Intraspecific and interspecific competition induces density‐dependent habitat niche shifts in an endangered steppe bird |
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| Authors: | Rocío Tarjuelo Manuel B. Morales Beatriz Arroyo Santiago Mañosa Gerard Bota Fabián Casas Juan Traba |
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| Affiliation: | 1. Terrestrial Ecology Group (TEG), Department of Ecology, Universidad Autónoma de Madrid, Madrid, Spain;2. Universidad Rey Juan Carlos, Móstoles, Spain;3. Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC, UCLM, JCCM), Ciudad Real, Spain;4. Department de Biologia Evolutiva, Ecologia i Ciències Ambientals, Institut de Recerca de la Biodiversitat (IRBio), Facultat de Biologia, Universitat de Barcelona, Barcelona, Catalonia, Spain;5. Biodiversity and Animal Conservation Lab, Forest Science Center of Catalonia (CTFC), Solsona, Catalonia, Spain;6. Estación Experimental de Zonas áridas (EEZA‐CSIC), Almería, Spain;7. Department of Biology, University of Maryland, College Park, MD, USA |
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| Abstract: | Interspecific competition is a dominant force in animal communities that induces niche shifts in ecological and evolutionary time. If competition occurs, niche expansion can be expected when the competitor disappears because resources previously inaccessible due to competitive constraints can then be exploited (i.e., ecological release). Here, we aimed to determine the potential effects of interspecific competition between the little bustard (Tetrax tetrax) and the great bustard (Otis tarda) using a multidimensional niche approach with habitat distribution data. We explored whether the degree of niche overlap between the species was a density‐dependent function of interspecific competition. We then looked for evidences of ecological release by comparing measures of niche breadth and position of the little bustard between allopatric and sympatric situations. Furthermore, we evaluated whether niche shifts could depend not only on the presence of great bustard but also on the density of little and great bustards. The habitat niches of these bustard species partially overlapped when co‐occurring, but we found no relationship between degree of overlap and great bustard density. In the presence of the competitor, little bustard's niche was displaced toward increased use of the species' primary habitat. Little bustard's niche breadth decreased proportionally with great bustard density in sympatric sites, in consistence with theory. Overall, our results suggest that density‐dependent variation in little bustard's niche is the outcome of interspecific competition with the great bustard. The use of computational tools like kernel density estimators to obtain multidimensional niches should bring novel insights on how species' ecological niches behave under the effects of interspecific competition in ecological communities. |
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| Keywords: | ecological release kernel density estimators
Otis tarda
species coexistence
Tetrax tetrax
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