An official website of the United States government
Abstract PremiseReproductive fitness in plants is often determined by the quantity and quality of pollen transferred by pollinators. However, many fitness studies measure only female fitness or rely on proxies for male fitness. Here we assessed how five bee taxon groups affect male fitness in a prairie plant by quantifying pollen removal, visitation, and siring success using paternity assignments and a unique pollinator visitation experiment. MethodsInEchinacea angustifolia, we measured per‐visit pollen removal for each pollinator taxon and estimated the number of pollen grains needed for successful ovule fertilization. Additionally, we directly measured pollinator influence on siring by allowing only one bee taxon to visit each pollen‐donor plant, while open‐pollinated plants acted as unrestricted pollen recipients. We genotyped the resulting offspring, assigned paternity, and used aster statistical models to quantify siring success. ResultsSiring success of pollen‐donor plants differed among the five pollinator groups. Nongrooming male bees were associated with increased siring success. Bees from all taxa removed most of the flowering head's pollen in one visit. However, coneflower‐specialist beeAndrena helianthiformisremoved the most pollen per visit. Female fitness and proxy measures of male fitness, such as pollinator visitation and pollen removal, did not align with our direct quantifications of male fitness. ConclusionsOur results illustrate the need for more studies to directly quantify male fitness, and we caution against using male fitness proxy measures. In addition, conservation efforts that preserve a diverse pollinator community can benefit plants in fragmented landscapes.
more »
« less
Pollination intensity and paternity in flowering plants
Abstract Background Siring success plays a key role in plant evolution and reproductive ecology, and variation among individuals creates an opportunity for selection to act. Differences in male reproductive success can be caused by processes that occur during two stages, the pollination and post-pollination phases of reproduction. In the pollination phase, heritable variation in floral traits and floral display affect pollinator visitation patterns, which in turn affect variation among plants in the amount of pollen exported and deposited on recipient stigmas. In the post-pollination phase, differences among individuals in pollen grain germination success and pollen tube growth may cause realized paternity to differ from patterns of pollen receipt. The maternal plant can also preferentially provision some developing seeds or fruits to further alter variation in siring success. Scope In this review, we describe studies that advance our understanding of the dynamics of the pollination and post-pollination phases, focusing on how variation in male fitness changes in response to pollen limitation. We then explore the interplay between pollination and post-pollination success, and how these processes respond to ecological factors such as pollination intensity. We also identify pressing questions at the intersection of pollination and paternity and describe novel experimental approaches to elucidate the relative importance of pollination and post-pollination factors in determining male reproductive success. Conclusions The relative contribution of pollination and post-pollination processes to variation in male reproductive success may not be constant, but rather may vary with pollination intensity. Studies that quantify the effects of pollination and post-pollination phases in concert will be especially valuable as they will enable researchers to more fully understand the ecological conditions influencing male reproductive success.
more »
« less
- PAR ID:
- 10136598
- Date Published:
- Journal Name:
- Annals of Botany
- Volume:
- 125
- Issue:
- 1
- ISSN:
- 0305-7364
- Page Range / eLocation ID:
- 1 to 9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Arceo-Gómez, Gerardo (Ed.)Abstract Researchers have long assumed that plant spatial location influences plant reproductive success and pollinator foraging behaviour. For example, many flowering plant populations have small, linear or irregular shapes that increase the proportion of plants on the edge, which may reduce mating opportunities through both male and female function. Additionally, plants that rely on pollinators may be particularly vulnerable to edge effects if those pollinators exhibit restricted foraging and pollen carryover is limited. To explore the effects of spatial location (edge vs. interior) on siring success, seed production, pollinator foraging patterns and pollen-mediated gene dispersal, we established a square experimental array of 49 Mimulus ringens (monkeyflower) plants. We observed foraging patterns of pollinating bumblebees and used paternity analysis to quantify male and female reproductive success and mate diversity for plants on the edge versus interior. We found no significant differences between edge and interior plants in the number of seeds sired, mothered or the number of sires per fruit. However, we found strong differences in pollinator behaviour based on plant location, including 15 % lower per flower visitation rates and substantially longer interplant moves for edge plants. This translated into 40 % greater pollen-mediated gene dispersal for edge than for interior plants. Overall, our results suggest that edge effects are not as strong as is commonly assumed, and that different plant reproduction parameters respond to spatial location independently.more » « less
-
