitness-related traits measured in their first three months of life, but inter-ploidy crosses typically yield non-diploid offspring, which are likely to have reduced contributions to future generations of diploids, and thus may represent an additional mode of reproductive interference. Our results imply that when sexuals naturally disperse into apomictic territory they will likely suffer decreased seed set and hybrid production that may explain the current observed lack of co-occurrence.
Item Metadata
Title |
The cost of co-occurrence : reproductive interference between close relatives in an open-pollinated common garden
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Creator | |
Supervisor | |
Publisher |
University of British Columbia
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Date Issued |
2024
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Description |
A widely observed pattern is closely related species typically do not co-occur, which can be a potential factor driving divergence in range. Close relatives often display similar traits and resource requirements, leading to more intensive ecological competition. However, reproductive interactions are also expected to be more intense in close relatives and therefore can also play a significant role in driving range divergence. We used a system in which one taxon reproduces sexually and the other asexually to disentangle these interactions. Townsendia hookeri (Easter Daisy) plants are either apomictic triploids, producing clonal offspring without fertilization of the ovule, or sexually reproducing diploids, requiring outcrossed pollen to produce offspring. As expected of close relatives, mixed populations are exceedingly rare, even in areas where the ranges overlap. Because apomicts produce vestigial pollen, reproductive interference is unidirectional; controlled hand crosses have shown that sexual plants produce fewer offspring when treated exclusively with apomictic pollen. Previous common garden work has shown that sexual plants can establish well in the northern range currently exclusively occupied by apomictic plants. We explore the reproductive dynamics between the two types when co-occurring in equal numbers in an open-pollinated garden. Achenes of sexual plants were collected, measured, germinated, and the offspring sequenced using GBS (genotyping-by-sequencing) techniques. We found evidence of early-stage reproductive interference in the form of reduced seed set of sexual plants closest to apomicts in our garden. Open-pollinated plants, assumed to receive a mixed pollen load, showed a similar decline in seed set as measured in previous controlled crosses but unlike previous results our plants showed no evidence of selfing. Among surviving offspring, 28% were hybrids sired by apomicts. Hybrid and outcrossed offspring did not significantly differ in their fitness-related traits measured in their first three months of life, but inter-ploidy crosses typically yield non-diploid offspring, which are likely to have reduced contributions to future generations of diploids, and thus may represent an additional mode of reproductive interference. Our results imply that when sexuals naturally disperse into apomictic territory they will likely suffer decreased seed set and hybrid production that may explain the current observed lack of co-occurrence.
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Genre | |
Type | |
Language |
eng
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Date Available |
2024-04-19
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0441445
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URI | |
Degree | |
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Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2024-05
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International