Pollinator-mediated selection on floral traits varies in space and between morphs in Primula secundiflora

Abstract

Elucidating how variation in selection shapes the evolution of flowers is key to understanding adaptive differentiation processes. We estimated pollinator-mediated selection through female function in L-morph (long-style and short-anther phenotype) and S-morph (short-style and long-anther phenotype) flowers among four Primula secundiflora populations with different pollinator assemblages. Variation in pollinator assemblage strongly contributed to differences in reproductive success among populations and between morphs of the primrose species. A wider corolla tube width was selected in the bumblebee-dominated populations, whereas shorter corolla tube length and wider corolla tube width were selected in the syrphid fly-dominated populations. Morph-specific variation in pollinator-mediated selection on corolla tube length was detected in the syrphid fly-dominated populations. A shorter corolla tube was selected in the L-morph flowers. However, similar selective pressure on this trait was not observed in the S-morph flowers. These results show that variation in pollinator assemblage leads to variation in selection in space and between morphs. The findings highlight the potential forces of different pollinator agents in driving floral evolution in this primrose species.

Pollinator-Mediated Selection on Floral Traits of Primula tibetica Differs Between Sites With Different Soil Water Contents and Among Different Levels of Nutrient Availability

“…One goal of evolutionary ecologists is to understand and predict floral evolutionary responses in complex biotic and abiotic environments ( Smith, 2010 ; Dalrymple et al, 2020 ). For biotic factors such as pollinators, an increasing number of studies have highlighted their critical role in driving spatial and temporal variation in floral differentiation ( Parachnowitsch and Kessler, 2010 ; Van der Niet et al, 2014 ; Wu et al, 2018 ). Pollinators generate selection pressures on many floral traits, including flowering phenology, floral display and traits affecting pollination efficiency ( Sandring and Ågren, 2009 ; Phillips et al, 2017 ; Sletvold et al, 2017 ).…”

The Context Dependence of Pollinator-Mediated Selection in Natural Populations

“…populations to determine which aspect is the most interesting. Studies of selection on floral traits in multiple populations or years are still surprisingly few, but existing examples involve the quantification of selection on floral traits in populations that vary in grazing pressure (Gómez and Zamora 2000;Ågren et al 2013), population size (Weber and Kolb 2013), seed predation (Kolb and Ehrlen 2010), coflowering community (Caruso 2000;2002), soilmicroenvironment (Carusoet al 2003), climate (Campbell and Powers 2015), altitude (Gross et al 2016), and pollinator assembly (Galen 1989;Gómez et al 2008Gómez et al , 2009Sletvold et al 2012;Chapurlat et al 2015;Wu and Li 2017;Wu et al 2018). Although this approach cannot pinpoint additional selective agents, it yields information on the scale and extent of variation in selection on floral traits, which in itself is interesting, and it may suggest what traits or environmental factors would be most interesting to explore to conclusively determine targets and agents of selection in a specific system.…”

“…Recent experimental approaches that quantify current pollinatormediated selection on floral traits have shown that the proportion of net selection that can be ascribed to pollinators varies widely among studies, as well as among populations, years, and traits within studies (e.g., Caruso et al 2010;Parachnowitsch and Kessler 2010;Bartkowska and Johnston 2012;Weber and Kolb 2013;Sletvold and Ågren 2014;Lavi and Sapir 2015;Chapurlat et al 2015, forthcoming;Zhao et al 2016;Paudel et al 2016;Trunschke et al 2017;Wu et al 2018). What factors are responsible for the nonpollinator-mediated selection, and how can we quantify the influence of additional factors?…”

Herbivore-Mediated Selection on Floral Display Covaries Nonlinearly With Plant-Antagonistic Interaction Intensity Among Primrose Populations

“…Spatial variation in selection is an important underlying mechanism of many evolutionary patterns and processes including the maintenance of heritable variation in quantitative traits ( Grant and Price, 1981 ), coevolutionary interactions ( Paudel et al, 2016 ), and the geographical differentiation of floral traits leading to speciation ( Siepielski et al, 2013 ). Numerous studies have shown the critical role of plant-pollinator interactions (mutualists) in contributing to spatial variation in natural selection on floral traits ( Chapurlat et al, 2015 ; Wu and Li, 2017 ; Wu et al, 2018 ). In addition to plant-pollinator interactions, plant populations often experience among-population variation in herbivory (antagonists), which can also contribute to spatial variation in natural selection acting on floral traits ( Vanhoenacker et al, 2013 ).…”