The evolution of self-fertilization and inbreeding depression under pollen discounting and pollen limitation

1SummaryTraditionally, we expect that self-incompatibility alleles (S-alleles), which prevent self-fertilization, should benefit from negative-frequency dependent selection and rise to high frequency when introduced to a new population through gene flow. However, the most taxonomically widespread form of self-incompatibility, the ribonuclease-based system ancestral to the core eudicots, functions through nonself-recognition, which drastically alters the process of S-allele diversification.We analyze a model of S-allele evolution in two populations connected by migration, focusing on comparisons among the fates of S-alleles originally unique to each population and those shared among populations.We find that both shared and unique S-alleles originating from the population with more unique S-alleles were usually fitter than S-alleles from the population with fewer. Resident S-alleles were often driven extinct and replaced by migrant S-alleles, though this outcome could be averted by pollen limitation or biased migration.Nonself-recognition-based self-incompatibility will usually either disfavor introgression of S-alleles or result in the whole-sale replacement of S-alleles from one population with those from another.

Download Full-text

Autonomous pollination alleviates pollen limitation in the endemic Cienfuegosia yucatanensis Millsp. (Malvaceae)

Botanical Sciences ◽

10.17129/botsci.2651 ◽

2020 ◽

Vol 99 (1) ◽

pp. 80-91

Author(s):

Víctor Parra-Tabla ◽

Conchita Alonso

Keyword(s):

Seed Production ◽

Inbreeding Depression ◽

Seed Weight ◽

Pollen Limitation ◽

Pollen Tubes ◽

Pollen Deposition ◽

Cross Pollination ◽

The North ◽

Hand Pollination ◽

Self Compatibility

Background: Self-compatibility is common on endemic plant species, but pollen limitation and self-pollination could be risk factors. Study species: The endemic Cienfuegosia yucatanensis (Malvaceae), whose distribution is mainly restricted to the north coast of the peninsula of Yucatán, México. Questions: a) Are flowers of C. yucatanensis autonomous for pollination? b) Are C. yucatanensis fruit or seed-set limited by pollen deposition? and, c) Is there evidence of early inbreeding depression in C. yucatanensis? Study sites and dates: Two sites in the north of the peninsula of Yucatán in a seasonally dry scrubland, in the rainy season of 2013 and 2014. Methods: Number of flowers and fruits were weekly recorded. Flowers were collected to count the number of conspecific pollen load and the number of pollen tubes. Autonomous pollination and pollen limitation were evaluated with a hand-pollination experiment. Inbreeding depression on fruit and seed production, and seed weight was evaluated. Results: Flower and fruit production occur simultaneously and last from August to October. Conspecific pollen deposition on stigmas occurred through the whole flowering season and a maximum of pollen tubes was observed in August. Autonomous pollination treatment lead to similar fruit and seed production than cross-pollination, but open pollination produced significantly more seeds. No significant differences among self- and cross-pollination treatments on fruit and seed production or seed weight, were found. Conclusions: Our results suggest that self-compatibility combined with a relatively efficient autonomous pollination, are suitable mechanisms for the reproductive assurance in C. yucatanensis, with no apparent effects of early inbreeding depression.

Download Full-text

Single Gene Control of Postzygotic Self-Incompatibility in Poke Milkweed, Asclepias exaltata L.

Genetics ◽

10.1093/genetics/154.2.893 ◽

2000 ◽

Vol 154 (2) ◽

pp. 893-907

Author(s):

Sara R Lipow ◽

Robert Wyatt

Keyword(s):

Inbreeding Depression ◽

Single Gene ◽

Diallel Cross ◽

Gene Control ◽

Self Incompatibility ◽

S Locus ◽

Fertile Plant ◽

Diallel Crosses ◽

Prezygotic Barriers ◽

Self Fertilization

Abstract Most individuals of Asclepias exaltata are self-sterile, but all plants lack prezygotic barriers to self-fertilization. To determine whether postzygotic rejection of self-fertilized ovules is due to late-acting self-incompatibility or to extreme, early acting inbreeding depression, we performed three diallel crosses among self-sterile plants related as full-sibs. The full-sibs segregated into four compatibility classes, suggesting that late acting self-incompatibility is controlled by a single gene (S-locus). Crosses between plants sharing one or both alleles at the S-locus are incompatible. An additional diallel cross was done among full-sib progeny from a cross of a self-sterile and a self-fertile plant. These progeny grouped into two compatibility classes, and plants within classes displayed varying levels of self-fertility. This suggests that the occasional self-fertility documented in natural pollinations is caused by pseudo-self-fertility alleles that alter the functioning of the S-locus.

Download Full-text