Résumé
The concept of umbrella species assumes that concentrating resources on
the protection of a single species contributes to the conservation of a
suite of species and ecological processes belonging to the same ecosystem.
The environmental requirements and geographical distribution of the
umbrella species should thus overlap those of the group of targeted
species. In western France, the conservation of several large grassland
floodplains relies on agri-environmental schemes targeting one single bird
species, the corncrake Crex crex. It is considered as an umbrella species
but no real assessment of its effectiveness has been carried out so far.
We used a two-step methodology to assess the potential of the corncrake to
act as an umbrella species by estimating niche overlap in the
environmental and geographic space between the main ground-nesting species
of the bird community in these grasslands, including the corncrake and
four passerines. The five species showed substantial differences in their
ecological niches so that their distributions did not perfectly overlap.
Overlaps in predicted distributions between pairs of species depended on
the threshold used to convert suitability to binary maps. Moreover, the
number of species that could be protected by a candidate umbrella species
was affected by the overlap criterion of success. Although the corncrake
may be used as an umbrella species, it would be outperformed by several
passerine species. Our study highlights the potential of using niche
overlap to select umbrella species. It also reveals the importance of
analysing the sensitivity of outputs when changing thresholds and overlap
criteria.