Beetle Species–Area Relationships and Extinction Rates in Protected Areas

SIMPLE SUMMARY: Larger areas tend to host more species. This general ecological pattern (known as the species–area relationship, SAR) can be used to calculate expected extinction rates following area (habitat) loss. Here, using data from Italian reserves, SAR-based extinction rates are calculated for beetle groups with different ecology: terrestrial predators, aquatic predators, dung feeders, herbivores, and detritivores. Reserve area was an important predictor of species richness in all cases. However, also other factors besides area were important correlates of species richness. For some groups, species richness tends to decline with elevation and/or northwards. Extinction rates are higher for dung beetles, due to their dependence on large grazing areas, and detritivores, due to their low dispersal capabilities, which reduce their ability to reach new places when environmental conditions became less favorable. The lower extinction rates predicted for other groups can be explained by their higher dispersal ability. Extinction rates by area loss are always relatively low. This means that, in reserves with few species, many extinctions might be unnoticed. ABSTRACT: The species–area relationship (SAR, i.e., the increase in species richness with area) is one of the most general ecological patterns. SARs can be used to calculate expected extinction rates following area (habitat) loss. Here, using data from Italian reserves, extinction rates were calculated for beetle groups with different feeding habits: Carabidae (terrestrial predators), Hydradephaga (aquatic predators), coprophagous Scarabaeoidea (dung feeders), phytophagous Scarabaeoidea (herbivores), and Tenebrionidae (detritivores). The importance of other factors besides area (namely latitude and elevation) was investigated. Reserve area was recovered as an important predictor of species richness in all cases. For Carabidae, Hydradephaga, and Tenebrionidae, elevation exerted a negative influence, whereas latitude had a negative influence on coprophagous Scarabaeoidea and Tenebrionidae, as a consequence of current and historical biogeographical factors. Extinction rates were higher for dung beetles, due to their dependence on large grazing areas, and Tenebrionidae, due to their low dispersal capabilities. The lower extinction rates predicted for Carabidae, phytophagous Scarabaeoidea, and Hydradephaga can be explained by their higher dispersal power. If other variables besides area are considered, extinction rates became more similar among groups. Extinction rates by area loss are always relatively low. Thus, in reserves with few species, many local extinctions might be unnoticed.