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Scale-invariance of niche breadth in fleas parasitic on small mammals


  • Boris R. Krasnov,

  • David Mouillot,

  • Irina S. Khokhlova,

  • Georgy I. Shenbrot,

  • Robert Poulin

B. Krasnov ( and G. I. Shenbrot, Mitrani Dept of Desert Ecology, Jacob Balustein Inst. for Desert Research, Ben-Gurion Univ. of the Negev, Sede-Boqer Campus, IL-84990 Midreshet Ben-Gurion, Israel and Ramon Science Center, P. O. Box 194, IL-80600 Mizpe Ramon, Israel. – D. Mouillot, UMR CNRS-UMII 5119 Ecosystemes Lagunaires, Univ. Montpellier II, CC093, FR-34095 Montpellier Cedex 5, France. – I. S. Khokhlova, Desert Animal Adaptations and Husbandry, Wyler Dept of Dryland Agriculture, Jacob Balustein Inst. for Desert Research, Ban-Gurion Univ. of the Negev, Sede-Boqer Campus, IL-84990 Midreshet Ben-Gurion, Israel. – R. Poulin, Dept of Zoology, Univ. of Otago, P. O. Box 56, 9054 Dunedin, New Zealand.


The resource specialization or niche breadth of a species is not fixed across populations, but instead varies over geographical space. A species may be a local specialist but a regional generalist, if it uses locally few resources that are substitutable across locations. In contrast, a species is a local generalist and a regional specialist if it uses locally many resources that cannot be substituted from 1 location to the next. Scale-dependence can thus be a major factor in estimation of niche breadth. Here, we test for relationships between local and global estimates of host specificity (a measure of niche breadth for parasites) in fleas (Siphonaptera) parasitic on small mammals from 49 different regions within the Holarctic. Across all fleas, we found a strong, positive relationship between the number of host species that a flea uses in 1 locality and the number of different host species that can serve as the flea's principal host (i.e. the one supporting the most fleas in a region) among all regions. Also, we observed a strong positive relationship between the taxonomic distinctness of the host species used in 1 locality and that of all known principal hosts among all localities. These relationships held after correcting for potentially confounding phylogenetic influences. We discuss the implications of scale-independent host specificity and its association with geographical range size and species-specific patterns of host use.

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