## Problem 175 — rank:164

**Title:** Evolution during spatial range expansion

**Added binding assumptions (LaTeX):**

```latex
Define the front at each census from contemporaneous sustained occupancy, including a no-occupied-deme outcome; a historically reached maximum can conceal subsequent retreat. Fitness load needs a positive and genuinely comparable environmental benchmark and may be negative if that benchmark is not an upper bound. Specify whether error targets concern the expected front summaries or noisy single-expansion estimates, and include replicate uncertainty.
```

**Direct edits:** 0. **Fresh external checks:** None; supplied sources retained as provenance.