Overview
Species accumulation curves show how the number of observed species increases with sampling effort.
They help assess sampling completeness and estimate total species richness.
Types of Curves
- Sample-size-based R/E curve:
- Shows how species richness increases with sampling effort
- Solid line shows rarefaction (interpolation)
- Dashed line shows extrapolation
- Shaded area represents confidence interval
- Sample completeness curve:
- Shows sample coverage (proportion of total species detected)
- Higher values indicate more complete sampling
- Helps determine if additional sampling is needed
- Coverage-based R/E curve:
- Shows species richness against sample coverage
- Allows fair comparison between assemblages
- Less sensitive to sample size differences
Diversity Order (q)
The diversity order q determines which diversity measure is calculated:
- q = 0: Species richness
- Counts all species equally
- Not sensitive to species abundances
- Most commonly used for basic accumulation curves
- q = 1: Shannon diversity
- Weighs species by their relative frequency
- Common and rare species contribute proportionally
- More informative when species have uneven detection rates
- q = 2: Simpson diversity
- Emphasizes common species
- Less sensitive to rarely detected species
- More robust to sampling variation
Higher values of q increasingly favor common species. Consider using multiple q values
to understand how diversity patterns change when accounting for species relative frequencies.
For camera trap data, this can help distinguish between truly rare species and those that
are just harder to detect.
Sampling Units
You can choose between two types of sampling units:
- Stations:
- Each camera location counts as one sampling unit
- Better for spatial coverage assessment
- Useful when comparing areas with different camera densities
- Days:
- Each survey day counts as one sampling unit
- Better for temporal coverage assessment
- Useful when comparing surveys of different durations
Important Notes
- These curves are based on observed detections only
- They do not account for imperfect detection
- Species may be present but not detected
- Consider using alongside occupancy analyses for more complete understanding
Using the Interface
- Basic Settings:
- Choose assemblage grouping (optional)
- Set diversity order (q)
- Select sampling unit type
- Species Selection:
- Select species to include in analysis
- Filter by minimum stations/records if needed
- All species are selected by default
- Curve Settings:
- Set confidence level and bootstrap replicates
- Adjust plot scaling for better visibility