Abstract PremiseCo‐occurring plant species that share generalist pollinators often exchange pollen. This heterospecific pollen transfer (HPT) impacts male and female reproductive success through pollen loss and reductions in seed set, respectively. The resulting fitness cost of HPT imposes selection on reproductive traits (e.g., floral color and shape), yet we currently lack strong predictors for the post‐pollination fate of heterospecific pollen, especially within community and phylogenetic contexts. MethodsWe investigated the fate of heterospecific pollen at three distinct stages of plant reproduction: (1) pollen germination on the stigma, (2) pollen tube growth in the style, and (3) fertilization of ovules. We experimentally crossed 11 naturally co‐flowering species in the subalpine meadows of the Colorado Rocky Mountains, across a spectrum of phylogenetic relatedness. Using generalized linear mixed models and generalized linear models, we evaluated the effect of parental species identity and phylogenetic relatedness on pollen tube growth at each reproductive stage. ResultsWe found that heterospecific pollen tubes can germinate and grow within pistils at each reproductive stage, even when parental species are >100 My divergent. There was no significant effect of phylogenetic distance on heterospecific pollen success, and no evidence for a mechanism that suspends heterospecific pollen germination or pollen tube growth within heterospecific stigmas or styles. ConclusionsOur results show that even in communities where HPT is common, pre‐zygotic post‐pollination mechanisms do not provide strong barriers to interspecific fertilization. HPT can result in the loss of ovules even between highly diverged plant species.more » « less
-
Abstract Pollen protein content has been demonstrated to be an essential nutritional component for bees and thus important in mediating plant–pollinator interactions. However, little is known on the drivers and consequences of among‐species variation in pollen protein content and how this can impact male and female reproductive success across plant species. Among‐species variation in resources allocated to pollen nutrition could further be constrained by life‐history strategies (e.g. survival‐reproduction trade‐offs) or evolutionary history.Here, we surveyed pollen protein content for 29 species within a diverse co‐flowering community and evaluated the effect of pollen protein on male and female reproductive success. We also tested the role of life history (annuals vs. perennials) and phylogeny in mediating differences in resource allocation to pollen nutrition.We found that pollen protein content influences components of male (bee visitor abundance and pollen dispersal) but not female (conspecific pollen deposition and pollen tube growth) reproductive success, suggesting this trait affects plants only via male function. This sex‐specific effect further suggests the potential for sexual conflicts driven by differential investment on this trait. We found no phylogenetic signal on pollen protein content. However, pollen protein content was higher in annual compared to perennial species suggesting survival versus reproduction trade‐offs also contribute to variation in pollen protein at the community level.Our study underscores the importance of understanding the ecological and evolutionary drivers of pollen protein content across plant species. Our results further suggest the existence of sexual conflicts and ecological trade‐offs mediated by differential investment in pollen nutritional quality, with important implications for community assembly and the structure of plant–pollinator interactions. Read the freePlain Language Summaryfor this article on the Journal blog.more » « less
-
Abstract PremiseChanges to flowering time caused by climate change could affects plant fecundity, but studies that compare the individual‐level responses of phenologically distinct, co‐occurring species are lacking. We assessed how variation in floral phenology affects the fecundity of individuals from three montane species with different seasonal flowering times, including in snowmelt acceleration treatments to increase variability in phenology. MethodsWe collected floral phenology and seed set data for individuals of three montane plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima). To examine the drivers of seed set, we measured conspecific floral density and conducted pollen limitation experiments to isolate pollination function. We advanced the phenology of plant communities in a controlled large‐scale snowmelt acceleration experiment. ResultsDifferences in individual phenology relative to the rest of the population affected fecundity in our focal species, but effects were species‐specific. For our early‐season species, individuals that bloomed later than the population peak bloom had increased fecundity, while for our midseason species, simply blooming before or after the population peak increased individual fecundity. For our late‐season species, blooming earlier than the population peak increased fecundity. The early and midseason species were pollen‐limited, and conspecific density affected seed set only for our early‐season species. ConclusionsOur study shows that variation in individual phenology affects fecundity in three phenologically distinct montane species, and that pollen limitation may be more influential than conspecific density. Our results suggest that individual‐level changes in phenology are important to consider for understanding plant reproductive success.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/aob/mcz159
