Winning in style: Longer styles receive more pollen, but style length does not affect pollen attrition in wild <i>Clarkia</i> populations

Mazer, Susan J.; Moghaddasi, Arrash; Bello, Alexandra K.; Hove, Alisa A.

doi:10.3732/ajb.1500192

Cited by 21 publications

(36 citation statements)

References 68 publications

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“…Pollen germination rates (measured as the percent of sampled styles in which at least one pollen tube was observed 2.5 h postpollination) were high in both taxa (84% in unguiculata and 94% in xantiana) (Hove and Mazer 2013). Pollen attrition rates (measured as the percent of pollen grains deposited on flower stigmas that fail to reach the style base), in natural populations of these taxa, however, are also high (≥65%) (Mazer et al 2016). Further studies investigating seasonal variation in pollen performance under field conditions are necessary to determine the extent to which environmentally mediated changes in pollen quality affects seed set.…”

Section: Discussionmentioning

confidence: 94%

“…Pollen attrition rates (measured as the percent of pollen grains deposited on flower stigmas that fail to reach the style base), in natural populations of these taxa, however, are also high (≥65%) (Mazer et al. ). Further studies investigating seasonal variation in pollen performance under field conditions are necessary to determine the extent to which environmentally mediated changes in pollen quality affects seed set.…”

Section: Discussionmentioning

confidence: 99%

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Seed set variation in wildClarkiapopulations: teasing apart the effects of seasonal resource depletion, pollen quality, and pollen quantity

Hove

Mazer

Ivey

2016

Ecology and Evolution

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In habitats where resource availability declines during the growing season, selection may favor early‐flowering individuals. Under such ephemerally favorable conditions, late‐blooming species (and individuals) may be particularly vulnerable to resource limitation of seed production. In California, a region prone to seasonal drought, members of the annual genus Clarkia are among the last to flower in the spring. We compared pollen limitation (PL) of seed set and outcrossing rates between early‐ and late‐flowering individuals in two mixed‐mating Clarkia taxa to detect whether flowering time is associated with changes in seed set due to resource depletion, PL, or increased selfing. In 2008–2010, we hand‐pollinated one flower on a total of 1855 individual plants either Early (near the onset of flowering) or Late (near the end of flowering) in the flowering season and compared seed set to adjacent, open‐pollinated flowers on the same stem. To assess the contribution of pollen quality to reproduction, we first (2008) used allozymes to estimate outcrossing rates of seeds produced by Early and Late open‐pollinated flowers. Second (2009), we conducted an anther‐removal experiment to estimate self‐pollen deposition. Seed set in Clarkia unguiculata was not pollen‐limited. Clarkia xantiana ssp. xantiana was pollen‐limited in 2008 and 2010, but not 2009. PL did not differ between Early and Late treatments. In both taxa, seed set of Early flowers was greater than Late flowers, but not due to PL in the latter. Reproduction was generally pollinator‐dependent. Most pollen deposition was xenogamous, and outcrossing rates were >0.7 – and similar between Early and Late periods. These results suggest that pollen receipt and pollen quality remain seasonally consistent. By contrast, the resources necessary to provision seeds decline, reducing the fitness benefits associated with resource allocation to ovules.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Seed set variation in wildClarkiapopulations: teasing apart the effects of seasonal resource depletion, pollen quality, and pollen quantity

Hove

Mazer

Ivey

2016

Ecology and Evolution

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“…For example, negative interactions among pollen genotypes may reduce pollen germination or growth rates, particularly when pollen deposition is high. Physical interference, competition for nutrients, or allelopathic interactions among pollen grains may occur in the stigma or style when space or resources provided by these organs are limited (Cruzan 1986;Holm 1994;Niesenbaum and Schueller 1997;Kerwin and Smith-Huerta 2000;Németh and Smith-Huerta 2002;Parantainen and Pasonen 2004;Mazer et al 2016;Swanson et al 2016). Alternatively, positive interactions among male gametophytes may occur if a minimum number of pollen grains must be deposited to induce the allocation of maternal resources to stigmas or styles, or if pollen grains or pollen tubes interact in a way that promotes their germination or growth (cf.…”

