Testing the Resource Hypothesis of Species–Area Relationships: Extinction Cannot Work Alone

Abstract

: The mechanisms that underpin the species–area relationship (SAR) are crucial for both the development of biogeographic theory and the application of biodiversity conservation. Since its origin, the resource hypothesis, which proposes that rich resources in vast ecosystems will lower extinction rates and shape the SAR, has not been tested. The impossibility to quantify resources and extinction rates using plants and animals as research subjects, as well as the inability to rule out the influences of the area per se, habitat diversity, dispersal, and the historical background of biodiversity, make testing this hypothesis problematic. To address these challenges and test this hypothesis, two sets of microbial microcosm experimental systems with positive and negative correlated resources and volumes were created in this work. The results of 157 high-throughput sequencing monitoring sessions at 11 time points over 30 consecutive days showed that neither of the experimental groups with positive or negative correlations between total resources and microcosm volume had a significant SAR, and there were no negative correlations between extinction rates and resources. Therefore, in our microcosmic system, resources do not influence extinction rates or shape the SAR. Dispersal should be the principal mode of action if the resource theory is correct.

Testing the passive sampling hypothesis: The role of dispersal in shaping microbial species-area relationship

“…The results of this study also show that a return to the three critical processes of speciation, dispersal, and extinction through design experiments can verify the formation mechanism of SAR one by one, thereby helping to elucidate the critical question of biodiversity patterns (Deng et al, 2022b). Although SAR is known as the first pattern of biodiversity, its formation mechanism is not clear.…”

“…The unique properties of microorganisms facilitate the experimental study of three fundamental processes. The microbial generation is short, the community dynamics change rapidly, and the community starting point can be controlled, which is especially suitable for quantitatively carrying out extinction and dispersal dynamic experiments on the temporal and spatial scale ( Deng et al, 2022b ). Microbial genomes are simpler and more variable than plants and animals and are expected to explore speciation’s role on biodiversity patterns in shorter time scales ( Chase et al, 2021 ).…”

“…The dispersal process appears to involve the movement of organisms in only two locations, but the consequences of this movement are very complex ( Leibold et al, 2004 ; Holyoak et al, 2005 ; Haegeman and Loreau, 2014 ). After dispersion, the community may be adjusted by the extinction process, which makes it difficult to distinguish the effects of dispersion and extinction in natural communities ( Deng et al, 2022b ).…”

Passive sampling hypothesis did not shape microbial species–area relationships in open microcosm systems

“…Microbial microcosm systems are an excellent way to construct a system for studying species–area relationships (Deng et al, 2021 ; Deng et al, 2022 ). In this study, an open microcosm system was created utilizing equal parts of homogeneously mixed paocai soup from the same period and open beakers.…”