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

Ivey, Christopher T.; Lipow, Sara R.; Wyatt, Robert

doi:10.1038/sj.hdy.6884530

Cited by 22 publications

(14 citation statements)

References 26 publications

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“…Indeed, only one other milkweed species has been found to have a completely self-compatible breeding system, namely A. incarnata (Swamp Milkweed). In studies of this species, Kephart (1981) documented nearly equivalent success rates of fruit-set in crossed treatments as compared to selfed treatments in a handpollination experiment, whereas Ivey et al (1999) found cross-pollinations to be more successful than self-pollinations in hand-pollination experiments as well as in open-pollinated progeny arrays.…”

Section: Discussionmentioning

confidence: 85%

Modes of reproduction in three invasive milkweeds are consistent with Baker’s Rule

2011

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According to Baker's Rule, uniparental reproduction is associated with colonizing plants because it provides a means for population establishment following single long-distance dispersal events. There is, however, limited evidence for the applicability of Baker's Rule to invasive plants. We determined the breeding systems of three invasive milkweed speciesAsclepias curassavica, Gomphocarpus fruticosus and G. physocarpus-in their invaded range in south-east Queensland, Australia. Although dependent on pollinators for reproduction, hand-pollinations revealed that all three species are self-compatible which is consistent with Baker's Rule and notable because milkweeds are generally self-incompatible. In progeny performance trials, seedlings from self-pollinations generally did not perform as well as those from cross-pollinations, but the differences were minor. Evidence for self-compatibility in G. physocarpus is a particularly noteworthy feature of this study, as this species has been reported to be selfincompatible in its native range and may thus have evolved self-compatibility during the invasion process. Furthermore, potential for hybridization between the two Gomphocarpus species was observed. Hybridization may have assisted the invasion of these species through providing additional sources of pollen and/or broadening genetic variation. Our study adds to the growing evidence that breeding systems are significant for the process of plant invasion.

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Section: Discussionmentioning

confidence: 85%

Modes of reproduction in three invasive milkweeds are consistent with Baker’s Rule

2011

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“…In all of these calculations, we included values of zero for flowers that did not set fruit, except in the case of A. incarnata hand-pollinated controls, for which we included only flowers that produced fruits or were known to have aborted fruits, because we suspect that many of our hand pollinations were unsuccessful. Although fruit set from hand pollinations under ideal greenhouse conditions is typically low (<50%) in this species (Ivey et al 1999), our hand pollinations were successful for only 2, 3, 7, 5, and 18 flowers in each phenological treatment; thus, fruit set was as low as 3% for some of our treatment groups (data not shown). We used the seed set of one open-pollinated flower per field control plant that produced at least one mature fruit, including zero values for each field control plant that did not produce fruit, as an additional gauge of the maximum pollination success of A. incarnata on any given field day.…”

Section: Methodsmentioning

confidence: 87%

“…Although A. incarnata populations vary in levels of self incompatibility (Ivey et al 1999), they are nonautogamous and therefore dependent on insects, with paired umbels of small pink flowers that produce nectar as the sole reward. Plants flower from late June to mid-August in our study area.…”

Section: Methodsmentioning

confidence: 99%

Pollinator effectiveness varies with experimental shifts in flowering time

Rafferty

Ives

2012

Ecology

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The earlier flowering times exhibited by many plant species are a conspicuous sign of climate change. Altered phenologies have caused concern that species could suffer population declines if they flower at times when effective pollinators are unavailable. For two perennial wildflowers, Tradescantia ohiensis and Asclepias incarnata, we used an experimental approach to explore how changing phenology affects the taxonomic composition of the pollinator assemblage and the effectiveness of individual pollinator taxa. After finding in the previous year that fruit set varied with flowering time, we manipulated flowering onset in greenhouses, placed plants in the field over the span of five weeks, and measured pollinator effectiveness as the number of seeds produced after a single visit to a flower. The average effectiveness of pollinators and the expected rates of pollination success were lower for plants of both species flowering earlier than for plants flowering at historical times, suggesting there could be reproductive costs to earlier flowering. Whereas for A. incarnata, differences in average seed set among weeks were due primarily to changes in the composition of the pollinator assemblage, the differences for T. ohiensis were driven by the combined effects of compositional changes and increases over time in the effectiveness of some pollinator taxa. Both species face the possibility of temporal mismatch between the availability of the most effective pollinators and the onset of flowering, and changes in the effectiveness of individual pollinator taxa through time may add an unexpected element to the reproductive consequences of such mismatches.

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“…Compatibility in milkweeds may vary among individuals and populations (cf. Ivey et al 1999;Lipow & Wyatt 2000). Even in self-compatible milkweeds, cross-pollination usually produces higher fruit set (Ivey et al 1999;Lipow & Wyatt 2000).…”

Section: Discussionmentioning

confidence: 98%

A test for Allee effects in the self‐incompatible wasp‐pollinated milkweedGomphocarpus physocarpus

Coombs¹,

Peter²,

Johnson

2009

Austral Ecology

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It has been suggested that plants that are good colonizers will generally have either an ability to self-fertilize or a generalist pollination system. This prediction is based on the idea that these reproductive traits should confer resistance to Allee effects in founder populations and was tested using Gomphocarpus physocarpus (Asclepiadoideae: Apocynaceae), a species native to South Africa that is invasive in other parts of the world. We found no significant relationships between the size of G. physocarpus populations and various measures of pollination success (pollen deposition, pollen removal and pollen transfer efficiency) and fruit set. A breeding system experiment showed that plants in a South African population are genetically self-incompatible and thus obligate outcrossers. Outcrossing is further enhanced by mechanical reconfiguration of removed pollinaria before the pollinia can be deposited. Self-pollination is reduced when such reconfiguration exceeds the average duration of pollinator visits to a plant. Observations suggest that a wide variety of wasp species in the genera Belonogaster and Polistes (Vespidae) are the primary pollinators. We conclude that efficient pollination of plants in small founding populations, resulting from their generalist wasp-pollination system, contributes in part to the colonizing success of G. physocarpus. The presence of similar wasps in other parts of the world has evidently facilitated the expansion of the range of this milkweed.

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

Cited by 22 publications

References 26 publications

Modes of reproduction in three invasive milkweeds are consistent with Baker’s Rule

Modes of reproduction in three invasive milkweeds are consistent with Baker’s Rule

Pollinator effectiveness varies with experimental shifts in flowering time

A test for Allee effects in the self‐incompatible wasp‐pollinated milkweedGomphocarpus physocarpus

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