Oak Leaf Shape Hybridization Study

ISEF Category: Plant Sciences

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

The Hook

Oak leaves can fool even experts. Two trees that look different may belong to the same group, while hybrids can sit right in the middle. Your job is to turn those shapes into numbers and see whether the leaves match public DNA IDs. That gives you a real shot at asking a question botanists care about.

What Is It?

This project asks whether leaf shape can help you spot hybrid oaks in a backyard population. Hybridization means two species cross and produce offspring with mixed traits. In oaks, that mix can show up in leaf lobes, leaf width, and the angle between veins and the blade. Think of it like face recognition for trees, except you are using leaf landmarks instead of eyes and noses.

Geometric morphometrics is the method that turns shape into data. You place the same set of points, called landmarks, on each leaf image, then compare the patterns across samples. TPS-Dig helps you record those points, and public DNA barcode records help you check whether the shapes line up with genetic IDs. If the leaf clusters match the DNA labels, that supports the idea that shape carries useful evolutionary signal. If they do not, that gives you a more interesting story, because oak shape may be messy, local, or hybrid-driven.

Why This Is a Good Topic

This is a strong science fair topic because you can test a real biological question with accessible tools. Leaves are easy to collect, photograph, and measure, and public DNA barcode databases let you compare your shape data with genetic IDs without running your own sequencing lab. You can learn sampling, landmark design, image analysis, and basic statistics in one project. The topic also connects to plant evolution, species ID, and hybridization, which makes the results feel bigger than one backyard tree.

Research Questions

• How does leaf shape vary among oak trees in a single backyard population?
• What is the effect of suspected hybrid status on leaf landmark coordinates?
• Does leaf shape cluster more strongly by DNA barcode ID than by tree location?
• To what extent can geometric morphometrics separate local oak groups that look similar to the eye?
• Which leaf landmarks best distinguish putative hybrid oaks from nonhybrid oaks?
• What is the effect of leaf position on the tree on shape measurements in oak samples?
• Does leaf shape predict public DNA barcode assignment better than simple leaf length and width?

Basic Materials

• Smartphone or digital camera with a fixed photo mode
• Plain white paper or a neutral background board
• Ruler or metric scale bar for photos
• Clipboard or notebook for field notes
• Fine-tip marker or small labels for sample IDs
• Clear tape or weighing paper for flattening leaves
• Computer with free image viewing and spreadsheet software
• TPS-Dig free software for landmark digitizing
• Public DNA barcode database access through BOLD Systems or GenBank.

Advanced Materials

• Flatbed scanner or DSLR camera with macro lens for higher-resolution leaf images
• Calibrated scale bars for image standardization
• ImageJ for image preprocessing and measurement checks
• TPS series software for landmark and shape analysis
• R with geomorph and ggplot2 for shape statistics and plots
• Access to verified herbarium vouchers or expert-identified oak reference samples
• DNA barcode reference records from BOLD Systems or GenBank
• Optional access to a school or university molecular biology lab for confirming species IDs.

Software & Tools

• TPS-Dig: Records landmark coordinates from leaf images for morphometric analysis.
• ImageJ: Measures leaf length, width, and image scale, and helps check photo quality.
• R: Runs shape statistics, plots clusters, and compares groups with reproducible code.
• BOLD Systems: Provides public DNA barcode records for comparing your oak IDs.
• GenBank: Lets you search sequence records tied to named oak species and vouchers.

Experiment Steps

1. Define your oak sample set and decide how you will label each tree or branch.
2. Choose the leaf landmarks that match oak shape well and can be placed consistently across samples.
3. Plan your imaging setup so every leaf is photographed or scanned in the same orientation and scale.
4. Build a data table that pairs each leaf image with its tree ID, location, and public DNA barcode reference.
5. Select the shape statistics you will use to test clustering, separation, or hybrid overlap.
6. Plan validation checks that compare your morphometric groups against simple size measures and barcode IDs.

Common Pitfalls

• Using leaves from mixed-age branches, which can make shape differences reflect development instead of hybridization.
• Photographing leaves at different angles, which changes landmark positions and breaks shape comparisons.
• Picking landmarks that are hard to find on every oak leaf, which adds noise and weakens the analysis.
• Treating public DNA barcode names as perfect ground truth, which can hide misidentified reference records.
• Sampling too few leaves per tree, which makes one odd leaf look like a species pattern.

What Makes This Competitive

A strong version of this project goes beyond simple shape comparison. You would separate within-tree variation from between-tree variation, test whether hybrids sit in intermediate shape space, and compare your morphometric groups with public barcode IDs in a careful way. Strong controls matter too, especially consistent imaging, repeated landmarking, and a clear plan for handling ambiguous reference records. If you add a solid statistical test and a thoughtful discussion of oak hybrid complexity, the project starts to look like real systematics work.

Project Variations

• Compare leaf-shape hybrid signals in two oak species pairs instead of one backyard population.
• Test whether scanned leaves and smartphone photos give the same morphometric results for the same oak trees.
• Add simple leaf trait measurements, such as lobing depth and aspect ratio, to see whether they improve species and hybrid separation.

Learn More

• TPS Software: Official geometric morphometrics tools, including TPS-Dig, with downloads and documentation from the State University of New York site.
• BOLD Systems: Search public DNA barcode records and specimen metadata for oak comparisons.
• GenBank: Look up sequence records and linked annotations through NCBI.
• NCBI Bookshelf: Read free background chapters on plant systematics, evolution, and DNA barcoding.
• USDA Plants Database: Check accepted plant names, range notes, and taxonomy for oak species in the United States.
• Missouri Botanical Garden Plant Finder: Find free plant profile pages and identification notes for many oak species.