Style Length, Pollination, and Fitness in *Nemophila menziesii*

A field-based ecology and evolution research project exploring plant reproductive traits, presented at the UCSB EEMB Undergraduate Research Symposium.

Research Overview

Project Title: Style Length, Pollen Deposition, and Reproductive Fitness for a Native California Wildflower
Presented at: UCSB EEMB Undergraduate Research Symposium (April 2023)
Affiliation: Mazer Lab, Department of Ecology, Evolution, and Marine Biology
Mentors: Helen Payne, Dr. Susan Mazer

This project investigated whether a physical floral trait—style length—affects pollination success and reproductive fitness in Nemophila menziesii, a native California wildflower dependent on insect pollinators. It integrates concepts from plant ecology, evolution, and reproductive biology to explore how morphology influences fitness in wild populations.

Research Questions

  1. Does style length influence:

    • a) the amount of pollen deposition?
    • b) lifetime fecundity (total fruit count × mean seeds per fruit)?

  2. Is longer style length under positive selection in this wild population?

Methods

Field Data Collection

  • 683 floral styles collected from 118 plants at the Hastings Natural History Reservation (Spring 2022)
  • Study site represented a typical drought year, influencing resource availability

Lab Techniques

  • Pollen Staining using Alexander’s stain to distinguish viable vs non-viable grains
  • Microscopy to quantify 60,929 pollen grains
  • Digital Morphometrics:
    • Used ImageJ to photograph and calibrate style measurements with a digital scale

Statistical Analysis

  • Multiple regression models to evaluate relationships between:
    • Style length and pollen deposition
    • Pollen deposition and lifetime fecundity
  • Controlled for covariates such as stem biomass, corolla size, and block effects

Results

  • Style length was positively associated with pollen deposition
  • No significant relationship between pollen deposition and lifetime fecundity
  • Suggests longer styles were not under directional selection in this season
Style Length ↑ ⇒ Pollen Deposition ↑
But ⇒ No Effect on Lifetime Fecundity