Pollinator-Mediated Competition, Reproductive Character Displacement, and the Evolution of Selfing in Arenaria uniflora (Caryophyllaceae)

Fishman, Lila; Wyatt, Róbert E.

doi:10.2307/2640435

Cited by 107 publications

(121 citation statements)

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“…If, however, selfed and outcrossed offspring remain equally fit as they mature and reproduce, selection would actually favour selfing, rather than reduce it (e.g. Schoen et al 1996;Fishman & Wyatt 1999). The current study's plants were larger than those used previously (Carlson 2007b), which helps explain discrepancies in seed production between this and earlier studies.…”

Section: Discussion (A) Sexual Selection Hypothesesmentioning

confidence: 51%

Hummingbird responses to gender-biased nectar production: are nectar biases maintained by natural or sexual selection?

Carlson

2008

Proc. R. Soc. B.

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Pollinators mediate the evolution of secondary floral traits through both natural and sexual selection. Gender-biased nectar, for example, could be maintained by one or both, depending on the interactions between plants and pollinators. Here, I investigate pollinator responses to gender-biased nectar using the dichogamous herb Chrysothemis friedrichsthaliana (Gesneriaceae) which produces more nectar during the male floral phase. Previous research showed that the hummingbird pollinator Phaethornis striigularis visited male-phase flowers more often than female-phase flowers, and multiple visits benefited male more than female fecundity. If sexual selection maintains male-biased rewards, hummingbirds should prefer morerewarding flowers independent of floral gender. If, however, differential rewards are partially maintained through natural selection, hummingbirds should respond to asymmetry with visits that reduce geitonogamy, i.e. selfing and pollen discounting. In plants with male biases, these visit types include single-flower visits and movements from low to high rewards. To test these predictions, I manipulated nectar asymmetry between pairs of real or artificial flowers on plants and recorded foraging behaviour. I also assessed maternal costs of selfing using hand pollinations. For plants with real flowers, hummingbirds preferred more-rewarding flowers and male-phase morphology, the latter possibly owing to previous experience. At artificial arrays, hummingbirds responded to extreme reward asymmetry with increased single-flower visits; however, they moved from high to low rewards more often than low to high. Finally, selfed flowers did not produce inferior seeds. In summary, sexual selection, more so than geitonogamy avoidance, maintains nectar biases in C. friedrichsthaliana, in one of the clearest examples of sexual selection in plants, to date.

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Section: Discussion (A) Sexual Selection Hypothesesmentioning

confidence: 51%

Hummingbird responses to gender-biased nectar production: are nectar biases maintained by natural or sexual selection?

Carlson

2008

Proc. R. Soc. B.

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“…First, less novel species may experience greater competition for pollinators (Fishman and Wyatt 1999;Brown et al 2002;Memmott and Waser 2002;Morales and Traveset 2008;Sargent and Ackerly 2008). Second, novel species may have more attractive floral traits, such as higher nectar production or larger floral displays, than less novel species.…”

Section: Pollen Limitation and Phylogenetic Noveltymentioning

confidence: 98%

A phylogenetically controlled analysis of the roles of reproductive traits in plant invasions

et al. 2011

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Reproductive traits are tightly linked to plant fitness and may therefore be mechanisms driving biological invasions, including the greater success of more phylogenetically novel introduced species in some systems. We present a phylogenetic comparative analysis of "Baker's law'', that introduced plants with the ability to reproduce autogamous or asexually may be better able to establish on introduction. We gathered data from both published and unpublished sources on pollen limitation of 141 species, including 26 introduced species and 115 native species. Our analysis compared differences in the proportion of autonomous autogamy, asexual reproduction, and pollen limitation among native, introduced noninvasive, and introduced invasive plant species, and included the phylogenetic novelty of the introduced species to the native species in that community. Introduced species were more likely to be autogamous than native species, consistent with Baker's law. On the other hand, introduced species were less likely to have the ability to reproduce asexually. Further, among species with no autonomous autogamy, pollen limitation was greater for introduced compared to native species. Such a result is consistent with the idea that plants entering a new continent receive lower quality or quantity of services from resident pollinators than species native to that continent. Finally, more phylogenetically novel invasive species had lower pollen limitation than less novel invasive species, potentially because they experience less competition for pollinators. This is the first evidence that enhanced pollination may be one mechanism driving the greater invasiveness of phylogenetically novel introduced species observed in some systems.

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“…We used the mean number of conspeciWc pollen grains received per stigma per plant as a measure of pollination that could beneWt plant female reproduction, and total pollen grains as a proxy for all pollinator visitation. The mean proportion of conspeciWc pollen received per stigma per plant was considered a measure of pollen quality since heterospeciWc pollen will not produce viable seeds, and in other systems heterospeciWc pollen deposition has been shown to reduce reproduction by clogging stigmas (Fishman and Wyatt 1999). Moreover, a reduction in the mean proportion of conspeciWc pollen received can indicate increased visits by pollinators that show little host-species Wdelity.…”

Section: Evects Of Nectar Alkaloids On Pollinator and Nectar Robber Vmentioning

confidence: 99%

Nectar alkaloids decrease pollination and female reproduction in a native plant

Adler

Irwin

2011

Oecologia

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The evolution of floral traits may be shaped by a community of floral visitors that affect plant fitness, including pollinators and floral antagonists. The role of nectar in attracting pollinators has been extensively studied, but its effects on floral antagonists are less understood. Furthermore, the composition of non-sugar nectar components, such as secondary compounds, may affect plant reproduction via changes in both pollinator and floral antagonist behavior. We manipulated the nectar alkaloid gelsemine in wild plants of the native perennial vine Gelsemium sempervirens. We crossed nectar gelsemine manipulations with a hand-pollination treatment, allowing us to determine the effect of both the trait and the interaction on plant female reproduction. We measured pollen deposition, pollen removal, and nectar robbing to assess whether gelsemine altered the behavior of mutualists and antagonists. High nectar gelsemine reduced conspecific pollen receipt by nearly half and also reduced the proportion of conspecific pollen grains received, but had no effect on nectar robbing. Although high nectar gelsemine reduced pollen removal, an estimate of male reproduction, by one-third, this effect was not statistically significant. Fruit set was limited by pollen receipt. However, this effect varied across sites such that the sites that were most pollen-limited were also the sites where nectar alkaloids had the least effect on pollen receipt, resulting in no significant effect of nectar alkaloids on fruit set. Finally, high nectar gelsemine significantly reduced seed weight; however, this effect was mediated by a mechanism other than pollen limitation. Taken together, our work suggests that nectar alkaloids are more costly than beneficial in our system, and that relatively small-scale spatial variation in trait effects and interactions could determine the selective impacts of traits such as nectar composition.

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Pollinator-Mediated Competition, Reproductive Character Displacement, and the Evolution of Selfing in Arenaria uniflora (Caryophyllaceae)

Cited by 107 publications

References 0 publications

Hummingbird responses to gender-biased nectar production: are nectar biases maintained by natural or sexual selection?

Hummingbird responses to gender-biased nectar production: are nectar biases maintained by natural or sexual selection?

A phylogenetically controlled analysis of the roles of reproductive traits in plant invasions

Nectar alkaloids decrease pollination and female reproduction in a native plant

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