Species Richness Estimation Alters Inferred Drivers of Marine Island Biogeography
Gustavo M. Martins, João Faria, Sérgio P. ÁvilaABSTRACT
Aim
This study aims to assess how species richness estimation methods influence the interpretation of biodiversity drivers in marine island systems.
Location
The Azores, Portugal.
Time Period
2009–2014.
Major Taxa Studied
Marine coastal macroalgae.
Methods
We compared species richness patterns derived from two data sources: (i) published species compilations based on over three decades of surveys, and (ii) standardized, sample‐based estimates from a consistent field sampling design across nine islands. We evaluated the performance of five non‐parametric richness estimators (ICE, Chao 2, Jackknife 1, Jackknife 2 and Bootstrap) to assess accuracy (difference between estimated and observed richness) and precision (standard deviation across randomization). Statistical analyses were conducted to identify the geographical and environmental predictors of species richness, particularly focusing on island area, elevation and geological age.
Results
Published species records showed a strong positive relationship between species richness and island area, while standardized estimates revealed a negative relationship with island elevation. Jackknife 2 provided the most accurate estimates, despite lower precision compared to other methods. The regression model for published data was marginally non‐significant, while the model for standardized estimates identified island elevation as a significant negative predictor of richness.
Main Conclusions
Methodological choices in species richness estimation can significantly alter the interpretation of biodiversity drivers. Our results suggest that environmental factors, particularly those linked to island topography and elevation, may have a stronger influence on marine island biodiversity than traditionally emphasised area effects. Integrating standardised sampling with historical inventories is essential for robust macroecological inference in marine island systems.