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1. Pollinators differ in their contribution to the male fitness of a self‐incompatible composite

   https://doi.org/10.1002/ajb2.16190  

   Pearson, Avery E. ; Zelman, Zeke ; Hill, Lauryn A. ; Stevens, Mia A. ; Jackson, Evan X. ; Incarnato, Miyauna M. ; Johnson, Ren M. ; Wagenius, Stuart ; Ison, Jennifer L. ( June 2023 , American Journal of Botany)

   Reproductive 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.

   InEchinacea 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.

   Siring 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.

   Our 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.

    

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2. Edge effects and mating patterns in a bumblebee-pollinated plant

   https://doi.org/10.1093/aobpla/plaa033  

   Christopher, Dorothy A ; Mitchell, Randall J ; Trapnell, Dorset W ; Smallwood, Patrick A ; Semski, Wendy R ; Karron, Jeffrey D ( August 2020 , AoB PLANTS)

   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. 

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3. Differences in individual flowering time change pollen limitation and seed set in three montane wildflowers

   https://doi.org/10.1002/ajb2.16123  

   Schiffer, Annie ; Loy, Xingwen ; Morozumi, Connor ; Brosi, Berry J. ( March 2023 , American Journal of Botany)

   Changes 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.

   We 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.

   Differences 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.

   Our 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.

    

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4. Where are the beachmasters? Unexpectedly weak polygyny among southern elephant seals on a South Shetland Island

   https://doi.org/10.1111/jzo.12936  

   Nichols, H. J. ; Fuchs, B. ; Paijmans, A. J. ; Lewis, G. ; Bonin, C. A. ; Goebel, M. E. ; Hoffman, J. I. ( November 2021 , Journal of Zoology)

   Intraspecific variation in animal mating systems can have important implications for ecological, evolutionary and demographic processes in wild populations. For example, patterns of mating can impact social structure, dispersal, effective population size and inbreeding. However, few species have been studied in sufficient detail to elucidate mating system plasticity and its dependence on ecological and demographic factors. Southern elephant seals (Mirounga leonina) have long been regarded as a textbook example of a polygynous mating system, with dominant ‘beachmaster’ males controlling harems of up to several hundred females. However, behavioural and genetic studies have uncovered appreciable geographic variation in the strength of polygyny among elephant seal populations. We, therefore, used molecular parentage analysis to investigate patterns of parentage in a small satellite colony of elephant seals at the South Shetland Islands. We hypothesised that dominant males would be able to successfully monopolise the relatively small numbers of females present in the colony, leading to relatively high levels of polygyny. A total of 424 individuals (comprising 33 adult males, 101 adult females and 290 pups) sampled over 8 years were genotyped at 20 microsatellites and reproductive success was analysed by genetically assigning parents. Paternity could only be assigned to 31 pups (10.7%), despite our panel of genetic markers being highly informative and the genotyping error rate being very low. The strength of inferred polygyny was weak in comparison to previous genetic studies of the same species, with the most successful male fathering only seven pups over the entire course of our study. Our results show that, even in a species long regarded as a model for extreme polygyny, male reproductive skew can vary substantially among populations.

    

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5. Hermaphroditism promotes mate diversity in flowering plants

   https://doi.org/10.1002/ajb2.1336  

   Christopher, Dorothy A. ; Mitchell, Randall J. ; Trapnell, Dorset W. ; Smallwood, Patrick A. ; Semski, Wendy R. ; Karron, Jeffrey D. ( August 2019 , American Journal of Botany)

   Genetically diverse sibships are thought to increase parental fitness through a reduction in the intensity of sib competition, and through increased opportunities for seedling establishment in spatially or temporally heterogeneous environments. Nearly all research on mate diversity in flowering plants has focused on the number of fathers siring seeds within a fruit or on a maternal plant. Yet as hermaphrodites, plants can also accrue mate diversity by siring offspring on several pollen recipients in a population. Here we explore whether mate composition overlaps between the dual sex functions, and discuss the implications for plant reproductive success.

   We established an experimental population of 49Mimulus ringens(monkeyflower) plants, each trimmed to a single flower. Following pollination by wild bees, we quantified mate composition for each flower through both paternal and maternal function. Parentage was successfully assigned to 240 progeny, 98% of the sampled seeds.

   Comparison of mate composition between male and female function revealed high mate diversity, with almost no outcross mates shared between the two sexual functions of the same flower.

   Dual sex roles contribute to a near doubling of mate diversity in our experimental population ofMimulus ringens. This finding may help explain the maintenance of hermaphroditism under conditions that would otherwise favor the evolution of separate sexes.

    

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