Spatial congruence between taxonomic, phylogenetic and functional hotspots: true pattern or methodological artefact?

Aim To assess the spatial congruence between hotspots based on taxonomic, phylogenetic and functional diversity, after accounting for the correlation between diversity metrics, and the spatial scale and sampling completeness of data. Location The Ordesa and Monte Perdido National Park (Central Pyrenees, Spain), a species-rich area subjected to intensive botanical sampling. Methods We selected hotspots using different diversity metrics and two different data sources (~49,000 occurrence records of 1379 vascular plants in 1 × 1 km grid cells and 1218 inventories of plant communities containing a total of 859 taxa) and compared their spatial congruence. The effect of sampling completeness of data was explicitly assessed. Phylogenetic diversity and functional diversity (measured with richness-dependent and richness-independent metrics) were based on a molecular phylogeny, and a functional dendrogram, respectively. The effectiveness of different types of hotspots in representing other diversity components was tested with permutation tests. Results We found that spurious correlations between diversity metrics explained the congruence between taxonomic, phylogenetic and functional hotspots. When richness-independent metrics were used, diversity hotspots were no longer congruent regardless of the source of data. Hotspots were biased towards intensively sampled grid cells, and the amount of diversity they captured was exaggerated due to the coarse spatial scale of species-occurrence data. The efficiency of hotspots in terms of integrating different diversity components was lower at community scale and not significantly higher than expected at random, regardless of the sampling completeness. Main conclusions Our results stress that the arbitrary use of diversity metrics and the scale of analyses along with the sampling bias in data can distort the true location of hotspots, and exaggerate their spatial congruence. After accounting for such methodological issues, we found a clear mismatch between diversity components that questions the utility of hotspots as a conservation tool of multiple diversity components.