Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation
Abstract Hybridization between species can affect the strength of the reproductive barriers that separate those species. Two extensions of this effect are (1) the expectation that asymmetric hybridization or gene flow will have asymmetric effects on reproductive barrier strength and (2) the expectat...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Oxford University Press
2021-02-01
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| Series: | Evolution Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/evl3.205 |
| _version_ | 1797727368122466304 |
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| author | Kate L. Ostevik Joanna L. Rifkin Hanhan Xia Mark D Rausher |
| author_facet | Kate L. Ostevik Joanna L. Rifkin Hanhan Xia Mark D Rausher |
| author_sort | Kate L. Ostevik |
| collection | DOAJ |
| description | Abstract Hybridization between species can affect the strength of the reproductive barriers that separate those species. Two extensions of this effect are (1) the expectation that asymmetric hybridization or gene flow will have asymmetric effects on reproductive barrier strength and (2) the expectation that local hybridization will affect only local reproductive barrier strength and could therefore alter within‐species compatibility. We tested these hypotheses in a pair of morning glory species that exhibit asymmetric gene flow from highly selfing Ipomoea lacunosa into mixed‐mating Ipomoea cordatotriloba in regions where they co‐occur. Because of the direction of this gene flow, we predicted that reproductive barrier strength would be more strongly affected in I. cordatotriloba than I. lacunosa. We also predicted that changes to reproductive barriers in sympatric I. cordatotriloba populations would affect compatibility with allopatric populations of that species. We tested these predictions by measuring the strength of a reproductive barrier to seed set across the species’ ranges. Consistent with our first prediction, we found that sympatric and allopatric I. lacunosa produce the same number of seeds in crosses with I. cordatotriloba, whereas crosses between sympatric I. cordatotriloba and I. lacunosa are more successful than crosses between allopatric I. cordatotriloba and I. lacunosa. This difference in compatibility appears to reflect an asymmetric decrease in the strength of the barrier to seed set in sympatric I. cordatotriloba, which could be caused by I. lacunosa alleles that have introgressed into I. cordatotriloba. We further demonstrated that changes to sympatric I. cordatotriloba have decreased its ability to produce seeds with allopatric populations of the same species, in line with our second prediction. Thus, in a manner analogous to cascade reinforcement, we suggest that introgression associated with hybridization not only influences between‐species isolation but can also contribute to isolation within a species. |
| first_indexed | 2024-03-12T10:58:50Z |
| format | Article |
| id | doaj.art-ac9cd74b5c134821a74d8e5ad4f55a17 |
| institution | Directory Open Access Journal |
| issn | 2056-3744 |
| language | English |
| last_indexed | 2024-03-12T10:58:50Z |
| publishDate | 2021-02-01 |
| publisher | Oxford University Press |
| record_format | Article |
| series | Evolution Letters |
| spelling | doaj.art-ac9cd74b5c134821a74d8e5ad4f55a172023-09-02T06:02:18ZengOxford University PressEvolution Letters2056-37442021-02-0151758510.1002/evl3.205Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolationKate L. Ostevik0Joanna L. Rifkin1Hanhan Xia2Mark D Rausher3Department of Biology Duke University Durham North Carolina 27708Department of Ecology and Evolutionary Biology University of Toronto Toronto ON M5S 3B2 CanadaCollege of Horticulture and Landscape Architecture Zhongkai University of Agriculture and Engineering Guangzhou 510225 ChinaDepartment of Biology Duke University Durham North Carolina 27708Abstract Hybridization between species can affect the strength of the reproductive barriers that separate those species. Two extensions of this effect are (1) the expectation that asymmetric hybridization or gene flow will have asymmetric effects on reproductive barrier strength and (2) the expectation that local hybridization will affect only local reproductive barrier strength and could therefore alter within‐species compatibility. We tested these hypotheses in a pair of morning glory species that exhibit asymmetric gene flow from highly selfing Ipomoea lacunosa into mixed‐mating Ipomoea cordatotriloba in regions where they co‐occur. Because of the direction of this gene flow, we predicted that reproductive barrier strength would be more strongly affected in I. cordatotriloba than I. lacunosa. We also predicted that changes to reproductive barriers in sympatric I. cordatotriloba populations would affect compatibility with allopatric populations of that species. We tested these predictions by measuring the strength of a reproductive barrier to seed set across the species’ ranges. Consistent with our first prediction, we found that sympatric and allopatric I. lacunosa produce the same number of seeds in crosses with I. cordatotriloba, whereas crosses between sympatric I. cordatotriloba and I. lacunosa are more successful than crosses between allopatric I. cordatotriloba and I. lacunosa. This difference in compatibility appears to reflect an asymmetric decrease in the strength of the barrier to seed set in sympatric I. cordatotriloba, which could be caused by I. lacunosa alleles that have introgressed into I. cordatotriloba. We further demonstrated that changes to sympatric I. cordatotriloba have decreased its ability to produce seeds with allopatric populations of the same species, in line with our second prediction. Thus, in a manner analogous to cascade reinforcement, we suggest that introgression associated with hybridization not only influences between‐species isolation but can also contribute to isolation within a species.https://doi.org/10.1002/evl3.205Gene flowhybridizationIpomoeamating systemreproductive barriersspeciation |
| spellingShingle | Kate L. Ostevik Joanna L. Rifkin Hanhan Xia Mark D Rausher Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation Evolution Letters Gene flow hybridization Ipomoea mating system reproductive barriers speciation |
| title | Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| title_full | Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| title_fullStr | Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| title_full_unstemmed | Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| title_short | Morning glory species co‐occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| title_sort | morning glory species co occurrence is associated with asymmetrically decreased and cascading reproductive isolation |
| topic | Gene flow hybridization Ipomoea mating system reproductive barriers speciation |
| url | https://doi.org/10.1002/evl3.205 |
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