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

Abstract

Abiotic environmental factors are predicted to affect plant traits and the intensity of plant-pollinator interactions. However, knowledge of their potential effects on pollinator-mediated selection on floral traits is still limited. We separately estimated the effects of soil water (two sites with different soil water contents) and N-P-K nutrient availability (different levels of nutrient addition) on pollinator-mediated selection on floral traits of Primula tibetica (an insect-pollinated perennial herbaceous species). Our results demonstrated that floral traits, plant reproductive success and pollinator-mediated selection on floral traits varied between sites with different soil water contents and among different levels of nutrient addition. The strength of pollinator-mediated selection was stronger at the site with low soil water content than at the site with high soil water content, and first decreased and then increased with increasing N-P-K nutrient addition. Our results support the hypothesis that abiotic environmental factors influence the importance of pollinators in shaping floral evolution.

Soil water and nutrient availability interactively modify pollinator‐mediated directional and correlational selection on floral display

“…Soil water and nutrient availability influenced plant trait expression, plant reproductive success and pollinator-mediated selection on floral display, and effects on reproductive success and selection were nonadditive. This demonstrates that the occurrence and magnitude of pollinator-mediated selection can strongly depend Soil water and nutrient availability are predicted to influence trait expression and plant reproductive success in similar ways (Burkle & Runyon, 2016;Friberg et al, 2017;Descamps et al, 2018;Wu et al, 2022), but to what extent the effect of one factor depends on the other has been little explored. Our results demonstrate interactive effects on fitness, the strength of pollen limitation, the covariance between trait and fitness, and the resulting phenotypic selection on floral display in P. tibetica.…”

“…Soil water and nutrient availability are predicted to influence trait expression and plant reproductive success in similar ways (Burkle & Runyon, 2016; Friberg et al ., 2017; Descamps et al ., 2018; Wu et al ., 2022), but to what extent the effect of one factor depends on the other has been little explored. Our results demonstrate interactive effects on fitness, the strength of pollen limitation, the covariance between trait and fitness, and the resulting phenotypic selection on floral display in P. tibetica .…”

“…However, several studies have documented that pollinator‐mediated selection on floral traits varies in space and time (Sletvold & Ågren, 2010; Chapurlat et al ., 2015; Wu & Li, 2017; Wu et al ., 2018), reflecting that plants live in complex and variable biotic and abiotic environments. The variation in strength and form of selection could be due not only to variation in the interaction intensity with pollinators (Sletvold & Ågren, 2014, 2016; Emel et al ., 2017; Trunschke et al ., 2017), but also to variation in interactive effects of other environmental factors, such as herbivory (Gómez, 2003; Ågren et al ., 2013; Sletvold et al ., 2015), reproductive assurance (Teixido & Aizen, 2019), co‐occurring species (Caruso, 2000; Eisen et al ., 2020) and soil resource availability (Sletvold et al ., 2017; Wu et al ., 2022). However, most studies focus on pollination in isolation, and the combined effects of several potential selective factors are poorly documented (reviewed in Sletvold, 2019).…”

“…In natural populations, the effects of multiple abiotic factors are particularly poorly known. Two abiotic environmental factors that are expected to have major and similar impacts on plant trait expression and reproductive success are soil water and nutrient availability (Murren et al ., 2005; Nicotra et al ., 2007; Wu et al ., 2022). First, both factors can affect plant reproductive success via pollination, by influencing floral traits (e.g.…”

“…The experiment was conducted in two sites that differed in soil water content (natural vs addition). Previous work has shown that P. tibetica produces taller plants with more and larger flowers, and higher seed production, at sites with abundant nutrients and high soil water content than at nutrient‐poor sites with low water availability (Wu et al ., 2022). Consequently, we expect that both environmental factors can influence plant fitness via attractiveness of flowers to pollinators and via direct effects on size.…”