Pollination genetics of the common milkweed, Asclepias syriaca L.

Shore, Joel S.

doi:10.1038/hdy.1993.15

Cited by 29 publications

(31 citation statements)

References 47 publications

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“…Snow (1989) comments on this aspect of a previous study (Piper & Waite, 1988). The potential for clonal geitonogamy (Wyatt, 1981;Pleasants, 1991;Shore, 1993) in conjunction with self-incompatibility (Wyatt, 1976) and the restricted number of sites for pollinia insertion available per flower (Wyatt, 1978;Kahn & Morse, 1991), mean that there is likely to be a nonlinear relationship between the number of pollinia insertions and female fertility. Analysis using selection gradients represents a first-order approximation of this complexity, and is unlikely to mislead when the nonlinear effects are as subtle as those suggested for A. syriaca.…”

Section: Resultsmentioning

confidence: 99%

Selection on reproductive characters: floral morphology in Asclepias syriaca

Morgan

Schoen

1997

Heredity

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Pollinia insertions and removals represent a convenient index of male and female fertilities in the Asclepiadaceae. This fact, in conjunction with regression analysis, allows estimation and comparison of gender-specific selection acting on floral characters in Asciepias syriaca. Univariate regression analysis indicates statistically significant selection on minute aspects of floral morphology through the male and especially female reproductive pathways. Analyses using multiple regression to correct for overall plant size do not qualitatively change the univariate results. The relatively large number of statistically significant selection gradients suggests active adaptation of floral morphological features to the pollinator fauna. Selection through female function differs significantly from selection on the same trait through male function for four traits, emphasizing an antagonism between genders in hermaphrodites. This antagonism and the absence of selection of the antagonistic traits through net fertility are consistent with an equilibrium quantitative genetic perspective, while greater opportunity for selection through female function is counter to expectations based on Bateman's principle of sexual selection.

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Section: Resultsmentioning

confidence: 99%

Selection on reproductive characters: floral morphology in Asclepias syriaca

Morgan

Schoen

1997

Heredity

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“…Schaal (1980) is inserted into a stigmatic chamber (Broyles & Wyatt, 1991;Nilsson et al, 1992;Shore, 1993).…”

Section: Discussionmentioning

confidence: 99%

Comparison of pollinator flight movements and gene dispersal patterns in Mimulus ringens

et al. 1995

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Pollinator movements and pollen-mediated gene dispersal were quantified in experimental populations of square-stemmed monkeyflower (Mimulus ringens), a wetland perennial herb with a mixed-mating system. Each population consisted of genets with unique multilocus combinations of homozygous genotypes, facilitating assignment of paternity to all sampled seeds. Replicate arrays were planted at each of three spacings spanning the range of densities typically observed in natural M. ringens populations. In all six arrays the distribution of gene dispersal distances differed significantly from the distribution of pollinator flight movements. The mean gene dispersal distance was 1.46 times as far as the mean pollinator flight distance. These differences were probably caused by pollen carryover as bumblebees visited up to 12 M. ringens plants on a single foraging trip. Although gene movements exceeded pollinator flight distances, estimates of neighbourhood size were consistently low, ranging from 1.66 to 5.53. Therefore, high levels of random local genetic differentiation are likely in this species.

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“…Geitonogamy is probably very high for swamp milkweed, as it is for other milkweeds (Shore, 1993). Thus, postpollination phenomena, such as competition-dependent fruit abscission (Becerra & Lloyd, 1992), may be important in determining outcrossing rate in this species.…”

Section: Discussionmentioning

confidence: 99%

“…Rates of self-pollination in natural milkweed populations, on the other hand, have been investigated. Using genetic markers, self-pollination rates have been estimated to be as high as 67% for A. syriaca (Shore, 1993). Thus, in natural populations, pollination dynamics appear to impose few barriers to self-fertilization.…”

Section: Introductionmentioning

confidence: 99%

Mating systems and interfertility of swamp milkweed (Asclepias incarnata ssp. incarnata and ssp. pulchra)

1999

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Mating systems and interfertility of swamp milkweed (Asclepias incarnatasspWe investigated the breeding system and interfertility of both subspecies of Asclepias incarnata. We performed hand-pollinations in the glasshouse to compare fruit-set from self-vs. crosspollinations and to assess interfertility in crosses between the subspecies. We also used horizontal starch-gel electrophoresis to infer mating-system parameters from open-pollinated progeny arrays in three natural populations over two consecutive years. Plants of ssp. incarnata were about 1/6 as likely to mature hand self-pollinated fruits as were ssp. pulchra plants.Furthermore, plants varied significantly in both self-and cross-fertility. Fertile offspring resulted from intersubspecific crosses, but hybrid plants showed reduced pollen fertility relative to parental plants, which is similar to what has been reported for wider hybrid crosses among milkweeds. Reduced pollen fertility in hybrids, along with geographical barriers, may contribute to maintaining subspecific differentiation. Based on allozyme markers, naturally pollinated populations were largely outcrossed (t m ranged from 0.881 to 0.986). Plants varied significantly with respect to outcrossed male fertility (r p ranged from 0.186 to 0.396) but not self-fertility (r t was not significantly different from 0). Outcrossing rate did not differ significantly among populations or between years. We found swamp milkweed to be neither fully self-compatible nor self-incompatible, which adds to growing evidence of the complexity of milkweed breeding systems. Variation in frequencies of alleles modifying the expression of the self-incompatibility system could explain some of this complexity.

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Pollination genetics of the common milkweed, Asclepias syriaca L.

Cited by 29 publications

References 47 publications

Selection on reproductive characters: floral morphology in Asclepias syriaca

Selection on reproductive characters: floral morphology in Asclepias syriaca

Comparison of pollinator flight movements and gene dispersal patterns in Mimulus ringens

Mating systems and interfertility of swamp milkweed (Asclepias incarnata ssp. incarnata and ssp. pulchra)

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