Legend Analysis:
- The red line represents the граница Российской Федерации (border of the Russian Federation).
- The republics mentioned in the legend are:
- Республика Саха (Якутия)
- Республика Карелия
- Республика Бурятия
Answer: The red line signifies the border of the Russian Federation. The republics listed are Sakha (Yakutia), Karelia, and Buryatia.