Section: Selectionmentioning

confidence: 99%

Divergence in pollen performance between Clarkia sister species with contrasting mating systems supports predictions of sexual selection

et al. 2018

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Animal taxa that differ in the intensity of sperm competition often differ in sperm production or swimming speed, arguably due to sexual selection on postcopulatory male traits affecting siring success. In plants, closely related self- and cross-pollinated taxa similarly differ in the opportunity for sexual selection among male gametophytes after pollination, so traits such as the proportion of pollen on the stigma that rapidly enters the style and mean pollen tube growth rate (PTGR) are predicted to diverge between them. To date, no studies have tested this prediction in multiple plant populations under uniform conditions. We tested for differences in pollen performance in greenhouse-raised populations of two Clarkia sister species: the predominantly outcrossing C. unguiculata and the facultatively self-pollinating C. exilis. Within populations of each taxon, groups of individuals were reciprocally pollinated (n = 1153 pollinations) and their styles examined four hours later. We tested for the effects of species, population, pollen type (self vs. outcross), the number of competing pollen grains, and temperature on pollen performance. Clarkia unguiculata exhibited higher mean PTGR than C. exilis; pollen type had no effect on performance in either taxon. The difference between these species in PTGR is consistent with predictions of sexual selection theory.

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“…Consequently, 24 h after stigmas first become receptive to pollen a higher frequency of long-styled florets is expected to be present in radiate relative to non-radiate capitula. Mazer et al (2016) recently highlighted the ubiquity of style length variation within and between plant taxa, emphasising its functional significance. In the case of S. vulgaris, our results suggest that style length variation in the species is a side effect of whether self-pollen deposition and germination has occurred or not.…”

Section: Further Considerations and Future Directionsmentioning

confidence: 99%

Self-pollination, style length development and seed set in self-compatible Asteraceae: evidence from Senecio vulgaris L.

Love

Graham

Irwin

et al. 2016

Plant Ecology & Diversity

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Background: Variation in style length has been reported in Senecio vulgaris and has been associated with outcrossing rate. Aims: To determine if (i) long styles lack germinated pollen on stigmas left to self-pollinate, (ii) successful self-pollination causes styles to stop elongating and shrink in length and (iii) seed set increases with the amount of pollen deposited on stigmas. Methods: Determined germinated self-pollen on stigmas of long and short styles after auto-self-pollination; scored style length over 48 h in self-pollinated and non-pollinated florets; recorded seed set after placing different amounts of pollen on stigmas.Results: Most long-styled florets had zero or low amounts of germinated pollen on stigmas in contrast to most short-styled florets. Styles initially elongated to the same length in self-pollinated and non-pollinated florets, then shrank in length in self-pollinated florets while continuing to elongate in non-pollinated florets. Seed set increased with number of pollen grains deposited on stigmas. Conclusions: Successful self-pollen deposition and/or germination on stigmas of S. vulgaris are indicated by presence of short styles, whereas the opposite is indicated by presence of long styles in florets left to self-pollinate. Self-pollination causes styles to shrink after initially elongating. Seed set is dependent on the amount of pollen deposited on stigmas.

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Winning in style: Longer styles receive more pollen, but style length does not affect pollen attrition in wild Clarkia populations

Cited by 21 publications

References 68 publications

Seed set variation in wildClarkiapopulations: teasing apart the effects of seasonal resource depletion, pollen quality, and pollen quantity

Seed set variation in wildClarkiapopulations: teasing apart the effects of seasonal resource depletion, pollen quality, and pollen quantity

Divergence in pollen performance between Clarkia sister species with contrasting mating systems supports predictions of sexual selection

Self-pollination, style length development and seed set in self-compatible Asteraceae: evidence from Senecio vulgaris L.

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