Integrating multiple scales in rarity assessments of invertebrate taxa
Article first published online: 19 JAN 2013
© 2013 John Wiley & Sons Ltd
Diversity and Distributions
Volume 19, Issue 7, pages 794–803, July 2013
How to Cite
Leroy, B., Canard, A., Ysnel, F. (2013), Integrating multiple scales in rarity assessments of invertebrate taxa. Diversity and Distributions, 19: 794–803. doi: 10.1111/ddi.12040
- Issue published online: 13 JUN 2013
- Article first published online: 19 JAN 2013
- Management monitoring;
- occurrence data;
- rare species;
- rarity hotspots;
- western Palearctic
To provide a procedure for measuring the rarity of both invertebrate species and assemblages of species from multiple scales without the need for fine-resolution datasets over broad areas.
The western Palearctic (WP) and western France.
On the basis of different datasets from different geographical extents, we applied a multiscale rarity weight to species occurrence from multiple scales. Multiscale rarity weights were then averaged at an assemblage level in a multiscale index of relative rarity (IRR). These rarity weights were calculated using a flexible, scale-dependent method that ensures equitable contributions of each scale to the final index. We provided a simple two-scale example of the application, on spiders of western France, for which we obtained occurrence information from a regional-extent dataset (regional scale) and a western Palearctic-extent dataset (WP scale). Thus, we showed the necessity of a two-scale approach by successively analysing species occurrence, multiscale rarity weights of species and multiscale indices of species assemblage. Finally, we presented a case study within a nature reserve.
Species occurrences are not predictable from one scale to another, and rarity indices of assemblages are poorly congruent among scales, which supports the necessity of a two-scale approach. Multiscale rarity weights accurately showed information on species rarity from both scales. Multiscale indices of assemblages were congruent but with additional information over each one-scale index.
The novelty of the multiscale method developed here is to accurately combine different datasets of varying extents and resolutions to provide multiscale rarity weights for species and indices for assemblages. Given the increasing availability of datasets for invertebrate taxa, this method represents a significant improvement for rarity and conservation studies on invertebrates.