Population differences in self‐fertility in the “self‐incompatible” milkweed <i>Asclepias exaltata</i> (Asclepiadaceae)

Lipow, Sara R.; Broyles, Steven B.; Wyatt, Robert

doi:10.2307/2656974

Cited by 30 publications

(19 citation statements)

References 48 publications

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“…Quantitative variation of SI among individuals has often been observed within species (Kokubun et al, 2006;Levin, 1996;Lloyd, 1968;Reinartz and Les, 1994;Stebbins, 1957;Stephenson et al, 2003), and the geographic distribution of individuals categorized by SI strength was also confirmed (Goodwillie and Ness, 2005;Inoue, 1988;Kokubun et al, 2006;Lipow et al, 1999;Lloyd, 1968;Lyons and Antonovics, 1991;Ortiz et al, 2006;Stone et al, 2006;Tsukamoto et al, 1999). These previous studies, however, covered only a few populations (but see Kokubun et al, 2006;Lloyd, 1968) and estimated SI/SC as a qualitative trait, but not a quantitative trait.…”

Section: Discussionmentioning

confidence: 86%

Phylogenetic Relationship between Degree of Self-compatibility and Floral Traits in Lilium longiflorum Thunb. (Liliaceae)

Sakazono

Hiramatsu

Huang

et al. 2012

J. Japan. Soc. Hort. Sci.

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Lilium longiflorum is endemic to the islands of the Ryukyu Archipelago in Japan and to the eastern seacoasts and satellite islands of the mainland of Taiwan. The species is an important ornamental plant, and is cultivated throughout the world. Lilium longiflorum has long been regarded as a self-incompatible species but the existence of selfing in some natural populations was suggested by isozyme analysis in a previous study. To confirm the occurrence of self-compatible individuals and to clarify the evolutionary shift of floral traits associated with degree of self-compatibility in L. longiflorum by comparative analysis, we used 17 populations of L. longiflorum, and two populations of L. formosanum, the genetically closest species of L. longiflorum, covering the entire species distribution. Artificial self-pollination revealed that not all L. longiflorum individuals are self-incompatible and there is substantial quantitative variation of self-incompatibility among L. longiflorum individuals and populations. Self-compatible dominant populations allopatrically and independently evolved at the periphery of the species distribution area, the northern Ryukyu Archipelago and Taiwan. Increasing degree of selfcompatibility in L. longiflorum correlated with reduced corolla length, corolla width, corolla volume, and anther length for the Ryukyu Archipelago, in contrast to only reduced corolla width and volume for Taiwan. Approach between anther and stigma was not observed in any populations. Our data indicate that in the Ryukyu Archipelago increasing degree of self-compatibility evolved floral traits related to mating system evolution, to selfing, that does not depend on adjacency between anther and stigma position, but not in Taiwan.

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Section: Discussionmentioning

confidence: 86%

Phylogenetic Relationship between Degree of Self-compatibility and Floral Traits in Lilium longiflorum Thunb. (Liliaceae)

Sakazono

Hiramatsu

Huang

et al. 2012

J. Japan. Soc. Hort. Sci.

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“…Reproductive assurance is especially important in small populations (Baker, 1955), where low S-allele diversity may limit the number of compatible mates (Byers and Meagher, 1992;Reinartz and Les, 1994;Vallejo-Marín and Uyenoyama, 2004), or where pollinator vectors may be scarce (Barrett et al, 1989;Fausto et al, 2001). Biosystematic work has documented numerous examples of centrally located SI species or populations characterized by large population sizes, with derivative self-compatible (SC) species or populations characterized by colonizing lifestyles or peripheral habitats (Stebbins, 1957;Lloyd, 1980;Barrett and Shore, 1987;Wyatt, 1988;Barrett et al, 1989;Lipow et al, 1999). In several species of South American SI Solanaceae, SC populations have been found only at the periphery of the species ranges (Solanum pennellii, Rick and Tanksley, 1981;Lycopersicon peruvianum, Rick, 1986;L.…”

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confidence: 99%

Variation in the self‐incompatibility response within and among populations of the tropical shrub Witheringia solanacea (Solanaceae)

