Mating system transitions from self‐incompatibility (SI) to self‐compatibility (SC) are common in plants. In the absence of high levels of inbreeding depression, SC alleles are predicted to spread due to transmission advantage and reproductive assurance. We characterized mating system and pistil‐expressed SI factors in 20 populations of the wild tomato species We found that a single SI to SC transition is fixed in populations south of the Rio Chillon valley in central Peru. In these populations, SC correlated with the presence of the We suggest that the
Variation in mating systems is prevalent throughout angiosperms, with many transitions between outcrossing and selfing above and below the species level. This study documents a new case of an intraspecific breakdown of self-incompatibility in a wild relative of tomatillo, Physalis acutifolia. We used controlled greenhouse crosses to identify self-incompatible (SI) and self-compatible (SC) individuals grown from seed sampled across seven sites across Arizona and New Mexico. We measured 14 flower and fruit traits to test for trait variation associated with mating system. We also quantified pollen tube growth in vivo and tested for the presence of the S-RNase proteins in SI and SC styles. We found that seed from six of the seven sites produced SI individuals that terminated self-pollen tubes in the style and showed detectable S-RNase expression. By contrast, seed from one Arizona site produced SC individuals with no S-RNase expression. These SC individuals displayed typical selfing-syndrome traits such as smaller corollas, reduced stigma–anther distances, and a smaller pollen–ovule ratio. We also found plasticity in self-incompatibility as most of the SI individuals became SC and lost S-RNase expression roughly after 6 months in the greenhouse. While fixed differences in mating systems are known among the SI wild species and the often SC domesticated tomatillos, our study is the first to demonstrate intraspecific variation in natural populations as well as variation in SI over an individual’s lifespan.
more » « less- NSF-PAR ID:
- 10361819
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- AoB PLANTS
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2041-2851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary Solanum habrochaites from the southern half of the species range.hab‐6 S ‐haplotype that encodes a low activity S‐RNase protein. We identified a single population segregating for SI/SC andhab‐6 . Intrapopulation crosses showed thathab‐6 typically acts in the expected codominant fashion to confer SC. However, we found one specificS ‐haplotype (hab‐10 ) that consistently rejects pollen of thehab‐6 haplotype, and results in SIhab‐6 /hab‐10 heterozygotes.hab‐10 haplotype could act as a genetic mechanism to stabilize mixed mating in this population by presenting a disadvantage for thehab‐6 haplotype. This barrier may represent a mechanism allowing for the persistence of SI when an SC haplotype appears in or invades a population. -
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Premise Long‐distance dispersal has been important in explaining the present distributions of many plant species. Despite being infrequent, such dispersal events have considerable evolutionary consequences, because bottlenecks during colonization can result in reduced genetic diversity. We examined the phylogeographic history of
Lycium carolinianum , a widespread taxon that ranges from southeastern North America to several Pacific islands, with intraspecific diversity in sexual and mating systems.Methods We used Bayesian, likelihood, and coalescent approaches with nuclear and plastid sequence data and genome‐wide single nucleotide polymorphisms to reconstruct the dispersal history of this species. We also compared patterns of genetic variation in mainland and island populations using single nucleotide polymorphisms and allelic diversity at the
S‐RNase mating system gene.Results Lycium carolinianum is monophyletic and dispersed once from the North American mainland, colonizing the Pacific islands ca. 40,100 years ago. This dispersal was accompanied by a loss of genetic diversity in SNPs and theS‐RNase locus due to a colonization bottleneck and the loss of self‐incompatibility. Additionally, we documented at least two independent transitions to gynodioecy: once following the colonization of the Hawaiian Islands and loss of self‐incompatibility, and a second time associated with polyploidy in the Yucatán region of Mexico.Conclusions Long‐distance dispersal via fleshy, bird dispersed fruits best explains the unusually widespread distribution of
L. carolinianum . The collapse of diversity at theS‐RNase locus in island populations suggests that self‐fertilization may have facilitated the subsequent colonization of Pacific islands following a single dispersal from mainland North America. -
• Reinforcement is the process through which prezygotic reproductive barriers evolve in sympatry due to selection against hybridization between co-occurring, closely related species. The role of self-fertilization in reinforcement and reproductive isolation is uncertain in part because its efficiency as a barrier against heterospecific mating can depend on the timing of autonomous selfing. • To investigate whether increased autonomous selfing has evolved as a mechanism for reinforcement, we compared Phlox cuspidata populations across their native Texas range using both estimates of genetic diversity and experimental manipulation with morphological measurements. Specifically, we investigated patterns of variation in floral traits and timing of selfing between individuals from allopatric populations of P. cuspidata and from populations sympatric with the closely related species, P. drummondii. • We infer intermediate rates of selfing across field-collected individuals with no significant difference between allopatric and sympatric populations. Among greenhouse grown plants, we find no differences in timing of selfing or other floral traits including anther dehiscence timing, anther-stigma distances, autonomous selfing rate and self-seed count between allopatric and sympatric populations. However, our statistical analyses indicate that P. cuspidata individuals sympatric with P drummondii seem to have generally larger flowers compared to allopatric individuals. • Despite strong evidence of costly hybridization with P. drummondii, we find no evidence of trait divergence due to reinforcement in P. cuspidata. Although we document nearly complete autonomous self-seed set in the greenhouse, estimates of selfing rates from genetic data imply realized selfing is much lower in nature suggesting an opportunity for reinforcing selection to act on this trait.more » « less
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