# Nutrient Enrichment Alters Phenotypic Selection on Plant Traits in an Annual Herb on the Tibetan Plateau

## TL;DR

This study shows that adding nutrients to soil can change how plant traits evolve in an alpine meadow on the Tibetan Plateau.

## Contribution

The study reveals that nutrient enrichment alters phenotypic selection on plant traits, influencing floral trait evolution.

## Key findings

- Nutrient addition increased plant height but reduced tube length and nectar production per flower.
- Nitrogen addition favored greater nectar production, altering phenotypic selection patterns.
- Seed number per plant responses to nutrient addition varied between years.

## Abstract

Nutrient enrichment is an increasingly important consequence of anthropogenic activities. Nutrient enrichment can alter the composition, diversity, and functioning of terrestrial plant communities, yet its effect on evolutionary processes in plant populations has been less well studied. To understand the evolutionary consequence of long‐term soil nutrient enrichment, we examine the effects of nutrient addition (N or P) on plant traits, female reproductive success, and pattern of phenotypic selection in the annual plant Pedicularis szetschuanica M. in an alpine meadow on the Tibetan Plateau. Nutrient addition generally increased plant height and reduced tube length and nectar production per flower. Surprisingly, the effects of N and P addition on seed number per plant were reversed between years. Despite variation in traits, mean fitness, and opportunity for selection among nutrient treatments, patterns of selection changed only for nectar production, where we detected N‐mediated selection favoring greater nectar production. This study suggests that nutrient enrichment can alter patterns of phenotypic selection, potentially influencing the evolution of floral traits even if pollinators play a limited role in selection.

This study examined the effects of nutrient addition on plant traits, female reproductive success, and patterns of phenotypic selection in the annual plant Pedicularis szetschuanica M. in alpine meadow on the Tibetan Plateau. The results suggest that nutrient enrichment can alter patterns of phenotypic selection, potentially influencing the evolution of floral traits even if pollinators play a limited role in selection.