We investigated the influence of body size on rarity patterns at a regional scale using the tenebrionid beetles of Latium (Central Italy). For this we calculated geographical range size (no. of 10 km square cells), habitat breadth (no. of phytoclimatic units), and abundance (no. of sampled individuals) using a large database containing 3,561 georeferenced records for 84 native species. For each species, we used total body length to correct rarity measures for body size. Then we calculated vulnerability (Kattan) indices using both corrected and uncorrected rarity scores. Finally we used species range trends (expanded vs. contracted) as a measure of actual species decline. We found that range trends were correlated with vulnerability index independently from body size correction, the species with the highest vulnerability being those that experienced the strongest range contraction for both corrected and uncorrected measures. Also, we found that correcting for body size may be problematic because of the weak correlations between body size and geographical and ecological rarity (notably, abundance was not correlated). These findings indicate that correcting rarity for body size is not only theoretically questionable, but also practically difficult and possibly useless for conservation purposes.

Should we correct rarity measures for body size to evaluate arthropod vulnerability? Insights from Mediterranean tenebrionid beetles

FATTORINI, SIMONE;
2013

Abstract

We investigated the influence of body size on rarity patterns at a regional scale using the tenebrionid beetles of Latium (Central Italy). For this we calculated geographical range size (no. of 10 km square cells), habitat breadth (no. of phytoclimatic units), and abundance (no. of sampled individuals) using a large database containing 3,561 georeferenced records for 84 native species. For each species, we used total body length to correct rarity measures for body size. Then we calculated vulnerability (Kattan) indices using both corrected and uncorrected rarity scores. Finally we used species range trends (expanded vs. contracted) as a measure of actual species decline. We found that range trends were correlated with vulnerability index independently from body size correction, the species with the highest vulnerability being those that experienced the strongest range contraction for both corrected and uncorrected measures. Also, we found that correcting for body size may be problematic because of the weak correlations between body size and geographical and ecological rarity (notably, abundance was not correlated). These findings indicate that correcting rarity for body size is not only theoretically questionable, but also practically difficult and possibly useless for conservation purposes.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/111689
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