Stone

Sasuclark

Blomberg

2006

American J of Botany

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Breakdown of genetically enforced self-incompatibility (SI), an extremely common and important evolutionary transition in plants, has conventionally been conceived as a qualitative rather than a quantitative change. We evaluated qualitative and quantitative variation in SI for four populations of Witheringia solanacea in Costa Rica, examining growth of self-pollen tubes in pollinations of buds and mature flowers. We also measured levels of RNase production in styles to determine whether enzyme production was correlated with differences in self-rejection. The two small populations contained both self-compatible (SC) individuals and obligate outcrossers (female or SI). Plants in the two large populations were uniformly SI as revealed by pollen tube growth, although several of these individuals sporadically set seed autogamously. Stylar RNase activity did not differ significantly between bud and mature flowers, but self-pollen tube growth did differ, suggesting that a gene product in addition to S-RNase is responsible for developmental onset of SI. Population-level differences in RNase activity were consistent with differences in the strength of the rejection response in bud pollinations, suggesting that a threshold level of S-RNase, in combination with other factors, is necessary for SI. Our results support a growing body of evidence that not only qualitative variation in SI, but also quantitative variation may be functionally significant.

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“…Although self-pollinations are common on A. syriaca (Pleasants 1991;Shore 1993) and A. exaltata (S. B. Broyles, unpubl. data), both species appear to possess a late-acting self-incompatibility system (Sage and Williams 1991;Lipow 1998;Lipow et al 1999), which inhibits self-fertilization in most flowers. At least one hybrid plant produced from hand-pollination and grown in cultivation is known to be self-compatible (S. B. Broyles, unpubl.…”

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confidence: 99%

Hybrid Bridges to Gene Flow: A Case Study in Milkweeds (Asclepias)

Broyles¹

2002

Evolution

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Abstract. Natural hybridization occurs throughout areas of sympatry for the North American milkweeds Asclepias exaltata and A. syriaca (Asclepiadaceae), even though the formation of F 1 hybrid seed is a rare event. For introgressive hybridization to proceed, F 1 and advanced hybrids must be released from reproductive barriers and successfully mate with one or both parental species. I investigated the mating system of natural hybrids between A. exaltata and A. syriaca in three populations in Shenandoah National Park, Virginia. Allozyme data and a maximum-likelihood procedure were used to estimate the frequency of six genotypic classes (parentals, F 1 , F 2 , and backcrosses) of the hybridizing populations, the pollinia received by hybrid plants, and the paternal parents of seeds produced by hybrids. F 1 hybrids, backcross A. syriaca, and parental A. syriaca individuals were common in three hybrid populations. Even though self-pollinations and interhybrid pollinations were common, F 2 seed production and the occurrence of F 2 individuals were rare in hybrid populations. Hybrid plants received more pollen from A. syriaca than A. exaltata, which resulted in the production of more backcross-A. syriaca seed than backcross-A. exaltata seed. Asclepias exaltata was rare in the hybrid populations, but A. exaltata pollinia were received by hybrids and this species sired between 15% and 36% of the seeds produced on hybrids. The potential for introgression with A. exaltata populations is lower because this species is unsuccessful as the maternal parent in interspecific and backcross hand-pollinations. The asymetry of hybridization with A. syriaca as the maternal parent is further supported by the incorporation of maternally inherited chloroplast DNA markers in hybrids. Hybrid milkweeds frequently backcross with both parental species and may be released from the reproductive barriers that limit the formation of F 1 hybrids in natural populations. The direction of interspecific gene flow and introgression in milkweeds is influenced by the reproductive biology of hybrids, the constituency of the surrounding population, and failure of some crosses to produce seeds. Finally, introgressive hybridization remains an important evolutionary force even when the initial formation of F 1 hybrids in natural populations is rare.

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Population differences in self‐fertility in the “self‐incompatible” milkweed Asclepias exaltata (Asclepiadaceae)

Cited by 30 publications

References 48 publications

Phylogenetic Relationship between Degree of Self-compatibility and Floral Traits in Lilium longiflorum Thunb. (Liliaceae)

Phylogenetic Relationship between Degree of Self-compatibility and Floral Traits in Lilium longiflorum Thunb. (Liliaceae)

Variation in the self‐incompatibility response within and among populations of the tropical shrub Witheringia solanacea (Solanaceae)

Hybrid Bridges to Gene Flow: A Case Study in Milkweeds (Asclepias)

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