Reptiles and breeding birds on Mt. Hermon: Patterns of altitudinal distribution and species richness

We review and analyze the altitudinal distribution of reptiles (from museum collections) and breeding birds (from literature records and a recent fiel d sampling project) on Mt. Hermon (latitude ca. 33 degrees 30'N), over the range 300-2814 m. Species richness was greater in breeding birds (n = 86-90 ) than in reptiles (n = 34), declining with increasing altitude in both gro ups, but more steeply so in birds. We suggest that the simplification of ve getation structure with increasing altitude may explain this difference, be cause birds probably better use the three-dimensionality of densely-vegetat ed habitats that dominate low elevations. But in both taxa the overall decl ine was nonlinear; species richness actually increased from low to mid-elev ations, forming a hump-shaped pattern. Standardization of species richness for surface area, across altitudinal belts of 100 m up to 1,900 m, revealed the area effect as both significant and unpredictable. It did not affect t he overall decline, but contrary to a general expectation of a linear trend turning hump-shaped, the hump-shaped curve became concave, i.e., from low to mid-elevations the number of species per unit area declined sharply, and at higher elevations it remained fairly stable. In a comparison with other mountains in the Mediterranean Basin (between latitudes 35 degrees 00' and 42 degrees 30'N), the very same reptile species reached higher maximum ele vation's on Mt. Hermon, while the same bird species reached similar elevati ons in both areas. This difference may reflect lesser ability of reptiles, compared to birds, to inhabit high elevations at higher latitudes, but thei r altitudinal distribution on Mt. Hermon showed no evidence for such a phys iological difference. In general, in contrast with other reports, we found no positive correlation between the extent of altitudinal range of the spec ies and their position on the altitudinal gradient, as would have been impl ied by Rapoport's altitudinal rule. Future mapping of local distributions o f the Mt. Hermon biota, required for efficient conservation, should derive from planned, extensive field sampling, augmented with museum records for c larification of taxonomic uncertainties.