The habitat amount hypothesis predicts that fragmentation poses a threat to biodiversity: A reply to Fahrig

2021 ◽  
Author(s):  
Santiago Saura
Keyword(s):  
Habitat Amount ◽  
Habitat Amount Hypothesis

scholarly journals The Habitat Amount Hypothesis implies negative effects of habitat fragmentation on species richness and occurrence

2020 ◽  
Author(s):  
Santiago Saura
Keyword(s):  
Species Richness ◽  
Habitat Fragmentation ◽  
Spatial Configuration ◽  
Spatial Scales ◽  
Conservation Strategies ◽  
Negative Effects ◽  
Habitat Amount ◽  
Habitat Configuration ◽  
Habitat Amount Hypothesis ◽  
Individual Site

AbstractThe Habitat Amount Hypothesis (HAH) predicts that species richness, abundance or occurrence in a habitat site increases with the amount of habitat in the ‘local landscape’ defined by an appropriate distance around the site, with no distinct effects of the size of the habitat patch in which the site is located. It has been stated that a consequence of the HAH, if supported, would be that it is unnecessary to consider habitat configuration to predict or manage biodiversity patterns, and that conservation strategies should focus on habitat amount regardless of fragmentation. Here, I assume that the HAH holds and apply the HAH predictions to all habitat sites over entire landscapes that have the same amount of habitat but differ in habitat configuration. By doing so, I show that the HAH actually implies clearly negative effects of habitat fragmentation, and of other spatial configuration changes, on species richness, abundance or occurrence in all or many of the habitat sites in the landscape, and that these habitat configuration effects are distinct from those of habitat amount in the landscape. I further show that, contrary to current interpretations, the HAH is compatible with a steeper slope of the species-area relationship for fragmented than for continuous habitat, and with higher species richness or abundance for a single large patch than for several small patches with the same total area (SLOSS). This suggests the need to revise the ways in which the HAH has been interpreted and can be actually tested. The misinterpretation of the HAH has arisen from confounding and overlooking the differences in the spatial scales involved: the individual habitat site at which the HAH gives predictions, the local landscape around an individual site, and the landscapes or regions (with multiple habitat sites and different local landscapes) that need to be analysed and managed. The HAH has been erroneously viewed as negating or diminishing the relevance of fragmentation effects, while it actually supports the importance of habitat configuration for biodiversity. I conclude that, even in the cases where the HAH holds, habitat fragmentation and configuration are important for understanding and managing species distributions in the landscape.

scholarly journals Influence of landscape structure on Euglossini composition in open vegetation environments

2017 ◽  
Vol 17 (1) ◽  
Author(s):  
Eduardo Freitas Moreira ◽  
Rafaela Lorena da Silva Santos ◽  
Maxwell Souza Silveira ◽  
Danilo Boscolo ◽  
Edinaldo Luz das Neves ◽  
...  
Keyword(s):  
Species Richness ◽  
Landscape Structure ◽  
Multiple Scales ◽  
Landscape Heterogeneity ◽  
Species Abundance ◽  
Information Criterion ◽  
Landscape Configuration ◽  
Habitat Amount ◽  
Savanna Vegetation ◽  
Habitat Amount Hypothesis

Abstract The fauna of Euglossini bees is poorly known in savanna regions, making it difficult to understand how these bees use open vegetation environments. The aim of this study was to evaluate the influence of landscape structure on species abundance and composition of Euglossini bees in naturally heterogeneous savanna landscapes. Nine sites were sampled monthly using six traps with chemical baits. Three aromatic essences (eucalyptol, methyl salicylate and vanillin) were used to attract the Euglossini. Surrounding environmental conditions were measured using three independent variables, calculated in multiple scales: index of local vegetation and two landscape indices (Shannon Diversity and area-weighted shape). We compared the competing hypotheses through model selection based on Second-order Akaike Information Criterion (AICc). The four competing hypothesis were: (1) The local vegetation complexity favors Euglossini bees species richness and/or abundance (local vegetation hypothesis); (2) The proportion of the native vegetation types favors Euglossini bees species richness and/or abundance (habitat amount hypothesis); (3) Higher landscape diversity shall increase species richness of Euglossini bees (landscape heterogeneity hypothesis); (4) More complex landscape configuration shall favor the Euglossini bees richness and/or abundance (landscape heterogeneity hypothesis). We sampled 647 individuals belonging to six species of two distinct genera. Our results support the habitat amount hypothesis since bees’ abundance was strongly related with the proportion of habitat in the surrounding landscape. This may be related to the availability of floral and nesting resources in some types of savanna vegetation.

scholarly journals Experimental evidence does not support the Habitat Amount Hypothesis

Ecography ◽  
2016 ◽  
Vol 40 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Nick M. Haddad ◽  
Andrew Gonzalez ◽  
Lars A. Brudvig ◽  
Melissa A. Burt ◽  
Douglas J. Levey ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Habitat Amount ◽  
Habitat Amount Hypothesis

Fair tests of the habitat amount hypothesis require appropriate metrics of patch isolation: An example with small mammals in the Brazilian Atlantic Forest

2018 ◽  
Vol 226 ◽  
pp. 264-270 ◽  
Author(s):  
Marcus Vinícius Vieira ◽  
Mauricio Almeida-Gomes ◽  
Ana Cláudia Delciellos ◽  
Rui Cerqueira ◽  
Renato Crouzeilles
Keyword(s):  
Atlantic Forest ◽  
Small Mammals ◽  
Brazilian Atlantic Forest ◽  
Habitat Amount ◽  
Patch Isolation ◽  
Habitat Amount Hypothesis

Testing the habitat amount hypothesis for South American small mammals

2017 ◽  
Vol 209 ◽  
pp. 304-314 ◽  
Author(s):  
Geruza Leal Melo ◽  
Jonas Sponchiado ◽  
Nilton Carlos Cáceres ◽  
Lenore Fahrig
Keyword(s):  
Small Mammals ◽  
South American ◽  
Habitat Amount ◽  
Habitat Amount Hypothesis
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