The biotic environment and conservation of scarce species

In any given community most species are rare. Scarce species are among the first species to go extinct. Combating rarity includes understanding its causes, one of which may be interspecific competition. We tested the hypothesis that Gerbillus. henleyi (GH) (10g), the smallest species of a pssamophilic guild in Israel, is scarce on relatively productive dunes of the Israeli desert, due to negative interactions from the common G. allenbyi (GA) (24g) and G. pyramidum (GP) (40g). We estimated experimentally, in a set of large rodent proof enclosures, the isoclines of GH competing with GA, GP, and both, using a technique we developed elsewhere. The stability analysis suggested that interspecific competition from accounts for 90.3% reduction in GH density, relative to when it is alone. When alone, about 25 GH can live in each 1-ha enclosure. With this result in mind, we suggest a method to conserve scarce species whose rarity is caused by negative interactions from other species. Creation of “artificial islands”, such as large enclosures, will allow pure populations of the scarce species to build source populations, due to lack of competition from other species, and serve as a source population to a much larger area.