Which of the following species are restricted to an area?

Options

A. Sibling species
B. Endemic species
C. Allopatric species
D. Sympatric species

Answer

To determine which species are restricted to a specific area, we can analyze the definitions of the options provided:

1. **Sibling Species**: These species are morphologically identical and can produce fertile offspring. They are not necessarily restricted to a specific area, as they can exist in overlapping regions.

2. **Endemic Species**: These species are restricted to a particular area. They often have specific habitat requirements and can be found in biodiversity hotspots, which are regions with a high level of species richness and endemism. Endemic species are also referred to as native species.

3. **Allopatric Species**: These species arise due to geographical barriers that separate populations, leading to speciation. While they may be restricted to different areas, they are not inherently restricted to a single area.

4. **Sympatric Species**: These species originate from a single ancestor and are formed due to reproductive isolation, but they inhabit the same geographic area. Therefore, they are not restricted to a specific area.

Based on this analysis, the species that are restricted to an area are **endemic species**.

### Step-by-Step Solution:
1. **Identify the Definitions**: Understand the definitions of sibling, endemic, allopatric, and sympatric species.
2. **Analyze Each Option**: Evaluate which of these species are restricted to a specific area.
3. **Conclude**: Determine that endemic species are the ones restricted to a particular area.

### Final Answer:
The species that are restricted to an area are **endemic species**.