Pollen Shape and Plant Family Trees

ISEF Category: Plant Sciences

Subcategory: Systematics and Evolution  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Pollen can act like a tiny fingerprint. In some plant groups, shape and surface patterns track ancestry, but in others, they do not. If you can compare what you see under a microscope with a family tree, you can ask a real evolutionary question with local plants. That makes this a strong project for a student who wants original research without a university lab.

What Is It?

This project asks whether pollen shape helps predict relatedness inside Asteraceae, the daisy family. You collect plants from local meadows, image their pollen with a Foldscope or USB microscope, and compare traits like size, shape, and surface texture. Then you ask whether species that look similar under the microscope also sit near each other on a molecular phylogeny, which is a family tree built from DNA data.

Think of it like comparing handwriting to a family photo album. Some traits travel through evolution and stay similar in close relatives. Other traits change fast because pollinators, climate, or development push them in different directions. Your job is to test which pattern pollen follows in the plants you sampled.

Why This Is a Good Topic

This topic works well because you can measure visible traits, compare them across species, and test a clear hypothesis about evolution. You do not need a wet lab to start, because public DNA trees and microscope images can give you a strong data set. The project connects to plant identification, pollination, and evolutionary biology, and you can learn image analysis, trait scoring, and basic statistics.

Research Questions

• How does pollen size vary among Asteraceae species from local meadows? ?
• What is the effect of pollen surface texture on similarity to molecular phylogeny? ?
• Does pollen shape cluster species in the same way as DNA-based family trees? ?
• To what extent do closely related Asteraceae species share similar pollen traits? ?
• Which pollen traits best predict branch proximity on a molecular phylogeny? ?
• How does sample location affect pollen trait variation within the same species? ?

Basic Materials

• Foldscope or USB microscope
• Smartphone or laptop camera for image capture
• Clean microscope slides and cover slips
• Fine forceps or tweezers
• Small paper envelopes or coin envelopes for pollen samples
• Plant identification guide for local Asteraceae
• Notebook or spreadsheet for field notes
• Ruler or calibration slide for image scaling
• Gloves and labels for sample tracking

Advanced Materials

• Compound light microscope with camera port
• Scanning electron microscope images from published sources or a university core facility
• Micropipettes and basic pollen prep supplies
• Acetolysis reagents, if approved by your lab and supervisor
• Reference herbarium specimens
• DNA phylogeny software or access to sequence databases
• Image analysis calibration standards
• Statistical software for multivariate trait analysis

Software & Tools

• ImageJ: Measures pollen dimensions, shape ratios, and texture features from microscope images.
• Python: Organizes measurements, runs comparisons, and makes plots for trait clustering.
• R: Handles statistical tests, ordination, and correlation with phylogenetic distance.
• iNaturalist: Helps you identify meadow Asteraceae species before you sample them.
• PubMed: Helps you find review articles and methods papers on pollen morphology and phylogeny.

Experiment Steps

1. Define the Asteraceae species you can sample locally and decide how many individuals per species you will compare.
2. Choose the pollen traits you will score, such as size, outline shape, and surface pattern, and write a repeatable scoring rule.
3. Plan how you will collect and photograph pollen so each image has the same scale, angle, and lighting.
4. Build a trait matrix, then pair it with a molecular phylogeny from published DNA data or public databases.
5. Decide how you will compare visual similarity with evolutionary distance, using correlation, clustering, or another phylogenetic test.
6. Set controls for within-species variation, image quality, and species identification so your results are not just noise.

Common Pitfalls

• Mixing up pollen from different plants during collection, which makes species-level comparisons unreliable.
• Taking images at different magnifications without calibration, which breaks size comparisons across samples.
• Sampling too few individuals per species, which hides real within-species variation.
• Comparing your image-based clusters to an outdated or poorly resolved phylogeny, which can make the pattern look weaker than it really is.
• Scoring pollen shape by eye without a fixed rubric, which adds bias and makes your data hard to defend.

What Makes This Competitive

A stronger project would go beyond simple photo comparison. You could test several pollen traits at once, then use a phylogenetic method that accounts for shared ancestry instead of treating every species as independent. You could also compare local meadow species against a published reference set or test whether habitat or pollination type explains mismatches between pollen and DNA trees. Clean methods, strong statistics, and careful sampling would make the work much more convincing.

Project Variations

• Compare pollen morphology in one meadow Asteraceae genus, such as Solidago or Aster, to see whether one lineage fits the tree better than the full family.
• Test whether native and invasive Asteraceae species differ in pollen trait diversity and whether that affects their placement on a phylogeny.
• Compare pollen images from Foldscope photography and USB microscope photography to see whether the lower-cost setup changes trait measurements.

Learn More

• USDA PLANTS Database: Search for local Asteraceae species, range maps, and plant names to plan field sampling.
• JSTOR Global Plants: Search herbarium specimens and pollen references through an accessible academic database.
• PubMed: Search review articles on pollen morphology, palynology, and Asteraceae phylogeny.
• National Center for Biotechnology Information, NCBI: Use the taxonomy browser and GenBank to find DNA-based plant relationships.
• Plant Systematics textbooks from a library or school library: Read chapters on phylogenetics, character traits, and evolutionary interpretation.