Beetle Species-Area Relationships and Extinction Rates in Protected Areas.

Simone Fattorini

doi:10.3390/insects11090646

Abstract

Simple SummaryLarger 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.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.

Highlights

The species–area relationship (SAR, i.e., the increase in species richness with area) is an almost ubiquitous ecological pattern [1]
Reserve area was an important predictor of species richness in all investigated beetle groups, which is consistent with the almost ubiquitous pattern known as the species–area relationship (SAR)
For Carabidae, Hydradephaga, and Tenebrionidae, elevation exerted a negative influence—a possible reflection of the general decline in species richness with altitude commonly observed in many taxa

Summary

Introduction

The species–area relationship (SAR, i.e., the increase in species richness with area) is an almost ubiquitous ecological pattern [1]. Insects 2020, 11, 646 the best size and shape of natural areas [5,6,7,8], and the prediction of species extinction [9,10]. There is a debate about how accurate species extinction rates based on the SAR are [10]. The basic idea in the use of the SAR to predict species loss is that a reduction in area size implies a reduction in species number. The same function which is used to model the SAR can be used, in a reverse way, to predict species loss. Empirical evidence largely supports that, at least for isolates, most systems are adequately modelled by the power function (1):

Methods

Results

Conclusion